X-Planes: Hiller X-18

The Hiller X-18 tilted its entire wing to take off vertically. The tilting is the easy part. The hard part is that a wing pointed at the sky is a wing pointed away from the oncoming air, and a wing at ninety degrees to the flow is stalled. The configuration works only where the propeller slipstream keeps the flow attached, and the fraction of the wing that sits in the slipstream is fixed at design time. This article is the nineteenth in the X-Planes series, following the X-1, the X-2, the X-3, the X-4, the X-5, the X-6, the X-7, the X-8, the X-9, the X-10, the X-11, the X-12, the X-13, the X-14, the X-15, the X-16, and the X-17.

The series has met the vertical take-off problem twice already, at the X-13 and the X-14. Both solved it by pointing a jet downward. The X-18 is the first attempt in this series to solve it with a wing, a different problem with a different failure mode, and that failure mode arrived.

The standard inventory entry remains Jenkins Landis and Miller 2003 American X-Vehicles, An Inventory X-1 to X-50, which the National Aeronautics and Space Administration publishes as Monographs in Aerospace History No. 31, and the vehicle compilation is Miller 2001 The X-Planes, X-1 to X-45. The tilt-wing design literature is McCormick and Mallen 1956 and its later textbook form McCormick 1967 Aerodynamics of V/STOL Flight.

The Research Question

The question is not whether a wing can be tilted. It obviously can. The question is whether a continuous, controllable path exists from hover to wing-borne flight, and for a tilt-wing that path is constrained by something the pilot cannot adjust.

The Keystone Is Slipstream Immersion

The keystone is the fraction of the wing that sits inside the propeller slipstream.

At zero forward speed the aircraft is held up by propeller thrust, and the wing does nothing except get in the way. At cruise the wing does everything. In between, the wing must take over progressively, and to do that it must be generating lift at wing tilt angles far beyond any ordinary stall angle.

Only the slipstream permits that. Air leaving a propeller disc at eighty metres per second does not care that the aircraft is stationary, and a wing immersed in it is flying regardless. A wing outside it is not.

So the configuration divides the wing into two parts that behave completely differently throughout the conversion, and the division is set by propeller diameter against span, which is frozen when the aircraft is drawn.

Why This Was the Binding Unknown in 1957

The alternatives were understood and each had a known defect. A helicopter has a low disc loading and cannot cruise efficiently. A tail-sitter, as the Convair XFY-1 showed, asks the pilot to land looking over his shoulder. A deflected-jet aircraft, as the X-14 showed, spends an enormous fraction of its thrust simply on being controllable.

A tilt-wing promised a genuine transport aircraft, one that hovers like a helicopter and then cruises like an aeroplane with the whole wing working. Design studies of the period compare the options directly, in Irvin and Swan 1956 and Boeing Co Morton Pa Vertol Div 1956, and the tilt-wing’s commercial case is argued in Mazzitelli 1957.

Design requirements for the configuration were being written at the same time, in Stuart 1956, Dallas and Irvin 1956, and the successive treatments of McCormick and Mallen 1957. Earlier convertiplane flight experience is recorded in Marks 1956 and the critical advance ratio problem in Doetsch and Mark 1953.

The tilt-wing and its relatives were studied continuously from the mid-1950s to the present, across McCormick 1956, Feldman 1956, Stepniewski 1957, Stuart 1957, Ward 1960, Quigley and Koenig 1960, Kuhn and Grunwald 1960, Tosti 1961, O’Rourke and Rutherford 1991, Totah 1992, Rutherford and Bass 1992, Sullivan 1993, Harris 2003, Armutcuoglu et al 2004, de Madrid et al 2007, Holsten et al 2011, Cui et al 2019, Rohr et al 2019, Binz et al 2019, Geuther et al 2020.

What nobody had in 1957 was flight evidence that the conversion was flyable at full scale, and the smaller Vertol VZ-2 made its first full transition only in July 1958. The X-18 was built to obtain that evidence in a large aircraft, and it failed to obtain it. The inventory records that it was conceived to assess the feasibility and practicality of a large tilt-wing aircraft.

Programme Origin

The X-18 is the most conspicuously improvised aircraft in this series. Hiller built it from parts that already existed. The fuselage came from a Chase YC-122C Avitruc assault transport. The turboprops came from two cancelled tail-sitting fighter programmes, the Convair XFY-1 Pogo and the Lockheed XFV-1, which had used the same Allison T40 driving contra-rotating propellers. A Westinghouse J34 turbojet went in the tail. The National Aeronautics and Space Administration’s inventory records the same YC-122C fuselage and two turboprop engines surplused from the Navy’s cancelled vertical take-off fighter programme.

The X-18 was thus a research aircraft assembled from the wreckage of the previous generation of answers to the same question, and the point matters because the components carried their assumptions with them. The engines were chosen for a tail-sitter, not for a tilt-wing.

The programme began as a company proposal and became an Air Force contract. The official history of the Air Force’s 16th Special Operations Wing records that Hiller proposed a tilt-wing aircraft to both the Army and the Air Force early in 1954 as an alternative to the helicopter, that design work began in 1955, and that the Air Force funded and contracted for the aircraft, which was designated the X-18 in October 1957 and unveiled on 8 December 1958. The inventory lists the Air Force and the Navy as its sponsors.

Hiller’s own engineering record exists, on paper only. The company’s reports on the aircraft, its Model 1051, are catalogued in the Bernard Lindenbaum Vertical Flight Research Collection at Wright State University, and every one of them that names a contract names the same Air Force contract. They include a preliminary design study summary of October 1956, an estimate of flight-test performance of May 1957, an analysis of the variation of pitching moment in transition flight of May 1958, force tests and remote-controlled free-flight tests of a one-eighth scale model in October 1958, an analysis of the thrust available from the J34-WE-36 pitch control engine of October 1958, and a simulation of the X-18 in hover for Edwards Air Force Base of February 1959. None of the catalogued items reports flight results, and none is digitised, so the programme’s design intentions are on record and its flight measurements are not.

The Vehicle

The compiled specification in the encyclopaedia entry, which cites Jane’s All the World’s Aircraft and Miller, gives a span of 48 feet, a wing area of 528 square feet, a length of 63 feet, an empty weight of 27,052 pounds, a maximum take-off weight of 33,000 pounds, and two Allison T40-A-14 turboprops of 5,850 equivalent horsepower each. The two contra-rotating propellers are 16 feet in diameter in its text and 16 feet 1 inch in its table, and this article uses 16 feet. The Air Force history calls the aircraft sixteen and a half tons, which in short tons of 2,000 pounds is

\[W = 16.5 \times 2{,}000 = 33{,}000\ \text{lb}\]

the same maximum weight from an independent official source.

The sources disagree about the first flight by four days. The inventory gives a first flight on 20 November 1959, and the Air Force history gives 24 November 1959 at Edwards Air Force Base. The encyclopaedia entry reconciles them as a first hop on 20 November and a first full flight on 24 November, after preliminary testing at Moffett Field. The inventory records 20 flights in all, the last in July 1961, with a fastest flight of 253 miles an hour and a highest of 35,300 feet.

Before relying on the published figures, it is prudent to confirm that they are internally consistent, and they are. Aspect ratio from span and area is

\[A = \frac{b^{2}}{S} = \frac{48^{2}}{528} = 4.364\]

against a quoted 4.36, and the wing loading at maximum weight is

\[\frac{W}{S} = \frac{33{,}000}{528} = 62.50\ \text{lb/ft}^{2}\]

Sizing From First Principles

How Much of the Wing Is Immersed

The raw geometric ratio is two propeller diameters against the span,

\[f_{\text{raw}} = \frac{n D_p}{b} = \frac{2 \times 16}{48} = 0.667\]

so two thirds of the span sits behind a propeller. That figure is optimistic, because a slipstream contracts. Momentum theory gives the fully developed slipstream area as half the disc area, so the diameter contracts by the square root of two,

\[D_{\text{slip}} = \frac{D_p}{\sqrt{2}} = \frac{4.877}{1.414} = 3.448\ \text{m} = 11.31\ \text{ft}\]

which would immerse only 47.1 percent of the span. The wing sits close behind the disc, where contraction is partial, so the true figure lies between.

Station	Diameter factor	Immersed span
At the disc	1.000	66.7 percent
Just behind the disc	0.850	56.7 percent
Fully developed	0.707	47.1 percent

Taking a representative value, about 57 percent of the span is immersed and about 43 percent is not. The rest of the article follows from that number.

Is the Un-Immersed Wing Actually Stalled

The outer wing meets the freestream at an angle of attack equal to the wing tilt plus the fuselage attitude. With the fuselage level,

\[\alpha_{\text{free}} = i_w\]

and taking a stall angle of 15 degrees, which is an assumption and a generous one for a thick unswept wing, the outer panel is stalled for any tilt above 15 degrees. A conversion runs from zero tilt to about ninety, so the stalled fraction of the conversion is

\[\frac{90 - 15}{90} = 0.833\]

Maximum lift and stalling behaviour of full-scale wings had been catalogued since Sweberg and Dingeldein 1945, and the leading-edge stall mechanism at high incidence in Black 1956, so the designers were not working blind about the stall itself. They were working blind about what a propeller does to it.

Stall, maximum lift and the installation of propellers on wings were studied extensively over the same decades, in Sharp 1950, Hickey and Aoyagi 1960, Feistel et al 1978, Nelson and Mouch 1978, Wang 1979, Vincent et al 1979, Smith and Levin 1981, Bennett et al 1983, Anderson and Cho 1984, Bartlett 1985, Hoadley and Pederson 2001, Catalano 2004, Delamore-Sutcliffe and Greenwell 2006, Uhlig and Selig 2008, Fan et al 2019, S.P et al 2022, Xiao et al 2022, Goharshadi and Mirzaei 2022.

The outer wing is stalled for five sixths of the conversion. The cause is geometric, and no amount of section design removes it, because the wing is pointed away from the oncoming air by construction. The stall behaviour of exactly this configuration was measured, in Giulianetti and Weiberg 1964, and the prediction of span loading on a propeller-blown wing up to stall is the subject of McVeigh et al 1975.

What the Slipstream Buys

Momentum theory for an actuator disc at static thrust gives the induced velocity at the disc and the fully developed slipstream behind it,

\[v_i = \sqrt{\frac{T}{2 \rho A}}, \qquad v_s = 2 v_i\]

At maximum weight each propeller carries half of it,

\[T = \frac{33{,}000}{2} = 16{,}500\ \text{lbf} = 73.4\ \text{kN}\]

over a disc area of 18.68 square metres, for a disc loading of

\[\frac{T}{A} = \frac{73{,}400}{18.68} = 3{,}929\ \text{N/m}^{2} = 82.1\ \text{lb/ft}^{2}\]

and gives

\[v_i = \sqrt{\frac{73{,}400}{2 \times 1.225 \times 18.68}} = 40.05\ \text{m/s}\]

with a fully developed slipstream at 80.09 metres per second. Taking an assumed part-developed value of $1.5 v_i$ at the wing, the dynamic pressure over the immersed panel at zero forward speed is

\[q_{\text{slip}} = \tfrac{1}{2} \rho (1.5 v_i)^{2} = \tfrac{1}{2} \times 1.225 \times 60.07^{2} = 2{,}210\ \text{Pa}\]

which corresponds to an equivalent airspeed of

\[V_{\text{eq}} = \sqrt{\frac{2 q_{\text{slip}}}{\rho}} = 60.1\ \text{m/s} = 117\ \text{kt}\]

That is the static case. With forward speed the induced velocity solves

\[v_i = \frac{T}{2 \rho A \sqrt{V^{2} + v_i^{2}}}\]

which reduces to the expression above at zero speed. The induced velocity falls as the aircraft accelerates, from 40.05 metres per second at rest to 24.71 at sixty, while the freestream rises faster, so the total dynamic pressure over the immersed panel climbs from 2,210 to 5,772 pascals through the conversion.

The handover is helped by the physics, not fought by it. The immersed panel gets a more energetic flow at every stage of the conversion, and that rising flow goes a long way toward explaining why the configuration is viable.

The immersed wing is flying at about 117 knots while the aircraft is standing still. The configuration depends on that equivalence, and without it a tilt-wing could not work. The immersed wing never stops flying. The un-immersed wing never starts.

The Relation That Makes the Configuration Work

The article has so far asserted that the slipstream keeps the immersed panel flying without giving the relation that makes it true. That relation is the local angle of attack, the most important equation here.

The propeller axis lies along the wing chord, so the slipstream adds velocity along the chord while the freestream arrives at the wing tilt angle. Resolving the two,

\[\alpha_{\text{local}} = \arctan\left(\frac{V \sin i_w}{V \cos i_w + v_s}\right)\]

For the un-immersed panel $v_s = 0$ and this collapses to $\alpha = i_w$. The claim made earlier is therefore a limiting case of the relation, no longer a separate assertion. For the immersed panel it does something remarkable.

Speed	15° tilt	30°	45°	60°	75°	90°
0 m/s	0.0	0.0	0.0	0.0	0.0	0.0
10 m/s	2.1	4.2	6.0	7.6	8.8	9.5
20 m/s	3.7	7.4	10.8	13.9	16.5	18.4
30 m/s	5.0	9.9	14.6	19.1	23.1	26.5
60 m/s	7.5	15.0	22.5	30.0	37.5	45.0

The interference this relation idealises is the central aerodynamic subject of the configuration and has a long literature, in Thoren and Johnson 1940, Stiesz 1940, Brenckmann 1958, Kuhn 1959, Vidal et al 1960, Grunwald 1961, Weiberg and Holzhauser 1961, Kuhn and Grunwald 1961, Rizk 1980, Katz et al 1980, Welge et al 1981, Moens and Gardarein 2001, Renooij and Slingerland 2004, Wang et al 2019, Wang et al 2019, Mikhalyov et al 2019, Xue and Zhou 2020.

At zero forward speed the immersed wing is at exactly zero angle of attack, at any tilt whatever. The only flow it sees comes straight down its chord. It is not stalled, not marginal, and needs no high-lift device to be unstalled. The un-immersed panel meanwhile sits at the full tilt angle at every speed in the table.

Where the Immersed Panel Finally Does Stall

Setting $\alpha_{\text{local}}$ equal to the stall angle and solving for tilt gives the limit.

Speed	Maximum tilt before the immersed panel stalls
10 m/s	90.0°
20 m/s	66.0°
30 m/s	46.2°
40 m/s	37.9°
60 m/s	30.0°

The tolerable tilt falls as speed rises, the favourable direction, because a faster aircraft needs less tilt anyway. The two curves are moving the same way, and whether a corridor exists depends on whether the required tilt falls faster than the allowed one.

What the Immersed Wing Can Carry

With 57 percent of the span immersed, the immersed area is 27.80 square metres against 21.26 outside.

Lift coefficient	Immersed lift	Fraction of maximum weight
0.8	11,049 lbf	33.5 percent
1.0	13,811 lbf	41.9 percent
1.4	19,336 lbf	58.6 percent

The wing alone cannot hover the aircraft, as expected, because in hover the propellers carry the weight directly as thrust. The relevant test is continuity of the handover, and lifting the aircraft in hover is no part of it, and the table shows there is a substantial contribution available from the immersed panel throughout.

The Conversion Corridor Exists

Level flight during conversion requires

\[T \sin i_w + L = W, \qquad T \cos i_w = D\]

with the lift coming from the immersed panel at slipstream dynamic pressure and the rest of the wing at freestream dynamic pressure,

\[L = q_{\text{slip}} S_{\text{imm}} C_{L,\text{imm}} + q_\infty (S - S_{\text{imm}}) C_{L,\text{free}}\]

Solving for the tilt that balances weight at each speed, and setting it beside the tilt the immersed panel will tolerate, gives the corridor.

Speed	Tilt required	Tilt allowed	Margin
10 m/s	52.0°	90.0°	38.0°
20 m/s	37.4°	66.0°	28.6°
30 m/s	26.7°	46.2°	19.6°
40 m/s	23.5°	37.9°	14.4°
50 m/s	20.5°	33.1°	12.6°
60 m/s	17.0°	30.0°	13.0°

The transition problem, and the control, handling and powerplant questions around it, occupied the powered-lift community for decades, across Boeing Co Morton Pa Vertol Div 1956, Smith 1958, Loewy and Yntema 1958, Baxter and Finvold 1958, Mallen and Dancik 1959, NASA Conference on V/STOL 1960, NACA 1960, Conference on V/Stol Aircraft a Co, Tapscott 1960, Tapscott 1960, Anderson 1960, Stapleford 1980, Roberts et al 1981, Fluk 1981, Hill 1981, Verma and Junkins 2000, Chana 2002, Ng and Datta 2019, Wang et al 2019, Wang et al 2019.

A corridor exists at every speed. The point needs stating plainly, because the argument so far has emphasised what is stalled and could leave the impression that the configuration is marginal. It is not. The tilt-wing works, with a margin of between twelve and thirty-eight degrees of tilt throughout. The X-18 was under-equipped for the configuration, not attempting an impossible one.

The margin is narrowest in the middle of the conversion, around forty to fifty metres per second, where the aircraft has neither the slipstream authority of low speed nor the freestream dynamic pressure of high speed.

Descent Closes the Corridor

The corridor above is for level flight. Descending at rate $w$ adds to the angle of attack, because the freestream arrives from below,

\[\alpha_{\text{eff}} = \alpha_{\text{local}} + \arctan\frac{w}{V}\]

so a tilt-wing can be stalled by its own rate of descent at constant tilt and constant speed. Computing the descent rate that consumes the whole margin at the required tilt,

Speed	Descent that closes the corridor
10 m/s	1.44 m/s, or 284 ft/min
20 m/s	2.07 m/s, or 408 ft/min
30 m/s	3.26 m/s, or 641 ft/min
50 m/s	4.98 m/s, or 980 ft/min
60 m/s	6.85 m/s, or 1,349 ft/min

The observation is not novel, and the literature confirms it directly. The descent capability of two-propeller tilt-wing configurations, the X-18’s exact arrangement, was measured and reported in Hassell and Kirby 1966. The wider subject, including the vortex ring state that a lifting rotor meets in descent and its modern computational treatment, runs through Hassell and Kirby 1966, Johnson 1977, Lee 1985, Inoue et al 1997, Johnson 2004, Johnson 2005, Prasad and Chen 2006, Young 2010, Stalewski and Surmacz 2019, Stalewski and Surmacz 2020, Makeev et al 2021, Makeev et al 2021.

Two hundred and eighty-four feet per minute at the slow end is a gentle descent by any normal standard, and it exhausts the margin. Here lies the tilt-wing descent problem. It is why these aircraft carried restricted descent envelopes such as the rate-of-descent limitations in Pegg’s VZ-2 flight tests, and it explains why the approach, not the take-off, was the difficult half of the flight.

The period record agrees, and finds the table optimistic. Kirby’s paper in the 1960 conference on vertical and short take-off aircraft, NACA 1960, Conference on V/Stol Aircraft a Co, resolves the freestream and the slipstream increment into the wing’s angle of attack as above, notes that the portions of the wing outside the slipstream meet a very high angle of attack, and adds that in descent the reduced power also lowers the slipstream increment, so the angle of attack rises from both causes. The relation above holds the slipstream fixed, so the descent rates in the table are upper bounds. In the same compilation Drinkwater reports that pilots of the tilt-wing and deflected-slipstream test beds set their steep-approach limits by the rate of descent appropriate to the conversion angle, and that a pilot who did not know those limits could turn a steep descent into a series of stall recoveries.

Pegg’s summary of the VZ-2 flight tests measured this on a tilt-wing that flew the full conversion. Its most critical region was decelerating conversion and descent, where wing stall and separation produced buffeting, erratic motion and general difficulty in handling. In level flight with the wing raised to 20 degrees, abrupt flow breakdown set in near 60 knots as speed fell from 75. A leading-edge droop on the outboard wing added about 600 feet per minute of descent capability near 60 knots and an inboard droop about another 500,

\[\Delta \dot{h} = 600 + 500 = 1{,}100\ \text{ft/min}\]

which is the additional descent capability Pegg’s conclusions give for the full-span droop. The fix was a stall delay on the wing, and no source cited here records such a device on the X-18.

Disc Loading as the Cost of the Configuration

\[\frac{W}{n A} = \frac{146{,}800}{2 \times 18.68} = 3{,}929\ \text{N/m}^{2} = 82.1\ \text{lb/ft}^{2}\]

against roughly 11.7 pounds per square foot for a single 60 foot helicopter rotor at the same weight. The tilt-wing carries seven times the disc loading of a helicopter, the price of having propellers small enough to fit on a wing. Hover power follows from the same momentum theory,

\[P = n\, T \sqrt{\frac{T}{2 \rho A}}\]

which evaluates to 5,879 kilowatts, or 7,883 ideal shaft horsepower. Against an installed power of

\[P_{\text{shaft}} = 2 \times 5{,}850 = 11{,}700\ \text{hp}\]

from the two T40 engines of the compiled specification, that implies a figure of merit of

\[\text{FM} = \frac{P_{\text{ideal}}}{P_{\text{shaft}}} = \frac{7{,}883}{11{,}700} = 0.674\]

an entirely ordinary propeller figure of merit, and the strongest available check that the published weight, propeller diameter, and engine power describe one consistent aircraft.

Dependent Systems

The Pitch Jet Repeats the X-13 and X-14 Answer

The X-18 carried a turbojet in the tail whose exhaust was deflected up or down purely for pitch control at low speed, and Hiller’s October 1958 analysis of the thrust available from that J34-WE-36 installation is among the reports in the Lindenbaum collection. The reason is the relation the previous two vertical take-off articles both used. Aerodynamic control scales with dynamic pressure and vanishes at zero speed, while thrust does not,

\[M_{\text{aero}} = q S \bar{c}\, C_{m\delta_e} \delta_e \propto V^{2}, \qquad M_{\text{jet}} = T_{\text{jet}}\, l\]

No source gives the jet’s arm or its deflected thrust, so both are assumed here. Taking the arm as 0.45 of the 63 foot length and a deflected thrust of a thousand pounds force, under a third of the 3,400 pounds the encyclopaedia entry gives for the J34,

\[l = 0.45 \times 63 \times 0.3048 = 8.64\ \text{m}, \qquad M_{\text{jet}} = 4{,}448 \times 8.64 = 38.4\ \text{kN m}\]

with an assumed elevator effectiveness of 1.2 per radian at an assumed 20 degrees of deflection. Setting the two equal and solving for speed gives the crossover at which the elevator takes over,

\[V_{\text{cross}} = \sqrt{\frac{2 M_{\text{jet}}}{\rho S \bar{c}\, C_{m\delta_e} \delta_e}} = 30.2\ \text{m/s} = 58.6\ \text{kt}\]

The control-power requirement that makes such a system necessary was being established across the same years, in Reeder 1958, Carlson 1958, Slaughter 1958, and Crim 1959, with the underlying hovering-stability question in McCaskill 1953 and the variable-stability technique that produced much of it in Harper 1955.

The control-power and handling-qualities literature that establishes how much authority is enough includes Gray et al 1953, Daughaday and Duwaldt 1955, Anderson 1960, Bull 1960, Newsom 1962, Newsom 1962, Van Dam et al 1980, Hess 1981, Goldstein 1982, Helicopter Handling Qualities 1982, Corless and Blanken 1983, Harris et al 2000, Teofilatto 2001, Srinathkumar 2011, Baughman and Longeauay 2015, Portapas and Cooke 2020, Humphreys-Jennings et al 2020, Campos and Marques 2021, Guo 2021.

Below about sixty knots the jet is doing the work. The X-18 is the third vertical take-off aircraft in this series, after the X-13 and the X-14, to carry a separate thrust-based control system for this reason, and the pattern is the clearest recurring result the series has produced.

The Engines and the Missing Cross-Shaft

The encyclopaedia entry states that the two turboprops were not cross-linked, and the Air Force history confirms it in contrasting the XC-142A, whose engines were linked so that a single engine could turn all four propellers and the tail rotor. The failure of one X-18 engine therefore removed that propeller’s thrust entirely. In hover that is half the lift, applied at the propeller’s lateral station. Taking the propeller at an assumed quarter span of the 48 foot wing, $y = 12 \times 0.3048 = 3.658$ metres, and

\[M_{\text{roll}} = T y = 73.40 \times 3.658 = 268\ \text{kN m}\]

Against that, roll control comes from the ailerons, whose effectiveness scales with dynamic pressure,

\[L_{\delta_a} = q S b\, C_{l\delta_a} \delta_a\]

evaluated with an assumed $C_{l\delta_a}$ of 0.08 per radian and an assumed 20 degrees of deflection.

Freestream	Aileron moment	Fraction of the upset
0 m/s	0.0 kN m	0.00 percent
10 m/s	1.2 kN m	0.46 percent
20 m/s	4.9 kN m	1.83 percent
30 m/s	11.0 kN m	4.12 percent

The ailerons supply under one percent of what is needed in hover and still only four percent at thirty metres per second. The statement in the encyclopaedia entry that the failure of one engine meant the airplane would crash is therefore not a caution. It is arithmetic, and cross-shafting is not a refinement but the only available fix. The same entry records that thrust was controlled through throttle changes, which were too slow for acceptable height and roll control, and that the programme’s two lessons were cross-shafting between the engines and direct propeller pitch control for height and lateral control in hover. The problem was recognised in the period literature for turboprops generally, in Kirchner 1955, and engine failure, drive systems and the interconnecting shafting that mitigates them are treated across Holzhauser et al 1964, Overfield and Crawford 1967, Bucsek 1974, Johnson 1975, Stewart 1987, Arnold et al 1987, Carlson et al 1999, Schroijen and Slingerland 2007, Wandini et al 2016, Harish et al 2018, Casadei et al 2019, Leelaburanathanakul et al 2021, and Hoogreef and Soikkeli 2022. The powerplant itself, including the propeller pitch control that one account says failed on the final flight, appears in Zucrow 1949, Mock 1951, Rice 1955, Hooker 1956, Rasmussen 1960, NACA 1978, Hirschkron et al 1979, Hirschkron et al 1979, Banach and Reynolds 1981, Wynn 1982, Stoten 1983, Scott 2009.

The Wing and Its Devices

A tilt-wing’s outer panel is stalled through most of the conversion, so any device that delays stall is valuable. The period answer was boundary layer control by blowing, investigated over flaps and combinations in Spreemann and Kuhn 1956 and Spreemann 1958, with mechanical sliding and slotted flaps and a slat in Kuhn 1957, and large-chord slotted arrangements in Kirby 1956.

Free-floating and stall-flutter behaviour of tilt-wing models was investigated later, in Ormiston 1972.

High-lift and boundary-layer-control devices are the standard remedy, investigated on tilting wings, on STOL and jet transport configurations and on other wings, in Passamanick 1948, Cook et al 1958, Kelly et al 1958, Aoyagi and Hickey 1959, Maki 1959, Aoyagi and Hickey 1963, Fink 1967, Phelps et al 1973, Quigley et al 1974, Caruso et al 1988, Lee and Roberts 1990, Kondor et al 2003, Beck et al 2014. The effectiveness of blowing is measured by a momentum coefficient,

\[C_\mu = \frac{\dot{m} V_j}{q_\infty S}\]

and at the low freestream dynamic pressures of a conversion even a modest jet is a large coefficient, reaching 0.125 at twenty metres per second for an illustrative fifteen hundred newtons of jet momentum.

No source cited here records any of that on the X-18. As the encyclopaedia entry describes it, the aircraft had a tilting wing, two turboprops and a pitch control jet, the minimum experiment and not the best aircraft.

The Propellers

Propeller behaviour at zero and low forward speed forms a separate subject, and static thrust in particular is not simply the cruise propeller evaluated at zero advance ratio, as Webb and Willer 1952 sets out, with later estimation methods in Brusse and Cronk 1965. Propeller design for this class of aircraft is treated in Biermann 1954 and the ducted alternative in Zabinsky and Laszewski 1956. The propeller also has to work across an enormous range of advance ratio,

\[J = \frac{V}{n D}\]

which is zero in hover and of order one in cruise. At an assumed propeller speed of 1,100 revolutions per minute on a 4.877 metre diameter, $J$ runs from 0 to 1.12 between hover and 100 metres per second, so the same blades meet the flow at completely different angles at the two ends of the conversion. Propeller behaviour across that range, including static thrust, blade design and contra-rotating arrangements, is treated in Gray and Biermann 1941, Lerbs 1955, Reynolds et al 1957, Tosti 1962, Deckert et al 1964, Blaurock 1975, Jeracki and Mitchell 1981, Hanson 1986, Applin et al 1994, Campos and Lau 2006, Envia 2014, Sree and Stephens 2014, Ferraro et al 2014, Huo et al 2019. A range that wide calls for variable pitch, which matters because one account of the last flight names the pitch control system as what failed. The pitch-change mechanism is a further subject, because twisting a loaded blade against its aerodynamic and centrifugal moments is a structural problem and not an aerodynamic one. The coupled behaviour of a turbine and its propeller under pitch control is treated in Oppenheimer and Jacques 1951, and the actuator and control design problem in Steinetz et al 1986 and Schwartz et al 1986, the latter two from the propfan era rather than this one. Helical tip Mach number at 60 metres per second, the fastest conversion speed tabulated above, is

\[M_{\text{tip}} = \frac{\sqrt{(\pi n D)^{2} + V^{2}}}{a} = \frac{\sqrt{280.9^{2} + 60^{2}}}{340.3} = 0.844\]

so the blade tips are transonic while the aircraft is not. Direct measurements of the interference between a propeller and the wing behind it, the defining aerodynamic problem of the configuration, appear in Winston and Huston 1962, Goland et al 1964, and Butler et al 1966.

The Downwash

A disc loading of 82.1 pounds per square foot is seven times a helicopter’s, and the slipstream leaving the propellers at eighty metres per second has to go somewhere. Near the ground it strikes the surface, spreads, and recirculates, which changes the lift, erodes unprepared surfaces, and can ingest debris.

This article computes none of that and should say so. The lift side of it was measured for this aircraft. Schade’s paper in the 1960 conference compilation, NACA 1960, Conference on V/Stol Aircraft a Co, reports that tilt-wing configurations usually experience a small favourable ground effect, that the effect was greater for a model of the X-18 because of its wide flat-bottomed fuselage, that full-scale X-18 tests verified a favourable ground effect of about the same magnitude, and that the ground made the model’s attitude stable as it approached. The smaller VZ-2 met the opposite kind of trouble, with ground interference causing erratic motions that limited operation within 19 feet of the ground without automatic stabilisation, in Pegg’s flight tests. Ground effect at this disc loading is studied in Schuldenfrei 1942, Huston and Winston 1960, Obryan 1960, Morse and Newhouse 1960, Curtiss et al 1985, Eshlemen 1985, Eshleman et al 1986, Allen 2004, Radhakrishnan and Schmitz 2005, Radhakrishnan and Schmitz 2006, Hwang and Kwon 2019, Greene 2020, and the X-13 article met the same problem from the jet-lift side. A tilt-wing at this disc loading still needs a prepared surface against erosion and debris, though not for the loss of lift that Schade finds cannot be eliminated by fixes on a single-jet aircraft, a constraint that the transport mission the X-18 was built to prove would have inherited.

The Flight Test Record

The X-18 made twenty flights between November 1959 and July 1961, and the inventory calls the flight test programme short and inconclusive. No source records a hover or a completed conversion. The wing was tilted in flight, and the compiled specification gives a maximum wing-tilt speed of 178 miles an hour, but the hover control was still to be tested on the ground when the programme ended.

The sources disagree about how the flying ended. The inventory says that an engine failure on the twentieth flight prematurely terminated the flight test programme. The encyclopaedia entry says that on that flight, in July 1961, the X-18 had a propeller pitch control problem while attempting to convert to a hover at ten thousand feet and went into a spin, from which the crew regained control and landed. Neither account is a flight-test report. The two are compatible on the inference that a pitch control fault on one propeller of an aircraft without cross-shafting acts as a partial engine failure, but no source says so. The X-18 never flew again. In the encyclopaedia entry, ground testing continued, a vertical take-off test stand was built on which a single engine run reached the full 15 foot wheel height, and the programme was cancelled on 18 January 1964 before further stand testing, which agrees with the Air Force history in dating the end of the programme to 1964. The entry says the aircraft was cut up for scrap, while the inventory finds no definitive information on its fate and says only that it is generally assumed to have been scrapped at Edwards Air Force Base.

How Much Asymmetry That Took

Asymmetric propeller pitch is asymmetric thrust, which is both a direct rolling moment and an asymmetric slipstream, so the two wings stall at different times. A fractional thrust difference $\varepsilon$ gives

\[M_{\text{roll}} = \varepsilon\, T y\]

and the aileron authority available must exceed it. At ten thousand feet, where the density is 0.9046 kilogrammes per cubic metre or 73.8 percent of sea level,

Speed	Aileron moment	Tolerable thrust asymmetry
30 m/s	8.2 kN m	3.04 percent
40 m/s	14.5 kN m	5.40 percent
50 m/s	22.7 kN m	8.44 percent

A few percent of thrust asymmetry exhausts the roll control. A pitch control failure on a propeller is not a small disturbance, so a departure is the expected outcome rather than bad luck.

There is a further and slightly bitter point. The same asymmetry at sea level would be tolerable up to 4.12 percent at thirty metres per second rather than 3.04, because

\[\frac{\varepsilon_{\text{SL}}}{\varepsilon_{10{,}000}} = \frac{\rho_{\text{SL}}}{\rho_{10{,}000}} = 1.354\]

Converting at ten thousand feet rather than near the ground cost about 26 percent of the available roll authority. The altitude gave room to recover, and it made the departure more likely while making it more survivable. Both of those are true and the programme got the survivable half.

Comparison With Ground Prediction

The tilt-wing was tested extensively in wind tunnels before and during the X-18’s life, including the large-scale unswept tilt-wing tests of Giulianetti and Weiberg 1964, and the neighbouring convertiplane had full-scale longitudinal stability tests of the XV-1 in Hickey 1956. The smaller Vertol VZ-2 flew the configuration first, and Pegg’s summary of its flight tests found its hovering control power inadequate in yaw, marginal in pitch and excessive in roll. Hiller force-tested and flew a remote-controlled one-eighth scale model of the X-18 in 1958, in reports catalogued in the Lindenbaum collection, and small-scale X-18 model data on ground effect appear in Schade’s 1960 paper.

For the XC-142A that followed, descent is what the small tunnel models got wrong. Goodson’s comparison of wind-tunnel and flight results records that models predicted the slow-speed level-flight characteristics very well but that small models underpredicted the airplane’s descent capability, while models of about half scale agreed better.

What the ground testing did not predict, and arguably could not, is the consequence of a control failure during conversion. A wind tunnel measures the vehicle’s aerodynamics. It does not measure what happens when a propeller governor misbehaves at a moment when the aircraft has almost no roll authority. The X-18’s loss was a systems failure expressed through an aerodynamic vulnerability, and only the second half of that is testable on the ground.

What the Data Changed

The configuration went forward and the aircraft did not. The LTV XC-142 followed, and the inventory records that X-18 data was used in its design and development. It had four propellers rather than two along the wing and, in the Air Force history, engines linked so that a single engine could turn all four propellers and the tail rotor. Every one of those changes addresses something this article has computed.

Four propellers on a wing immerse more of it than two. Cross-shafting removes the engine-out roll upset entirely, because a failed engine no longer removes a propeller. The X-18’s contribution is a demonstration of what a minimum tilt-wing cannot do, and the next aircraft was designed against that list.

What it did not change is the underlying limit. The outer wing is still stalled during conversion on any tilt-wing, and descent remained the critical region for the XC-142A, whose descent capability small tunnel models underpredicted in Goodson’s comparison and whose lateral and directional motion becomes less stable as the descent angle increases in tests of a tenth-scale model reported by DiCarlo. The configuration was eventually set aside in favour of the tilt-rotor. In the survey of Deckert and Franklin in 1989, the tilt-wing line of the VZ-2, X-18, CL-84 and XC-142 has no ongoing research and technology, while the tilt-rotor line of the XV-3 and XV-15 has the V-22 scheduled for full-scale development. The tilt-rotor keeps the wing pointed into the wind and tilts only the rotors, which is the arrangement that survives today in the V-22.

The Contemporary Literature

Cluster	Records
Flight control, handling qualities and hover control power	945
Wing stall, maximum lift and high-lift devices	918
Tilt-rotor and other V/STOL configurations	881
Propeller aerodynamics, static thrust and contra-rotation	700
Momentum theory, rotor aerodynamics and hover performance	604
Noise of propellers and lifting rotors	508
Propeller slipstream and wing interaction	448
Ground effect, downwash and the vertiport	390
Transition, the conversion corridor and its optimisation	302
Electric vertical take-off and urban air mobility design	264
Energy, batteries and sizing	266
The tilt-wing configuration	249
Distributed electric propulsion	240
Certification, airspace and operations	226
Engine failure, cross-shafting and redundancy	165
Wind tunnel testing and the correlation with flight	133
Descent and the vortex ring state	130
The atmosphere and the flight condition	66
Computational methods, surrogates and autonomy	71
Rotor and airframe structures, dynamics and reliability	70
Powerplants, turboprops and jet-lift propulsion	50
Other rotorcraft and powered-lift literature	146
Total	7,772

The tilt-wing was abandoned after the CL-84, which first flew in 1965, and returned with the GL-10 of 2014 and the Vahana of 2018, so the subject is live rather than historical. Such continuity is unusual in this series. Most of these aircraft asked a question that was answered and closed. The X-18 asked one that was set aside for fifty years because the answer was too expensive, and then became affordable for a reason nobody in 1959 could have anticipated.

The review below is organised by the analysis above, so that each modern field can be set against the quantity it addresses. Recent work on the tilt-wing and on the electric vertical take-off field around it includes Kwak 2026, Barsotti et al 2026, Beak and Kim 2026, Bosch et al 2026, Burton et al 2026, Cai et al 2026, Chaohui et al 2026, Choi et al 2026, Choi and Suk 2026, Critchfield and Ning 2026, Deng et al 2026, DiMaggio et al 2026, Gandhi et al 2026, Gholamian and Beik 2026, Han and Pei 2026, Hasselmann 2026, Hong et al 2026, Hu et al 2026.

Propeller and Wing Interaction Became Computable

The interference the X-18 could only measure is now simulated, in Fei 2019 and Zizkovsky and Klesa 2019, with transient rotor and wing interaction for tiltrotors in Wu et al 2019.

Those methods compute properly the quantity estimated here with momentum theory and a contraction factor. The immersed fraction is no longer a ratio of diameters but a computed pressure field.

Distributed Electric Propulsion Changes the Immersed Fraction

The X-18’s fundamental limitation was that two propellers immerse only part of a wing. Electric propulsion removes the reason there were only two. A distributed arrangement of many small propellers can immerse nearly the whole span, and the keystone then disappears.

The Keystone Was Dissolved Rather Than Solved

This article’s keystone is the immersed fraction, and its value for the X-18 was set by having exactly two propellers. Nothing about tilt-wings requires two. Each one needed a turboprop and a gearbox of its own, and the X-18 had two because it was built around the two turboprops surplused from the cancelled tail-sitter programmes, in the inventory.

Electric propulsion breaks that tie between each propeller and a dedicated engine. Spread along the span, many small motors immerse essentially all of it, and their aerodynamics, stability, noise and powertrain are studied in Chen et al 2025, Chen et al 2025, Liu et al 2025, Machado et al 2025, Ni and Lee 2025, Shang et al 2025, Böhnisch et al 2026, Chen et al 2026, Ciliberti and Nicolosi 2026, Deng et al 2026, Keller 2026, Shen et al 2026, Wang et al 2026, Wei et al 2026.

That does not solve the X-18’s problem. It deletes it. With the whole span immersed there is no un-immersed panel to be stalled through the conversion, the quantity this article spends its length computing goes to unity, and the tilt-wing becomes what its advocates always claimed it was. The configuration was not wrong in 1959 and was not buildable then either, a distinction the historical record tends to blur.

Interaction Is Computed Rather Than Measured

The propeller and wing interference that the X-18 could only obtain from wind tunnels and pressure taps, and the rotor-on-rotor interference of coaxial and compound configurations, are now modelled, simulated and measured with modern instruments, in Duivenvoorden et al 2025, Lee and Jung 2025, Okawa et al 2025, Pasupuleti et al 2025, Savino and Zanotti 2025, Comunian et al 2026, Duivenvoorden et al 2026, Jun et al 2026, Jun et al 2026, Koch 2026, Lan et al 2026, Liu and Xu 2026, Mohamed and Nabawy 2026, Niu et al 2026, Saetti et al 2026, Yang et al 2026.

The immersed fraction, obtained in the sizing section from a contraction factor and a judgement, is what those methods now resolve. The 0.85 that carries so much weight here is not a quantity a modern analysis would need to guess.

The Corridor Is an Optimisation Problem

The corridor above is computed by hand at six speeds and reported as a margin. The modern treatment optimises the trajectory through it, in Cheng et al 2022, Cong et al 2024, Daud Filho and Belo 2024, Hsu et al 2024, Li et al 2024, Jin and Zhao 2025, Panish and Bacic 2025, Farid and Jungers 2026, Lee et al 2026.

The shape of the answer is unchanged and the method is unrecognisable. A conversion schedule is now the output of a constrained optimisation rather than a line on a pilot’s card.

Descent Is Still the Hard Part

Descent is the strongest continuity in this survey. The sizing analysis finds that descent closes the corridor at 284 feet per minute at the slow end, and the modern literature is still working on descent, the vortex ring state, and steep approach, in Efimov and Chernigin 2022, Pickles et al 2023, Pickles et al 2023, Makeev et al 2024, Zeng et al 2024, Qi et al 2025, Tran and Lopez 2025, Wang et al 2025, Jeong et al 2026, Makeev 2026.

Seventy years on, the approach is still the difficult half of a powered-lift flight. The persistence reflects no failure of the intervening work. The underlying problem, a lifting surface meeting air that arrives from below, has no configuration-level fix.

Redundancy Replaced Cross-Shafting

The X-18’s fatal deficiency was two engines with no interconnection. The XC-142 answered with cross-shafting, in the Air Force history. The modern answer is neither, in Antonakis and Biannic 2024, Kang et al 2024, Hung and Dai 2025, Jing and Ma 2025, Liao et al 2025, Luo et al 2025, Ahmadi Dastgerdi and Nabavi-Chashmi 2026, Krug et al 2026, May et al 2026, Strampe and Klingauf 2026, Cui et al 2027.

With enough independent motors the loss of one is a control-allocation problem rather than a catastrophe, and the rolling moment of 268 kilonewton metres computed above for a two-propeller aircraft becomes a small perturbation for an eight-motor one. The engine-out case stopped being an aerodynamic problem and became a redundancy-architecture problem, a change in the kind of engineering required rather than in its difficulty.

Handling Qualities Became Criteria

The control-power question the X-13, X-14 and X-18 each met separately has turned into a problem of formal criteria and of flight control design, in Deng et al 2024, He et al 2024, Ko et al 2024, Li et al 2024, Antonakis 2025, Ruggia 2025, Saetti 2025, Su et al 2025, Cavalcanti et al 2026, Ioannis and Ioannis 2026, Janetzko et al 2026, Jing and Ma 2026, and Kang et al 2026. Simplified vehicle operations, meaning low workload and minimum required pilot training, is a design objective rather than an aspiration in Lombaerts et al 2020, which would have been an extraordinary claim in 1959.

The Constraint Moved to Certification

The largest single difference between the X-18’s world and the present lies here. A 1959 research aircraft needed to fly. A modern powered-lift aircraft needs to fly, be certified against a category that had to be invented for it, and be operated in airspace it shares, in Veras Neto and de Andrade 2022, Schweiger and Preis 2022, Takacs and Haidegger 2022, Cabaleiro et al 2024, Cartile et al 2025, Farooqui 2025, Laplante et al 2026, Lei 2026, Shubert et al 2026.

The X-18’s flying ended with a propeller pitch control fault or an engine failure. Its descendants must also satisfy means-of-compliance documents written for their category, which the European Union Aviation Safety Agency was still issuing in 2025, and an article that treated only the aerodynamics would miss where the difficulty now lies.

The Noise the X-18 Never Had to Face

None of the X-18 sources cited here records an acoustic requirement for a 1959 military testbed flown at Edwards. A vehicle intended to operate from a city rooftop has one that may bind before any aerodynamic limit does, in Araghizadeh et al 2025, Bauer 2025, Goldschmidt and Ukeiley 2025, Jung et al 2025, Kekus-Kumor and Sieradzki 2025, Kim et al 2025, Lotinga et al 2025, Paswan et al 2025, Pereira et al 2025, Czech et al 2026, Georgiou et al 2026, Kyi and Feng 2026, Page et al 2026, Rizzi et al 2026.

Noise is a new constraint, not an old one made stricter. Nothing in this article’s analysis touches it, and a modern tilt-wing designer would trade immersed fraction against tip speed in a way the X-18’s designers never had to consider.

Energy and Sizing, the Modern Disc Loading

The disc loading derived above is 82.1 pounds per square foot and the figure of merit 0.674, and the analysis treats power as something the engines either have or do not. The modern equivalent is energy and the sizing of electrified powertrains, in Hoenicke and Willich 2025, Golombek et al 2026, Jiang et al 2026, Jiao and Yang 2026, Li et al 2026, Mokotoff et al 2026, Park 2026, Park and Park 2026, Qiao and Zhou 2026, Shah and Ansell 2026, Xie et al 2026, Yang et al 2026, Yang et al 2026.

Disc loading has not stopped mattering and has stopped being the binding constraint. A battery-powered vehicle is limited by stored energy rather than by installed power, which inverts the sizing problem the X-18 faced.

Ground Effect and the Vertiport

The downwash this article raises and does not compute reappears as an infrastructure question, in García Crespillo et al 2024, Guo et al 2025, Guo et al 2025, Li et al 2025, Zhang and Hwang 2025, Lee et al 2026, Li et al 2026, Lyu and Feng 2026, Mirković et al 2026, Nagrare and Lieb 2026, Park and Kim 2026, Rohrmeier et al 2026. A tilt-wing at 82 pounds per square foot needs a prepared surface, and the modern field calls that a vertiport and writes design specifications for it, as in EASA 2022. The requirement is the same, now with a name and a standard attached.

Methods and Autonomy

Surrogate modelling, reduced-order rotor aerodynamics, multidisciplinary optimisation and autonomous trajectory planning are the current toolset, in Baldan and Guardone 2024, Cornelius and Schmitz 2024, Dabaghian et al 2025, Doran et al 2025, Liu et al 2025, Lopez and Biancolini 2025, Sterpu et al 2025, Wang et al 2025, Yan and Shi 2025, Yang et al 2025, Fernandez et al 2026, Wang et al 2026, Zhang et al 2026. The trade performed here by hand across six speeds has become a computed surface.

The Configuration Returned Because the Constraint Changed

Electric vertical take-off aircraft such as the GL-10 and the Vahana have revived tilting configurations at small scale, where the engine-out case is managed by having many motors rather than by cross-shafting two, and where the binding question is certification, not aerodynamics.

Flight control, handling qualities and hover control power

How much authority is enough, and how it is delivered. Hover and low-speed control, handling-qualities criteria and pilot ratings, stability augmentation and reaction control, and the flight control laws of tilt-rotor, tilt-wing, tail-sitter and multirotor vehicles. Handling qualities span the whole record. 257 titles name handling or flying qualities, 54 of the dated ones from before 1970 and 44 from 2019 or later.

Wing stall, maximum lift and high-lift devices

The wing the slipstream does not reach. Stall and maximum lift, post-stall and dynamic stall, leading-edge droop, slats and slotted flaps, boundary layer control by blowing and suction, the jet flap and circulation control. The jet flap is a period device and circulation control outlived it. 47 titles name a jet flap, with a median year of 1972, while 96 name circulation control, with a median year of 2006. Dynamic stall, which the quasi-steady corridor above leaves out, is named in 101 titles.

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2018] [Jaquet 1953] [Jarrah 1989] [Jarrah 1990] [Jee] [Jenkins 1971] [Jeon et al 2023] [Jeon et al 2025] [Jing et al 2024] [Jirasek and Amoignon 2009] [Johns et al 1979] [Johnson 1970] [Johnson et al 1979] [Johnson et al 1980] [Johnson et al 1994] [Jones et al 2017] [Joseph and Badrya 2026] [Joseph et al 2026] [Baculi et al] [Jouannet and Krus 2002] [Jovičić and Breuer] [Xiong et al] [Kang Ning and Shi YouMin 2018] [Kanistras et al 2014] [Kanistras et al 2015] [Kanistras et al 2015] [Kanistras et al 2018] [Karim and Acharya 1993] [Karim and Acharya 1994] [Katz and Feistel 1987] [Katz et al 1995] [Kaufmann et al 2016] [Kaushal 2026] [Kaza and Kvaternik 1976] [Kelley and Rouser 2025] [Kelly 1957] [Kelly et al 1958] [Kentfield 1993] [Kerney 1971] [Khodadoust and Shmilovich 2007] [Khodadoust and Washburn 2007] [Kiedaisch et al 2007] [Kieszek et al 2024] [Kim et al 2011] [Kim et al 2015] [Kirby 1956] [Kobayakawa et al 1993] [Kobayashi and Chiba 2025] [Kok et al 2017] [Koklu et al 2019] 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[Lissaman 1973] [Little and Samimy 2010] [Little et al 2008] [Little et al 2009] [Liu et al 2001] [Liu et al 2004] [Liu et al 2005] [Liu et al 2011] [Liu et al 2020] [Lizak 1960] [Lo 1970] [Lopez and Shen 1971] [Lorber 1992] [Lorber et al 1991] [Loth and Boasson 1983] [Loth and Boasson 1984] [Loth et al 1974] [Lu et al 2022] [Luchkov et al 2020] [Luckring 1978] [Luitel and Karki 2025] [Luitel and Karki 2026] [Holman et al 2012] [Magrini et al 2024] [Mai et al 2008] [Maki 1959] [Man and Fung 1995] [Manar and Jones 2017] [Manning et al 2025] [Manor et al 1993] [Marañon et al 2014] [Marchman and Chang 1988] [Margason and Morgan 1975] [Marouf et al 2019] [Marouf et al 2024] [Martinez-Rodriguez and Takahashi 2022] [Masuda et al 2024] [Mathias et al 1996] [Matiz-Chicacausa and Sedano 2018] [May and Widdison 1971] [May and Widdison 1971] [McBreen and Zha 2024] [McCloud III 1972] [McCullough and Gault 1947] [McCullough and Gault 1948] [McGowan et al 2006] [McKechnie and Barakos 2025] [McKechnie and Barakos 2026] [McLemore 1958] [McLemore and Peterson 1960] [McMillan et al 1984] [McVeigh and McHugh 1984] [McVeigh et al 1975] [Measurement and Analysis of 2006] [Melo De Sousa and Camara 2013] [Memon and Altman 2016] [Mendenhall and Perkins 1999] [Menees 1958] [Miklosovic and Perry 2014] [Miklosovic et al 2012] [Miklosovic et al 2016] [Milillo 1972] [Millikan 1934] [Min et al 2026] [Mixson et al 1975] [Miyakawa et al 1993] [Mizoguchi et al 2014] [Mokhtarian and Modi 1984] [Mongin et al 2023] [Monner et al 2009] [Monner Hans Peter and Riemenschneider Johannes 2012] [Moosavi 2025] [Moriya et al 2024] [Morris et al 2020] [Mouton et al 2026] [Mukherjee et al 2003] [Nair and Goza 2022] [Narramore 1981] [Narramore 1987] [Nayman and Perez 2022] [Nelson and Mouch 1978] [Newsom et al 1982] [Nichols and Englar 1980] [Nichols and Englar 1981] [Nikolic 2007] [Nimmanmongkol et al 2023] [Niu et al 2018] [Nonweiler 1955] [Nonweiler 1955] [Northrop Aircraft Inc Hawthorne Ca 1952] [Northrop Aircraft Inc Hawthorne Ca 1953] [Northrop Corp Hawthorne Ca Norair Div 1964] [Northrop Corp Hawthorne Ca Norair Div 1964] [Numerical Study of Geometrical 2023] [O’Hara et al 2005] [O’Hara et al 2006] [Oh and Tavella 1986] [Okoronkwo et al 2026] [Browne et al] [Olson and Stridsberg 1979] [On the role of 2018] [Orazi et al 2011] [Ormiston 1972] [Ormsbee and Chen 1972] [Ortiz-Melendez et al 2019] [Ortiz-Melendez et al 2020] [Ortiz-Melendez et al 2022] [Ortiz-Melendez et al 2023] [Oshima 1994] [Otsuka et al 2022] [Otto et al 2022] [Overview of Circulation Control 2006] [Owen 1995] [Ozgören et al 2002] [Pandya et al 2011] [Papadakis et al 1996] [Paranjape 2022] [Parikh et al 1990] [Pasandideh Fard and Sahaf 2016] [Passamanick 1948] [Patten 1988] [Patterson and Bartlett 1987] [Patton 2004] [Pavelka and Tatum 1980] [Pavelka and Tatum 1981] [Pavlenko and Pigusov 2018] [Pavlenko et al 2023] [Pavlenko O.V. et al 2026] [Perry and Miklosovic 2012] [Pershing 1964] [Peters 1975] [Peters and Schrage 1978] [Petrilli et al 2013] [Petz and Nitsche 2007] [Petz et al 2006] [Pfingsten and Radespiel] [Pham] [Phelps and Smith 1973] [Phelps et al 1973] [Phelps et al 1976] [Phillips and Alley 2007] [Pisano et al 2025] [Pivko 1957] [Platzer 1976] [Pneumatic Flap Performance for 2006] [Pohl and Semaan 2020] [Polak 1972] [Polevoy et al 2022] [Polhamus 1966] [Polonsky 2026] [Poplingher and Raveh 2023] [Posada] [Post and Corke 2003] [Prabhakar 2013] [Precup et al 2015] [Pugliese and Englar 1979] [Pullin and Simmons 1985] [Pınar and Özer 2026] [Qu et al 2026] [Quackenbush et al 2020] [Quan et al 2013] [Quigley et al 1960] [Quigley et al 1974] [Quinn 1946] [Quinn 1947] [Quinn 1947] [Qureshi et al 2006] [Gunadi 2013] [Rahal and Dutta 2024] [Stallings 1986] [Racisz and Quinn 1948] [Ramakrishna et al 2025] [Ramirez Zeigler and Avery 2026] [Ran et al 2012] [Rane and Sahni 2018] [Rao 1984] [Rao 1992] [Rao 1992] [Raspet 1957] [Razak 1954] [Reader 1980] [Reddy and Woszidlo 2023] [Reed 1954] [Regenie et al 1992] [Reisenthel 1995] [Reisenthel and Childs 1994] [Report no. 618, Comparative 1938] [Reuster and Baeder 2000] [Reuster and Baeder 2001] [Kuhn and McKinney 1965] [Ritter 2015] [Rival et al 2010] [Rizzetta and Garmann 2024] [Rizzetta and Garmann 2025] [Rizzetta and Garmann 2025] [Rizzetta and Visbal 2016] [Roberts 1965] [Robertson et al 2014] [Rockwell 1993] [Rohith and Sinha 2017] [Role of Turbulence Modeling 2006] [Rom 1992] [Roos 1996] [Ross and Perkins 1992] [Ross and Perkins 1994] [Ross et al 1991] [Roy and Mukherjee 2020] [S.P et al 2022] [Saadi and Bahi 2018] [Saenz et al 2021] [Saez] [Sahin et al 2000] [Sahin et al 2003] [Salari and Roache 1990] [Salem Said and Ragab 2008] [Samuel and Mukherjee 2016] [Sang 2009] [Sang et al 2007] [Sano et al 1984] [Santos et al 2024] [Santos et al 2024] [Sarlak et al 2018] [Sato et al 1993] [Satran et al 1985] [Scheib and Sandlin 1985] [Schlichting and Gersten 2000] [Schlichting and Gersten 2016] [Schmeer 1955] [Schmeer 1956] [Schmeer and Cooper 1955] [Schmidt and Wild 2026] [Schollenberger et al 2023] [Schumacher 1970] [Schuster and Byrd 2003] [Schuster and Byrd 2004] [Schwartzberg 1959] [Schweikert et al 2022] [Sears 1983] [Segall and Gajdjis 1991] [Seifert et al 1993] [Sellars et al 2002] [Sellers III et al 2002] [Selvaraj and Sharma 2019] [Semaan 2020] [Semaan et al 2018] [Sementi 2002] [Semeraro et al 2019] [Seraj and Martins 2021] [Seraj and Martins 2022] [Sereez et al 2024] [Shahrokhi et al 2024] [Shankara and Snyder 2012] [Sharp 1950] [Shen and Qin 1986] [Sheppard and Rival 2018] [Shigemi 1993] [Shiihara et al 2025] [Shinohara et al 1974] [Shivers 1967] [Shojae and Karimian 2024] [Siliang et al 2019] [Silva and Wolf 2023] [Simulation of Steady Circulation 2006] [Sinha et al 1984] [Skillen et al 2013] [Smeltzer et al 1983] [Smith 1981] [Smith and Levin 1981] [Smith et al 1974] [Somers 2005] [Sommerwerk et al 2013] [Sorenson 1974] [Sosa et al 2004] [Sosa et al 2006] [Spence 1956] [Spence 1958] [Stalker 1935] [Stall Characteristics 2003] [Stall Speed Measurement 2003] [Stallings and Lamb 1981] [Staples and Nagati 1990] [Starikovskiy 2017] [Starikovskiy et al 2017] [Sterpu et al 2025] [Stewart 1985] [Stoll and Koenig 1983] [Stoll and Minter 1981] [Stolt et al 2017] [Storms and Jang 1993] [Stratford 1956] [Stratford 1956] [Stratford 1956] [Stratton and Spyropoulos 2024] [Stuermer 2015] [Sudharsan and Sharma 2021] [Sudharsan et al 2022] [Sudharsan et al 2022] [Sudharsan et al 2023] [Sweberg and Dingeldein 1945] [Tagawa et al 2021] [Tai et al 1996] [Takallu and Gentry 1992] [Takeda et al 2001] [Tallarovic and Franke 1994] [Tamaki and Imamura 2026] [Tan et al 2022] [Tan et al 2023] [Tang and Dowell 1992] [Tanner 2007] [Taylor 1969] [Taylor and Gursul 2004] [Telionis 1995] [Telionis 2001] [Teng et al 2016] [The Pursuit of Maximum 1955] [The use of jet 2015] [Thein and Teperina 2016] [Theisen et al 1973] [Thin Wing Sections 2012] [Thomas 1965] [Thompson et al 1990] [Tilvaldyev et al 2025] [Tobak and Schiff 1974] [Tokel and Sisto 1978] [Townend 1931] [Trailing Edge Circulation Control 2006] [Tran and He 2021] [Tran and Nguyen 2021] [Traub 2014] [Traub 2016] [Traub and Biegner 2013] [Trenka et al 1963] [Trobaugh et al 1980] [Troia and Waters 2005] [Truong 2017] [Tu et al 2019] [Turner et al 2008] [Twiss et al 2019] [Tyan et al 2013] [Uhlig and Selig 2008] [Ullah et al 2022] [Valarezo and Chin 1992] [Valarezo and Chin 1994] [Valenti and Yukish 2022] [Valls Badia et al 2025] [Van Den Berg et al 1992] [Van Dommelen 1995] [van Dommelen and Yapalparvi 2014] [Van Treuren et al 2025] [Vandyken and Chandrasekhara 1992] [Vasilescu and Dancila 2006] [Vasista et al 2019] [Vechalapu et al 2025] [Vechalapu et al 2026] [Velazquez Salazar et al 2021] [Vidal et al 1961] [Vincent et al 1979] [Vinogradov et al 2021] [Vinogradov et al 2021] [Visbal and Garmann 2016] [Volle et al 2026] [von Kármán and Millikan 1935] [Vrchota 2017] [Vu and Lee 2015] [Vukasinovic et al 2024] [Waggoner and Allison 1987] [Wagner et al 1984] [Walchli et al 1992] [Valarezo et al 1993] [Walters and Ashworth 1974] [Wan Mohamed et al 2021] [Wang 1979] [Wang and Khalid 2025] [Wang and Zha 2009] [Wang and Zha 2019] [Wang et al 1985] [Wang et al 2016] [Wang et al 2022] [Wang et al 2024] [Wang et al 2025] [Wang et al 2026] [Wannenburg 1963] [Ward and Stout 1986] [Watson et al 2008] [Wei et al 2025] [Weiberg and Holzhauser 1961] [Weil and Sleeman 1948] [Whitcomb and Norton 1961] [White 1963] [White 1982] [White and Crimi 1961] [White et al 1976] [Whittle and Fink 1950] [Wild 2021] [Wild 2021] [Wild 2021] [Wild 2021] [Wild 2021] [Williams and Alexander 1957] [Williams and Bernitt 1970] [Williams and Howe 1970] [Williams and Nelson 1995] [Willmer et al 1987] [Wilson and Liperra 1984] [Winkelmann and Tsao 1981] [Winkelmann et al 1980] [Wong 2008] [Wong et al 1993] [Wood and Nielsen 1986] [Wood and Roberts 1987] [Wood and Roberts 1989] [Wootton 1967] [Wu and Wu 1993] [Wu et al 1996] [Wygnanski 1966] [Xia et al 2026] [Xiao 2016] [Xiao et al 2022] [Xing et al 2020] [Xing et al 2020] [Xiong et al 2026] [Xu and Zha 2022] [Yang 1994] [Yang and Przekwas 1993] [Yang and Zha 2018] [Yang and Zha 2018] [Yang et al 2026] [Yen 1960] [Yen and Ahmed 2013] [Yon and Katz 1997] [Yongxi Lyu et al 2016] [Yoo 2018] [Yoshihara and Zonars 1975] [Yuan 1969] [Yuan 1970] [Yuan et al 2006] [Yuan et al 2024] [Zakir et al 2024] [Zalovcik 1945] [Zarutskaya and Arieli 2005] [Zeising and Gerhardt 1993] [Zhang 2026] [Zhang and Tang 2004] [Zhang et al 2008] [Zhang et al 2016] [Zhang et al 2016] [Zhang et al 2017] [Zhang et al 2024] [Zhang et al 2026] [Zhao and Zhao 2015] [Zhao and Zhao 2015] [Zhao et al 2024] [Zhu and Qiu 2005] [Zhu et al 2004] [Zohar and Er-El 1988] [Zverkov et al 2012] [Štorch and Nožička 2017]

Tilt-rotor and other V/STOL configurations

The neighbours that tilt something else. The tilt-rotor and proprotor, the tilt-duct and lift fan, the tail-sitter, jet-lift and deflected-thrust aircraft, and STOL configurations, with the XV-15 and the V-22. Whirl flutter is the tilt-rotor’s own aeroelastic subject. 87 titles name it, the earliest dated one from 1988. The 22 titles that name the XV-15 have a median year of 1982, and the 44 that name the V-22 or the Osprey a median year of 1997.

881 records. [A Preliminary Study of 1961] [Abhishek et al 2017] [Abiko and Harada 2020] [Acree 2005] [Acree 2026] [Acree and Sheikman 2018] [Adebimpe 2023] [Adeyemi et al 2026] [Aiken 1977] [Akinwale and Datta 2023] [Akinwale and Datta 2025] [Aksteter et al 1994] [Albers and Zuk 1990] [Albers and Zuk 1992] [Albrecht 1972] [Ale Isaac Khoueini] [Alexander et al 1974] [Alexander et al 1975] [Alford and Harris 1966] [Alford and Luoma 1960] [Alford et al 1963] [Alperin and Wu 1981] [American Helicopter Society Inc Washington Dc 1965] [Anantha and Atkins 2023] [Anderson 1977] [Anderson 1983] [Anderson 1990] [Anderson and Innis 1965] [Annamalai and Selvakumaran 2020] [Aoyagi 1979] [Aplicação de transdutores piezoelétricos 2022] [Application of Computational Fluid 1990] [Arif and Sasongko 2021] [Armutcuoglu et al 2004] [Aubert 2007] [Aulehla and Kissel 1981] [NASA National Civil Tiltrotor 1989] [Avionics displays for V-22 2000] [Aбдуллаев 2021] [Aбдуллаев 2022] [Baird et al 1972] [Barfoot 1963] [Barnes] [Basnight et al 2025] [Bath et al 2021] [Bath et al 2022] [Bath et al 2023] [Bauer et al 1999] [Bautista et al 2017] [Bay 1977] [Bayruns and Koenig] [Baêsso et al 2026] [Bear et al 1979] [Beard and Foley 1982] [Beebe 1968] [Beeler 1965] [Bell Aerospace Co Buffalo Ny 1970] [Bennett et al 1988] [Berkowitz 2000] [Bi and Haas 2002] [Biesiadny et al 1993] [Biggers et al 1966] [Biggi et al 2024] [Bilger et al 1981] [Bilger et al 1981] [Bilger et al 1982] [Bilger et al 1982] [Binion 1969] [Binion and Lo 1970] [Binion 1970] [Binion 1975] [Black 1968] [Black and Brownrigg 1966] [Boothe and Ledder 1973] [Borland 1959] [Born et al 1969] [Bottasso 2003] [Bowen et al 2025] [Bowman 1955] [Bowman 1955] [Bowman 1957] [Bradfield 1981] [Bray 1995] [Brick and Fischer 1998] [Brown 1981] [Brown and Edenborough 1977] [Brown et al 1977] [Brown et al 1978] [Bruff and Dagli 2003] [Brunson and Rais-Rohani 1996] [Buchholz 2002] [Buley 1970] [Bullard 1997] [Buller and Toplis 1972] [Burley 1979] [Burstadt and Johns 1983] [Bustamante et al 2019] [Acree 2022] [Acree 2022] [Acree 2024] [Acree 2026] [Acree et al 2022] [Cai et al 2016] [Calvano and Harney 1998] [Campbell 1965] [Campbell 1967] [Campbell 1968] [Cao et al 2017] [Carico] [Carico and Garcia-Otero 1995] [Carlson and Papachristos 2021] [Carlson and Papachristos 2024] [Carlson and Zhao 2003] [Carpenter et al 1980] [Cassinelli et al 2023] [Cassoni 2023] [Cecrdle 2012] [Cecrdle and Malecek 2014] [Cecrdle et al 2015] [Cecrdle et al 2017] [Cetinsoy 2014] [Cetinsoy 2015] [Chambers 1971] [Chambers 1991] [Chana and Sullivan 1993] [Chang et al 2016] [Charnov 2006] [Charnov 2007] [Chattopadhyay et al 1995] [Chaybi 2016] [Chen et al 2019] [Chen et al 2020] [Cheney 1977] [Choi and Kim 2010] [Chopra and Srinivas 1996] [Chu et al 1983] [Churchill and Gerdes 1984] [Clarke et al 1973] [Clough 1990] [Cobey 1953] [Collins et al 2008] [Collins et al 2009] [Convertiplane described 1959] [Convertiplane” A dual-purpose 1959] [Cook 1985] [Cook and Hickey 1965] [Cook and Hickey 1967] [Coolican 2002] [Cooper et al 2009] [Coplin 1967] [Corle et al 2019] [Cornish 1964] [Corsiglia et al 1989] [Coty and Kesling 1967] [Courtin et al 2020] [Crafa and Reed 1980] [Craig 1961] [Craig and Heffley 1972] [Craig et al 1991] [Crane and Schade 1965] [Cronkhite and Tanner 1985] [Crossley and Bass 1992] [Cummings and Hall 2002] [Cummings et al 2020] [Cunningham 1976] [Currie 1999] [Curtiss 1969] [Curtiss and Warburton 1992] [Czyba and Kronhof 2020] [da Luz et al 2025] [Dall’Aglio et al 2022] [Dansby et al 1964] [Davenport et al 1972] [Davis 1964] [Davis and Mertens 1958] [Deal et al 1967] [Deckert 1967] [Deckert 1977] [Deckert 1979] [Deckert 1993] [Deckert and Hickey 1967] [Deckert and Hickey 1970] [Deckert and Holzhauser 1973] [Defense Science Board Washington Dc 1979] [DeHoff 1979] [Deng et al 2025] [Denham 2002] [Denning 1972] [Design and Simulation of 2025] [Design, control, and autonomous] [Detore and Gaffey 1969] [Dewa et al 2024] [Dicarlo et al 1966] [Diedrich et al 1971] [Ding et al 2025] [Doherty and Butzel 1979] [Dong and Li 2022] [Doonan 1984] [Doonan et al 1983] [Dougherty 1968] [Dreier 2007] [Dreier 2017] [Dreier 2026] [Ducted Fan Model ala 2026] [Dudley 2016] [Dudley et al 1990] [Duffy et al 2012] [Dumond 1969] [Dunn 1966] [Eberhard and Salbashian 2013] [Eckard and Poth 1983] [Edenborough 1967] [Edenborough 1968] [Egerton and Fitzpatrick 1967] [Eisenberg 1982] [Eisenberg and Bowles 1986] [Elliott 1991] [Emelyanova et al 2017] [En Chao 2013] [Enenakpogbe et al 2024] [Enenakpogbe et al 2024] [Englar and Campbell 2002] [Englar and Campbell 2002] [Englar and Campbell 2005] [English et al 1966] [Erhart et al 1980] [Escareno et al 2006] [Eskey et al 1984] [Espinosa and Groepler 1992] [Experimental Development and Evaluation 2006] [Faass 1998] [Falarski et al 1980] [Falarski et al 1981] [Falarski et al 1982] [Favale et al 2021] [Feddersen and Cea 1977] [Felker 1988] [Felker 1991] [Few and Edenborough 1977] [Floros et al 2006] [Foley and Woodrey 1980] [Ford 1999] [Ford CEng MRAes 1988] [Foster 2003] [Foster and Morris 1960] [Fraga and Liiva 1972] [Franklin 1993] [Franklin and Innis 1977] [Franklin and Stortz 1989] [Frederking 2000] [Freeman and Newsom 1966] [Frisby 1957] [Frost et al 1978] [Frost et al 1979] [Fry and Zabinsky 1967] [Funabiki et al 1993] [Gali and Riso 2024] [Gali et al 2023] [Gambucci et al 1976] [Gandhi and Paik 2007] [Garner 1967] [Garren and Kelly 1966] [Garren et al 1964] [Gass et al 1986] [Gatlin and Riso 2024] [Gazdag and Alton 1990] [General Electric Co Cincinnati Oh 1962] [General Electric Co Cincinnati Oh 1963] [General Electric Co Cincinnati Oh 1964] [Gennaretti and Greco 2008] [Gerald-Yamasaki 1996] [Gerdes 1993] [Gerdes et al 1971] [Gibertini et al 2011] [Gibson et al 2012] [Gilbert 1985] [Gili and Battipede 1998] [Gill and Sauer 1983] [Gleiter 1985] [Gokce and Camci 2010] [Goldberger 1966] [Goldsmith and Hickey 1963] [Goodarzi et al 2025] [Gorham 1977] [Graf and Holley 1988] [Grauer et al 1988] [Green and Andrews 1989] [Green and Hoffmann 1986] [Gress 2003] [Griffin 1983] [Gul and Datta 2022] [Gul and Yeo 2024] [Rosenstein et al 1973] [Hackett and Justice 1971] [Hackett and Justice 1973] [Hall 2002] [Hall and Cummings 2002] [Hall et al 1967] [Hall et al 1967] [Hamilton and Richardson 1988] [Hammond 1971] [Haramura Bastos and de Vasconcellos 2023] [Haramura Bastos and de Vasconcellos 2024] [Haramura Bastos and de Vasconcellos 2024] [Haramura Bastos and Grombone de Vasconcellos 2023] [Hardy 2002] [Harned and Nay 1963] [Harper 1966] [Harris 1956] [Harris 2003] [Heyson and Grunwald 1966] [Hassan 2004] [Hassan 2008] [Hassell and Judd 1972] [Hathaway and Gandhi 2003] [Hathaway and Gandhi 2004] [Hathaway and Gandhi 2006] [Hathaway and Gandhi 2007] [Hatta and Matsuki 1964] [Hayama et al 2019] [Hayama et al 2021] [He et al 2025] [Hebert et al 1973] [Heffley and Jewell 1978] [Hegarty et al 1965] [Hegedűs 2017] [Heintzman 1965] [Helfrich and Young 2010] [Henderson 1964] [Hess 1977] [Hickey and Kirk 1993] [Hill 1971] [Hindson and Hardy 1980] [Hirschberg 2014] [Hoffman et al 1972] [Hoh 1977] [Hohenemser 1955] [Hollingsworth et al 1977] [Holloway et al 1972] [Holzhauser and Innis 1960] [Holzhauser and Innis 1971] [Holzhauser et al 1965] [Honda et al 2023] [Hooker et al 2013] [Hoskin 1993] [Hsin 1974] [Hu et al 2022] [Hu et al 2025] [Hu-Sheng Wu et al 2015] [Hua et al 2025] [Huang et al 2020] [Huang et al 2022] [Huang et al 2026] [Hunt et al 1977] [Hutchison et al 1983] [Hwang et al 2024] [Hynes et al 1987] [Innis and Quigley 1961] [Innis and Quigley 1976] [Inokuchi 1994] [Integration and simulated flight 1977] [Introduction to the Flight 2007] [Introduction to the Flight 2018] [Isaac 2008] [Ivanco et al 2025] [Jacobs 1973] [Jacobson 1964] [Jacobson 1965] [Jatsun et al 2019] [Jatsun et al 2020] [Jenkins 1973] [Jensen and Pera 1977] [Campbell 1964] [Johnson and Maddali 2008] [Johnson et al 2003] [Johnston 1964] [Jones 1971] [Jones 1971] [Joppa 1968] 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1971] [Pei and Roithmayr 2022] [Peterson 1964] [Petit and Scholey 1973] [Petit and Scholey 1973] [Petit and Scholey 1973] [Pfeiff 1965] [Pilsch 1975] [Pinson and Ryan 1972] [Platzer and Margason 1976] [Pogust and Taylor 1972] [Pope 2009] [Potonides 1979] [Potonides et al 1979] [Potsdam and Silva 2004] [Poulin and Katz 1991] [Price 1964] [Price 1964] [Pricker and Armanini 2023] [Primatesta et al 2022] [Przedpelski 1965] [Qi et al 2024] [Qing et al 2022] [Quackenbush et al 1995] [Quigley 1964] [Quigley and Koenig 1960] [Quigley and Koenig 1961] [Quintana et al 2020] [Quintana et al 2021] [Quintana et al 2022] [Quintana et al 2023] [Rae 1967] [Rae and Shindo 1969] [Raeisi 2021] [Raiford and Dall 1993] [Rais-Rohani and Baker 1994] [Ramirez et al 1980] [Rangacharyulu and Moore 1991] [Ransone 1972] [Ransone 2002] [Razak and Craig 1961] [Reber 1993] [Reed and Avery 1966] [Reeder 1965] [Reeder 1967] [Renselaer 1974] [Representative Operations of V/STOL 2002] [Reveles and Rajagopal 2024] 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2017] [Shen and Liu 2025] [Shen and Tsuchiya 2022] [Sheng et al 2022] [Sheridan 1985] [Shimizu and Miwa 2019] [Shimizu and Miwa 2020] [Shoemaker 1958] [Shubert Jr. et al 2008] [Sidestick Control Evaluation Completed 1985] [Simioni et al 2013] [Simoes Pessoa] [Sinacori 1970] [Singh and Chopra 2002] [Singh and Chopra 2003] [Singh et al 2014] [Sivan 1971] [Slaby and Smith 2011] [Smith 1977] [Smith and Parsons 1970] [Snyder 2014] [Snyder and Thurman 2009] [Soistmann 1992] [Solis and Meyn 2016] [Solomon 1972] [Soykasap 2001] [Soykasap and Hodges 1998] [Soykasap and Hodges 1999] [Speas and Schmidt 1964] [Special Tool Used for 1987] [Spong et al 1979] [Spreemann 1961] [Srinivas and Chopra 1996] [Srinivas and Chopra 1998] [Srinivas and Chopra 1998] [Srinivas et al 1995] [Srinivas et al 1998] [Statler 1966] [Stevens 1982] [Stewart and Paulson 1984] [STOL Intratheater Transport 2026] [STOL, VTOL, and V/STOL 1971] [Stone 2002] [Strand 2010] [Stroub 1986] [Su et al 2022] [Sutherland et al 2022] 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Gilbertson 1984] [Wigeland et al 1977] [Wild 2020] [Williams 1972] [Williams and Ybarra 1981] [Willis and Genever-Watling 1977] [Willis et al 2020] [Wilson and White 1993] [Winborn 1969] [Wind tunnel and ground 1976] [Wood 1972] [Woolard 1974] [Wu and Chen 2021] [Wu et al 2020] [Xiao et al 2018] [Xu et al 2022] [Xu et al 2022] [Xu et al 2026] [Xu et al 2026] [Yamato et al 1988] [Yan et al 2023] [Yan et al 2024] [Yang and Xia 2011] [Yang et al 2015] [Yassini and Syrovy 2002] [Yatsun et al 2018] [Yeo and Kreshock 2019] [Yeo and Kreshock 2020] [Yeo et al 2021] [Yeo et al 2023] [Yip and Paulson 1977] [Yoeli 2002] [Yoo and Strash 1989] [Yoo et al 2008] [Young 2023] [Young et al 2002] [Youngshin Kang et al 2008] [Yu et al 2006] [Yuan et al 2020] [Yuan et al 2022] [Zabinsky and Burnham 1975] [Zabinsky and Burnham 1976] [Zanon and De Gennaro 2022] [Zhang and Smith 2015] [Zhang et al 2017] [Zhang et al 2018] [Zhang et al 2023] [Zheng et al 2025] [Zhou et al 2021] [Zimmerman 1960] [Zimmermann 1963] [Čečrdle 2015] [Čečrdle 2015] [Čečrdle 2015] [Čečrdle 2015] [Čečrdle 2015] [Čečrdle 2018] [čečrdle 2023] [čečrdle 2023] [čečrdle 2023] [čečrdle 2023] [čečrdle 2023] [Čečrdle et al 2024] [Čečrdle et al 2025]

Propeller aerodynamics, static thrust and contra-rotation

The propeller at the two ends of the conversion. Static thrust and low advance ratio, operation at high incidence, blade design and pitch control, contra-rotating and ducted propellers, and whirl. Contra-rotation has returned. 42 titles name contra-rotating or counter-rotating propellers, rotors or propfans, with a median year of 2020, while the 20 that name static thrust have a median year of 1969.

700 records. [A “New Type Adjustable-Pitch 2017] [Adamson 1968] [adebimpe 2023] [Adler 1960] [Adnan Fadilah and Furqon Era 2018] [Aerodynamic design of low-speed 1986] [Aerodynamics in the Age 1997] [Aerodynamics of Propellers 2007] [Aerodynamics of Propellers 2018] [Agostinelli et al 2013] [Agung Nurachmat et al 2023] [Agus Sugiharto et al 2025] [Ahmad and Ullah 2026] [Ahmed et al 2025] [Ahn and Lee 2013] [Akkoyun et al 2018] [Al-Sa’D 2023] [Albaker et al 2015] [Albert et al 2013] [Alcañiz-Brull et al 2026] [Alesin et al 2020] [Alexiou et al 2016] [Alfaridzi and Kurniawan 2022] [Alfiannor et al 2022] [Aljabri 1983] [Aljabri et al 1986] [Christy et al] [Christy et al 2026] [Altamirano et al 2025] [Amin et al 2018] [Amin et al 2018] [Amjad and Khan 2017] [Anand et al 2023] [Appendix L Propeller Design 2002] [Applin et al 1994] [Arafat et al 2024] [Arai et al 2003] [Ardito Marretta et al 1999] [Army Service Forces Washington Dc 1940] [Asghar et al 2018] [Atlam and Kolhe 2013] [Atmasari et al 2020] [Baek et al 2015] [Baek et al 2021] [Balcerak et al 1969] [Balmaseda Aguirre and Yeo 2025] [Balmaseda Aguirre and Yeo 2026] [Barnes 1999] [Barnes 2017] [Barry et al 2024] [Barth et al 2012] [Battelle Memorial Inst Columbus Oh 1959] [Bay and Kara 2025] [Beek 1978] [Behbahani et al 2011] [Bell Aerospace Co Buffalo Ny 1956] [Bell Aerospace Co Buffalo Ny 1956] [Bell Aerospace Co Buffalo Ny 1956] [Simmons] [Simmons 2021] [Simmons and Hatke 2021] [Bennett and Reed 1963] [Bennett and Thomas 2026] [Berman 2003] [Berry and Chopra 2013] [Berry and Chopra 2015] [Betz 1922] [Betz 1928] [Betz 1928] [Betz 1966] [Betzina and Nguyen 2004] [Bezpalyy and Pushilin 2024] [Biermann 1954] [Biermann and Hartman 1940] [Biot 1940] [Black 2007] [Black and Michael 2003] [Black and Wainauski 1967] [Blade Propeller 2011] [Blaurock 1975] [Blunt 2014] [Bober and Mitchell 1980] [Borst 1968] [Borysiuk and Rudkin 2026] [Boschetti et al 2015] [Bose 2012] [Boswell and Miller 1968] [Bousquet 1986] [Bousquet and Gardarein 2000] [Boyle 2002] [Boyle 2003] [Boyle et al 1999] [Bradley 1986] [Bridges 2021] [Bridges et al 1977] [Brockett 1972] [Brown and Chopra 2023] [Brown and Chopra 2026] [Brusse and Cronk 1965] [Brusse and Kettleborough 1975] [Bryant and Walters 2021] [Burger and Hartfield 2007] [Burnell and Fan 1957] [Burrage 2013] [Cai et al 2024] [Capitao Patrao et al 2016] [Carlton 2007] [Carlton 2007] [Carlton 2007] [Carlton 2012] [Carlton 2012] [Carlton 2012] [Carlton 2018] [Carlton 2019] [Carlton 2019] [Carlton 2019] [Carroll and Carroll 2005] [Castles et al 1960] [Catana and Cican 2016] [Cavcar 2011] [Cazenave et al 2011] [CFD Results on Propeller 2017] [Chandrasekaran 1987] [Chang and Sullivan 1982] [Chang et al 2020] [Chang et al 2024] [Chapman 1989] [Chapter 3. Propeller and 1957] [Chauhan and Martins 2024] [Chen 2012] [Chen and Chopra 1995] [Chen and Chopra 1997] [Chen et al 1989] [Chen et al 2024] [Chen et al 2026] [Cheng 1969] [Chiaramonte et al 1996] [Choi and Kinnas 1997] [Chu et al 2021] [Chung et al 1990] [Ciftci and Cadirci 2024] [Cinoğlu and Durak 2024] [Clark and Valarezo 1990] [Composite propeller blade 1972] [Computer techniques for propeller 1976] [Conroy and Matveev 2023] [Controllable Pitch Propeller 1940] [Conway and Biermann 1941] [Coward 1955] [Crandall and Dugundji 1981] [Cronk 1965] [Cross 1976] [Culpepper et al 2021] [Culpepper et al 2022] [Cummings 1968] [Curtiss and Howard C. 1969] [Dacharla 2026] [Dai et al 2025] [Dantsker et al 2017] [Davenport et al 1985] [De Bothezat 1920] [Decker 1966] [De Gaudemaris] [De Roche 2025] [de Souza and Ciloni 2021] [De Young 1965] [DeLaurier 2022] [Deng et al 2017] [DeStories and Takahashi 2014] [Deyoung 1979] [Di Felice et al 2003] [Dias et al 2025] [Diehl 1934] [Dingeldein and Schaefer 1945] [Doan 2023] [Doetsch and Mark 1953] [Dorange et al 2024] [Dorfling and Rokhsaz 2014] [Droandi and Gibertini 2015] [Dunham and Gentry 1989] [Dunham et al 1985] [Dunham et al 1986] [Dunno 2014] [Dunno and Batt 2009] [Echavarria and Poroseva 2015] [Engine-Propeller Matching 2024] [Enos 1937] [Erickson and John C. 1969] [Erickson et al 1965] [Evans and Liner 1948] [Eyerci̇oğlu and Aladağ 2021] [Fabri and Siestrunck 1953] [Faisal Mahmuddin et al 2023] [Faishal et al 2024] [Fan et al 2021] [Fanoe 1974] [Faraaz et al 2023] [Farghaly et al 2012] [Farrar and Agarwal 2014] [Fatigue Fracture of a 2019] [Favier et al 1988] [Feil et al 2016] [Feil et al 2019] [Felli 2020] [Felli et al 2006] [Feng et al 2025] [Fernandez et al 2023] [Filippone 2022] [Fisher 1950] [Fortin and Ahuja 2024] [Fournis et al 2026] [Fratello et al 1991] [Fresk and Nikolakopoulos 2014] [Fry 1967] [Tamilselvan and Niresh 2022] [Gahlot et al 2025] [Gayle and Jeracki 1989] [Gazzaniga and Rose 1992] [Geometry of a screw 2026] [Altamirano et al] [Ghenaiet and Halimi 2014] [Ghoddoussi and Miller 2016] [Gill and D’Andrea 2017] [Gogidze et al 2023] [Gowtham et al 2026] [Gran 1973] [Gray 1941] [Gray and Biermann 1941] [Greenberg and Ordway 1964] [Zilliac 2026] [Gu and Kinnas 2003] [Gubskiy et al 2020] [Gupta and Abdallah 2018] [Gur 2014] [Gur and Rosen 2005] [Gómez-Tejedor et al 2024] [Gördebil and Temirel 2025] [Hall et al 1981] [Hall et al 1991] [Hammack 1947] [Hanson 1945] [Hanson 1982] [Harrington 1951] [Harris 2017] [Harrison et al 2015] [Hartzell performance propeller upgrade 2003] [Hasnaoui et al 2024] [Havill 1934] [Hawks 1982] [He et al 2019] [He et al 2026] [Heaton 2025] [Heidelberg and Woodward 1989] [Heinzen 2018] [Heinzen et al 2010] [Hendricks 2011] [Hieke et al 2025] [Hiller Aircraft Corp Palo Alto Ca 1956] [Hillman 1981] [Hiraki and Kai 2022] [Hiraki et al 2019] [Hiremath et al 2016] [Hnidka et al 2020] [Hoehne and Hoffman 1961] [Hoff 1942] [Hongwei et al 2024] [Hoover and Shen 2018] [Hoover and Shen 2019] [Hoover and Shen 2019] [Hossain and Krouglicof 2010] [Hough 1961] [Hough and Ordway 1965] [Howard and Ulisnik 1965] [Hu et al 2019] [Hu et al 2024] [Hua et al 2025] [Hughes and Gazzaniga 1989] [Humphrey et al 2004] [Hunsaker and Snyder 2006] [Huo] [Huo et al 2019] [Ibrahim 2003] [Iek et al 1992] [Iek et al 1993] [Influence of propeller characteristics 2015] [Ishaque et al 2026] [Ismail et al 2024] [Itoh and Satoh 2019] [Iyer 2026] [Jarzyna 1986] [Jeracki and Mitchell 1981] [Jiang 2003] [Jimenez and Singh 2015] [Johnson 1948] [Johnson and Yamauchi 1996] [Johnson et al 1991] [Johnston and Sullivan 1990] [Johnston and Sullivan 1992] [Joshi et al 2020] [Junaidin et al 2026] [Jung et al 2022] [Kapucu and Şimşek 2021] [Kasim et al 2019] [Katz et al 1982] [Kawamura 2021] [Kawanami 2010] [Kearns 1939] [Kearns 1941] [Kerwin 1961] [Kettleborough 1969] [Khalid] [Khan et al 2018] [Khasyofi and Hartono 2019] [Kher et al 2026] [Kim 2023] [Kinnas and Pyo 1997] [Kinney 2000] [Kinney 2001] [Kirby 1957] [Kirby 1960] [Kirby 1961] [Klesa 2014] [Koch 2025] [Koch and Koert 2023] [Koch and Koert 2024] [Kochersberger et al 2000] [Kolar 2017] [Kolesar et al 1970] [Komizunai et al 2020] [Konrad et al 2017] [Konrad et al 2026] [Koyama] [Kruger 1949] [Krynytzky 1988] [Kuantama and Tarca 2017] [Kucharski et al 2026] [Kutty and Rajendran 2017] [Kwon et al 2013] [Labonté 2025] [Laitone 2000] [Lampton 1938] [Lange and McLemore 1950] [Lapoint and Granlund 2024] [Lefevre et al 2022] [Lefevre et al 2022] [Lenfers 2012] [Leng et al 2019] [Leong Chee Hang et al 2022] [Lepicovsky and Bell 1983] [Lerbs 1955] [Lesieutre and Sullivan 1986] [Level Flight Performance Flight 2003] [Lewis et al 2023] [Li and Kwok 2024] [Li and Stefko 1984] [Li et al 2022] [Lieberman and Hoffman 1964] [Liu et al 2019] [Liu et al 2022] [Liu et al 2023] [Liu et al 2025] [Lopez et al 2017] [Louis and Louis 2020] [Loukakis and Politis 1981] [Lowry 1997] [Lowry 1999] [Luan et al 2023] [Lush and Moakes 1959] [Lysenkov 2018] [Lytwyn and Young 1967] [Maasdorp et al 2020] [Macey 1956] [MacNeill and Verstraete 2017] [Madureira and de Almeida 2026] [Makeev et al 2021] [Malick and Agarwal 2015] [Manca et al 2023] [Manchin et al 2019] [Margoulis 1922] [Marretta et al 1999] [Mas Intan et al 2023] [Mautner and Gillcrist 1992] [McAndrew et al 2018] [McBain 2019] [McCormick 1956] [McHugh 1935] [McHugh 1939] [McHugh and Derring 1939] [McNay 1958] [Meheut 2013] [Mei and Zhou 2015] [Meneghetti Bomfim et al 2024] [Meyerhoff and Zvengrowski 1962] [Mieloszyk et al 2013] [Mieloszyk et al 2013] [Milenković-Babić 2018] [Miley 1982] [Misztal 1933] [Mkoyan et al 2023] [Moens and Gardarein 2001] [Mohamed Ali et al 2024] [Molland and Turnock 2002] [Montagner 2026] [Morgan 1954] [Morgan 1961] [Mortimer et al 2026] [Mueller et al 1992] [Muhafiz and Rayhan 2026] [Mukund and Kumar 2016] [Munazid Ali et al 2023] [Munk 1922] [Munk 1924] [Murakami et al 2019] [Muscarello and Quaranta 2019] [Muscarello and Quaranta 2023] [Muscarello and Quaranta 2024] [Muth and Peter 2015] [Naka and Kagami 2020] [Nakashima 1981] [Nakashima 1982] [Nallasamy and Groeneweg 1989] [Nallasamy and Groeneweg 1990] [Nangia and Palmer 2001] [Naoki et al 2022] [Naoki et al 2025] [Narbut 1975] [Nardone et al 2014] [Nash and Laplante 2004] [National advisory committee for 1936] [Nayak and Prasanna Kumar 2023] [Nederlof et al 2022] [Nelson 1964] [Nelson and Shen 2021] [Nelson and Shen 2022] [Nelson and Shen 2023] [New ATP Propeller Begins 1985] [Nguyen and Ngo 2017] [Niec and Roberts 2026] [Nimal and Venkatesan 2019] [Nishida 1983] [Nishii et al 2021] [Nitzsche 1989] [Nitzsche 1991] [Nitzsche 1994] [Nixon 1987] [No. 1 Propeller Company 2017] [Norris and Bauer 1993] [Norton 1956] [Numerical Simulations of the 2025] [Okawa et al 2025] [Omur Icke and Baysal 2021] [Oppenheimer and Jacques 1951] [Orakzai et al 2025] [Ordway and Greenberg 1961] [Ortolani et al 2022] [Osovskii and Sharatov 2019] [Ostroukhov 2009] [Pahonie et al 2018] [Panjwani et al 2020] [Pantel] [Park and Sankar 1993] [Park et al 2021] [Parker et al 1972] [Parlett et al 2025] [Parlett et al 2026] [Pasialakos 2024] [Pass 1941] [Patience and Nahon 2024] [Pelletier and Schetz 1985] [Von Hardenberg and Flack] [von Hardenberg et al 2024] [von Hardenberg et al] [Pavel et al 2018] [Pendley 1945] [Perisho 1959] [Petroff et al 1954] [Pełczyński and Bajerlein 2025] [Pełczyński and Bajerlein 2026] [Pfeiffer 1988] [Piancastelli 2025] [Pitkin 1943] [Podsędkowski et al 2020] [Podsędkowski et al 2023] [Prabhu et al 2021] [Prakash 2018] [Propeller basic theory 2026] [Propeller Design Tools 2018] [Propeller Design-Problem Description 2024] [Propeller Development 1981] [Propeller Effect Over Air-Vehicle 2024] [Propeller Geometric Definition 2024] [Propeller History 2024] [Propeller Model 2026] [Propeller Performance 2012] [Propeller Performance 2022] [Propeller system for Bush 1999] [Propeller Theory 2003] [Proprietary propeller de-ice product 2007] [Pu et al 2022] [Putra et al 2025] [Pyo 1995] [Quackenbush et al 2011] [Ragni et al 2011] [Rajagopalan 1989] [Maki and Giulianetti 1966] [Recent Developments of the 1950] [Reed 1966] [Reis Rodrigues and Melo De Sousa 2022] [Report no. 340. Full 1930] [Report No. 481, Working 1934] [Reynolds et al 1957] [Rhodes 1990] [Ristea et al 2025] [Rizk 1988] [Roberts 1964] [Roberts and Yaggy 1950] [Robinson and Herrnstein 1937] [Rogallo et al 1951] [Rogers 1957] [Romig 1912] [Roosenboom and Schröder 2010] [Rostami 2024] [Rostami et al 2022] [Rouser et al 2025] [Rubin and Zhao 2021] [Ruiz-Sanchez 2016] [Saari and Wallner 1946] [Sabzehparvar 2005] [Sajith Kumar et al 2019] [Salters and Norton 1952] [Samarth Pathak 2025] [Sartwell and Legg 2004] [Savino and Zanotti 2025] [Schetz 1984] [Schmaus and Chopra 2015] [Schmaus and Chopra 2015] [Schmidt 1985] [Schroeder and Dai 2010] [Schöne 1988] [Seo et al 2022] [Shah 2019] [Shankar et al 2022] [Shao et al 2025] [Shimamoto et al 2011] [Showers 1952] [Sihaan et al 2022] [Sikora and Mendenhall 1974] [Silvestre et al 2013] [Simmonds 1967] [Simmonds 1967] [Simmonds 1967] [Simmons et al 2023] [Sinacori and Lange 1961] [Singh et al 2026] [Sinha 2025] [Sleeman 1953] [Sleeman and Byrnes 1953] [Sleeman and Morrison 1953] [Sluchak 1997] [Smedresman et al 2011] [Smith 2005] [Smith et al 2019] [Song and Kim 2018] [Stearns et al 1956] [Stefko and Jeracki 1985] [Stephenson 1952] [Stickle et al 1941] [Stokkermans and Veldhuis 2021] [Stokkermans et al 2018] [Stokkermans et al 2019] [Stokkermans et al 2021] [Strand and Levinsky 1969] [Strength of propeller 2026] [Stroub 1978] [Stuermer 2004] [Suk and Čerňan 2021] [Sullivan 1977] [Sullivan and Evans 2008] [Sunarto et al 2022] [Sundar and Sullivan 1986] [Suranto et al 2022] [Suwandito 2023] [Swanson 1943] [Sweberg 1942] [Sweberg 1942] [Szafran et al 2014] [Sørensen and Filippone 2026] [Tachmindji 1956] [Takagi 1960] [Takagi 1961] [Takallu and Lessard 1991] [Takinaci and Atlar 2002] [Talbot et al 1994] [Taniguchi and Oyama 2022] [Taylor 1935] [Taylor 1950] [Taylor 1958] [Thamke et al 2025] [The effect of propeller 2018] [The Measurement of Propeller 1921] [The Propeller That Took 2017] [Theodorsen 1960] [Theodorsen 1960] [Theodorsen and Nomicos 1961] [Thom and Duraisamy 2013] [Thompson 1978] [Tian and Kinnas 2012] [Traub 2016] [Traub 2021] [Traum 2011] [Trenka 1966] [Turnbull 1931] [Uppoor and Chopra 2026] [Uppoor et al 2025] [Use of reinforced plastics 1974] [Uyar et al 2012] [Uçar et al 2025] [Valarezo and Hess 1986] [van Eck 2026] [Van Treuren and Wisniewski 2022] [Veldhuis and Luursema 2000] [Veldhuis et al 2013] [Vijayanandh et al 2022] [Vogeley 1951] [Vollo and Brassaw 1956] [Wachspress and Quackenbush 2008] [Wainauski 1968] [Wales et al 2022] [Walz 1976] [Walz 1978] [Wan et al 2023] [Wang 1969] [Wang and Chen 2015] [Wang and Li 2025] [Wang et al 2019] [Wang et al 2020] [Wang et al 2023] [Wang et al 2025] [Warwick 2021] [Watanabe et al 2024] [Watts] [Watts and Biggers 1972] [Waugh 1947] [Webb and Willer 1952] [Weir 1986] [Weiss et al 2013] [Wenhui and Kun 2023] [Westmoreland et al 2008] [Westmoreland et al 2014] [Widmayer and Tomassoni 1971] [Wieselsberger 1934] [Wild et al 2025] [Windler 1937] [Witkowski et al 1989] [Worobel and Peracchio 1968] [Wrench 1957] [Wright and Turnbull 1929] [Wróblewski et al 2025] [Wróblewski et al 2025] [Wu et al 1972] [Wu et al 2024] [Xia et al 2020] [Fei 2021] [Xie and Haberland 1999] [Xie et al 2020] [Xu et al 2024] [Yang et al 2013] [Yangang et al 2016] [Yassini 2007] [Yauwenas et al 2022] [Yeremiyev et al 2019] [Yildiz et al 2023] [Yilmaz et al 2015] [Yomchinda 2018] [Yu and Chen 1984] [Yu et al 2021] [Zabinsky 1956] [Zabinsky and Laszewski 1956] [Zabunov and Mardirossian 2018] [Zalewski 2015] [Zhang and Ma 2018] [Zhang et al 2001] [Zhang et al 2021] [Zhang et al 2022] [Zhang et al 2022] [Zhang et al 2023] [Zhang et al 2023] [Zhang et al 2025] [Zhang et al 2025] [Zhao and Sheng 2015] [Zhao and Shkarayev 2019] [Zhao and Wang 2016] [Zhao et al 2022] [Zheng and Chopra 2025] [Zheng et al 2016] [Zhenyu et al 2018] [Zhou et al 2026] [Zosimovych 2022] [Öznalbant et al 2016] [Özyurt and Akbıyık 2025]

Momentum theory, rotor aerodynamics and hover performance

The disc that holds the aircraft up. Momentum and actuator disc theory, induced velocity and inflow, rotor wakes, hover performance and the figure of merit, and the aerodynamics of rotors in forward flight. 41 titles name an actuator disc, the earliest dated one from 1964.

604 records. [Abras and Hariharan 2015] [Abras et al 2019] [Abrego et al 1999] [Acree et al 1999] [Acree et al 2001] [Actuator Disk 2013] [Additional Induced-Velocity Models 2024] [Aeroelastic response, loads, and 1995] [Agarwal and Deese 1986] [Agarwal and Deese 1987] [Aguirre et al 2023] [Ahmad and Biedron 2011] [Ahmad and Chaderjian 2011] [Ahmad et al 2013] [Ahmed Snikdha and Chen 2023] [Albachten 1956] [Albang and Roberts 1974] [Allen 2006] [Allen 2007] [Allen and Jones 1998] [An and Kim 2026] [Steering the laminar leading-edge 2025] [Arcidiacono 1964] [Arents 1977] [Army Aviation Board Fort Rucker Al 1968] [Asper and Sirohi 2024] [Atesoglu and Guzel 2013] [Axten and Johnson 2021] [Bachmaier and Anderson 2021] [Baculi et al 2023] [Baeder and Khanna 1996] [Baeder et al 2014] [Bagai and Leishman 1995] [Bagai and Leishman 1996] [Balcerak 1967] [Balch 1983] [Balch 1984] [Balch 1985] [Barakos and Jimenez-Garcia 2016] [Barakos et al 2019] [Barbely and Komerath 2016] [Barbely et al 2016] [Baron 1981] [Baron and Kleinman 1972] [Baron et al 1964] [Bastankhah et al 2026] [Bates et al 1951] [Beaumier et al 1996] [Benedict et al 2013] [Benedict et al 2013] [Simmons et al] [Berenger et al 1996] [Bernhard and Chopra 1998] [Berry 1988] [Berry et al 1987] [Bertelsen 2016] [Bettschart 1999] [Bhagwat 2011] [Bhagwat and Leishman 2000] [Bhagwat et al 2006] [Bi et al 1991] [Bielawa 1988] [Biezad 1994] [Binion 1971] [Blade Element Rotor BER 2026] [Blade Element Rotor BER 2026] [Blade Element Rotor BER 2026] [Blade Element Rotor BER 2026] [Blade Element Rotor BER 2026] [Blade Element Rotor Overview 2026] [Blade-Element/Momentum Theory 2024] [Boatwright and Clingan 1969] [Boeing Vertol Co Philadelphia Pa 1977] [Boeing Vertol Co Philadelphia Pa 1977] [Boniface et al 1995] [Bouchet and Rahier 2000] [Bowden and Shockey 1970] [Bramwell et al 2000] [Bramwell et al 2000] [Brand et al 1986] [Brand et al 1990] [Branum and Tung 1990] [Briassulis and Andreopoulos 1991] [Briassulis and Andreopoulos 1993] [Brown 1965] [Brown and Fischer 1967] [Brown and Fisher 1968] [Buchtala et al 2000] [Buffum and Robertson 1966] [Burley et al 2002] [Burley et al 2003] [Burpo and Darlington 1965] [Calcaterra and Schubert 1969] [Cameron and Sirohi 2019] [Cao et al 2025] [Caprace et al 2022] [Carlson and Cassarino 1973] [Carlson and Hilzinger 1965] [Carpenter and Hodgkinson 1981] [Carpenter and Paulnock 1949] [Carpenter and Paulnock 1950] [Cassarino 1970] [Celi 1991] [Celi and Friedmann 1988] [Cell 1992] [Celniker et al 1964] [Chaimovich et al 1992] [Chang and Cesnik 2025] [Chapter 14. Control of 1994] [Charles and Hassan 1988] [Chattopadhyay et al 1997] [Chattot 2014] [Chattot 2020] [Chen and Guo 2025] [Chen and Hubner 2021] [Chen et al 1987] [Chen et al 2019] [Chen et al 2019] [Chen et al 2022] [Choephel and Maughmer 2014] [Choi et al 2022] [Chopra and Prahlad 2002] [Chopra and Smith 1992] [Clark 1985] [Coffen et al 1991] [Conlisk 1999] [Conway 2003] [Cook 1974] [Cornelius and Schmitz 2024] [Cox-Gross and Collins 2025] [Crespo da Silva 1991] [Crim 1959] [Crimi 1965] [Crispin 1982] [Crouse and Leishman 1993] [Csencsitz et al 1973] [Cui et al 2023] [Curtis et al 2007] [Curtiss 1976] [Dai et al 2025] [Dalang-Secretan and Ballin 1990] [Damen et al 2016] [Darabi and Wygnanski 2003] [Davis and Chang 1986] [Davis et al 1961] [Dawson 1982] [Dayhoum et al 2020] [De Santis and Schwering 1975] [Deal et al 1967] [DeBenedictis and Woestman 1973] [Delgado and Datta 2024] [Delgado and Datta 2025] [Delgado and Datta 2026] [Delgado et al 2026] [Desopper 1985] [Dick et al 2019] [Dietz et al 2007] [Dooley 1976] [Dreyfus and Pellman 1978] [Drinkwater et al 1965] [DuWaldt and Piziali 1963] [Dyke 1963] [Edwards and Miao 1977] [Egolf and Landgrebe 1984] [Egolf et al 2000] [Ellenrieder and Brinson 1998] [Engblom and Ochoa 1988] [Equations of Motion for 2002] [Erhard and Alonso 2024] [Erhard and Alonso 2024] [Eshcol et al 2018] [Eshow 1990] [Eshow 1992] [Etemadi] [Euler/Navier-Stokes Computations of the 1990] [Nitzsche 2001] [Fei and Peters 2012] [Fei and Peters 2013] [Fejtek 1993] [Fejtek and Roberts 1989] [Fejtek and Roberts 1991] [Fejtek and Roberts 1992] [Felker 1993] [Felker and Light 1986] [Felker and Light 1986] [Felker et al 1985] [Felker et al 1988] [Ferguson and Dreier 2005] [Fletcher and Brown 2010] [Ford 1989] [Fortin and Ahuja 2024] [Fourie and Jones 2015] [Free-wake computation of helicopter 1993] [Friedmann and Shanthakumaran 1983] [Friedmann and Shanthakumaran 1983] [Fries 2000] [Funk and Komerath 1995] [Funk et al 1993] [Gaffey and Maisel 1974] [Gahlot and Sankar 2024] [Gamme et al 2017] [Ganguli 2002] [Ganti and Baeder 2012] [Gao et al 2022] [Garcia-Duffy et al 2009] [Garg and Schmidt 1989] [Garren et al 1965] [Gennaretti et al 2010] [Gerdes and Rolls 1969] [Gerhold and Buchholz 2002] [Stich et al] [Ghee and Elliott 1992] [Ghoreishi and Vermeire 2023] [Giles 1987] [Giles 1988] [Gillespie and Carter 2026] [Givens 1965] [Glaz et al 2006] [Goorjian 1972] [Gray 1956] [Gray et al 1953] [Greenberg 1972] [Griffin 1975] [Gupta and Baeder 2002] [Gupta and Loewy 1973] [Guruswamy 2010] [Gustafson and Calapodas 1976] [Guzel and Atesoglu 2014] [Dabaghian et al 2025] [Hah and Lakshminarayana 1980] [Ham and Madden 1965] [Hammond 1966] [Han 2005] [Harada et al 2012] [Hariharan 2020] [Hariharan and Sankar 2000] [Hariharan et al 2014] [Hariharan et al 2017] [Harris 1961] [Harris 1987] [Harris 1999] [Harvey et al 2024] [He and Zhao 2008] [He et al 2025] [Heimerl and Benedict 2022] [Heimerl et al 2021] [Heintz et al 2024] [Heiser 1972] [Hejranfar and Moghadam 2011] [Hermes and Wood 1969] [Heyson 1958] [Heyson 1980] [Heyson 1980] [Ho and Yeo 2016] [Hoad 1991] [Hodges and Ormiston 1973] [Hodges and Ormiston 1976] [Hodges et al 1988] [Hohenemser and Crews 1972] [Hoskin et al 1991] [Hough and Ordway 1964] [Hur et al 2019] [Ickes et al 2014] [Identification of Orientation Dynamics 2013] [Jacobsen and Greif 1972] [Jacobson et al 2016] [Jain 2015] [Jain 2016] [Jain 2018] [Jain 2024] [Jain and Conlisk 2000] [Jain and Potsdam 2014] [Cornelius and Schmitz] [Cornelius] [Jayaraman and Potsdam 2016] [Jeon and Lee 2000] [Ji et al 2026] [Jiang and Zhang 2018] [Jiao et al 2018] [Jimenez Garcia and Barakos 2015] [Jimenez-Garcia and Barakos 2017] [Jimenez-Garcia et al 2017] [Johnson 1976] [Johnson 2001] [Johnson and Barakos 2011] [Johnston and Fleeter 1995] [Jones 1965] [Jung et al 2014] [Kamman and Hall 1978] [Kaul and Ahmad 2011] [Kawachi 1981] [Kellen and Benedict 2018] [Kelly and Jemcov 2019] [Khader and Dhaher 1998] [Khier] [Kim 2004] [Kim and Komerath 1993] [Kim and Komerath 1995] [Kim et al 2001] [Kim et al 2002] [Kim et al 2011] [Kirby 1954] [Kisielowski et al 1967] [Klaren 1978] [Klimchenko et al 2017] [Klimchenko et al 2023] [Klingloff et al 1965] [Ko and Lee 2023] [Komerath and Wong 2001] [Komerath et al 1985] [Komerath et al 1988] [Komerath et al 1998] [Komerath et al 2009] [Komerath et al 2015] [Kominer and Rosen 2013] [Konstantinov et al 2021] [Korkan and Cross 1984] [Kottapalli 1998] [Kottapalli and Acree 2019] [Kozapalli and Warmbrodt 1997] [Kraft 1974] [Kreshock et al 2025] [Kurtulus and Yenipazar 2024] [Kwon and Hodges 1989] [Lai and Le Tri 2017] [Lakshmikantham and Aravamudan 1973] [Lakshmikantham and Rao 1972] [Lakshminarayan et al 2006] [Lakshminarayana 1976] [Landgrebe 1969] [Landgrebe 1971] [Landgrebe 1972] [Landi and Caccetta 2025] [Lee 1984] [Lee and Baeder 2004] [Lee and Kim 1993] [Lee et al 2017] [Lee et al 2021] [Lehman 1968] [Lei and Wang 2020] [Lei and Ye 2020] [Lei et al 2020] [Lei et al 2021] [Lei et al 2023] [Leishman and Bagai 1991] [Leishman and Bagai 1996] [Lemont and Upton 1978] [Li et al 2023] [Light et al 1994] [Lim and Moerder 2007] [Lim et al 2026] [Liou et al 1988] [Liou et al 1990] [Liu 1962] [Liu and Wang 2024] [Liu et al 1983] [Liu et al 2026] [Livingston 1965] [Loeffler and Vanderbilt 1978] [Loenbaek et al 2020] [Lohar 2000] [Lovas 2026] [Lovell et al 1951] [Luo et al 2026] [Magee and Alexander 1973] [Magier and Fellouah 2025] [Mahalingam and Komerath 1998] [Mahalingam and Komerath 1998] [Maisel and Harris 1981] [Makeev 2026] [Makeev 2026] [Manwaring and Fleeter 1988] [Margason 1970] [Marpu et al 2014] [Martin et al 1999] [Mathur] [Mathur and Rajagopalan 1991] [Wilbur et al 2000] [Mavris et al 1989] [McAlister 1996] [McCroskey et al 1983] [McCroskey et al 1985] [McDaniel et al 1983] [McElreath et al 2020] [McHugh and Taylor 1976] [McVeigh et al 1983] [Meakin 1995] [Mihaila et al 2026] [Miller 1962] [Miller 1964] [Miller 1982] [Min and Wake 2015] [Min and Wake 2018] [Mistry and Gandhi 2012] [Mittal 2005] [Mobley et al 2021] [Modarres and Peters 2013] [Modarres and Peters 2015] [Momentum Theory 2024] [Moore et al 2022] [Morduchow et al 1953] [Morris et al] [Mortimer and Sirohi 2024] [Moushegian 2024] [Mueller et al 2009] [Murata et al 2025] [Murata et al 2025] [Nagabhushanam et al 1997] [Narducci 2017] [Nargi et al 2018] [Naumowicz and Smith 1992] [Nayak et al 2026] [Nguyen et al 2022] [Nikolaev and Nikolaeva 2020] [Zawodny et al] [Nikolsky 1959] [Nunez Garcia et al 2026] [Oates 1972] [Ockier and Celi 1991] [Olivares-Espinosa et al 2014] [Olson 1992] [Olson and Rumberger 1991] [Oo] [Osa et al 2014] [Osa et al 2016] [Osa et al 2017] [Osman et al 2026] [Paglino 1971] [Panayotov et al 2020] [Papachristos et al 2013] [Park and Kwon 2022] [Peters et al 1989] [Peters et al 2014] [Phelps 2014] [Pieper] [Pieper et al] [Pieper et al 1996] [Piziali 1966] [Piziali and Duwaldt 1962] [Platzer et al 2016] [Pomin and Wagner 2001] [Pomin and Wagner 2002] [Position Estimation for Autonomous 2014] [Potsdam and Strawn 2002] [Povarov 2021] [Prach et al 2016] [Prasad et al 2011] [Proulx-Cabana et al 2022] [Proulx-Cabana et al 2024] [Prouty 1975] [Prouty 1976] [Pruyn et al 1966] [Qiu 2025] [Quackenbush 1987] [Quackenbush et al 2019] [Quaranta] [Quinto and Paulson 1983] [Rajagopalan 1988] [Rajagopalan 1989] [Rajendiran Vijayaraj et al 2024] [Ramachandran and Tung 1992] [Ramachandran et al 1989] [Ramasamy 2013] [Ramasamy and Leishman 2006] [Ramasamy et al 2010] [Rinehart 1970] [Ringland et al 1971] [Rodriguez et al 2021] [Rogers 1996] [Rosen and Gur 2008] [Rossow 1985] [Rotaru et al 2016] [Rotary Wing Aerodynamics 2022] [Rotor Aerodynamics in Forward 2011] [Rotor in Vertical Flight 2011] [Saberi et al 2026] [Saetti 2024] [Sagaga and Lee 2020] [Samad et al 2025] [Sankar and Komerath 1988] [Sankar et al 1995] [Sankar et al 2015] [Schlechtriem and Ballmann 1994] [Schmidt 1987] [Schroeder et al 1994] [Schwartz and Rogers 1992] [Schweikhard 2007] [Scully 1967] [Segel 1965] [Seher-Weiß and Jones 2021] [Sengupta et al 2025] [Shahjahan and Ahuja 2026] [Shahmiri 2017] [Shaidakov and Brusov 2017] [Shamie and Friedmann 1976] [Shang and Hodges 1995] [Shankar et al 2025] [Sharon 1975] [Shaw and Qin 1999] [Sheng and Zhao 2026] [Sheng et al 2014] [Sheng et al 2015] [Sheng et al 2016] [Shipman 1974] [Shipman and Wood 1970] [Shulman 1956] [Sicard and Sirohi 2010] [Sieradzki 2018] [Silwal and Raghav 2020] [Simmons and Ackerman 2026] [Singh et al 2019] [Sivaneri and Kawiecki 1989] [Smith and Betzina 1986] [Smith and Chopra 1993] [Smith and Sankar 1991] [Smith et al 1951] [Son and Kim 2023] [Spalart 2003] [Spalart 2004] [Spinner et al 2020] [Srinivasan and McCroskey 1987] [Stahl et al 2018] [Stalker et al 2004] [Stammers 1970] [Stauffer et al 1990] [Wright] [Stepniewski 1979] [Stepniewski and Keys 1984] [Stewart et al 1983] [Stockman et al 1973] [Stoddard and Scully 1969] [Stratton and Landman 2021] [Stratton et al 2023] [Sutherland et al 2024] [Swanson 1993] [Tai and Runyan 1984] [Tai and Vorwald 1993] [Takahashi and Friedman 1988] [Tapscott 1960] [Tapscott 1960] [Throneberry et al 2021] [Throneberry et al 2021] [Throneberry et al 2022] [Tischler et al 1985] [Tischler et al 1996] [Tosti et al 1954] [Totah and Patterson 1988] [Tracy and Chopra 1993] [Tracy and Chopra 1996] [Tsoubanos 1975] [Tsujimoto and Murata 1978] [Tung and Lim 2005] [Tyler et al 2026] [Upton and Young 1965] [Valdez and Tinney 2022] [Valdez and Tinney 2022] [van der Vegt 1983] [van der Wall 2011] [van der Wall et al 2015] [van Kuik 2016] [van Kuik 2017] [Vasilescu 2006] [Villeneuve et al 2021] [Wachtell 1970] [Wadcock et al 2011] [Wake et al 1985] [Wall et al 1973] [Wallis 1961] [Walsh 1991] [Wardwell and Hange 1993] [Webster et al 1995] [Weller and Warmbrodt 1983] [Wenren and Steinhoff 2009] [Wheatley 1935] [Wie et al 2009] [Wilkerson 1983] [Winston et al 1975] [Wohllebe and Migdal 1979] [Wong et al 2005] [Wu and Goorjian 1972] [Wu and Sigman 1975] [Xu et al 2005] [Yamaguchi 2026] [Yamauchi and Wadcock 1998] [Yang and Zhuang 2000] [Yang et al 2012] [Yang et al 2023] [Yemenici et al 2010] [Yoo et al 2010] [Yoshida et al 2021] [Yuan and Friedmann 1994] [Yuan et al 1994] [Zerle et al 1997] [Zhang et al 2019] [Zhang et al 2026] [Zhao 2018] [Zhao and He 2016] [Zhao and Sheng 2021] [Zhao and Sheng 2022] [Zhao and Sheng 2024] [Zhao et al 2019] [Zhao et al 2021] [Zhe Jiang et al] [Zhou et al 2022]

Noise of propellers and lifting rotors

The constraint the X-18 never faced. Propeller and rotor noise, blade-vortex interaction, powered-lift and flap noise, community noise, annoyance and psychoacoustics. The noise literature is an urban air mobility literature. 152 of these titles name urban air mobility or an electric vertical take-off aircraft, and 140 of the 142 dated ones are from 2019 or later.

508 records. [A computational study of 1993] [A. et al 2018] [Aalmoes and Sieben 2021] [Aalmoes et al 2025] [Abergo et al 2025] [Abergo et al 2025] [Aerodynamics and acoustics of 1993] [Afari et al 2025] [Afshari and Karimian 2024] [Ahmed 1996] [Aihara et al 2020] [Akiwate and Parry 2023] [Akkermans et al 2014] [Allen and Korkan 1991] [Alvarez et al 2020] [Amargianitakis et al 2026] [Ananthan et al 2020] [Anderson et al 2026] [Araghizadeh et al 2024] [Araghizadeh et al 2025] [Arndt and Borgman 1970] [Arndt and Borgman 1971] [Badea and Crunteanu 2026] [Baerens 2024] [Bai and Li 2024] [Bain et al 2026] [Baker and Manhardt 1977] [Bao et al 2023] [Barakos 2024] [Barbarino et al 2022] [Barton 1975] [Baskaran et al 2023] [Bauer 2021] [Bauer 2023] [Baumeister and Eversman 1986] [Bausch et al 1971] [Becker and Maus 1977] [Bensignor et al 2026] [Bergmann et al 2022] [Bergmann et al 2024] [Bergmann et al 2024] [Bergmann et al 2025] [Bernardini et al 2014] [Betzina et al 2000] [Beyer et al 1984] [Bezuidenhout et al 2026] [Bezuidenhout et al 2026] [Bhat and Gall 1975] [Blandeau and Joseph 2010] [Blandeau et al 2009] [Block et al 1986] [Blumrich et al 2016] [Boelens et al 2000] [Borchers 2009] [Botre et al 2023] [Boucher et al 2023] [Boujo et al 2025] [Boussard et al 2022] [Boyd et al 2004] [Bricker et al 2026] [Brieger et al 1987] [Brooks and Burley 2004] [Brown and Farassat 1976] [Brown et al 2026] [Brungart 2021] [Caillet et al 2025] [Caillet et al 2026] [Campos 1999] [Campos and Lau 2006] [Casagrande Hirono et al 2022] [Casagrande Hirono et al 2023] [Casalino and Barbarino 2011] [Casalino and Barbarino 2012] [Castelucci] [Chaitanya et al 2025] [Chen et al 2026] [Chen et al 2026] [Cho et al 2024] [Chow and Bowen 2024] [Chyla 2024] [Clark et al 1973] [Clarke and Alonso 2021] [Clarke and Botero 2023] [Clarke et al 2025] [Coffen 1992] [Coffen and George 1993] [Cole and England 1967] [Stutz et al 2026] [Combey et al 2026] [Combey et al 2026] [Comparative acoustic wind-tunnel measurements 1981] [Connor and Martin 1987] [Czech et al 2026] [Boyd] [Delattre et al 2016] [Deming 1940] [Boyle et al 2021] [Di Verniere et al 2026] [Diehl et al 2026] [Dierke et al 2012] [Dittmar 1989] [Doherty and Butzel 1979] [Duong] [Begault] [Durbin and Groeneweg 1982] [Edwards et al 2001] [Effect of Forward Speed 1976] [Eißfeldt 2019] [Eißfeldt 2020] [Envia 1991] [Envia 2014] [Eversman 1989] [Fajinmi 2025] [Falck et al 2018] [Falissard and Delattre 2014] [Farazi and Zou 2024] [Farvolden et al 2024] [Feng 2026] [Feng et al 2026] [Flap Noise Prediction Method 1975] [Fletcher et al 2009] [Simon et al] [Frota et al 1998] [Fulton and Gandhi 2026] [Gaeta and Young 2010] [Gallman et al 1995] [Gandhi et al 2022] [Gandhi et al 2026] [Gao et al 2026] [Gasaway 1969] [Gasaway 1970] [Gautam et al 2025] [Gennaretti et al 2023] [George 1978] [George 1996] [George and Polak 1994] [George et al 1989] [George et al 1992] [Georgiou et al 2026] [Gervais 2001] [Gervais and Schmitz 2002] [Gervais and Schmitz 2003] [Gervais and Schmitz 2004] [Gill and Lee 2024] [Gill and Lee 2025] [Glegg and Devenport 2024] [Glinka 2000] [Gnemmi et al 1991] [Go et al 2026] [Goldschmidt and Ukeiley 2023] [Goldschmidt and Ukeiley 2025] [Goldschmidt et al 2026] [Golub et al 1990] [Gonzalez et al 2026] [Goudswaard et al 2024] [Goyal et al 2021] [Goyal et al 2024] [Goyal et al 2025] [Gregorio et al 2024] [Groeneweg 1990] [Gruschka 1972] [Guerrero et al 2025] [Guerrero et al 2026] [Guerrero et al 2026] [Gur et al 2021] [Guérin et al 2023] [Santos et al 2025] [Hakansson et al 2025] [Halwes 1970] [Ham 2024] [Hambrey] [Han et al 2008] [Hanson 1986] [Hanson 1995] [Hanson et al 2022] [Hanson et al 2023] [He et al 2021] [Heidelberg and Woodward 1987] [Heller and Splettstoesser 1983] [Highly Noise-Suppressed Bypass 6 1975] [Hilton et al 1960] [Hinterkeuser 1968] [Ho and Yeo 2017] [Hoad et al 1992] [Homans et al 1978] [Horne and Burnside 2013] [Huang et al 2025] [Hubbard et al 1972] [Hummel et al 2026] [Hur et al 2023] [Huston et al 1989] [Hybrid Dynamic Mesh Redistribution 2022] [Iannotta et al 2024] [Jadidi et al 2026] [Jardin et al 2023] [Jayaraman et al 2012] [Jente et al 2017] [Jente et al 2018] [Jente et al 2024] [Jeong et al 2021] [Jeong et al 2023] [Jia and Lee 2019] [Jia and Lee 2020] [Jia and Lee 2021] [Jia and Lee 2022] [Jia and Li 2025] [Li et al] [Li et al 2021] [Li et al 2021] [Johnson 1973] [Johnson 1974] [Johnson 2001] [Josephson 2020] [Jung et al 2025] [Kallergis 2024] [Kanjere et al 2012] [Kekus-Kumor and Sieradzki 2023] [Kekus-Kumor and Sieradzki 2025] [Kevin Li and Lee 2021] [Kim 2022] [Kim and Lee 2024] [Kingan 2024] [Kingan and Parry 2019] [Kingan and Parry 2020] [Kingan and Parry 2020] [Kipersztok and Sengupta 1981] [Kitaplioglu 1986] [Kitaplioglu and Kinney 1986] [Kitaplioglu et al 2000] [Ko et al 2024] [Ko et al 2026] [Koch et al 2022] [Koehler et al 2021] [Konzel et al 2023] [Kopyt and Ogrodnik 2026] [Kottapalli and Kitaplioglu 2000] [Kotwicz Herniczek] [Krejsa 1990] [Krishnamurthy and Rizzi 2022] [Kuntz 1996] [Kyi and Feng 2026] [Pascioni et al] [Lade and Guérin 2026] [Lattari et al 2023] [Weist et al 2026] [Lawrence and Self 2015] [Le Bras et al 2024] [Lee and Baeder 2003] [Lee and Haan 2025] [Lee and Lee 2019] [Lee and Lee 2023] [Lee and Mosher 1979] [Lee and Shlesinger 2020] [Lee et al 2024] [Lee et al 2025] [Lee et al 2026] [Li 2023] [Li and Lee 2024] [Li and Liu 2026] [Li et al 2021] [Li et al 2021] [Li et al 2022] [Li et al 2023] [Li et al 2024] [Li et al 2026] [Lieser et al 1994] [Light aircraft propeller 1993] [Lim et al 2003] [Lima Pereira et al 2024] [Little et al 2022] [Liu 2011] [Liu and Wang 2026] [Liu et al 2025] [Liu et al 2026] [Livebardon et al 2016] [Loeffler et al 1980] [Lohmann 1981] [Lotinga et al 2025] [Lowson 1972] [Ma et al 2020] [Ma et al 2022] [Macaluso 1971] [Mahan and Fuller 1986] [Maita et al 1990] [Groom et al] [Malpica et al 2016] [Mani 1990] [Manoha et al 2018] [Marinus et al 2009] [Marinus et al 2010] [Betzina and Nguyen 2003] [Marino 2010] [Marques et al 2025] [Marques et al 2026] [Marques Goncalves et al 2024] [Marques Goncalves et al 2025] [Martin et al 1990] [Casanova et al 2025] [McKay et al 2021] [Menger et al 1983] [Mengle 2011] [Modini et al 2014] [Radotich] [Miranda and Lee 2023] [Moreau et al 2024] [Morhy Cavalcante et al 2026] [Moroianu and Fuchs 2005] [Mosher and Light 1994] [Moshkov and Yakovlev 2023] [Muench] [Mukherjee et al 2022] [Musser et al 2023] [Nallasamy et al 1988] [Nallasamy et al 1989] [Naseer et al 2026] [Naseer et al 2026] [Naseer et al 2026] [Naseer et al 2026] [Nelson and Franklin 2021] [Ng 2022] [Zawodny et al 2025] [Zawodny et al 2023] [Nixon 2023] [Noise Reduction Through Circulation 2006] [Oh et al 2026] [Okoronkwo et al 2024] [Okoronkwo et al 2025] [Okoronkwo et al 2026] [Oleson and Patrick 1998] [Page et al 2021] [Page et al 2026] [Panel Discussion STOL and 1975] [Panel Discussion STOL Noise 1976] [Park 2026] [Park et al 2026] [Parry and Kingan 2019] [Parry and Kingan 2020] [Paruchuri et al 2023] [Parzych and Shattuck 1986] [Pascioni et al 2024] [Pascioni et al 2026] [Paswan et al 2025] [Patrick and Nagel 1989] [Pegg 1970] [Pegg et al 1977] [Peng] [Pereira et al 2025] [Pereira et al 2025] [Perennes and Roger 1998] [Perusek 1994] [Pettingill et al 2021] [Pla et al 1989] [Plunkett et al 1984] [Podsedkowski et al 2022] [Polak and George 1998] [Pope et al 1987] [Posa 2023] [Powered-Lift Aerodynamics and Acoustics 1976] [Preis et al 2025] [Prichard 2000] [Propeller Acoustics 2024] [Propulsive-Lift Noise of an 1976] [Qi et al 2025] [Quackenbush and Wachspress 2006] [Rahier and Delrieux 1997] [Raza and Stansbury 2025] [Reddy 1975] [Rimjha et al 2021] [Rinaldi et al 2026] [Rinehart 1970] [Rinehart 1971] [Rizzi 2020] [Rizzi and Rafaelof 2021] [Rizzi and Scata 2022] [Rizzi et al 2022] [Rizzi et al 2024] [Rizzi et al 2026] [Rizzi et al 2026] [Robison and Peake 2010] [Roiati et al 2024] [Romani et al 2022] [Rotor Noise V/STOL Rotor 1976] [Rozman and Grace 2025] [Runyan 1980] [Runyan 1982] [Saetti and Bugday 2023] [Schaefer 1986] [Scheiman and Hoad 1977] [Schlegel and Bausch 1970] [Schlegel et al 1966] [Schlinker and Amiet 1983] [Schmitz 1995] [Schmitz and Stepniewski 1971] [Schmitz and Stepniewski 1973] [Schmähl et al 2021] [Schoenster et al 1976] [Schram and Roger 2025] [Shao et al 2026] [Shapiro and Healy 1968] [Shenoy 1989] [Shivashankara et al 1990] [Si-Yu et al 2017] [Krishnamurthy] [Simon et al 2023] [Smith et al 2021] [Smith et al 2024] [Son et al 2025] [Soni et al 2023] [Sorensen et al 2026] [Sorokin et al 2019] [Sowers 1965] [Spencer et al 1996] [Splettstoesser et al 1987] [Sree and Stephens 2014] [Stalnov et al 2022] [Rizzi] [Rizzi 2020] [Rizzi and Scata] [Rizzi et al] [Rizzi] [Rizzi] [Rizzi et al 2023] [Sternfeld and Hinterkeuser 1970] [Sticchi et al 2026] [Stone and Gutierrez 1972] [Strawn and Biswas 1995] [Stuermer and Akkermans 2014] [Sun et al 2024] [Sun et al 2025] [Surriani et al 2022] [Takeyeldein 2026] [Tan et al 2023] [Tani et al 2014] [Tejnil and Zhang 2018] [Thai and Bain 2025] [Timushev et al 2021] [Tinney and Sirohi 2018] [Tinney and Valdez 2024] [Tinney and Valdez 2025] [Tinney and Valdez 2026] [Tinney et al 2025] [Tinney et al 2026] [Tokarev and Makarenko 2021] [Tonannavar and Garg 2026] [Torija et al 2021] [Tracy et al 2024] [Trembois et al 2024] [Unruh 1987] [Unruh 1988] [Valente et al 2023] [Van Treuren and Wisniewski 2019] [Van Treuren et al 2018] [Vascik and Hansman 2018] [Vaughn and Christian 2024] [Vaughn and Christian 2024] [Vella et al 2026] [Vieira et al 2026] [Voropayev et al 2025] [Voropayev et al 2026] [Voropayev et al 2026] [Bauer 2025] [Walker and Cuppoletti 2022] [Wall et al 2017] [Wang et al 2016] [Wang et al 2025] [Wang et al 2025] [Wang et al 2025] [Wei et al 2026] [Weir et al 1995] [Weitsman and Greenwood 2021] [Wickersheim et al 2025] [Willis et al 1977] [Willshire and Martin 1984] [Wisniewski 2021] [Wisniewski and Van Treuren 2022] [Wisniewski et al 2025] [Wong] [Woodward 1987] [Woodward 1990] [Woodward 1992] [Woodward and Gordon 1988] [Woodward and Hughes 1989] [Wright 1969] [Wróblewski et al 2026] [Wu et al 2023] [Yang et al 2022] [Yang et al 2023] [Yang et al 2024] [Yang et al 2026] [Yang et al 2026] [Ye et al 2024] [Yin 2019] [Yokokawa et al 2009] [Yu 1996] [Yu et al 2020] [Yuan et al 2024] [Yuen 2026] [Yunus et al 2023] [Yunus et al 2024] [Zawodny et al 2018] [Zeitvogel and Wisniewski 2022] [Zeng et al 2026] [Zeng et al 2027] [Zha et al 2019] [Zhao et al 2026] [Zhong et al 2021] [Zhu and Zhao 2015] [Zhu et al 2018]

Propeller slipstream and wing interaction

The keystone’s own literature. The propeller slipstream and its effect on the wing, propeller and wing interference in tractor, pusher, wingtip and over-the-wing positions, deflected slipstream and blown wings. The vocabulary moved from the slipstream to the interaction. 194 titles name a slipstream, with a median year of 2003, while 127 name the propeller and the wing together as a propeller-wing or wing-propeller system, with a median year of 2023.

448 records. [Acevedo Giraldo] [Aerodynamic Interaction Effects of 2019] [Agostinelli et al 2015] [Ahamed et al 2026] [Ahmed and Raghav 2024] [Ahmed et al 2025] [Ahuja and Litherland 2023] [Akiwate et al 2022] [Alba et al 2017] [Alba et al 2018] [Alesin et al 2020] [Ali et al 2025] [Aminaei et al 2018] [Ananda et al 2018] [Ananda Krishnan et al 2013] [Aref et al 2018] [Arnhem et al 2019] [Arumugam and Chidambaram 2025] [Avallone et al 2018] [Barker et al 2023] [Beck et al 2014] [Beck et al 2015] [Beckers et al 2026] [Belák and Hromčík 2023] [Bencze et al 1978] [Biber 2005] [Biber 2011] [Biermann and Hartman 1942] [Bohari et al 2018] [Bohari et al 2019] [Bolster 1937] [Boots] [Borer and Moore 2015] [Bouquet and Vos 2017] [Litherland et al] [Brenckmann 1958] [Brown and Chopra 2024] [Brown et al 2024] [Brown et al 2025] [Burgers 1995] [Butler et al 1966] [Böhnisch et al 2024] [Böhnisch et al 2024] [Bölk et al 2021] [Cai et al 2025] [Cao et al 2023] [Cao et al 2024] [Cao et al 2026] [Catalano 2004] [Catalano and Stollery 1993] [Chadha et al 2016] [Chandukrishna and Venkatesh 2023] [Chang et al 2022] [Chao and Zhenghong 2019] [Chapman 1945] [Chauhan 2025] [Chauhan and Martins 2020] [Chauhan and Martins 2021] [Chen and Hubner 2020] [Chen and Wang 2019] [Chen and Yang 2022] [Chen et al 2015] [Chen et al 2016] [Chen et al 2019] [Chen et al 2023] [Chen et al 2023] [Chen et al 2026] [Chen et al 2026] [Chinwicharnam and Thipyopas 2016] [Chinwicharnam et al 2015] [Chiocchia and Pignataro 1995] [Cho and Cho 1999] [Cho and Williams 1990] [Clarke et al 2021] [Clements and Rais-Rohani 2000] [Cole and Jordan 1952] [Cole et al 2017] [Cole et al 2019] [Colella et al 2012] [Colli et al 2026] [Comunian et al 2026] [Conway 1998] [Crouse and Leishman 1992] [Cui et al 2019] [Czinczenheim 1977] [D’Angelo et al 2022] [Dallas and Irvin 1956] [de Vries and Vos 2022] [de Vries et al 2019] [de Vries et al 2019] [Deckert et al 1968] [Delany 1949] [Derda et al 2026] [Ding et al 2026] [Drinkwater and Vomaske 1966] [Duan et al 2012] [Duivenvoorden et al 2022] [Duivenvoorden et al 2025] [Duivenvoorden et al 2026] [Qin et al 1998] [Ellis 1966] [Elsaadawy and Britcher 2000] [Elsaadawy and Britcher 2002] [Elsaadawy and Britcher 2002] [Elsaadawy and Britcher 2003] [Elsaadawy and Britcher 2004] [Empey and Nahon 2022] [Exalto et al 2024] [Falarski and Mort 1971] [Favier et al 1991] [Faye et al 1987] [Fei 2019] [Ferrari 1937] [Ferraro et al 2014] [Fink 1963] [Forward Velocity Effects on 1976] [Fournier and Coe 1976] [Franco et al 2026] [Franke and Weinig 1939] [Fu et al 2012] [Furey 1980] [Furusawa and Kitamura 2020] [Furusawa et al 2024] [Furusawa et al 2024] [Gao et al 2012] [Gao et al 2024] [Gentry and Margason 1968] [Gentry et al 1966] [Ghoshal and Nahon 2025] [Gilman 1944] [Goetzendorf-Grabowski 2014] [Goland et al 1964] [Gong et al 2017] [Gonçalves and da Silva 2025] [Gray 1943] [Groom et al 2022] [Groom et al 2025] [Grunwald 1961] [Hammond and Margason 1964] [Han 2026] [Hawkswell et al 2022] [Hayes et al 1958] [Hebbar et al 2022] [Heidersbach et al 2024] [Herfray and Nahon 2024] [Hoad 1974] [Holzhauser et al 1964] [Holzhauser et al 1965] [Hooker et al 2020] [Houbolt and Reed 1962] [Howard and Miley 1989] [Howard et al 1985] [Howard et al 1985] [Huang et al 2018] [Huang et al 2023] [Huang et al 2023] [Hwang et al 2007] [Ikami et al 2019] [Ikami et al 2021] [Ikami et al 2022] [Ishaque et al 2025] [Ishaque et al 2026] [Iwasaki 1959] [Içke and Baysal 2021] [Jamaluddin et al 2022] [James et al 1959] [Jameson 1970] [Jayasundara et al 2020] [Jayasundara et al 2023] [Jia et al 2021] [Jie et al 2017] [Johnson and White 1983] [Johnson and White 1986] [Jun et al 2026] [Jun et al 2026] [Kambampati and Smith 2017] [Katz and Ashby 1991] [Katz et al 1980] [Katzoff 1940] [Khan and Nahon 2014] [Khan and Nahon 2015] [Khan et al 2013] [Kim et al 2025] [Kimball et al 1997] [Kimberlin and Sinha 1983] [Kirby 1956] [Klemstein and Liu 1972] [Koch 2026] [Kohn 1983] [Konishi et al 2015] [Koyuncuoglu and He 2022] [Koyuncuoglu and He 2023] [Kroo 1986] [Kubo et al 2009] [Kubo et al 2010] [Kuhn 1957] [Kuhn 1959] [Kuhn and Grunwald 1960] [Kuhn and Grunwald 1961] [Kuhn and Spreemann 1956] [Kuijvenhoven 1990] [Kurane et al 2018] [Lan 1975] [Lan et al 2026] [Lee and Jung 2025] [Lenfers et al 2017] [Leng et al 2020] [Lesley and Woods 1924] [Lester and Fuller 1986] [Letkiewicz et al 2026] [Levin et al 1986] [Li and Da Ronch 2026] [Li et al 2023] [Li et al 2024] [Lin et al 2023] [Ljunggren et al 1989] [Lobb et al 2026] [Lobb et al 2026] [Luthra 1984] [Makino and Nagai 2014] [Makofski and Menkick 1956] [Mallen and Dancik 1959] [Marcos] [Marcus et al 2018] [Marretta 1997] [Matsuo and Hirano 1985] [Matsuo and Hirano 1986] [McKinzie 1976] [Mechanisms of Externally Blown 1975] [Melo] [Mendoza 1979] [Meng et al 2023] [Merola et al 2024] [Metcalfe 1985] [Mikhalyov et al 2019] [Miley et al 1985] [Miley et al 1986] [Miley et al 1988] [Minervino et al 2022] [Miranda and Brennan 1986] [Mishra and Joshi 2024] [Misiorowski et al 2019] [Mohamed and Nabawy 2026] [Montieth 1926] [Morelli et al 2022] [Munk 1923] [Murnieks et al 2024] [Murnieks et al 2024] [Müller et al 2012] [Müller et al 2014] [Müller et al 2014] [Müller et al 2014] [Narain 1983] [Nederlof et al 2023] [Nederlof et al 2025] [Newsom 1967] [Newsom and Tosti 1962] [Nguyen 2021] [Nickle and Freeman 1939] [Zawodny et al] [Niro et al 2024] [Nishida et al 1991] [Niu et al 2026] [Numerical Investigation of Propeller-Wing 2025] [Ohman et al 1995] [Okawa et al 2023] [Okumoto and Elsanker 1973] [Page and Aiken 1971] [Parlett et al 1973] [Paruchuri et al 2022] [Passe et al 2015] [Pasupuleti et al 2025] [Patil and Navrátil 2024] [Peri and Mishra 2026] [Petrov 1993] [Pham and Marshall 2011] [Phillips 2002] [Plijter et al 2025] [Poggi et al 2021] [Popowski and Dąbrowski 2018] [Prabhu and Tiwari 1983] [Prabhu et al 1985] [Propeller Slipstream Effects on 2025] [Purser and Spear 1946] [Qaissi et al 2026] [Qiao and Barakos 2025] [Quinlan et al 1996] [Wickens and Nguyen 1991] [Raghavan et al 1990] [Rais-Rohani 1999] [Ralston and Hultburg 2010] [Rangwalla and Wilson 1987] [Rauhut and Slingerland 2003] [Ren and Liu 2021] [Ren and Liu 2022] [Ren and Zha 2024] [Ren and Zha 2025] [Renooij and Slingerland 2004] [Reveles et al 2020] [Ribeiro et al 2023] [Ribner 1944] [Riccobene et al 2023] [Rizk 1980] [Rizk 1980] [Rizk 1981] [Roosenboom and Schröder 2009] [Roosenboom et al 2007] [Roosenboom et al 2009] [Roosenboom et al 2009] [Roosenboom et al 2010] [Saetti et al 2026] [Salikuddin et al 1985] [Salikuddin et al 1987] [Sandahl 1945] [Santos et al 2026] [Santos et al 2026] [Schipholt et al 1993] [Schollenberger et al 2019] [Schollenberger et al 2022] [Schollenberger et al 2025] [Schollenberger et al 2026] [Schouten 1982] [Schouten 1993] [Schouten 1999] [Schroijen and Slingerland 2007] [Seibert and Lewis 2005] [Selig 2010] [Setiawarman et al 2026] [Shahjahan et al 2026] [Shams et al 2020] [Shao et al 2025] [Sharpe and Agarwal 2019] [Sheridan 1978] [Shi 2019] [Shivers et al 1976] [Shruti and Sivapragasam 2021] [Silva] [Silva] [Silva et al 2022] [Simmons et al 2025] [Simmons et al 2026] [Sinnige and Della Corte 2024] [Sinnige et al 2018] [Sinnige et al 2019] [Sinnige et al 2019] [Sinnige et al 2021] [Sleeman and Phelps 1976] [Slotnick et al 2000] [Smith et al 2023] [Snyder and Zumwalt 1969] [Song et al 2024] [Sowyrda 1961] [Sparks and Miley 1983] [Spreemann 1957] [Spreemann 1958] [Spreemann and Kuhn 1956] [Sridhar and Smith 2026] [Sridhar and Smith 2026] [Sridhar et al 2025] [Srivathsan and Rauleder 2023] [Srivathsan and Rauleder 2023] [Srivathsan and Rauleder 2024] [Srivathsan et al 2024] [Stapleford et al 1974] [Stiesz 1940] [Stokkermans et al 2019] [Stoll 2015] [Stone 2002] [Stone 2008] [Strash et al 1998] [Stuermer 2006] [Stuper 1938] [Sudhakar et al 2016] [Swift and Bartel 1989] [Swihart and Nortin 1953] [Takagi and Inumaru 1967] [Tang and Chung 2022] [Teodosio et al 2024] [Theodorsen 1944] [Thoren and Johnson 1940] [Tran and Lim 2020] [Tran and Lim 2022] [Tran and Lopez 2025] [Turhan et al 2025] [Turner and Drinkwater 1963] [Unruh 1986] [Unruh 1987] [Unruh 1987] [Unruh 1988] [Van Den Borne and Van Hengst 1990] [van der Kooij 1986] [Van der Leer and Hoogreef 2022] [van der Wall 2024] [Veldhuis and Khajehzadeh 2019] [Veldhuis and Rentema 1995] [Vidal et al 1960] [Ahuja and Litherland] [Vogeley and Hart 1955] [Vonglahn et al 1972] [Wang and Jin 2025] [Wang and Lee 2025] [Wang and Lee 2026] [Wang et al 2014] [Wang et al 2019] [Wang et al 2021] [Wang et al 2025] [Wang et al 2027] [Waterman 2024] [Wechtler et al 2025] [Wei et al 2026] [Weiberg et al 1973] [Welge and Crowder 1978] [Welge et al 1981] [Westcott et al 2025] [Whitfield and Jameson 1983] [Whitfield and Jameson 1984] [Whitt and Gandhi 2023] [Wilson 1942] [Winston and Huston 1962] [Wood 1932] [Wood 1933] [Wu et al 2019] [Xi et al 2025] [Xiong et al 2026] [Xu et al 2012] [Xue and Zhou 2020] [Xue and Zhou 2020] [Yan et al 2025] [Yang et al 2014] [Yang et al 2015] [Yang et al 2022] [Yang et al 2024] [Yin and Stuermer 2010] [Ying et al 2015] [Zanotti et al 2024] [Zawodny et al 2021] [Zha 2023] [Zha and Ren 2023] [Zha et al 2024] [Zhang et al 2010] [Zhang et al 2013] [Zhao and Xu 2019] [Zhao et al 2022] [Zheng et al 2024] [Zhou et al 2020] [Zhou et al 2021] [Zikyamov and Panayotov 2025] [Zizkovsky and Klesa 2019]

Ground effect, downwash and the vertiport

What the downwash does on arrival. Ground effect on rotors, propellers and jets, suckdown and fountain flow, hot gas ingestion, downwash and outwash, brownout, and the vertiport. The ground literature moved from the aircraft to the site. 36 titles name hot gas, ingestion, suckdown or the fountain, with a median year of 1992, while 134 name a vertiport, none dated before 1990, with a median year of 2025.

390 records. [Adarkar and Hall 1968] [Adarkar and Hall 1969] [Afzal and Malik 2018] [Allen 2004] [Amuedo et al 1989] [Amuedo et al 1991] [Andronikos et al 2021] [Angle et al 2003] [Aoyagi and Hickey 1963] [Appel et al 2024] [Arora et al 2022] [Asdurian 1967] [Aslani et al 2022] [Babu and Ramamoorthy 2026] [Bae et al 2022] [Baltazar et al 2026] [Barata 2013] [Bardera Mora and Matías García 2022] [Bassey 2025] [Batther et al 2026] [Bauer 1987] [Bauknecht et al 2019] [Bernyk et al 2023] [Bevilaqua et al 2007] [Bevilaqua et al 2010] [Bhattacharya et al 2003] [Bhattacharyya and Conlisk 2003] [Binion 1970] [Blake and Laughrey 1987] [Bodson and Athans 1985] [Bolanovich and Marks 1959] [Brinkman and Johnson 2021] [Brinkman et al 2020] [Bris and Nguyen 2022] [Bris and Nguyen 2023] [Brown and Whitehouse 2003] [Butler and Thomas 1964] [Cacciavillani and Ielmini 2019] [Cai and Gunasekaran 2024] [Calvert and Wenren 2019] [Campbell et al 1977] [Campbell et al 1978] [Cao 1999] [Cao and Su 2003] [Carangui et al 2016] [Carico] [Castells and Mishler 1973] [Chae et al 2023] [Chamberlain et al 2026] [Chati et al 2026] [Chawla et al 1990] [Chen et al 2026] [Cheng et al 2026] [Choi et al 2021] [Choi et al 2025] [Choi et al 2026] [Chun 2003] [Cohen 1996] [Cohen and Shaheen 2021] [Conrad et al 2024] [Cook et al 2005] [Curtis 2002] [Curtis et al 2005] [Curtiss 1965] [Curtiss et al 1985] [Dawson and Omar 1977] [deBrun et al 2003] [Deng 2019] [Deng et al 2017] [Deng et al 2018] [Design concepts for minimizing 1981] [Dombrovschi et al 2025] [Dudley et al 1986] [DuWaldt 1966] [Eberhart and Wilhelm 2017] [Eshleman et al 1986] [Eshlemen 1985] [Evaluation of the navigation 1979] [Fanucci et al 1969] [Feng et al 2026] [Foshag 1966] [Freitas et al 2026] [Fricker et al 1992] [Fricker et al 1994] [Fujisawa et al 2022] [Furlan et al 2026] [García Crespillo et al 2024] [Garrick et al 2013] [Gentry and Margason 1966] [George et al 1964] [Ghareeb 1964] [Gilmore 2025] [Goodson 1967] [Gottschalg et al 2025] [Gouveia et al 2022] [Greco et al 1997] [Green and Zanine 1984] [Greene 2020] [Griffiths and Leishman 2002] [Griffiths et al 2005] [Grunwald 1964] [Guo et al 2024] [Guo et al 2025] [Guo et al 2025] [Ha et al 2024] [Ha et al 2026] [Halder and Gandhi 2025] [Hall 1967] [Hall 1970] [Hange and Wardwell 1992] [Hange and Wardwell 1993] [Hange et al 1996] [Harman et al 1994] [Harry and Trobaugh 1966] [Heyson 1962] [Heyson 1962] [Hazen and Seckel 1950] [He and Leang 2024] [He et al 2023] [He et al 2026] [Henriksson et al 2015] [Heo and Lee 2024] [Heo et al 2026] [Hess et al 2024] [Heyson 1961] [Higgins and Wainwright 1964] [Higgins et al 1966] [Hijazeen et al 2026] [Hill et al 1982] [Hinshaw et al 1964] [Hoad and Gentry 1975] [Hoad and Gentry 1977] [Hosseini et al 2010] [Hot gas ingestion and 1984] [Hot-Gas Ingestion 2007] [Houlihan and Thompson 1972] [Hsu 1963] [Huang and Macinnes 1988] [Huggett 1959] [Huh et al 2026] [Hussien et al 2026] [Huston and Winston 1960] [Huynh et al 2025] [Hwang and Kwon 2019] [Hwang and Tsou 1981] [Ignatkin et al 2021] [Ing and Zhang 1993] [Ison 2025] [Jenkins and Marks 1975] [Jensen 1990] [Jiménez-Losada et al 2025] [Jin and Ma 2025] [Johns et al 1988] [Johnson et al 2024] [Johnson et al 2025] [Junjie et al 2026] [Kai et al 2022] [Kalra and Baeder 2017] [Kalra and Greiwe 2026] [Kalra et al 2011] [Kapulu and Tekinalp 2017] [Karemaa et al 1979] [Kemp 1967] [Kemp 1969] [Kim 2025] [Kim and Hong 2024] [Kim and Park 2022] [Kim and Yee 2020] [Kim et al 2024] [Kim et al 2024] [Kiran et al 2025] [Koc¸er et al 2008] [Kotansky 1982] [Kotansky and Bower 1977] [Kotansky and Bower 1977] [Kotansky and Bower 1978] [Krois et al 2024] [Kuhn 1965] [Kuhn 1979] [Kuhn 1982] [Kuhn 1987] [Kuhn 1987] [Kuhn et al 1993] [Kuhn et al 1993] [Kumar and Vijayakumar 2020] [Kumar et al 2023] [Köse and Özuysal 2023] [Laghrib et al 2024] [Lake et al 2000] [Lavi 1967] [Le Bris and Nguyen 2023] [Lee and Cho 2025] [Lee et al 2024] [Lee et al 2025] [Lee et al 2026] [Leese 1964] [Leese and Knight 1974] [Lehman 1971] [Leonard 2001] [Lepe and Huynh 2026] [Levin and Wardwell 1997] [Li et al 2020] [Li et al 2025] [Li et al 2025] [Li et al 2026] [Liaw et al 1993] [Lim and Yee 2026] [Lissaman 1967] [Lissaman 1969] [Liu et al 2026] [Loeffler and Steinhoff 1984] [Long 1944] [Lord 1985] [Loth and McCormick 1986] [Louis-Ferdinand et al 2025] [Louisse and Marshall 1974] [Louisse and Marshall 1976] [Lu and Lee 2019] [Lu et al 2025] [Lu et al 2026] [Luo and Chen 2026] [Lv et al 2021] [Lyu and Feng 2026] [Ma and Xiao 2026] [Ma et al 2025] [Maksoud et al 2025] [Maleki et al 2024] [Maleki et al 2025] [Maleki et al 2026] [Mannan and Hassanalian 2024] [Mannan et al 2025] [Mayo et al 2016] [McMuldroch 1979] [Mehrabi and Davari 2020] [Mendonca et al 2022] [Mercan et al 2024] [Mercan et al 2025] [Merrick 1984] [Miccio et al 2024] [Migdal et al 1979] [Milluzzo and Leishman 2017] [Minervino et al 2016] [Mirković and Sindik 2024] [Mirković et al 2026] [Moore and Hassanalian 2025] [Morse and Newhouse 1960] [Morse and Newhouse 1961] [Morse and Newhouse 1961] [Morse et al 2024] [Mourtos et al 1995] [Mulyanto et al 2026] [Myers and McLaughlin 2015] [Nagrare and Lieb 2026] [Neumann et al 2020] [Nordquist et al 1972] [O’Bryan 1961] [O’Hara] [Obryan 1960] [Oliver and Stanzione 1993] [Otsuka et al 2024] [Pan et al 2014] [Park and Kim 2022] [Park and Kim 2026] [Peisen and Ferguson 1996] [Peksa et al 2023] [Penrose and Smith 1996] [Perrotta 2015] [Peters and Shirazi 2025] [Petit and Ribeiro 2025] [Pickles et al 2018] [Polsky 2000] [Porcacchia et al 2023] [Preis 2021] [Preis 2023] [Preston 1994] [Pruyn and Lönroth 1993] [Pruyn and Taylor 1970] [Pruyn and Taylor 1971] [Pruynn and Shannon 1980] [Pulla and Conlisk 2005] [Qiao et al 2026] [Qu et al 2017] [Radford and Andrisani 1980] [Radhakrishnan and Schmitz 2003] [Radhakrishnan and Schmitz 2005] [Radhakrishnan and Schmitz 2006] [Radhakrishnan and Schmitz 2007] [Radotich 2026] [Rajendiran Vijayaraj et al 2025] [Rakas 2022] [Ramasamy and Yamauchi 2017] [Ramasamy et al 2015] [Rawat and Kupietz 2026] [Renselaer 1975] [Renselaer 1977] [Richardson et al 2007] [Rimjha and Trani 2021] [Robins et al 1994] [Rohrmeier et al 2026] [Romander et al 2026] [Rotor Downwash Modeling 2018] [Rozhdestvensky 2000] [Rozhdestvensky 2000] [Rozhdestvensky 2000] [Rozhdestvensky 2000] [Rozhdestvensky 2000] [Rozhdestvensky 2000] [Rupert 2008] [Saddington et al 2002] [Saddington et al 2008] [Saddington et al 2009] [Saijo et al 2003] [Saleh and Young 2023] [Saripalli et al 1997] [Schuldenfrei 1942] [Schultz et al 2009] [Schwarz et al 2019] [Schwarz et al 2020] [Seiffer et al 2015] [Sheth 2023] [Siclari et al 1980] [Silva and Riser 2011] [Smith et al 1993] [Souza Branco et al 2025] [Stefana et al 2024] [Stevens 1985] [Stevens 1987] [Stewart and Walters 1996] [Strong 2011] [Study on the Ground 2022] [Su et al 2024] [Su et al 2024] [Swaid et al 2023] [Tan et al 2018] [Taylor et al 2020] [The moving wall effect 1993] [Thipyopas and Moschetta 2010] [Tokutake et al 2022] [Tümse et al 2021] [VanOverbeke and Holdeman 1990] [Vascik and Hansman 2019] [Veneruso et al 2023] [Volakakis and Mahmassani 2024] [Volakakis and Mahmassani 2025] [Wachspress et al 2026] [Wang et al 2025] [Wang et al 2026] [Wardwell et al 1993] [Warner et al 1985] [Watson et al 1967] [Weber and Gay 1975] [Welsch and Fichter 2023] [Wernicke 1981] [White et al 1960] [Wille et al 2026] [Wingrove 1974] [Wingrove 1975] [Winter et al 2025] [Wu et al 2025] [Wu et al 2026] [Wu et al 2026] [Xie et al 2026] [Xin et al 2015] [Xiong et al 2023] [Yang et al 2019] [Yang et al 2026] [Yilmaz et al 2019] [Yoon et al 2024] [Yoon et al 2025] [Young 2015] [Yu 2023] [Zalay et al 1979] [Zame et al 2026] [Zare et al 2025] [Zare et al 2026] [Zelinski 2020] [Zhang and Wang 2026] [Zhang et al 2022] [Zhang et al 2025] [Zhang et al 2026] [Zhang et al 2026] [Zhang et al 2026] [Zhao and Feng 2024] [Zhao and Han 2026] [Zhao et al 2023] [Zhao et al 2025] [Zhou et al 2026] [Zhou et al 2026] [Zhou et al 2026] [Zhou et al 2026]

Transition, the conversion corridor and its optimisation

The path between hover and wing-borne flight. Transition and conversion, their dynamics and control, the corridor and the trajectory through it. The corridor is a recent word. Twelve titles name a corridor, and none is dated before 2021, which agrees with the review above in placing the optimised corridor in the present literature.

302 records. [Akhtar and Maqsood 2024] [Alcañiz-Brull et al 2026] [Alsharif et al 2026] [Amargianitakis et al 2022] [Angelov and Holzapfel 2022] [Ansari et al 2018] [Gardner et al] [Appleton et al 2021] [Arias et al 2025] [Aroussi 2026] [Avanzini et al 2001] [Bai et al 2025] [Batther and Lee 2022] [Bhardwaj et al 2018] [Bhardwaj et al 2019] [Biyela and Rawatlal 2019] [Boekfah 2017] [Burton et al 2023] [Burton et al 2026] [Cai et al 2026] [Carnes and Coder 2019] [Carnes and Coder 2019] [Carnes and Coder 2022] [Chang et al 2021] [Chen 2019] [Chen 2023] [Chen et al 2021] [Chen et al 2024] [Chen et al 2026] [Choi et al 2010] [Choi et al 2025] [Chu et al 2009] [Clark et al 1982] [Coles 1968] [Cong et al 2024] [Cong et al 2024] [Cong et al 2025] [Dai Chao et al 2016] [Dawe et al 2025] [de Paula et al 2025] [Deng et al 2021] [Deng et al 2025] [Di et al 2025] [Dollinger et al 2021] [Dollinger et al 2021] [Dony and Islam 2026] [Dragos Daniel et al 2026] [Drinkwater 1960] [Duvivier and McCallum 1960] [Elanchezhian and Anitha 2023] [Engelland 1991] [Englar and Kirkpatrick 1969] [Erhard et al 2025] [Exadaktylos et al 2023] [Fan et al 2022] [Fan et al 2025] [Farid and Jungers 2026] [Fenny and Hart 2000] [Frank et al 2007] [Franklin and Innis 1980] [Fu et al 2018] [Fu et al 2020] [Gao et al 2017] [Gao et al 2024] [Gao et al 2025] [Gao et al 2025] [Garcia Perez et al 2025] [Gardner et al 2019] [Gardner et al 2021] [Garg et al 1990] [Gentry and Margason 1968] [Girard 1959] [Grahame 1968] [Guan et al 2025] [Górska et al 2024] [Hadytama and Sasongko 2016] [Hadytama and Sasongko 2017] [Han et al 2021] [Heineck et al 2020] [Heister 2013] [Heister 2016] [Hernandez-Garcia and Rodriguez-Cortes 2015] [Hill 1981] [Hoadley 1979] [HongqianJiang et al 2026] [Hu et al 2024] [Hu et al 2024] [Hua et al 2026] [Huan et al 2021] [Huang and German 2025] [Huang et al 2020] [Huangzhong et al 2014] [Huntley 1972] [Hyun et al 2023] [INAV-Based Adaptive Transition Control 2025] [Irmawan et al 2023] [Jain 2017] [Jamaluddin et al 2021] [Heineck et al] [Jeong et al 2010] [Ji et al 2016] [Jiang et al 2025] [Bullock et al] [Johnson and Craig 1974] [Junquan et al 2017] [Yokesh et al 2025] [Kahne 2000] [Kang et al 2026] [Ke et al 2014] [Kelley 1962] [Key 1970] [Kim 2026] [Kim et al 2025] [Kim et al 2025] [Kirkpatrick and Murphy 1968] [Kjerstad and Paulson 1993] [Kottapalli and Meza 1992] [Krishna et al 2018] [Kuhn 1981] [Kuhn and Vogler 1965] [Kumar 2026] [Kumar and Mukherjee 2024] [Kunz et al 2024] [Vu et al 2025] [Lee and Kim 2024] [Lee et al 2025] [Lee et al 2025] [Lee et al 2026] [Levinsky et al 1968] [Li 2008] [Li and Xia 2018] [Li and Yang 2025] [Li et al 2020] [Li et al 2024] [Li et al 2025] [Li et al 2025] [Li et al 2025] [Li et al 2026] [Li et al 2026] [Liang et al 2025] [Liang et al 2026] [Lin et al 2023] [Liu et al 2017] [Liu et al 2018] [Liu et al 2018] [Liu et al 2024] [Lou et al 2024] [Lou et al 2025] [Lovell et al 1953] [Lu et al 2022] [Ma and Wang 2018] [Magariyama and Abiko 2020] [Magee and Taylor 1971] [mao et al 2026] [Marchini] [Margason 1966] [Margason and Hoad 1979] [Martin 1964] [Marvakov and Holzapfel 2021] [McCormick 1956] [McGuirk 2007] [Mohammadi et al 2023] [Moitra 2014] [Morino et al 2000] [Morscheck 2021] [Mukherjee et al 2023] [Muraoka et al 2024] [Nabi et al 2019] [Nie et al 2024] [North et al 2018] [Orndorff and Hwang 2022] [Orndorff et al 2023] [Otis 1962] [Overmeyer and Martin 2017] [Overmeyer et al 2018] [Paiva et al 2018] [Panish and Bacic 2023] [Parra et al 2026] [Parwani and Coder 2018] [Patel et al 2022] [Pelletier and Giroux 2000] [Peng et al 2013] [Peng et al 2014] [Peng et al 2015] [Peng et al 2026] [Perraud and Moens 2007] [Petersen 1986] [Pirera 1983] [Pobikrowska and Goetzendorf-Grabowski 2025] [Prabhakar et al 2025] [Qing et al 2023] [Qing et al 2023] [Rae Jr. 1972] [Ramnath 1969] [Ramnath 1970] [Rampy 1966] [Reiss et al 2021] [Ren et al 2025] [Righetti et al 2017] [Riley et al 1989] [Saetti 2025] [Safi’i et al 2021] [Sagan et al 2021] [Sagan et al 2025] [Sakai and Abiko 2020] [Salahudden et al 2023] [Salahudden et al 2024] [Semelka and Rauleder 2026] [Sharma et al 2025] [Sheng 2018] [Sheng and Zhao 2016] [Shimizu and Miwa 2018] [Shimizu and Miwa 2019] [Single Engine Failure during 2005] [Siniff 1999] [Skelton 1968] [Smith 1958] [Smith 1958] [Song et al 2024] [Spadão et al 2026] [Spreemann 1960] [Spreemann 1966] [Spreemann 1968] [Staruk and Datta 2019] [Staruk et al 2017] [STOL Operation Transition-in-Ground Effect 2007] [Stoll and Veble Mikić 2022] [Sun et al 2009] [Sun et al 2022] [Sunkara et al 2014] [Surmann et al 2025] [Takii et al 2020] [Tal et al 2023] [Tapscott and Kelley 1960] [Theys et al 2016] [Thirumaleshwar Hegde et al 2020] [Thirumaleshwar Hegde et al 2021] [Three-bladed propeller conversion 1999] [Tian et al 2026] [Tran and Yeo 2022] [Tran and Yeo 2023] [Tran et al 2023] [Transition Dynamics of VTOL 2010] [Trenka 1967] [Verling et al 2017] [Verma and Junkins 2000] [Vogler 1966] [Vorsin and Arogeti 2017] [Wang et al 2019] [Wang et al 2024] [Wang et al 2025] [Wang et al 2026] [Wang et al 2026] [Wang et al 2026] [Wen et al 2020] [Westcott et al 2025] [Wu and Hu 2014] [Wu et al 2024] [Wu et al 2026] [Xi et al 2021] [Xi et al 2025] [Xi et al 2025] [Xu et al 2024] [Xu et al 2027] [Xue et al 2026] [Yan et al 2023] [Yang et al 2022] [Yang et al 2023] [Yang et al 2024] [Yang et al 2026] [Yang et al 2026] [Yangping and Honggang 2018] [YAV-8B reaction control system 1993] [Ye and Zong 2025] [Yeo and Liu 2018] [Yeo and Saberi 2020] [Yeo and Saberi 2021] [Ying and Liang 2013] [Yu and Zhao 2026] [Yu et al 2017] [Yu et al 2025] [Yuan et al 2015] [Yue and Xia 2009] [Yuksek and Inalhan 2022] [Yuksek et al 2016] [Zaludin 2024] [Zaludin and Gires 2019] [Zaludin and Harituddin 2019] [Zaludin et al 2021] [Zhang et al 2018] [Zhang et al 2019] [Zhang et al 2023] [Zhang et al 2023] [Zhang et al 2024] [Zhao et al 2014] [Zhao et al 2023] [Zhao et al 2024] [Zheng et al 2011] [Zheng et al 2020] [Zheng et al 2026] [Zhou et al 2025] [Zuo et al 2025]

Electric vertical take-off and urban air mobility design

The configuration’s modern market. Electric vertical take-off aircraft and urban air mobility, their design, demand, acceptance and operation. 256 of these titles name an electric vertical take-off aircraft, urban air mobility or an air taxi, and none of the dated ones is earlier than 2017.

264 records. [Abraham et al 2026] [Acheson et al 2025] [Edsel et al] [Afonso et al 2021] [Ahmed] [Al labbad] [Aldao et al 2023] [Alhatim 2024] [Angel 2026] [Antcliff et al 2019] [Tang] [Are We Ready to 2019] [Asfour et al 2025] [Barsotti et al 2026] [Beak and Kim 2026] [Adelstein et al] [Biehle 2022] [Bogdanović et al 2024] [Bonaventura and Guardone 2025] [German et al] [Bridgelall 2024] [Bridgelall et al 2022] [Brignardello 2023] [Brown and Harris 2020] [Bueno Luque Filho and Azevedo 2025] [Campanale and Grace 2025] [Cha et al 2024] [Challenges and Countermeasures of 2025] [Ci̇zreli̇oğullari et al 2022] [Clare 2026] [Cureton 2020] [Deniz et al 2024] [DeVore et al 2022] [Nithya et al 2025] [Thipphavong] [Zahn et al 2024] [Dempsey 2021] [Deniz et al 2023] [Design and Simulation of 2024] [Ding et al 2022] [Doo 2020] [Doo 2022] [Doo 2022] [Doo 2023] [Du et al 2025] [Edwards 2019] [Hendricks et al] [eVTOL 2026] [Factors Influencing Public Intention 2023] [Fardin et al 2026] [Feary 2018] [Feary 2026] [Fedrigo 2023] [Ferrare] [Ferrell and Anderegg 2020] [Fraticelli Rivera et al 2025] [Furqan 2025] [Garg and Moon 2026] [Garrow and Kim 2024] [Gaspari and Di Guardo 2023] [German et al 2023] [Gertz and Manderscheid 2025] [Gomes de Souza and Silva 2025] [Gong et al 2026] [Gonzalez et al 2026] [Greenfeld 2020] [Gutierrez] [Hakim 2024] [Halder and Gandhi 2026] [Hasselmann 2026] [Arneson and Thipphavong] [Hendricks et al 2020] [Hermyt and Pastucha 2024] [Hine et al 2024] [Hine et al 2025] [Hoffmann et al 2023] [Ng] [How to Tackle The 2022] [Hu] [Hu and Dong 2023] [Hu and Dong 2024] [Hu et al 2026] [Tang et al] [Huang et al 2023] [Huang et al 2025] [Häckel et al 2024] [Ilapuram] [Ismail et al 2024] [Ito et al 2019] [Putnam and Littell] [Putnam and Littell] [Putnam et al] [Putnam et al] [Chamberlain et al] [Jang et al 2024] [Jarvi and Nadler 2026] [Jeong et al 2024] [Kaneshige et al] [Doo et al 2021] [Johnson and Silva 2018] [Littell and Pellettiere] [Littell and Pellettiere] [Jäckel et al 2021] [Kalush and Chierichetti 2021] [Kaneko and Martins 2024] [Kaneshige et al 2024] [Kang et al 2023] [Kang et al 2024] [Karimli and Marano 2025] [Kawamura et al 2024] [Freeman 2023] [Freeman and Garcia] [Freeman and Garcia] [Freeman et al] [Goodrich and Theodore 2021] [Kim and Zhang 2025] [Kim et al 2025] [Kim et al 2025] [Kim et al 2026] [Wasson et al 2022] [Shish et al] [Kopardekar 2017] [Kopardekar 2019] [Kopardekar 2019] [Kopardekar 2020] [Kopardekar 2020] [Koshekov et al 2026] [Koumoutsidi et al 2022] [Kumar 2026] [Moolchandani et al] [Kwak 2026] [Humphrey et al] [Lerro 2020] [Li et al 2025] [Li et al 2026] [Lin 2023] [Littell 2019] [Lowry 2018] [Luciano] [Feary et al] [Madjdi and Zolfaghari 2023] [Maia and Lourenço da Saúde 2021] [Mak et al 2026] [Marzouk 2025] [Matheis and Norrefeldt 2026] [Matveev et al 2023] [McKillip 2022] [McQueen 2021] [Melo and Verri 2026] [Acheson et al] [Feary et al] [Vincent] [Michaud et al 2026] [Milde 2003] [Milde Jr. et al 2003] [Xue] [Mpala and Chakraborty 2025] [Sarkar et al] [Myasnikov and Ilyin 2023] [Mendonca] [Nassir Tafreshi 2026] [Neogi et al] [Jones et al] [Brown et al] [Campbell et al] [Namuduri and Gambold 2025] [Navarrete 2026] [Nguyen and Marion 2026] [Nguyen and Marion 2026] [Nguyen and Marion 2026] [Craven et al] [Ogden 2023] [Okpara 2025] [Okpara 2026] [Okusuga and Morimoto 2026] [Omorodion 2023] [Ott 1998] [Kopardekar] [Patil and García-Sánchez 2025] [Patterson 2025] [Pavel 2022] [Santos et al 2026] [Suh et al] [Phadke and Majumdar 2025] [Pradeep et al 2022] [Pradeep et al 2022] [Pukhova et al 2021] [Qanbari and Skorupski 2025] [Qi et al 2025] [Rahn et al 2024] [Ratei et al 2023] [Rathinasamy et al 2024] [Rizzi 2026] [Salvador 2022] [Santhosh 2023] [Seren and Hornung 2023] [Shah 2025] [Shin 2025] [Sharma and Murphy] [Krishnamurthy et al] [Whiteside and Welstead] [Silva et al 2018] [Simmons 2022] [Simmons 2023] [Bogner et al 2025] [Souza et al 2026] [Spühler et al 2025] [Stanzione et al 2019] [Stoll and Bevirt 2022] [Surmann et al 2022] [Tacke 2026] [Tan and Low 2021] [Tang 2021] [Tang et al 2022] [Tepylo and Laliberté 2025] [Tepylo et al 2024] [Terpecz 2023] [Terpecz and Schuster 2024] [Terpecz and Schuster 2025] [Thompson et al 2023] [Tokuoka et al 2025] [Transport - Medical Aircraft 2022] [Tremblay 2026] [Tripaldi and Bianchi 2025] [Nguyen 2025] [Tuccillo and Ruocco 2025] [Tumuluru Ramesh and Pandurangi 2022] [Ugwueze et al 2023] [Ulahannan et al 2025] [Urban Air Mobility UAM 2023] [Varnousfaderani et al 2025] [Vegh et al 2019] [Ventura Diaz and Yoon 2018] [Ventura Diaz and Yoon 2019] [Verma et al 2019] [Vieira et al 2019] [Bulusu] [Bulusu] [Bulusu 2020] [Bulusu 2020] [Vuppala et al 2024] [Wang 2026] [Wang et al 2024] [Wu et al 2025] [Wyzykowski 2025] [Xie and Chen 2026] [Xue 2020] [Yan et al 2026] [Yanev and Staack 2026] [Yang et al 2026] [Yavas and Yavaş Tez 2023] [Yavuz 2024] [Yeganehdoust et al 2023] [Yuan et al 2026] [Zeng et al 2021] [Zhang et al 2021] [Zhang et al 2024] [Zhao and Sheng 2025] [Zhao et al 2024] [Zheng and Merret 2022] [Zheng and Merret 2023] [Zhengqi et al 2022] [Šimeček 2023] [Аналіз Правил Експлуатації Evtol 2025]

Energy, batteries and sizing

The modern disc loading. Batteries, fuel cells and hybrid powertrains, energy and mission analysis, sizing and conceptual design. 67 titles name a battery, 65 of them from 2019 or later, and the 18 that name a fuel cell or hydrogen are none of them dated before 2019.

266 records. [Aboelela et al 2026] [Acree 2014] [Adolf and Andert 2010] [AI-Based Optimization of Battery 2024] [Alba-Maestre et al 2021] [Alulema et al 2026] [An et al 2022] [Anthony et al 2009] [Datta 2021] [Ashok et al 2015] [Aбдуллаев 2021] [Bai et al 2024] [Bando et al 1993] [Barboza and Moffatt 1988] [Batra et al 1986] [Battery Testing for The 2023] [Beals 2018] [Beliautsou and Beliautsou 2024] [Beyne and Castro 2022] [Bhandari and Chakraborty 2025] [Blume 2026] [Bortkiewicz 1999] [Bosse et al 1970] [Bossler and Robert B. 1965] [Brito] [Cavcar and Cavcar 2005] [Chai et al 2025] [Chakraborty et al 2023] [Chaohui et al 2026] [Chen et al 2021] [Chen et al 2024] [Cheng et al 2025] [Chu et al 2026] [Clay et al 1987] [Coe and Fournier 1976] [Coelho et al 2022] [Collins and Atkins 2026] [Conceptual Design of a 2026] [Costa 2012] [Coy 2006] [Critchfield and Ning 2026] [Crossley and Rutherford 1995] [Davis and Ela 1969] [Detore and Sambell 1975] [Diaz Flores Caminero et al 2024] [Dixit et al 2024] [Dixit et al 2024] [Donateo and Çinar 2022] [Dong et al 2025] [Dutton 1967] [Ednie et al 1988] [Fay and Johnstone 1960] [Fay et al 2025] [Feng et al 2024] [Fisler and Datta 2019] [Forville 1977] [Furlan et al 2026] [Gabel et al 1961] [Gamble 2023] [Thomas et al] [Gertsma and Zigan 1973] [Glaudel 2021] [Goldsmith and Hickey 1963] [Golombek et al 2026] [Gong et al 2026] [Goshtasbi et al 2024] [Goshtasbi et al 2025] [Govindarajan and Sridharan 2021] [Graf et al 2024] [Granado et al 2022] [Gregoire 2023] [Guerrero and Clarke 2026] [Guibert et al 2024] [Harris 2017] [Hascaryo and Merret 2020] [Hatherall et al 2024] [He et al 2024] [He et al 2025] [Head 1981] [Hegdahl 1993] [Heidary and Kosari 2024] [Hess 2019] [Hiller Aircraft Corp Palo Alto Ca 1955] [Hoffrichter 1978] [Howard 2012] [Hoyos et al 2021] [Hu et al 2026] [Hudson and Gee 1977] [Huuva et al 2018] [Ibrahim and Bil 2013] [Irvin and Swan 1956] [Islam et al 2026] [Ito 2018] [Putnam] [Putnam et al] [Jexembaeyva and Alexander 2025] [Jiang et al 2025] [Jiao and Yang 2026] [Jin 2026] [Johnson 1995] [Joppa 1966] [Littell et al] [Kaneko and Martins 2023] [Kang and Chung 2024] [Kefford and Munch 1975] [Kelly and Lloyd 2015] [Kesling 1968] [Kohn 1972] [Kolluri et al 2021] [Kraenzler et al 2019] [Krismadinata et al 2026] [Kunwar et al 2023] [Kutney 1964] [Kutney 1964] [Lai et al 2026] [Leishman et al 2004] [Leutzinger 1968] [Lewis 1989] [Li and Jiang 2026] [Li et al 2018] [Li et al 2025] [Lieblein 1970] [Lira Sassett et al 2025] [Littell et al 2019] [Logan 1974] [Logan 1989] [Louthan 1980] [Lu et al 2017] [López et al 2022] [Ma and Liu 2025] [Ma et al 2019] [Maciolek and Wallischeck 1977] [Magee et al 1974] [McAvoy and Gopalarathnam 2002] [Mihara et al 2021] [Mo et al 2026] [Mohana Sundaram and Kavya Santhoshi 2024] [Mokotoff et al 2026] [Molinaro and Fioriti 2026] [Morris and Alexander 1978] [Nabiyev et al 2020] [NACA 1978] [Namukasa et al 2024] [Nederlof et al 2025] [Ng and Datta 2019] [Ng et al 2019] [Ng et al 2021] [Oyama et al 2024] [Paek 2025] [Paek et al 2021] [Palaia et al 2021] [Panigrahi et al 2021] [Park 2026] [Park and Yee 2025] [Park and Yee 2026] [Park et al 2022] [Park et al 2022] [Park et al 2022] [Park et al 2024] [Park et al 2024] [Park et al 2025] [Park et al 2026] [Paw and Ang 2023] [Payne 2002] [Phung et al 2024] [Piasecki 2026] [Pichitkul et al 2023] [Prabhakar et al 2026] [Propeller Propulsion Systems 2010] [Putnam et al 2026] [Putra and Chakraborty 2023] [Qasem et al 2024] [Qian et al 2023] [Qian et al 2026] [Qin et al 2023] [Rajendran 2025] [Rosenstein 1989] [Rosenthal et al 1988] [Rutherford et al 1991] [Sambell 1976] [Sanderson and Holly 1993] [Santos et al 2025] [Conley et al] [Sato et al 2009] [Schoser et al 2022] [Scott and Schrage 2012] [Selleck 1978] [Senkans et al 2020] [Senkans et al 2021] [Serovy and Kavanagh 1974] [Shah and Ansell 2026] [Shao et al 2023] [Shentu et al 2026] [Shim et al 2023] [Shovlin and Gambucci 1978] [Silva and Johnson 2021] [Silva and Solis 2024] [Simpson 1967] [Sirigireddy and Ahner 2026] [Sissingh 1960] [Smith 1966] [Snyder 2016] [Snyder and Kohlman 2018] [Song and Underwood 2007] [Song et al 2024] [Sonkar et al 2020] [Soule and Badri-Nath 1973] [Spierling et al 2025] [Spillman 1965] [Spillman 1967] [Vashi et al] [Sridharan and Govindarajan 2022] [Stahl et al 2020] [Stanzione 2025] [Steele 2026] [Stein and Vichness 1971] [Stevenson et al 2020] [Stuermer 2008] [Stuermer and Yin 2012] [Sulkoske et al 1977] [Suti et al 2025] [Schmitz et al] [Schmitz et al] [Tan et al 2010] [Tang et al 2020] [Tang et al 2023] [Tanigawa and Kurose 2024] [Topac et al 2024] [Tu et al 2025] [Tulino et al 1971] [Ugwueze et al 2022] [Veres and Thurman 2010] [Wadia et al 2022] [Wahler et al 2025] [Wakabayashi and Katsui 2024] [Wang et al 2025] [Ward 1989] [Wentz 1977] [Wernicke 1980] [Wernicke et al 1980] [Widdison et al 1974] [Wilde et al 2022] [Wilson and Bennett 1983] [Winter et al 2021] [Wu et al 2024] [Wu et al 2026] [Xu and Raghavan 2023] [Xu and Raghavan 2024] [Xu et al 2024] [Yan and Wiston 2026] [Yan and Wiston 2026] [Yan et al 2021] [Yang et al 2026] [Yang et al 2026] [Ayalew et al] [Young 2018] [Yu et al 2026] [Zabinsky and Burnham 1977] [Zabinsky et al 1974] [Zhao et al 2024] [Zheng et al 2026] [Zhou et al 2020] [Zhu et al 2024] [Zinjarde et al 2026] [Çelik et al 2023] [Çınar and Tunçel 2026]

The tilt-wing configuration

The configuration itself. The tilt-wing from the period programmes to the present, its stability, control, transition and design. The configuration returned. 230 titles name the tilt-wing, 42 of the dated ones from before 1970 and 150 from 2010 or later. 77 titles in this cluster name an electric vertical take-off aircraft, an unmanned aircraft or a drone, the earliest dated one from 2009, while the 17 that name the XC-142, the CL-84 or the VZ-2 have a median year of 1965 and none of them is dated 2010 or later.

249 records. [Aihaitijiang and Onal 2019] [Alvaro D. H. Arroyo et al 2021] [Aoki and Muraoka 2019] [Arroyo] [Autenrieb et al 2019] [Barra et al 2020] [Bauer 2023] [Simmons and Murphy] [Benkhoud and Bouallegue 2016] [Benkhoud et al 2017] [Beppu et al 1966] [Binz et al 2019] [Birckelbaw and Corliss 1992] [Birckelbaw and Corliss 1992] [Birckelbaw and Corliss 1994] [Birckelbaw et al 1994] [Bouallegue and Khoud 2016] [Breul 1963] [Busan et al 2021] [Cetinsoy et al 2012] [Chakraborty and Mishra 2023] [Chakraborty et al 2022] [Chakraborty et al 2025] [Chambers and Grafton 1966] [Chambers and Grafton 1968] [Chambers and Grafton 1970] [Champine 1971] [Champine et al 1970] [Chana and Sullivan 1992] [Chana and Sullivan 1993] [Chance Vought Corp Dallas Tx 1963] [Chapman 2019] [Chauhan and Martins 2020] [Chen et al 2020] [Choi et al 2026] [Comer and Chakraborty 2023] [Comer and Chakraborty 2024] [Comer et al 2026] [Cook 2025] [Cook et al 2025] [Cooper et al 2018] [Crawford et al 1996] [Curtiss et al 1967] [Dancik et al 1958] [Danielmeier et al 2022] [Daud Filho] [Daud Filho and Belo 2024] [Perez et al] [Day 1965] [de Madrid et al 2007] [Deckert et al 1964] [Deckert et al 1968] [Deng et al 2026] [Design and Aerodynamic Analysis 2021] [DiMaggio et al 2025] [DiMaggio et al 2026] [Doff-Sotta et al 2022] [Doff-Sotta et al 2023] [Doff-Sotta et al 2025] [Dolan 1964] [Escamilla et al 2020] [Fatemi 2024] [Fay 1963] [Fay 1964] [Fenwick 1967] [Fink 1966] [Fink 1967] [Fink 1969] [Fink and Mitchell 1967] [Fink et al 1964] [Fink et al 1966] [Fling 1965] [Frost et al 2002] [Fry 1965] [Geuther et al 2020] [Giulianetti and Weiberg 1964] [Gold and Walchli 1974] [Goodson 1966] [Goodson 1967] [Gregory et al 2015] [DiMaggio et al] [Grima 2016] [Grunwald 1961] [Grunwald 1965] [Grunwald 1966] [Guerrero and Corliss 1991] [Guerrero and Corliss 1991] [Hancer et al 2010] [Hargraves 1961] [Hartmann et al 2017] [Hartmann et al 2017] [He 2024] [He et al 2020] [Hendricks et al 2019] [Hesse 1965] [Higgins et al 2020] [Holsten et al 2011] [Hong et al 2025] [Hong et al 2026] [Hospodář and Kulhánek 2026] [Hrishikeshavan and Chopra 2012] [Hsu et al 2024] [Huang et al 2024] [Ibrahim et al 2026] [Hassell and Kirby 1966] [Jeong et al 2015] [Jin and Zhao 2025] [Kratz and Culley] [Judas and Deligiannidis 2013] [Katagiri et al 2025] [Katagiri et al 2025] [Kimball 1993] [Kirby and Newsom 1964] [Kirby et al 1963] [Kolesar 1971] [Kolesar et al 1970] [Kolesar et al 1970] [Konrad 1967] [Konuk and Landman 2023] [Kratz and Culley 2021] [Krimphove et al 2023] [Kukla 2026] [Kulhánek et al 2023] [König et al 2023] [Li et al 2026] [Lindqvist et al 2015] [Liu et al 2025] [Liu et al 2026] [Lockhart] [Loewy and Yntema 1958] [Longhurst 1966] [Lovell and Parlett 1956] [Lovell and Parlett 1957] [Mahadev et al 2024] [Marsh 1965] [Martin 1963] [Martin 1963] [Masuda and Uchiyama 2018] [Masuda and Uchiyama 2019] [May et al 2022] [May et al 2023] [May et al 2024] [May et al 2024] [May et al 2025] [May et al 2026] [May et al 2026] [May et al 2026] [McCormick and Mallen 1956] [McCormick and Mallen 1957] [Michaelsen 1971] [Mikami and Uchiyama 2015] [Milz and Looye 2022] [Milz et al 2024] [Milz et al 2024] [Milz et al 2025] [Milz et al 2026] [Misra et al 2022] [Mita et al 2021] [Mix et al 2004] [Monnier 2026] [Monnier and Litherland 2026] [Muraoka et al 2009] [Muraoka et al 2016] [Murphy and Landman 2015] [Müller and Moormann 2024] [Newsom 1962] [Newsom 1962] [Newsom and Tosti 1959] [Nichols 1963] [Nichols 1990] [Nonami et al 2010] [O’Heron et al 1992] [O’Rourke and Rutherford 1991] [Ostermann 2016] [Ott et al 2026] [Panish and Bacic 2022] [Panish and Bacic 2025] [Panish et al 2023] [Partridge et al 2021] [Pegg et al 1974] [Persson and Lawrence 2017] [Phillips 1965] [Phillips 1969] [Pradeep and Wei 2018] [Putman 1961] [Putman 1969] [Rohr et al 2019] [Rostami et al 2023] [Rothhaar et al 2014] [Rutherford and Bass 1992] [Samadikhoshkho and Lipsett 2025] [Sanchez et al 2019] [Sanchez-Rivera et al 2019] [Sanchez-Rivera et al 2020] [Sanchez-Rivera et al 2020] [Sandoz et al 2018] [Sato and Muraoka 2013] [Sato and Muraoka 2013] [Schmid et al 2025] [Schütt et al 2018] [Shahjahan et al 2024] [Shinde et al 2025] [Shinozuka et al 2024] [Sim et al 2022] [Simmons and Murphy 2021] [Simmons and Murphy 2022] [Small et al 2016] [Stagliano and Hornung 2012] [Stepniewski 1957] [Stuart 1957] [Stuart 1959] [Stuart 1956] [Studiger and Cook 2025] [Sullivan 1972] [Sullivan 1993] [Takayama et al 2020] [Taubert et al 2021] [Taubert et al 2023] [Templin et al] [The Canadair CL-84 experimental 1990] [Tosti 1959] [Tosti 1961] [Tosti 1962] [Totah 1991] [Totah 1992] [Totoki et al 2015] [Totoki et al 2016] [Wang et al 2018] [Wang et al 2018] [Wang et al 2019] [Wang et al 2021] [Wang et al 2025] [Wang et al 2026] [Ward 1960] [Watanabe and Muraoka 2026] [Xiang et al 2025] [Yamaguchi and Hara 2022] [Yeh and Du 2023] [Yeh et al 2023] [Yildiz et al 2015] [Yokota and Fujimoto 2022] [Yokota et al 2021] [Yue et al 2025] [Yue et al 2026] [Zhang et al 2019] [Zhao et al 2025] [Zheng et al 2024] [Zhu et al 2025] [Çakir and Kurtuluş 2022]

Distributed electric propulsion

The arrangement that deletes the keystone. Distributed electric and hybrid propulsion, its aero-propulsive coupling and lift augmentation, and its control and noise. 186 titles name distributed propulsion, none dated before 2004, with a median year of 2023.

240 records. [Ahmed et al 2024] [Alonso Castilla et al 2021] [Anibal and Duensing 2025] [Armstrong et al 2015] [Bai and Zhou 2023] [Barbosa Marques and Silva 2021] [Baris and Landman 2017] [Benjamin 2023] [Benjamin et al 2025] [Simmons] [Benyamen and Keshmiri 2022] [Boissinot and Kheiri 2023] [Bonnin et al 2023] [Borer and Patterson 2020] [Bowen 2025] [Bowen et al 2023] [Böhnisch et al 2022] [Böhnisch et al 2026] [Cakin et al 2020] [Chan 2019] [Chau et al 2025] [Chelemen et al 2023] [Chen et al 2021] [Chen et al 2023] [Chen et al 2025] [Chen et al 2025] [Cheng et al 2022] [Choi 2014] [Choi et al 2014] [Ciliberti and Nicolosi 2026] [Comunian et al 2025] [Corcau et al 2026] [Critchfield and Ning 2023] [Cui et al 2027] [Cunningham et al 2022] [Cuppoletti et al 2024] [Cusati et al 2023] [Daniel and Hendrick 2023] [Darmstadt et al 2021] [North et al] [Davis et al 2025] [Deere et al 2017] [Deere et al 2017] [Deere et al 2017] [Deere et al 2018] [Demers Bouchard et al 2015] [Deng et al 2026] [Dillard et al 2025] [Dippold et al 2004] [Distributed Electric Propulsion 2018] [Donateo et al 2023] [Dorfling and Traub 2023] [Dos Santos et al 2024] [Duffy 2015] [Dumanli et al 2026] [Dyson 2018] [Economou et al 2019] [El Idrissi and D’Arpino 2024] [Electric and Hybrid-Electric Propulsion] [Eqbal et al 2022] [Eqbal et al 2023] [Erhard et al 2021] [Feng et al 2025] [Firnhaber Beckers et al 2022] [Firnhaber Beckers et al 2023] [Firnhaber Beckers et al 2023] [Fredericks et al 2013] [Fredericks et al 2013] [Freeman and Klunk 2018] [Galbraith 1979] [Gallani et al 2020] [Garrett et al 2019] [Gholamian and Beik 2026] [Ginn 2014] [Ginn 2015] [Gnadt et al 2019] [Goldberg et al 2015] [Goldberg et al 2017] [Golovanov et al 2019] [Gothing 2025] [Gothow et al 2023] [Gothow et al 2024] [Guddanti et al 2022] [Gul and Yeo 2025] [Guérin and Tormen 2023] [Hange 2016] [Harada 2022] [Harish et al 2018] [Herzog et al 2021] [Hoenicke and Willich 2025] [Hoover 2024] [Hoover and Shen 2018] [Hu et al 2026] [Huangfu et al 2024] [Jedamski et al 2023] [Jiang and Pakmehr 2022] [Jois et al 2024] [Kang et al 2014] [Kang et al 2014] [Kang et al 2026] [Kawauchi 2026] [Keller 2023] [Keller 2026] [Kim et al 2018] [Kirsch and Friedrichs 2023] [Klunk and Freeman 2018] [Kou et al 2023] [Kuzniar et al 2020] [Kuźniar and Orkisz 2019] [Lampl and Armanini 2023] [Laskaridis 2015] [Lee 2026] [Lei and Zhao 2023] [Li 2024] [Li et al 2022] [Li et al 2025] [Li et al 2025] [Li et al 2025] [Li et al 2026] [Lindner et al 2023] [Lindner et al 2024] [Litt 2024] [Litt 2026] [Liu et al 2025] [Haworth et al] [Love 2022] [Luo et al 2024] [Ma et al 2022] [Machado et al 2025] [Miyairi et al 2015] [Models of Electric and] [Moore and Ning 2018] [Morani et al 2024] [Nark et al 2017] [Nathan 2026] [Nguyen et al 2016] [Ni and Lee 2025] [Borer] [Nguyen et al 2025] [Nicolosi et al 2022] [Nishikawa and Rinoie 2024] [Nolan et al 2016] [North et al 2021] [Notash et al 2023] [Odukoya and Jo 2026] [Oldeweme et al 2024] [Oldeweme et al 2024] [Oldeweme et al 2026] [Orefice et al 2019] [Orefice et al 2020] [Papathakis] [Papathakis 2017] [Papathakis et al 2016] [Papathakis et al 2016] [Papathakis et al 2017] [Park and Park 2026] [Patterson et al 2016] [Patterson et al 2021] [Perry et al 2019] [Pham et al 2022] [Pieper et al 2018] [Posada and Vargas 2020] [Pradeep et al 2021] [Qiao and Zhou 2026] [Qiao et al 2023] [Raush et al 2016] [Rizzi et al 2017] [Viggiano et al] [Schiltgen and Freeman 2019] [Schiltgen et al 2011] [Schiltgen et al 2012] [Schiltgen et al 2013] [Schiltgen et al 2013] [Schmidt et al 2025] [Schneider et al 2026] [Schrage et al 2018] [Sener et al 2020] [Serrano et al 2021] [Shang et al 2025] [Sharpe and Agarwal 2019] [Shaw et al 2015] [Shen et al 2026] [Shi et al 2024] [Siddavatam et al 2023] [Sinha 2026] [Soikkeli et al 2023] [Song et al 2024] [Song et al 2024] [Song et al 2025] [Sorensen et al 2025] [Spada et al 2025] [Stoll and Veble Mikic 2016] [Sun et al 2024] [Suppes and Suppes 2024] [Suppes and Suppes 2024] [Suzuki et al 2019] [Synodinos et al 2018] [Takahashi et al 2014] [Tatsis 2026] [Thapa et al 2025] [Theron et al 2020] [Thosar et al 2026] [Trainelli 2026] [Tsoi et al 2014] [Turhan et al 2023] [Upadhyay and Zaman 2021] [Valencia et al 2019] [Valencia et al 2019] [Varela Martínez] [Vecchia et al 2018] [Vepa 2020] [Vos 2019] [Vouros et al 2022] [Wang and Hu 2026] [Wang et al 2019] [Wang et al 2023] [Wang et al 2026] [Wang et al 2026] [Wang et al 2026] [Wickersheim et al 2023] [Wiston and Yan 2025] [Wu and Litt 2023] [Wu et al 2023] [Xie et al 2023] [Xie et al 2026] [Yang and Huang 2023] [Yang and Zha 2018] [Yang et al 2024] [Yang et al 2025] [Yu et al 2021] [Yu et al 2026] [Zeng et al 2021] [Zhang et al 2023] [Zhang et al 2023] [Zhao et al 2024] [Zhao et al 2025] [Zhao et al 2025] [Zhao et al 2026] [Zheng et al 2025] [Zong et al 2024]

Certification, airspace and operations

Where the constraint now lives. Certification and airworthiness of powered-lift aircraft, airspace integration, air traffic management for urban air mobility, and the operations, demand and acceptance of the services. 52 titles name certification or airworthiness, with a median year of 2022.

226 records. [Abryandoko et al 2026] [Almasabi and Zhang 2026] [Altouq et al 2025] [Andriesen and Honaker 1987] [Ariante and Papa 2024] [Asher 1969] [Ayalew et al 2026] [Bae et al 2020] [Barbano and Costa 2023] [Barrett-Gonzalez et al 2023] [Behme and Planing 2020] [Blackwell 1970] [Borer et al 2014] [Borer et al 2023] [Bosch et al 2026] [Burrous et al 1974] [Cabaleiro et al 2024] [Caldwell and Lafavor 1980] [Carlucci et al 2026] [Cartile et al 2025] [Denham et al] [Cayot et al 1972] [Certification of Tactics and 2000] [Cha et al 2025] [Chakraborty et al 2023] [Chakraborty et al 2024] [Chakraborty et al 2026] [Chang et al 2026] [Charnsethikul et al 2025] [Chatterji 2020] [Cheyno 1967] [Cho et al 2026] [Choi and Suk 2026] [Comer and Chakraborty 2023] [Conrad et al 2023] [Dai] [Hartman et al 2023] [Hartman et al 2023] [Doo 2021] [Dousis] [Ducard and Carughi 2024] [Edwards and Price 2020] [Ellis et al 2023] [Farooqui 2025] [Farris et al 1983] [Favaro et al 2025] [Favaro et al 2025] [Feistel et al 1972] [Ferreira Filho and Cardoso Júnior 2024] [Fraser et al 2018] [Fregnani and Balvedi 2026] [Gappa 1964] [Garren et al 1970] [Altamirano et al] [Lee et al 2022] [Price et al 2020] [Goericke et al 2024] [Gottschall et al 2022] [Grant et al 2017] [Greenfeld 2019] [Guerreiro et al 2020] [Gunnarson 2014] [Lee et al] [Lee et al] [Lee et al] [Harrison et al 2019] [Hasan 2019] [Heffley et al 1977] [Heilein and Crespillo 2024] [Hill and Garrow 2021] [Hollister 1969] [Hollister and Leet 1970] [Hollister et al 1970] [Homola and Tiwari 2023] [Honaker 1987] [Huang et al 2022] [Hudock and Leonard 1969] [Human Factors Certification of 2000] [Hynes and Scott 1976] [Iriarte et al 2026] [Ison 2024] [Ito and Furue 2019] [Jacobson and Kuhlthau 1972] [Janetzko et al 2024] [Janetzko et al 2025] [Prince et al 2024] [Jiang et al 2026] [John 2026] [Jones and Jusko 2022] [Jusko et al 2022] [Littell] [Kaczmarek et al] [Kang et al 2024] [Kazlauskas and Balčiūnas 2026] [Kannan et al] [Goodrich] [Goodrich] [Klyde et al 2022] [Kopyt et al 2024] [Kotwicz Herniczek et al 2019] [Kress 1980] [Kundu et al 2020] [Moolchandani] [Moolchandani 2021] [Moolchandani et al] [Laplante et al 2026] [Lawrence and Head 2024] [Lebacqz and Scott 1984] [Lebacqz and Scott 1985] [Lei 2026] [Leonard et al 2021] [Letica and Rizzi 2024] [Spirkovska et al] [Lim et al 2023] [Lippoldt et al 2023] [Lombaerts et al 2020] [Lv et al 2026] [Ma and Ding 2023] [Ma et al 2024] [Ma et al 2025] [Mahony and Lozano 1999] [Shaw-Lecerf et al] [McDonald 2015] [McGee et al 1978] [McIntyre et al 1977] [Meiklem 1969] [Merrick and Gerdes 1977] [Merrick and Gerdes 1983] [Metrological support features during 2022] [Min et al 2026] [Monemi Nodehi et al 2026] [Montaruli et al 2026] [Neogi et al] [Nguyen and Marion 2026] [Nguyen and Marion 2026] [Oh et al 2026] [Oliveira and D’Amore 2026] [Darmstadt et al 2021] [Pearson 1965] [Pedrioli et al 2024] [Peng et al 2022] [Pleffken et al 2024] [Pleffken et al 2026] [Pradeep and Wei 2018] [Pradeep and Wei 2018] [Pradeep and Wei 2020] [Preis and Cheng 2022] [Preis and Hornung 2022] [Preis and Hornung 2022] [Preis and Hornung 2022] [Puvrez 1964] [Puvrez 1965] [Rakas et al 2021] [Ratei et al 2024] [Reeder 1964] [Reid et al 1973] [Mogford and Johnson 2023] [Bhandari et al] [Bhandari et al] [Rogers and Belluomini 2026] [Goyal et al 2018] [Ren and Heng 2026] [Roltgen and Byrnes 1991] [Roman 2026] [Rudolph 1972] [Verma et al 2020] [Verma et al] [Saxena et al 2026] [Schneider 1989] [Schrage and Arterburn 2016] [Schrage et al 2018] [Schweiger and Knabe 2023] [Schweiger and Preis 2022] [Schweiger et al 2023] [Seon Yang et al 2025] [Shaik 2026] [Shiva Prakasha et al 2022] [Shon and Lee 2025] [Shubert et al 2026] [Sieb et al 2023] [Silsby and Sawyer 1973] [Smith 2025] [Smith and Vickers 1970] [Das Biswas et al 2025] [Song 2022] [Song and Yeo 2021] [Song et al 2021] [Spedicato et al 2016] [Strother and Upton 1971] [Study on Urban Air 2025] [Bharadwaj et al] [Bharadwaj et al 2021] [Murthy et al] [Murthy et al 2022] [Takacs and Haidegger 2022] [Tan et al 2014] [Tang et al 2026] [Thipphavong et al 2018] [Trimarchi 2023] [Tuck 1970] [Turchetti and Condé Rocha Murça 2024] [Umapathy et al 2021] [Unverricht et al 2024] [Vandy 2026] [Veldhuizen et al 2026] [Veras Neto and de Andrade 2022] [Wang and Xu 2026] [Wild 2021] [Cummings et al] [Taye et al 2024] [Wang and Zhang 2020] [Wei et al 2022] [Windolph 1969] [Wing et al 2020] [Wu et al 2026] [Yan et al 2024] [Yokoyama et al 2025] [Young and Rajagopalan 2013] [Young et al 2011] [Zhang and Hwang 2025] [Zhang et al 2025] [Ziakkas 2026] [Zintl et al 2024] [Zongo and Wei 2026] [Čečrdle 2015] [čečrdle 2023]

Engine failure, cross-shafting and redundancy

What the X-18 lacked. Engine failure and the inoperative engine, asymmetric thrust, drive systems and cross-shafting, and the fault-tolerant control of multirotor and distributed vehicles. Fault tolerance has overtaken engine failure. 62 titles name a fault, the earliest dated one from 2007, with a median year of 2022, while the 44 that name an engine failure, an inoperative engine or one engine have a median year of 2018.

165 records. [Ahmadi Dastgerdi and Nabavi-Chashmi 2026] [Air Force Test Pilot School Edwards Afb Ca 1992] [Allel et al 2023] [Alwi and Edwards 2013] [Ambroziak et al 2023] [Ames and Fetty 2007] [Antonakis and Biannic 2024] [Arnold et al 1987] [Avant et al 2018] [Babin and Dattel 2021] [Babin et al 2020] [Baldini et al 2020] [Benischke and Thielecke 2015] [Berger et al 2025] [Biber 2000] [Biber 2000] [Boskovic et al 2007] [Bowen 1970] [Brinkman and Visser 2007] [Bucsek 1974] [Burova et al 2025] [Burroughs 1965] [Carlson and Zhao 2002] [Carlson and Zhao 2004] [Carlson et al 1999] [Casadei et al 2019] [Castaldi et al 2020] [Chaturvedi and Sahoo 2023] [Chen et al 1995] [Chen et al 1998] [Chung and Son 2020] [Cooper et al 1966] [Córdoba 2007] [Daniel 1964] [Darmstadt et al 2022] [Thipphavong] [Delisle and Takahashi 2018] [Diget et al 2022] [Double engine failure 2002] [Du et al 2024] [Du et al 2024] [Duello 2002] [Engine Failure in Light 1980] [Falconì et al 2018] [Fang 2022] [Frank and Rempe 2026] [Fuhrer et al 2019] [Fulton et al 2026] [Garzon Galindo et al 2023] [Thomas and Malone] [Giribet et al 2019] [Gonzalez-Guerrero et al 2022] [Greuter and Zima 2012] [Grosveld 1983] [Guan and Shi 2019] [Guo and Wang 2010] [Hamadi] [Han and Pei 2026] [Hoffren and Raivio 2000] [Hoogreef and Soikkeli 2022] [Hou et al 2025] [Hou et al 2026] [Hou et al 2026] [Huff 1988] [Hung and Dai 2025] [Immersion and Invariance Adaptive 2026] [Iseler et al 1996] [Jiang et al 2014] [Jing and Ma 2025] [Johnson 1975] [Kang et al 2024] [Kapoor et al 2012] [Kaufman and Van Train 1965] [Kirchner 1955] [Kobayashi and Takahashi 2011] [Krug et al 2026] [Kuric et al 2017] [Lai et al 2026] [Leclercq et al 2012] [Lee et al 2024] [Leelaburanathanakul et al 2021] [Leishman 1966] [Li et al 2023] [Li et al 2025] [Liao et al 2023] [Liao et al 2025] [Liao et al 2025] [Liu and Xu 2026] [Luo et al 2025] [Ma et al 2025] [Ma et al 2025] [Mack 1965] [Mage and Nikolic 2022] [Malaek and Alipour 2020] [Mancinelli et al 2025] [Marks et al 2012] [Massey et al 2018] [Mazeh and Sahili 2019] [Mazeh et al 2021] [McKay et al 2023] [Mokotoff and Cinar 2026] [Mourning and Ghauri 2025] [Mousaei et al 2022] [Neves et al 2023] [Nieuwenhuijse and Franklin 1974] [Noh and Shin 2023] [Nunes et al 2025] [Oberschwendtner and Hornung 2024] [Ohgawara et al 2020] [Overfield and Crawford 1967] [Park and Roh 2025] [Pei et al 2025] [Reis et al 1977] [Rich 1969] [Rijal and Chakravarthy 2026] [Saied] [Saied et al 2019] [Saied et al 2019] [Saied et al 2024] [Sanjuan et al 2019] [Santos Martins Nunes and Su 2024] [Schacht-Rodrigue et al 2019] [Seo and Kim 2019] [Silva-Martinez et al 2015] [Slim et al 2021] [Smith 1969] [Stevens et al 1985] [Stewart 1987] [Stewart and Brown 1985] [Strampe and Klingauf 2026] [Swanke and Jahns 2021] [Swanke and Jahns 2022] [Swanke et al 2021] [Thomas and Malone 2023] [Trustee 1976] [Unruh 1989] [Vey and Lunze 2016] [Wandini et al 2016] [Wang 2003] [Wang and Zhang 2018] [Wang et al 2017] [Wang et al 2020] [Wang et al 2022] [Wang et al 2026] [Ward et al 1999] [Wen et al 2023] [Whelchel et al 2022] [Willis 1980] [Willis 1981] [Xia et al 2022] [Xia et al 2023] [Xiao et al 2018] [Xie et al 2020] [Xu and Zhang 2025] [Yan and Chen 2019] [Yang et al 2020] [Yu et al 2024] [Yuanqing et al 2014] [Zelina and Prazenica 2024] [Zhang et al 2024] [Zhang et al 2024] [Zhao et al 1995] [Zhao et al 2024] [Zhao et al 2025] [Zou 2017]

Wind tunnel testing and the correlation with flight

The ground prediction. Wind tunnel testing of powered-lift and rotorcraft models, wall and scale effects, free-flight and full-scale tests, and the correlation of tunnel with flight.

133 records. [Jacob da Motta 2020] [Abdessameud and Tayebi 2010] [Abdulrahim 2020] [Balch 1978] [Simmons] [Simmons] [Simmons et al] [Simmons et al] [Simmons 2023] [Blackwell et al 1981] [Bland and Konsewicz 1976] [Boeing Co Morton Pa Vertol Div 1961] [Boeing Vertol Co Philadelphia Pa 1974] [Brand et al 1989] [Brown and Duhon 1965] [Bruce 2009] [Campbell and Quinn 1973] [Corsiglia et al 1979] [Curtiss et al 1961] [Danis] [Deel et al 1972] [Dooley and Yeary 1979] [Reda et al 2017] [Ekquist 1965] [Experimental investigation of synthetic 2023] [Figueira et al 2025] [Flight test of a 1979] [Frey et al 2024] [Fukami et al 2004] [Gallington and Miller 1970] [Gebert et al 2000] [Ghanchi and Gururajan 2026] [Ghazi 1993] [Glezer 2009] [Glezer 2012] [González Mendoza 2026] [González Mendoza 2026] [Grafton et al 1974] [Gungor et al 2024] [Gustafson et al 1960] [Haleem 2023] [Hall 1968] [Hassell 1976] [Heyson 1973] [Heyson 1974] [Holway 1966] [Hughes and Wernicke 1974] [Jaffe 1972] [Foster et al 2020] [Jones 1971] [Littell and Putnam] [Littell et al] [Karli et al 2024] [Kelly 1972] [Kelly 1973] [Kelly and Smaus 1952] [Kirby 1954] [Kulkarni et al 2022] [LaForge and Rohtert 1970] [Landman et al 1999] [Lange et al 1946] [Lavi 1967] [Lebacqz and Radford 1978] [Lebacqz and Radford 1979] [Lechniak 2018] [Ledford 2007] [Lee et al 2026] [Lemnios et al 1976] [Lockheed-California Co Burbank 1964] [Loughran et al 2024] [Lovell 1953] [Lovell 1954] [Maier et al 1996] [Mangum 1965] [Mason 2013] [McKinney and Newsom 1962] [McKillip 1996] [McWherter 1961] [Milić et al 2025] [Moser 1961] [Mumford et al 2023] [Murphy et al 2021] [Murphy et al 2021] [Mychalowycz and Panda 1996] [Nagel and Thomas 1965] [Ossyra et al 2025] [Paglino and Beno 1971] [Pallister et al 1992] [Philipsen 2021] [Platou 1968] [Purser and Spear 1947] [Queijo et al 1953] [Raagaard] [Rabbott et al 1966] [Rae and Shojiro 1977] [Report No. 459, The 1933] [Report no. 515, full-scale 1935] [Riddle et al 1981] [Roberts and Tayebi 2011] [Rogers et al 1969] [Rooney et al 1977] [Roth 1991] [Conley and Shirazi] [Saripalli and Kroutil 1985] [Sarker et al 2026] [Satran 1986] [Shanmugam et al 2025] [Sigl and Strawn 1989] [Simmons and Busan 2024] [Simmons et al 2026] [Smith 1959] [Smith 1961] [Smith et al 1990] [Smith et al 2000] [Sopher and Kottapalli 1982] [Squires and Warmbrodt 1983] [Staley et al 1979] [Stange 1959] [Sutton et al 1982] [Symington 1940] [Thapa et al 2026] [Theron et al 2006] [Tomio et al 1993] [Traybar 1970] [Wang] [Wang et al 2022] [Wang et al 2022] [Warner and Rogers 2019] [Weber 1973] [Wright and Aubert 2014] [Yamauchi et al 2012] [Zierten and Rettie 1977] [Öznalbant and Kavsaoglu 2015]

Descent and the vortex ring state

The half of the flight that closes the corridor. Descent, steep approach, autorotation and the vortex ring state. 80 titles name the vortex ring, and 58 of the 80 dated ones are from 2010 or later.

130 records. [Abrego et al 2001] [Abrego et al 2002] [Agbormbai et al 2021] [Ahlin and Brown 2007] [Ahlin and Brown 2009] [Amoozgar and Huang 2026] [Ananthan et al 2002] [Andrien and Talaeizadeh 2022] [Anikin 2002] [Avionics-Part II Systems Steep 1969] [Azuma and Obata 1968] [Azuma et al 1966] [Barakos et al 2026] [Batther et al 2024] [Betzina 2001] [Binet et al 2025] [Brand et al 2007] [Brand et al 2011] [Bucherelli et al 2026] [Burke and Chevalier 1971] [Castles and Gray 1951] [Celi and Ribera 2007] [Chae et al 2022] [Charles 1975] [Chen and Prasad 2005] [Chen and Prasad 2005] [Chenglong et al 2015] [Clymer and Flora 1973] [Cocco et al 2024] [Boyd et al] [Dietz et al 2006] [Dziubinski and Stalewski 2007] [Efimov and Chernigin 2022] [Feng et al 2026] [Fitch et al 1970] [Gao et al 2024] [Gasparovic et al 2016] [Gessow 1950] [Grzegorczyk 2013] [Hahn et al 2025] [He et al 2000] [Heyson 1975] [Hickey 1956] [Hoinville and Renaud 2007] [Ignatkin et al 2018] [Ignatkin et al 2019] [Inoue et al 1997] [Isbono 2026] [Janakiram 1979] [Jeong et al 2024] [Jeong et al 2024] [Jeong et al 2026] [Johnson 1977] [Johnson 2004] [Johnson 2005] [Kamiya et al 2024] [Karpatne et al 2014] [Kesselring 1969] [Kholosi et al 2026] [Klein and Nicks 1998] [Lebacqz and Aiken 1975] [Lebacqz and Aiken 1975] [Lee 1985] [Lee et al 2025] [Lu et al 2023] [Lukianov 2021] [Ma et al 2026] [Macit et al 2025] [Makeev 2026] [Makeev et al 2021] [Makeev et al 2021] [Makeev et al 2022] [Makeev et al 2024] [Marshall et al 2024] [McAlister et al 2000] [McQuaid 2021] [McQuaid et al 2020] [Mihaila and Fuiorea 2025] [Mori et al 2024] [Mori et al 2024] [Mori et al 2025] [Peters and Chen 1982] [Peters and Wasileski 2000] [Pickles et al 2023] [Pickles et al 2023] [Prasad and Basset 2002] [Prasad and Chen 2006] [Qi et al 2025] [Qian et al 2014] [Research on Vortex ring 2015] [Rezaei et al 2024] [Richardson et al 2005] [Richardson et al 2006] [Savas¸ et al 2009] [Savino et al 2025] [Scheglova 2012] [Scott 1969] [Sheng and Zhao 2025] [Sheridan et al 1982] [Shetty and Selig 2011] [Stack 2004] [Stack et al 2005] [Stalewski and Surmacz 2019] [Stalewski and Surmacz 2020] [Suggs 1969] [Sullivan 1973] [Sun et al 2024] [Surmacz and Kowaleczko 2016] [Surmacz et al 2016] [Talaeizadeh et al 2020] [Talaeizadeh et al 2021] [Talbot and Schroers 1978] [Tolentino 2022] [Toropov and Stepanov 2016] [Veismann et al 2023] [Vortex Ring Model Applied 2026] [Vortex Ring Model Applied 2026] [Wang et al 2025] [Washizu et al 1965] [Wen et al 2022] [Wilson and Prazenica 2020] [Wolkovitch and Hoffman 1971] [Xu et al 2024] [Yan et al 2012] [Yeates 1958] [Young 2010] [Yurt et al 2026] [Zalewski 2016] [Zeng et al 2024] [Zhou et al 2026]

The atmosphere and the flight condition

The medium, named rather than assumed. Standard atmosphere tables and models. The density at ten thousand feet that sets the roll authority in How Much Asymmetry That Took is taken from the standard atmosphere, so the literature that defines it belongs in the survey.

Computational methods, surrogates and autonomy

The current toolset. Computational fluid dynamics, surrogate and reduced-order models, machine learning, optimisation and autonomy, where no more specific cluster claims the title.

71 records. [Ailon 2009] [Amer 1965] [Barakos 2014] [Bhandari et al 2023] [Boeing Co Morton Pa Vertol Div 1956] [Boeing Co Morton Pa Vertol Div 1956] [Branson 1994] [Cardullo et al 1985] [Chawla and Vandalsem 1993] [Chen et al 2021] [Chopra 2013] [Costantini 2024] [Curtiss 1965] [Daffer and Rogers 1973] [Davis 1974] [Feldman 1956] [Fernandez et al 2026] [Friedmann et al 2011] [Gopejenko et al 2026] [Grotz 1961] [Hagen et al 1977] [Han et al 2026] [Hays and Schultz 2025] [Hoffert 1964] [Holzhauser et al 1971] [Holzhauser et al 1972] [Jain et al 2010] [Janus et al 1996] [Jou and Metcalfe 1984] [Joy and Simonds 1955] [Kanishk Mahaveer Jain 2025] [Kathiresan et al 2024] [Liu et al 2016] [Liu et al 2025] [Lopez and Biancolini 2025] [Louie 2025] [Luu 2025] [Macdonald] [McCormick 2002] [McIntire and Monson 1970] [McTavish] [Merrick 1982] [Nugroho et al 2022] [O’Donnell et al 1988] [Olson 1967] [Papayanopoulos et al 2019] [Pour Razzaghi et al 2025] [Pour Razzaghi et al 2026] [Prieto et al 2023] [Reber 1981] [Reel and Baltadjiev 2018] [Saito and Kurose 2024] [Saito and Kurose 2025] [Sawata and Dinu 2025] [Sethi and Ahlawat 2022] [Sethi and Ahlawat 2022] [Sethi et al 2021] [Simpson 1969] [Sivaramakrishnan et al 2024] [Truong et al 2023] [Tugnoli et al 2021] [Van Dalsem et al 1990] [Vandalsem et al 1989] [Wang et al 2026] [Yan and Shi 2025] [Yin et al 2023] [Yu and Kwon 2017] [Zafirov 2013] [Zhang et al 2009] [Zhao et al 2025] [Zhou et al 2019]

Rotor and airframe structures, dynamics and reliability

What carries the loads. The structures, dynamics, aeroelasticity, icing and reliability of rotors and VTOL airframes, where no more specific cluster claims the title.

70 records. [Aditiya et al 2022] [Alexander 2026] [Anthony and Habashi 2021] [Artis Jr 1975] [Avera 2019] [Barton 1966] [Bloomfield 1959] [Boeing Vertol Co Philadelphia Pa 1977] [Cardinale 1969] [Cardinale et al 1969] [Conley 1966] [Cotton 1967] [Curtiss 1972] [Dean 1979] [Desjardins and Sankewitsch 1981] [Dixon 1980] [Dooley et al 1978] [Fagan 1967] [Faiz 1973] [Falcone et al 1974] [Fatra et al 2024] [Fernandez et al 2023] [Freidmann 2001] [Friedmann 1990] [Friedmann 2000] [Fries 2001] [Geier and Powell 1961] [Haley and Avery 1964] [Hansen 1983] [Harradine 1977] [Hasbrook 1957] [Heffley and Hardy 1978] [Hopkins and Kunz 1988] [Itt Systems Rome Ny 1987] [Kato and Yamane 1979] [Keith-Lucas 1959] [Kolwey 1999] [LaRue and Rivera 2026] [Levenetz 1973] [Lim et al 2014] [Liu et al 2024] [Lytwyn 1980] [Mayerjak 1978] [Minsk 1970] [Peters 1980] [Pradana et al 2021] [Qi et al 2026] [Rege et al 2015] [Rich 1969] [Santoso and Hariyanto 2022] [Conley 2023] [Schmidt 1963] [Shin and Cesnik 2001] [Sloman 2019] [Sloman and Scott 2018] [Smith and Brooks 1986] [Swingle 1995] [Tauke and Bordignon 2002] [Thompson 1980] [Venkatesan and Friedmann 1987] [Wang et al 2013] [Ward 1970] [Wehnert et al 1977] [Werner 1973] [Wijaya et al 2023] [Wilkie et al 1999] [Wokanubun et al 2023] [Wynn 2026] [Yeates 1964] [Yoon 2025]

Powerplants, turboprops and jet-lift propulsion

What turns the propellers. Turboprop, turboshaft and jet-lift powerplants, lift engines, inlets and exhaust, where no more specific cluster claims the title.

50 records. [A vectored-engine-over-wing propulsive-lift concept 1976] [Anderson and Petersen 1977] [Balke 1970] [Balke 1971] [Banach and Reynolds 1981] [Barrett 1952] [Boschma 1998] [Ciepluch et al 1979] [Christie et al 2016] [Cook 1993] [Darling et al 1970] [Duan 2022] [Fasching and Kutney 1964] [Flemming 1968] [Giurca 2014] [Giurca 2025] [Hewson 1959] [Hiller Aircraft Corp Palo Alto Ca 1965] [Hiller Aircraft Corp Palo Alto Ca 1965] [Hiller Aircraft Corp Palo Alto Ca 1965] [Hiller Aircraft Corp Palo Alto Ca 1965] [Hiller Aircraft Corp Palo Alto Ca 1965] [Hiller Aircraft Corp Palo Alto Ca 1965] [Hirschkron et al 1979] [Hirschkron et al 1979] [Hooker 1956] [Kleckner 1973] [Lepicovsky 2008] [Luidens 1976] [Mock 1951] [Moellmann and O’Connor 1967] [Nishimura 1980] [O’Malley 1959] [Quiet powered-lift propulsion 1979] [Quigley and Franklin 1977] [Rasmussen 1960] [Rice 1955] [Richard 1995] [Saboe 1963] [Scott 2009] [Steinetz et al 1986] [Stewart 1981] [Stoten 1983] [Suydam 1970] [van Holten and Pavel 2010] [Vance 1973] [Vaughn 1970] [Wang and Zhou 2026] [Wynn 1982] [Zucrow 1949]

Other rotorcraft and powered-lift literature

The residual, reported and not hidden. Powered-lift and rotorcraft literature that belongs to no other cluster, including programme overviews and conference proceedings, histories of vertical take-off development, configuration concepts and applications.

146 records. [Alvarez muñoz] [Aláez Gómez] [Army Aviation Board Fort Rucker Al 1964] [AV-95 Sun Devil High-Speed 1996] [Axten et al 2025] [Bardera et al 2020] [Barich 2002] [Barkley and Weaver 1977] [Bartie 2021] [Bauer 1963] [Berlin et al 2025] [Bertelsen 2018] [Bi et al 1989] [Binkley 1986] [Boeing Co Morton Pa Vertol Div 1961] [Boeing Co Morton Pa Vertol Div 1961] [Boeing Co Morton Pa Vertol Div 1961] [Boeing Co Morton Pa Vertol Div 1965] [Boeing Vertol Co Philadelphia Pa 1980] [Bonassar and Lucas 1980] [Bright 1966] [Brogan et al 1961] [Burks 1989] [Campbell 1976] [Carlson 2014] [Chana 2002] [Chen 1981] [Cheney 1969] [Corgiat et al 1993] [Cornes 2019] [Duraisamy et al 2024] [Durbin et al 2014] [Ellis et al 1976] [Emerson et al 2023] [Englar 1987] [Englar and Bushnell 2006] [Englar et al 1986] [Euan Hooper 1975] [Filippone 2006] [Flaig 1977] [Flater 1993] [Forge et al 1990] [Foulke 1965] [Fradenburgh 1961] [Freeman and Aboelezz 2026] [Gamon 1988] [Garren et al 1970] [Gessow 1993] [Goldberg 2023] [Gomez Ariza] [Goto and Miwa 2017] [Gowanlock 2025] [Grady and Lindenbaum 2000] [Grina 1975] [Ground tests of piasecki 1958] [Hafer and Sachs 1982] [Harned and Head 1965] [Hartley et al 1965] [Head 2025] [Hellyar 1970] [Hellyar 1971] [Hirschberg 2023] [Howze 1969] [Idachaba 2014] [Idachaba 2016] [Janetzko et al 2026] [Johnson 1980] [Karimatun Nisa’ et al 2026] [Kidwell and Wray 1964] [Klemin 1940] [Komerath et al 1985] [Laatsch 2003] [LaBiche 2003] [Lan 1974] [Lightfoot 1968] [Loh and Jacob 2014] [Loth and Funk 1987] [Love 1993] [Ludi 1966] [Boctor et al 1978] [Madden 1967] [McSwain et al 2017] [McVeigh and McHugh 1982] [Mearns 2025] [Melton and Hall 1968] [Moller 1998] [Moore 2015] [Multi-Rotors A Revolution In 2015] [Nagata and Buss 1969] [Nicholson and lowry 1966] [Pan et al 2025] [Parlier 1983] [Patkar et al 2013] [Patterson et al 1968] [Petrolo et al 2014] [Pines 2014] [Pogorzelski and Cable 2001] [Pridgen 2013] [Roberts 1978] [Roberts 1989] [Roberts and Imlay 1992] [Romero and Sartorius 2013] [Saj et al 2023] [Salkind 1973] [Sarames 1967] [Sayuti et al 2022] [Schaefer 2016] [Schrage and McKeithan 1989] [Schroers and Antoniou 1966] [Schwaiger and Wills 2016] [Schwoerer 1978] [Scott 1991] [Seckel 1964] [Serrano 2018] [Severinghaus and Kaniarz 2015] [Shefrin and Hill 1974] [Sisák and Škultéty 2020] [Stanzione 2025] [Stanzione 2026] [Stanzione and Schrage 2023] [Stanzione and Schrage 2024] [Sunada et al 2003] [Suppes and Suppes 2026] [Takita and Kashitani 2016] [Taylor 1958] [Tung and DuWaldt 1970] [Turkmen and Altug 2020] [Uehara et al 2019] [Unsworth and Sutton 1984] [Utley et al 1972] [Vanderborght 2015] [Virasak 2022] [Virasak 2021] [VTOL - 1968 1969] [VTOL Booster 1961] [Wang et al 2019] [Wardwell and Sandlin 1988] [Wardwell et al 1986] [Wax and Tocci 1966] [Westcott et al 2023] [Whitfield and Blackburn 1965] [Willard 1968] [Williams et al 1976] [Yang and Wang 2017] [Yoeli 2003] [Yukita et al 2024]

Where the Framing Breaks Down

It assumes a stall angle. The 15 degree figure used throughout is an assumption, and every corridor and descent figure scales with it directly. A thick wing with leading edge devices stalls later, and the fraction of the conversion spent stalled moves with it.

It treats the slipstream as uniform. Momentum theory gives an average. A real slipstream is non-uniform and differently deflected across the span, and the immersed wing does not see one dynamic pressure. Kirby notes that the simple resolution of velocities is the one obtained with counterrotating propellers, whose slipstream carries no rotation, so the X-18’s contra-rotating propellers are the case it describes best and the swirl of a single-rotation propeller is a lesser error here.

It uses a single representative contraction factor. The 0.85 is a judgement, and the immersed fraction ranges from 47 to 67 percent across defensible choices, a wide band on the article’s central quantity.

It treats the final flight as an aerodynamic event. In the encyclopaedia entry it was a propeller pitch control failure and in the inventory an engine failure. The aerodynamics explain why the consequence was severe and do not explain why the failure occurred, and no public account of the fault exists among the sources cited here.

The Source Base

The survey rests on 7,772 research records assembled from Crossref, the NASA Technical Reports Server and the Defense Technical Information Center, of which 1,561 are report primaries, being 20.1 percent, by the identifier rule set out under The Definition of Primary. 7,513 of the records carry a year, with a median of 2013.

Unlike the two preceding articles, this subject has a real technical literature. The tilt-wing was studied intensively by the National Advisory Committee for Aeronautics and its successor, and the configuration’s design considerations, wind tunnel behaviour, slipstream interference, and handling qualities are all documented in primary sources.

What is scarce is documentation of this aircraft. No report in the Technical Reports Server of the National Aeronautics and Space Administration carries the designation in its title, and no X-18 report appears among the Defense Technical Information Center records registered with Crossref. The aircraft’s own engineering record is the Hiller report series in the Lindenbaum collection, which is on paper only and contains no catalogued report of flight results. The closest published primary documents are Schade’s ground-effect measurements on an X-18 model, which cite full-scale X-18 tests, in NACA 1960, Conference on V/Stol Aircraft a Co, and the Air Force history. So the pattern is the inverse of the X-16 and X-17 articles, where the question had a literature and the vehicle did not. Here the configuration has a literature and the individual airframe does not, which is a milder version of the same difficulty.

One retrospective paper on the aircraft itself is on record. Nichols 1990 is a conference paper of the American Institute of Aeronautics and Astronautics on the lessons learned from the Hiller X-18. Its text is not drawn on here, so the dimensions, dates and flight record above rest on the inventory, the encyclopaedia entry and the Air Force history.

Every dimension and weight is from secondary compilation, and the one weight an official source states independently, the Air Force history’s sixteen and a half tons, agrees with it. The sources disagree on three points, the first flight date of 20 or 24 November 1959, whether the last flight ended with an engine failure or a propeller pitch control problem, and whether the aircraft’s scrapping is documented.

The Shape of the Reference Base

Of the 7,513 dated research records, 4,510 predate 2019 and 3,003 do not. The distribution runs 317 documents from before 1960, 1,351 from the 1960s and 1970s, 1,189 from the 1980s and 1990s, 1,653 from 2000 to 2018, and 3,003 from 2019 onward. The contemporary share is large because the configuration actually returned, so surveying the present state of it is surveying a live engineering field rather than an epilogue.

The single most apposite document in the article is the measurement of the descent capability of two-propeller tilt-wing configurations in Hassell and Kirby 1966, which is the X-18’s exact arrangement addressing the X-18’s exact difficulty.

The Definition of Primary

Primacy is a property of the document, and this survey derives it from the identifier. A record is a report primary when it is a NASA Technical Reports Server url or carries a digital object identifier under the 10.21236 prefix, which Crossref registers for Defense Technical Information Center reports. 1,053 of the records are reports-server urls, and the NACA and NASA tilt-wing, deflected-slipstream, descent and V/STOL handling-qualities reports on which the period argument rests are reached that way, so the rule counts them.

The rule does not reach the journal and conference literature of the American Institute of Aeronautics and Astronautics, abbreviated AIAA. 2,544 of the records carry its 10.2514 prefix, among them the retrospective paper on the X-18 and design and flight test papers written by the people who built the vehicles they describe. The Hiller company reports in the Lindenbaum collection are on paper only and are not in the survey at all. 20.1 percent is therefore a lower bound on how much of this survey is first-hand.

Thin Subjects

Eight subjects that this article’s derivations depend on have thin literatures. Each count below is the number of research records in this survey whose title carries at least one of the listed terms, with a hyphen read as a space.

Subject	Title terms counted	Records
the immersed fraction of the span	immersed, immersion	4
the contraction of the slipstream	contraction, contracting, contracted	4
the local angle of attack of a blown wing	local angle of attack, local incidence, effective angle of attack	0
cross-shafting and interconnected drives	cross shaft, interconnect	6
asymmetric and differential thrust	asymmetric thrust, thrust asymmetry, asymmetric power, differential thrust, differential propeller thrust	7
the hover figure of merit	figure of merit	1
the helical tip Mach number	tip mach, helical tip	8
density altitude and roll authority	density altitude	1

The keystone has no literature under its own name. The four titles that carry the word immersed or immersion concern immersion and invariance control, immersed-boundary numerical methods and immersion cooling, and none concerns a wing in a slipstream. The immersed fraction is studied as the slipstream and as propeller and wing interaction in the clusters above, and the article’s own figure of 57 percent stands on the geometry and the contraction factor shown in How Much of the Wing Is Immersed.

The contraction of the slipstream appears in four titles, Conway 1998, Iwasaki 1959, Sparks and Miley 1983 and Theodorsen 1944, which is why the contraction range of 0.707 to 1.0 is taken from momentum theory and the 0.85 is reported as a judgement. No title names the local angle of attack of a blown wing, so the relation in The Relation That Makes the Configuration Work stands on the resolution of velocities shown there and on Kirby’s period treatment of it.

Cross-shafting has five titles of its own, two of them on the landing reliability of V/STOL aircraft, Willis 1980 and Willis 1981, and the remaining title that carries interconnection concerns an electrical grid. The figure of merit appears in one title, on meshing rotors, so the check of 0.674 rests on momentum theory and the published weight and power, and density altitude appears in one, Strand and Ennis 2012, so the 26 percent loss of roll authority at ten thousand feet rests on the standard atmosphere. The helical tip Mach number is a noise subject in these titles, with seven of its eight records on noise or aural detection.

What the Survey Admits

Every research title has been read for relevance, and a record is admitted only when a person reading its title finds it on this article’s subject, which is a tilted wing in a propeller slipstream and everything the article dimensions to decide whether a conversion exists, from the actuator disc and the propeller at low advance ratio, through the stall of the wing and the devices that delay it, the corridor, descent and the vortex ring state, hover control and handling qualities and engine failure, to the ground environment and the electric successors that inherited the configuration. The tilt-rotor, deflected-slipstream, jet-lift and helicopter literatures are admitted where they treat a quantity the article computes.

Many words this subject depends on also name something else, and a record that shares only such a word is excluded. Propeller also names the screw of a ship, the runner of a hydro turbine, a current meter, a ventilating fan and a microcontroller, and controllable pitch is very largely a marine subject. Slipstream also names a form of fiction, a mode of program execution and a side stream in a coal gasification plant. Outwash is also a glacial landform and its aquifers, hot gas ingestion is also the ingestion of hot gas into the rim cavity of a turbine, and ground effect machines are air-cushion vehicles. Transition is also the laminar-turbulent transition of a boundary layer, stol is a chair in Danish and a round table in Croatian, the osprey is also a bird and Hiller is also the name of composers, artists and chemists. Standard atmosphere also names radio refraction, room acoustics, the greenhouse effect and the conditioning of test specimens. High angle of attack also names missile aerodynamics, vortex ring also names structures in a methane diffusion flame, disc loading also names the loading of the jaw joint, and certification also names the qualification of welding personnel, nursing credentials and halal certification. The wind tunnel also tests cars, trucks and buildings, and the correlation of tunnel with flight for fixed-wing aircraft outside powered lift is a different problem. Correction, erratum, corrigendum and retraction notices, figure, table and supplementary-file records and journal front matter are excluded as well, because a survey counts research works and those are parts of works or editorial events rather than works. Reviews of books, dictionary and other reference entries of two pages or fewer, news and other notices, and a second deposit of a document already in the survey are not admitted either, while an authored encyclopedia article of more than two pages and a textbook chapter are research works and stay.

Some records of doubtful relevance are kept. Wing-in-ground-effect craft and their theory, laboratory hover rigs, and actuator disc theory developed for wind turbines are kept for the ground effect and momentum theory they share with this article. Fixed-wing climb and descent, continuous descent in air traffic management, the fuel flow of an airliner in descent, a vortex ring generated by a microramp and a vortex-ring method for a flapping wing rotor are kept for the descent section, research issues in the transition to free flight and a state transition graph for trajectory optimisation for the transition section, and turbine vane cooling with one engine inoperative for the engine-out section. Aviation certification outside powered lift, machine learning prediction of aerodynamics outside powered lift, the communications and cybersecurity of urban air mobility, the jet-flap interaction noise of airliners, the management of the V-22 programme and propeller titles whose medium the title does not state are kept as the neighbouring field of a section of this article. A reader may weigh each accordingly.

Because every title has been read, the off-topic share that remains is a matter of reading judgement. The largest class removed is the marine propeller, because the propeller of a ship shares the vocabulary of pitch, thrust, wake and contra-rotation with the propeller of an aircraft.

Epistemic State

Historical fact. The X-18 was built from a Chase YC-122C fuselage with Allison T40 turboprops taken from the XFY-1 and XFV-1 programmes and a Westinghouse J34 in the tail for pitch control. Proposed in 1954, designated in October 1957 and unveiled on 8 December 1958 under Air Force funding. First flight 20 November 1959 in the inventory and 24 November 1959 in the Air Force history, twenty flights, last flight July 1961, fastest 253 miles an hour and highest 35,300 feet. The last flight ended in one account with a propeller pitch control problem during an attempted conversion at ten thousand feet and a spin from which the crew recovered, and in the other with an engine failure. No source records a hover or a completed conversion. The programme was cancelled in January 1964 and the aircraft was cut up for scrap in one account and is generally assumed to have been scrapped in the other. The engines were not cross-linked. The XC-142 followed with four propellers and engines linked so that one could turn all four.

Engineering analysis, reproducible from the stated inputs. The local angle of attack relation and its consequence that the immersed panel sits at exactly zero incidence at zero forward speed. The maximum tolerable tilt from 90 degrees at ten metres per second to 30 at sixty. The conversion corridor, which exists at every speed with a margin between 12.6 and 38.0 degrees of tilt. The descent rates that close it, from 284 feet per minute at the slow end to 1,349 at the fast end, which are upper bounds because the relation holds the slipstream fixed while a real descent reduces power. The induced velocity falling from 40.05 to 24.71 metres per second across the conversion while slipstream dynamic pressure rises from 2,210 to 5,772 pascals. The advance ratio range of 0 to 1.12 and the helical tip Mach number of 0.844. The aspect ratio of 4.364 against a quoted 4.36. The immersed span fraction of 66.7 percent uncontracted, 47.1 fully contracted, and about 57 at a representative factor. The stalled fraction of the conversion at 83.3 percent. The induced velocity of 40.05 metres per second, disc loading of 82.1 pounds per square foot, and slipstream dynamic pressure equivalent to 117 knots. The immersed lift fractions. The hover power of 7,883 ideal horsepower and the implied figure of merit of 0.674. The engine-out rolling moment of 268 kilonewton metres and the aileron fractions. The tolerable thrust asymmetry figures and the 26 percent authority loss at ten thousand feet. The pitch jet crossover at 59 knots.

Inference, and clearly labelled. That the outer wing being stalled is the configuration’s defining problem is an inference from the geometry and a stall angle, supported by the period literature on tilt-wing stall but not derived from X-18 flight data. That a corridor exists at every speed rests on a crude lift model in which the immersed panel is given a linear lift curve to its stall and the outer panel a constant stalled lift coefficient of 0.6. The shape of the result is robust and the individual margins are not. That the XC-142’s four propellers and cross-shafting were responses to the X-18’s specific failures is an inference from the design changes and their evident purpose.

Assumed values. No source states the following, and each is an assumption of this article. The stall angle of 15 degrees, the contraction factor of 0.85, the part-developed slipstream of 1.5 times the induced velocity at the wing, the immersed panel’s lift curve and the stalled outer-panel lift coefficient of 0.6, the propeller’s lateral station at a quarter span, the aileron effectiveness of 0.08 per radian at 20 degrees of deflection, the pitch jet’s arm of 8.64 metres and deflected thrust of a thousand pounds force, the elevator effectiveness of 1.2 per radian at 20 degrees of deflection, and the propeller speed of 1,100 revolutions per minute.

What the record does not settle. Whether the last flight ended with a propeller pitch control failure or an engine failure, and what caused it. Whether the scrapping of the aircraft is documented. Whether the X-18 would have converted successfully had it not been grounded. What immersed fraction the designers believed they had. Whether the aircraft was ever close to a hover.

The pitch jet crossover rests on an assumed elevator effectiveness. The crossover of 59 knots uses an elevator effectiveness coefficient of about 1.2 per radian, the correct order for an aircraft of this class. The crossover speed varies as the inverse square root of that coefficient, so a value of 0.02 per radian would put it at 454 knots, which is implausible for such an aircraft.

What the contemporary survey changes. The contemporary survey is organised by field, and its central observation revises the premise of the article and does not merely extend it. The keystone was dissolved rather than solved. This article spends its length computing an immersed fraction whose value was set by the X-18 having exactly two propellers, and nothing about a tilt-wing requires two. Each propeller needed a turboprop and a gearbox of its own, and the X-18 was built around two surplus turboprops. Electric propulsion breaks that tie between propeller and engine, and a distributed arrangement immerses essentially the whole span. The quantity this article is built on goes to unity, and the problem is deleted without being answered.

Information postdating the editorial date. The contemporary literature section is written from current knowledge.

Out of Scope

The XC-142 programme deserves its own treatment and gets a paragraph here. The V-22 and the tilt-rotor line generally are named as the surviving alternative and not analysed. The detailed aerodynamics of swirl in a propeller slipstream are cited rather than derived. No attempt is made to reconstruct the X-18’s flight envelope. The vortex ring state, which is the related descent hazard for a lifting rotor and which a tilt-wing can also meet, is not treated.

Conclusion

The X-18 asked whether a wing could be tilted through ninety degrees and flown all the way. It never found out, and the arithmetic of its geometry explains why.

Two sixteen-foot propellers on a forty-eight-foot wing immerse a little over half of it. The immersed part flies at an equivalent 117 knots while the aircraft stands still. The rest of the wing is stalled for five sixths of the conversion, and no wing design fixes that, because the wing is pointed away from the air by construction.

That would have been survivable with margin elsewhere. There was none. The ailerons supply under one percent of the rolling moment an engine failure produces in hover, the engines were not cross-linked so an engine failure was available to produce it, and a few percent of thrust asymmetry exhausts the roll control during conversion. When a propeller pitch control fault, or in the other account an engine failure, duly appeared, the aircraft departed.

The configuration was not wrong and this aeroplane was under-equipped for it, and the corridor calculation demonstrates it. A usable tilt margin exists at every speed, between twelve and thirty-eight degrees, so the tilt-wing is a sound idea that this particular aeroplane could not exploit. The XC-142 answered with twice the propellers along the wing and engines linked so that one could turn them all, in effect a list of the X-18’s deficiencies written as a specification. The X-18’s contribution was to establish, expensively and at the edge of a fatal accident, what the minimum version of the idea could not do.