X-Planes: McDonnell Douglas X-36

The McDonnell Douglas X-36 had no vertical tail and no horizontal tail, and every account of it begins there. The more interesting number is 28 percent. The aircraft was a subscale model, which the National Aeronautics and Space Administration’s programme account and its inventory of American X-vehicles both describe as a 28 percent scale representation of a fighter. It flew with nobody aboard, from a ground station whose pilot watched through a camera in its nose. Its test pilot’s report, Walker 1997, gives a takeoff gross weight of 1,245 pounds, and its published specification a height of 0.946 metres. This is the thirty-seventh article 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, the X-17, the X-18, the X-19, the X-20, the X-21, the X-22, the X-23, the X-24, the X-25, the X-26, the X-27, the X-28, the X-29, the X-30, the X-31, the X-32, the X-33, the X-34, and the X-35.

A scale factor is not a detail of the hardware. It decides what the experiment is able to measure, and here the decision has a sharp edge, because the choice that makes the aeroplane’s motions representative is the same choice that makes it harder to fly than the aircraft it represents.

The Research Question

The Question Everybody Asks

Can a fighter fly without a vertical tail? The tail costs weight, drag and radar return, and removing it would buy all three back. Nobody had done it because the vertical tail keeps the aeroplane pointing where it is going, the property known as directional stability. A fuselage in sideslip generates a yawing moment that turns it further into the sideslip, and the fin exists to overcome that. Take the fin away and the aircraft is directionally unstable, which means that a disturbance grows instead of decaying.

By 1996 that question had an obvious answer in principle. A digital flight control system can stabilise an unstable aeroplane, as the X-29 had already shown for a different instability, and the effectors to do it in yaw were available in the form of split ailerons and a vectoring nozzle. So the question was not whether it could be done. It was whether it could be done well enough to be worth doing, at the angles of attack where a fighter earns its living.

The Question This Article Asks Instead

The X-36 answered that question at 28 percent scale, and a 28 percent aeroplane is not a small aeroplane. It is a different aeroplane, obeying different combinations of the dimensionless groups that govern flight.

So this article asks what the scale factor bought and what it cost. Three quantities matter, they cannot all be matched at once, and the choice among them defines the experiment. The answer turns out to have an edge that the programme’s own accounts do not mention.

A preview. Matching the right quantity makes the model’s motions faithful and simultaneously makes them 1.89 times faster in real time than the full-scale aircraft’s. The delay in a video link and the reaction time of a human being do not get faster to match. The demonstration was therefore harder than the thing it demonstrated, by a factor this article computes, and that makes the result stronger and not weaker.

The previous article found the opposite. The X-35’s most famous sortie was flown in the easiest available ordering, at a weight the production aircraft would never see. This one was flown against a handicap the full-scale aircraft would never carry. Two consecutive demonstrators, opposite directions, and both differences are arithmetic, not opinion.

Programme Origin

Who Wanted the Answer

The programme was a partnership between McDonnell Douglas, whose Phantom Works built the aircraft, and the National Aeronautics and Space Administration, which supplied the flight research infrastructure at Dryden. The cost of the tail explains why the question was asked and why it was asked then. A vertical tail is a large flat surface standing proud of the fuselage, which makes it the worst thing to have on an aircraft designed to be difficult to see on radar, and Walker 1997, the programme’s test pilot, wrote that stealth had recently become an important design consideration.

Two aircraft were built, and the programme account records that their fabrication began in 1994.

Research on who wanted the answer, and why, is gathered in The Contemporary Literature in the cluster on the X-36, X-29 and X-31 demonstrators and the cluster on radar signature and low observability.

Why a Model Rather Than an Aeroplane

The alternative to a subscale demonstrator was a piloted one, and the arithmetic of that comparison favoured an X-36 over an X-36-sized fighter. A piloted aircraft needs a cockpit, an escape system, a life support system, redundant everything, and a structure certified to carry a person. None of that is cheap and none of it is relevant to the question being asked, which is whether a control law can hold a tailless configuration pointing straight. Walker 1997 records that cost was the major driver of the subscale decision, because cost correlates strongly with size.

The trade is that a model cannot answer every question, and the rest of this article is about which ones it cannot.

For the research on this question, see the clusters on similitude, dynamic scaling and subscale flight testing and on unmanned aircraft, ground stations and remote piloting, under The Contemporary Literature.

Sizing From First Principles

Three Dimensionless Numbers and Only One Can Be Matched

The design of the experiment follows from three lines of algebra. An aeroplane’s behaviour is governed by the ratio of inertia to gravity, the Froude number, by the ratio of inertia to viscosity, the Reynolds number, and by the ratio of speed to the speed of sound. The general requirement that a model reproduce its original is similitude. Writing $V$ for speed, $L$ for a length, $g$ for gravity, $\nu$ for kinematic viscosity and $a$ for the speed of sound,

\[\mathrm{Fr} = \frac{V^{2}}{gL} \qquad \mathrm{Re} = \frac{VL}{\nu} \qquad \mathrm{M} = \frac{V}{a}\]

A model in the same air as the full-scale aircraft has only one free variable, its speed, so it can match one of the three and must accept whatever the other two become. Writing $\lambda$ for the length ratio and $r_V$ for the velocity ratio,

\[\frac{\mathrm{Fr}_m}{\mathrm{Fr}_f} = \frac{r_V^{2}}{\lambda} \qquad \frac{\mathrm{Re}_m}{\mathrm{Re}_f} = r_V \lambda \qquad \frac{\mathrm{M}_m}{\mathrm{M}_f} = r_V\]

At $\lambda = 0.28$ the three choices are these.

Matched	Velocity ratio	Froude ratio	Mach ratio	Reynolds ratio
Froude	0.5292	1.000	0.5292	0.1482
Mach	1.000	3.571	1.000	0.2800
Reynolds	3.571	45.55	3.571	1.000

Read the last row first, because it disposes of an option people reach for. Matching Reynolds number would require the model to fly at 3.571 times the full-scale aircraft’s speed, and its Froude number would then be wrong by a factor of 45.55. A model flown that way does not fall the way an aeroplane falls. It is useless for flight dynamics and the row exists only to be dismissed.

Matching Mach number, as a wind tunnel usually does, leaves the Froude number wrong by 3.571. Such a model is fine for measuring pressures and useless for measuring motion, because the model’s weight and its aerodynamic forces are then in the wrong proportion.

So a free-flight model that is meant to move like an aeroplane must match Froude, and every other ratio follows from that decision.

The Contemporary Literature takes this subject up mainly in its cluster on similitude, dynamic scaling and subscale flight testing.

What Froude Matching Does to Everything Else

Setting the Froude ratio to one gives $r_V = \sqrt{\lambda}$, and the rest follows by dimensions alone.

\[r_V = r_t = \sqrt{\lambda} = \sqrt{0.28} = 0.5292\] \[r_\omega = \frac{1}{\sqrt{\lambda}} = 1.8898 \qquad r_{\dot\omega} = \frac{1}{\lambda} = 3.571\] \[r_m = \lambda^{3} \qquad r_I = \lambda^{5} = 0.001721 \qquad r_{\mathrm{Re}} = \lambda^{3/2} = 0.1482\]

Deriving the mass and inertia exponents is better than quoting them. Holding density common makes mass go as volume, the cube of length. A moment is a force times a length and a force at matched Froude number goes as mass, so

\[r_F = \lambda^{3} \qquad r_M = r_F \lambda = \lambda^{4} \qquad r_I = r_m \lambda^{2} = \lambda^{5}\]

and the angular acceleration ratio is the moment ratio over the inertia ratio,

\[r_{\dot\omega} = \frac{\lambda^{4}}{\lambda^{5}} = \frac{1}{\lambda} = 3.571\]

Each of those is an identity in the scale factor and holds at every value of it, not at 0.28 alone, because each exponent follows from dimensions and not from the particular aircraft.

Three of them deserve reading slowly.

Time runs at 0.5292 of full scale, which is to say every motion of the model happens 1.8898 times faster in real seconds than the corresponding motion of the aeroplane it represents.

Angular accelerations are 3.571 times larger. Not the angles and not the rates, but the accelerations, because moments scale as the fourth power of length and inertias as the fifth.

Reynolds number is 0.1482 of full scale, a penalty of 6.749. The penalty is the price of the choice, and it falls on the separated flow at high angle of attack that the experiment exists to study. How much it costs is a separate question from how large the ratio is, and the comparison section below computes both Reynolds numbers so that the factor does not have to speak for itself.

The Check That Costs Nothing

If the aeroplane is a Froude-scaled model then its weight fixes the aeroplane it stands for, because mass scales as the cube of length. Inverting,

\[W_f = \frac{W_m}{\lambda^{3}} = \frac{1{,}245}{0.28^{3}} = 56{,}715 \ \text{lb}\]

and its operating empty weight likewise gives 49,335 pounds, while its dimensions give a full-scale length of 19.82 metres and a span of 11.34 metres. The 1,270 pound maximum weight of the published specification would give 57,853 pounds instead, 2.008 percent more, which changes nothing that follows.

Those numbers describe a real class of aeroplane. Sixty-five feet long, thirty-seven feet in span and fifty-seven thousand pounds is the size of a heavy twin-engined fighter, a plausible class for the theoretical advanced fighter that the programme account says the aircraft represented. The consistency is not a proof, because the designers chose the model’s weight and could have chosen it to be consistent. It is a check that would have failed loudly had the aircraft not been dynamically scaled at all, and it did not fail.

The speeds convert the same way. Walker 1997 gives a dynamic pressure limit of 200 pounds per square foot, equal to 243 knots at sea level, and a 112 knot approach speed, and dividing each by the velocity ratio gives the full-scale equivalent,

\[V_f = \frac{V_m}{\sqrt{\lambda}} = \frac{243}{0.5292} = 459.2 \ \text{kt} \qquad V_f = \frac{112}{0.5292} = 211.6 \ \text{kt}\]

for model speed $V_m$ and full-scale speed $V_f$. A 212 knot approach is fast for a fighter.

The same cluster on similitude, dynamic scaling and subscale flight testing holds the research records behind this check.

The Handicap the Accounts Do Not Mention

Here is the edge on the scale factor, and it follows from the time ratio in one step.

The model’s motions run 1.8898 times faster than the full-scale aircraft’s. A delay in the command and video path does not run faster. It is a fixed number of milliseconds imposed by cameras, encoders, radio links and displays, the same whatever the aeroplane is doing. So its significance, measured against the dynamics it is trying to control, is multiplied by

\[\frac{1}{\sqrt{\lambda}} = 1.8898\]

Delay in the link	Worth this much at full scale
100 ms	189.0 ms
150 ms	283.5 ms
200 ms	378.0 ms
250 ms	472.5 ms

And the pilot is subject to the same multiplication. A human visual reaction time of roughly 200 milliseconds, set by the human and not by the aeroplane, counts for 378.0 milliseconds of full-scale response.

No latency figure for this aircraft’s link has been published, so the article does not claim one. What it claims is the structure. Whatever the delay was, it was worth 1.8898 times as much as the same delay in a piloted full-scale aircraft, and the ground pilot was flying an aeroplane whose divergences developed nearly twice as quickly as the ones the programme was trying to learn about.

This is why the result is stronger than it looks. A demonstration flown under a handicap that the operational article would not carry proves more than a demonstration flown without it, and the previous article in this series is the case where that ran the other way.

The clusters on time delay, latency and delay compensation and on handling qualities, pilot-induced oscillation and the pilot model, in The Contemporary Literature, gather the research on this handicap.

What the Missing Fin Costs

A fuselage in sideslip is destabilising and the reason is older than aeronautics. A slender body at an angle to the flow carries a moment that turns it further from alignment, and a fin behind the centre of gravity produces an opposing moment that grows with the same sideslip. The sum is the directional stability derivative. Writing $N$ for yawing moment, $q$ for dynamic pressure, $S$ for wing area, $b$ for span and $\beta$ for sideslip,

\[N = q S b \, C_{n\beta} \, \beta\]

With a fin, $C_{n\beta}$ is positive and the aircraft weathercocks. Without one it is negative and the aircraft diverges. The rest of this section follows from that sign change.

The magnitude can be derived, not assumed, and it should be. Slender-body theory gives the destabilising moment of a body from its volume alone, through the apparent-mass difference $k_2 - k_1$, which for a fineness ratio above about eight is near 0.9. The result is older than aeronautical stability and control as a discipline, having been set out by Max Munk in 1924 in a study of the aerodynamic forces on airship hulls, and the correction that makes it usable at real angles of attack, where the potential result must be supplemented by cross-flow drag, was published in Allen and Perkins 1951. Both are the primary sources for the relation this article displays. The derivative per radian is

\[C_{n\beta}^{\text{body}} = -\left(k_2 - k_1\right) \frac{2 \, \mathrm{Vol}}{S b}\]

The fuselage volume is not published either, so it is bracketed.

Fuselage volume	$C_{n\beta}$ per radian	Per degree
0.60 m³	0.1091	0.001905
0.80 m³	0.1455	0.002540
1.00 m³	0.1819	0.003175

The derived value at the middle of the bracket is 0.002540 per degree, which is 2.117 times the assumed value of 0.0012, a figure typical of a tailless configuration. That matters, and in a welcome direction. The assumed figure is the optimistic one, so the aircraft was more unstable than the rows computed from it suggest, and every conclusion that survives the optimistic case survives the derived one more comfortably. Both are carried through the tables that follow, and neither replaces the other.

The wing area is not published, so it is inverted from what is. The approach speed of 112 knots, a sea-level dynamic pressure of 2,033 pascals, and a landing weight of about 1,140 pounds or 5,070 newtons, taken as the operating empty weight with 35 percent of the usable fuel remaining, fix the product of area and lift coefficient, and at an approach coefficient of 0.8 that gives

\[S = \frac{W}{q C_L} = \frac{5{,}070}{2{,}033 \times 0.8} = 3.117 \ \text{m}^{2}\]

and the geometry follows from it,

\[\mathrm{AR} = \frac{b^{2}}{S} = \frac{3.175^{2}}{3.117} = 3.235 \qquad \bar{c} = \frac{S}{b} = 0.982 \ \text{m}\] \[\frac{W}{S} = \frac{1{,}245 \times 0.4536 \times 9.807}{3.117} = 1{,}777 \ \text{N/m}^{2}\]

The wing loading is therefore 1,777 newtons per square metre at takeoff gross weight, which at 28 percent scale corresponds to 6,346 at full size, since wing loading scales as the length ratio.

An aspect ratio near three is right for this planform class, and that agreement checks that the inversion is not nonsense. Across coefficients from 0.7 to 1.0 the aspect ratio runs from 2.830 to 4.043, so the conclusion does not depend on the choice.

How Fast the Divergence Grows

Neglecting damping, the yaw equation for a directionally unstable aircraft is

\[I_{zz} \ddot{\beta} = \lvert C_{n\beta} \rvert q S b \, \beta \qquad \Rightarrow \qquad \ddot{\beta} = \sigma^{2} \beta\]

which grows instead of oscillating. The yaw inertia is unpublished, so it is estimated from a radius of gyration taken as a fraction of length and reported across a bracket.

There are two answers to how long a doubling takes and they differ by a factor that is constant. The flight dynamics convention measures the growing eigen-solution,

\[t_{2} = \frac{\ln 2}{\sigma}\]

while a disturbance released from rest follows a hyperbolic cosine rather than an exponential, because it starts with no yaw rate at all, and needs

\[t_{2}^{\text{rest}} = \frac{\operatorname{arccosh} 2}{\sigma} = 1.900 \, t_{2}\]

The ratio is arccosh 2 over ln 2, it is 1.900, and it depends on nothing. The growth rate cancels from it, so it holds at every growth rate, and integrating the equation of motion under each of the two initial conditions reproduces both times without evaluating an exponent.

Radius of gyration	Modal, 112 kt	From rest, 112 kt	Modal, 243 kt	From rest, 243 kt
0.30 of length	0.737 s	1.401 s	0.340 s	0.646 s
0.35 of length	0.860 s	1.634 s	0.396 s	0.753 s
0.40 of length	0.983 s	1.868 s	0.453 s	0.861 s

Those use the assumed derivative. The derived one makes them shorter. At a radius of gyration of 0.35 the growth rate rises from 0.806 to 1.172 per second at approach and from 1.748 to 2.543 at maximum speed, so the modal doubling times fall to 0.591 seconds and 0.273 seconds,

\[t_{2} = \frac{\ln 2}{1.172} = 0.591 \ \text{s} \qquad t_{2} = \frac{\ln 2}{2.543} = 0.273 \ \text{s}\]

by the modal relation above.

Every entry is under two seconds and most are under one. That is the number the control system had to beat and the number the ground pilot’s link delay had to be small against.

The scaling makes the comparison worse in the obvious direction. The full-scale aircraft’s doubling times would be 1.8898 times longer than these, so the model diverged nearly twice as fast as the aeroplane it stood for, while the delay in reacting to it stayed the same. Both halves of the handicap point the same way.

Work on the divergence is listed in The Contemporary Literature in the cluster on slender bodies, fuselages and apparent mass, the cluster on directional stability and lateral-directional dynamics and the cluster on flight dynamics, stability derivatives and unstable modes.

The Delay Budget in Milliseconds

A fixed delay is amplified by 1.8898. Control theory turns that amplification into a budget, and the budget is small enough to force a conclusion about the architecture.

A loop that stabilises an unstable pole must cross over above it, because below the pole the loop gain is not yet doing anything. Writing $\omega_c$ for the crossover frequency and taking a multiple $\kappa$ of the growth rate,

\[\omega_c = \kappa \sigma\]

A pure delay contributes phase lag in direct proportion to frequency, and that proportionality makes delay dangerous and not merely annoying,

\[\Delta\phi = \omega \tau\]

so at crossover the delay consumes $\omega_c \tau$ of phase. Setting that equal to the phase margin a designer insists on gives the entire delay budget of the loop,

\[\tau_{\max} = \frac{\phi_m}{\omega_c} = \frac{\phi_m}{\kappa \sigma}\]

And $\sigma$ scales as one over the square root of the scale factor, so the budget scales as its square root. The amplification of 1.8898 reappears here in the units a control engineer would use.

At a phase margin of 45 degrees and a crossover three times the growth rate,

Condition	Growth rate	Crossover	Budget, model	Budget, full scale
112 kt, assumed derivative	0.806 /s	2.42 rad/s	324.9 ms	614.0 ms
243 kt, assumed derivative	1.748 /s	5.24 rad/s	149.8 ms	283.0 ms
243 kt, derived derivative	2.543 /s	7.63 rad/s	102.9 ms	194.5 ms

Read the fourth column, the model budget, against what a video link and a human cost. A camera, an encoder, a radio path and a display are not free, and a human visual reaction time alone is around 200 milliseconds. The entire budget at maximum speed is between 103 and 150 milliseconds.

So the ground pilot cannot have been inside the stabilisation loop, and the architecture follows from the arithmetic rather than from a preference. The inner loop that held this aeroplane pointing straight had to be onboard, closing around sensors and effectors with no radio in the path, while the pilot on the ground flew the aircraft through that loop. The aircraft was built that way, with a digital fly-by-wire system stabilising it in the programme account and the pilot flying every takeoff, test manoeuvre and landing in Walker 1997, and this article did not have to be told.

The budget also explains why the full-scale comparison matters. The same aeroplane at full size would have had between 195 and 283 milliseconds, which is roughly a human reaction time. A full-scale tailless aircraft could conceivably be flown by a pilot whose hands were in the loop. The 28 percent model could not, and that difference is an artefact of the scale alone. The configuration plays no part in it.

Research behind the delay budget sits in the clusters on stability margins and robust control and on time delay, latency and delay compensation.

Why a Nozzle Complements a Fin

This is the cleanest result in the article and it comes from noticing which terms carry dynamic pressure. A fin’s yawing moment is $q S b$ times a coefficient. The destabilising fuselage moment is $q S b$ times another coefficient. Both carry $q$, so their ratio does not change with speed, which is why a fin sized for one flight condition is sized for all of them.

A vectored nozzle carries no $q$ at all. Its moment is thrust times the sine of a deflection times a moment arm,

\[N_{\text{vec}} = T \ell \sin\delta = 3{,}114 \times 2.220 \times \sin 20^{\circ} = 2{,}364 \ \text{N m}\]

so the ratio of what the nozzle can do to what the aerodynamics demand goes as one over dynamic pressure. The nozzle is strongest exactly where the fin is weakest.

Speed	Aerodynamic moment at 10 degrees of sideslip	Nozzle authority ratio
60 kt	69.3 N·m	34.12
112 kt	241.4 N·m	9.792
160 kt	492.7 N·m	4.798
243 kt	1,137 N·m	2.080

Inverting for the speed at which the nozzle alone can no longer hold ten degrees of sideslip gives 350.5 knots, because the nozzle authority ratio $R$ falls as the square of speed from its value $R_{243}$ at 243 knots,

\[R(V) = R_{243} \left(\frac{243}{V}\right)^{2} = 1 \qquad \Rightarrow \qquad V_{\text{vec}} = 243 \sqrt{R_{243}} = 243 \sqrt{2.080} = 350.5 \ \text{kt}\]

which is above anything this aircraft ever flew, and well above the 206 knots it reached. So across its entire envelope the nozzle alone was sufficient.

The Unsettled Contribution of the Split Ailerons

A split aileron opens above and below to add drag on one wing, and the yawing moment is that drag increment acting at its spanwise centroid,

\[N_{\text{dr}} = q \, S_p \, \Delta C_D \, y\]

where $S_p$ is the panel area and $y$ the arm, here 1.111 metres at 35 percent of span.

The drag increment decides the answer, and it is not published, so it is bracketed across the range a split surface can produce, from lightly cracked to fully opened.

Drag increment	Moment at 243 kt as a share of the nozzle	Speed at which it equals the nozzle
0.10	21.0 percent	529.9 kt
0.30	63.1 percent	305.9 kt
0.60	126.2 percent	216.3 kt

This limits what can honestly be said. At the bottom of the bracket the nozzle dominates everywhere and the split ailerons are margin. At the top they overtake the nozzle inside the cleared envelope, at 216.3 knots, and become the primary yaw effector at high speed. The drag rudder’s moment rises as the square of speed while the nozzle’s is constant, so a split-aileron moment that is a share $s$ of the nozzle’s at 243 knots equals it at

\[V_{\times} = \frac{243}{\sqrt{s}} = \frac{243}{\sqrt{1.262}} = 216.3 \ \text{kt}\]

which lies inside the 243 knot limit and a little above the 206 knots the aircraft is recorded as reaching.

The bracket spans a factor of six and the conclusion flips inside it, so the correct statement is that it is not determined by public information. What survives is the structural claim, which does not depend on the increment at all. The nozzle’s authority is flat with speed and the drag rudder’s rises as the square of it, so whatever the crossover speed is, the nozzle owns the low-speed end and the split ailerons own the high-speed end. The configuration was built around this complementarity, which holds everywhere in the bracket.

The complementarity is the general lesson and it survives the particular numbers. A tailless aircraft needs an effector whose authority does not vanish with dynamic pressure, because the condition it most fears is high angle of attack at low speed, where every aerodynamic surface is working in separated flow and a fin would have stalled even if it were there.

The Contemporary Literature covers yaw effectors in its cluster on thrust vectoring, drag rudders and yaw effectors.

The Vehicle

Two aircraft were built. The configuration is a wing with a canard ahead of it, no vertical surface of any kind, split ailerons on the wing trailing edge that open into upper and lower halves to make drag on one side, and a thrust-vectoring nozzle. The weights, thrust and speeds below are those of Walker 1997, the dimensions and ceiling those of the published specification, and the fuel fraction and the thrust to weight ratio are the usable fuel and the thrust each divided by the takeoff gross weight,

\[\frac{162}{1{,}245} = 0.1301 \qquad \frac{700}{1{,}245} = 0.5622\]

The programme account gives rounder figures, about 1,250 pounds fully fuelled, 19 feet long and three feet high, with about 700 pounds of thrust. The Parsch directory also gives 1,245 pounds, and the specification’s 1,270 pounds maximum, 1,090 pounds empty, 180 pounds of fuel and 110 knot approach appear in none of these three sources.

Quantity	Value
Length	18 ft 2.5 in, 5.550 m, including the pitot boom
Span	10 ft 5 in, 3.175 m
Height	3 ft 1.25 in, 0.946 m
Operating empty weight	1,083 lb
Takeoff gross weight	1,245 lb
Usable fuel	162 lb, a fraction of 0.1301
Engine	Williams F112 turbofan, 700 lbf
Thrust to weight	0.5622
Approach speed	112 kt equivalent airspeed
Maximum speed	160 kt test limit at first, 243 kt at the 200 lb/ft² dynamic pressure limit
Ceiling	20,500 ft
Load factor	5 g

The fuel fraction of 0.1301 is the figure that most constrains the programme, because it is what limits a sortie to well under an hour, 35 to 45 minutes for a typical research flight in the programme account, and therefore what makes the flight count the resource rather than the flight hours.

Records on the engine fall in the cluster on turbofan performance, thrust and fuel consumption.

Dependent Systems

The Effectors

Walker 1997 lists the control effectors as canards, split ailerons, leading and trailing edge flaps and thrust vectoring, and the ailerons move asymmetrically for roll. Yaw comes from two places and neither of them is a rudder. The split ailerons open asymmetrically to put drag on one wing, producing a yawing moment that grows with dynamic pressure like a fin’s, and the nozzle vectors to produce one that does not.

An aircraft with more effectors than axes has to decide how to share a demand among them, the control allocation problem. That problem is why this configuration needs a digital flight control system and does not merely benefit from one.

For the research on the effectors, see the cluster on control allocation and redundant effectors and the cluster on thrust vectoring, drag rudders and yaw effectors in The Contemporary Literature.

The Ground Station

The pilot sat in a ground-based cockpit with a conventional fighter head-up display and a moving map, as the programme account describes the ground station, looking through a camera that the account places in the aircraft’s nose and that Walker 1997 places on its canopy. The arrangement keeps the latency argument above from being academic. Every element of that chain, the camera, the encoding, the radio link, the display and the human, contributes delay, and the aircraft’s dynamics were running at nearly twice full-scale speed while it did.

The cluster on unmanned aircraft, ground stations and remote piloting and the cluster on time delay, latency and delay compensation hold the research on this arrangement.

The Flight Test Record

Flights and Hours

Item	Value
First flight	17 May 1997
Final flight of the first programme	12 November 1997
Research flights	31
Flight time	15 hours 38 minutes, which is 938 minutes
Mean sortie	30.26 minutes
Campaign length	25 weeks

Thirty-one flights in twenty-five weeks is one flight every 5.6 days, which for a research aeroplane with no pilot aboard and a mean sortie of half an hour is a brisk rate and not a leisurely one.

The fuel load and the mean sortie together imply a fuel flow, useful as a check on the engine class but not as a datum. A mean sortie of 1,815 seconds burning 162 pounds gives

\[\dot{w}_f = \frac{162}{1815/3600} = 321.2 \ \text{lb/h} \qquad \Rightarrow \qquad \frac{\dot{w}_f}{T} = 0.459\]

A mean thrust specific fuel consumption of 0.459 pounds per pound force per hour, referred to maximum thrust, sits below the 0.683 of the Williams F107 from which the F112 was developed, as it should, because the engine did not run at maximum thrust for a whole sortie. It is a weak check and it passes, and the result is reported here as weak without dressing it up. The mean sortie sits below the 35 to 45 minutes the programme account gives for a typical research flight, so the mean includes shorter flights and the full fuel load was not burned on every one. Taking a typical 40 minute flight on the same 162 pounds instead gives

\[\dot{w}_f = \frac{162}{40/60} = 243 \ \text{lb/h} \qquad \Rightarrow \qquad \frac{\dot{w}_f}{T} = 0.347\]

which is lower again, so the check gives a lower bound on the consumption rather than measuring it.

Research on the X-36 and its two closest relatives is collected in the cluster on the X-36, X-29 and X-31 demonstrators.

The Often Omitted Second Programme

The aircraft flew twice more in December 1998, carrying the Air Force Research Laboratory’s Reconfigurable Control for Tailless Fighter Aircraft software, a neural-network scheme intended to adapt the control law in flight to damage or to an effector failure.

That was a different experiment from the first, and the more ambitious of the two. The 1997 campaign asked whether a fixed control law could fly a tailless aircraft. The 1998 flights asked whether a control law could work out for itself how to fly one whose effectors had changed underneath it.

For the later work on reconfigurable control, see the cluster on adaptive, neural and reconfigurable flight control, and for the aircraft itself the cluster on the X-36, X-29 and X-31 demonstrators.

Comparison With Ground Prediction

What the Model Could Check and What It Could Not

This section sorts the questions by the dimensionless group that governs each.

Question	Governed by	Could the model answer it?
Does the control law stabilise the divergence?	Froude, matched	Yes, and this is the experiment
Are the handling qualities acceptable?	Froude, matched	Yes, with the latency caveat
Does control allocation work with redundant effectors?	Froude, matched	Yes
Where does the flow separate at high angle of attack?	Reynolds, wrong by 6.749	Partly, and cautiously
When does a leading-edge vortex burst?	Reynolds, wrong by 6.749	Partly
What happens transonically?	Mach, wrong by 1.8898	No
What is the radar cross section?	Neither, wavelength governs	No

The middle rows are the honest difficulty and they deserve more than a shrug. The Reynolds penalty is a factor of 6.749, which sounds fatal until both numbers are computed. The Reynolds number needs the viscosity, which here comes from Sutherland’s law,

\[\mu = \mu_0 \left(\frac{T}{T_0}\right)^{3/2} \frac{T_0 + 110.4}{T + 110.4} = 1.7894 \times 10^{-5} \ \text{Pa s}\] \[\mathrm{Re} = \frac{\rho V \bar{c}}{\mu} = \frac{1.225 \times 125.0 \times 0.982}{1.7894 \times 10^{-5}} = 8.40 \times 10^{6}\]

so the model runs at 8.40 million on the mean chord at maximum speed and 3.872 million on approach, while the full-scale aircraft at the corresponding condition would run at

\[\mathrm{Re}_f = \frac{\mathrm{Re}_m}{\lambda^{3/2}} = \frac{8.40 \times 10^{6}}{0.1482} = 56.70 \times 10^{6}\]

Both of those are deep in the fully turbulent regime. The penalty does not move the model into a different flow regime for attached flow, and that counts as a genuine and slightly surprising mitigation. It does still matter where it matters most, because separation onset and vortex burst position are Reynolds sensitive well beyond transition, and those are the phenomena a high angle of attack experiment is about. So the correct statement is neither that the penalty is fatal nor that it is negligible, but that it is confined to the questions the article has just listed.

The Mach number tells the same story more simply. The model’s maximum speed limit is about Mach 0.367 at sea level. Nothing compressible happens there, and nothing compressible could be learned.

The Contemporary Literature collects the work on this check mainly in two clusters, one on Reynolds number effects and low Reynolds number aerodynamics and one on the viscosity of air and Sutherland’s law.

Turn Rate as a Second Witness

The published load factor limit is enough to compute the aircraft’s turn performance, and doing so produces the scaling result a second time from an entirely different quantity. A level turn at load factor $n$ has

\[\dot\psi = \frac{g\sqrt{n^{2} - 1}}{V} \qquad R = \frac{V^{2}}{g\sqrt{n^{2} - 1}}\]

Speed	Turn rate	Radius	Rate expressed at full scale
112 kt	47.77 deg/s	69 m	25.28 deg/s
160 kt	33.44 deg/s	141 m	17.70 deg/s
243 kt	22.02 deg/s	325 m	11.65 deg/s

The last column is the point. Turn rate goes as one over speed, speed scales as the square root of the scale factor, so turn rate scales as one over that square root, which is 1.8898 again. The model turns visibly faster than the aeroplane it represents, in exactly the ratio that its divergences develop faster and its delay budget shrinks. Three different quantities, one factor, and the article did not have to assume it for any of them.

The corner speed, where the load factor limit meets the lift limit, follows from the same figures,

\[V^{*} = \sqrt{\frac{2 n W}{\rho S C_{L\max}}} = 213.7 \ \text{kt}\]

which sits below the 243 knot maximum, so the aircraft could reach the most demanding point of its manoeuvre envelope.

Turn performance is surveyed in the cluster on turn performance, agility and manoeuvre.

The Envelope That Was Opened Rather Than Reached

Walker 1997 records a test envelope held at first to 160 knots against a dynamic pressure limit equivalent to 243 knots, and the published specification records the maximum speed limit moving from the one to the other during the programme, which is the ordinary signature of envelope expansion. The conditions actually reached were lower in speed and high in angle of attack. The programme account gives a speed envelope reaching 206 knots, an altitude of 20,200 feet and a maximum angle of attack of 40 degrees, and the inventory of American X-vehicles records 360 degree rolls at angles of attack up to 15 degrees and rapid turning and rolling manoeuvres at up to 35 degrees. The two accounts disagree on the size of the programme. The inventory lists 25 flights ending on 24 September 1997, a fastest flight of 204 miles per hour and a highest flight of 20,500 feet, while the programme account gives 31 flights ending on 12 November 1997 with a flight-time total, and this article follows the programme account as the more detailed of the two. What the published record gives at those angles of attack is thin. Walker 1997 reports Level 1 handling qualities for the phase that opened the envelope to 35 degrees and a normalised roll-time plot reaching a little above 30 degrees, but no time history is public, and since that is what the tailless argument turns on, the article notes the gap rather than filling it.

What the Data Changed

What the Programme Settled

It established that a tailless configuration of this class can be flown, and it did so under a handicap. The control law held an aeroplane whose divergence doubled in well under a second, through a command and video path with a delay whose effective size was nearly twice what the same delay would have been on a full-scale aircraft.

It established that the effector set works, meaning that split ailerons and a vectoring nozzle between them can replace a fin across the flight conditions tested, and Walker 1997 reports agility demonstrations flown with thrust vectoring both on and off.

And the 1998 flights established that a neural-network reconfigurable control law can compensate in flight for a failed effector, which at the time was a much less comfortable proposition than it now sounds, and the programme account reports it compensating for each simulated control-surface failure.

What It Fed Into

The configuration did not become an aeroplane and the control ideas did. No X-36 derivative was built. Tailless flying-wing planforms did reach production in the unmanned world, as in the RQ-170 Sentinel, and control allocation among redundant effectors, which this aircraft needed because it had no rudder, became a general subject in flight control instead of a speciality.

What It Failed to Influence

No manned tailless fighter followed it into service, although crewed tailless prototypes such as the Chengdu J-36 were flying by the end of 2024. The X-36 did not fail. The question it answered was not the binding one. A production fighter’s tail is a compromise among signature, control, weight and the cost of certifying an aircraft that cannot be flown without its computers. The X-36 addressed exactly one of those four.

The Contemporary Literature

Cluster	Records
Adaptive, neural and reconfigurable flight control	433
Handling qualities, pilot-induced oscillation and the pilot model	355
Unmanned aircraft, ground stations and remote piloting	306
Flight test method, instrumentation and system identification	250
High angle of attack, vortex flow and departure	227
Tailless aircraft and flying wings	214
Flight control law design and fly-by-wire systems	204
Reynolds number effects and low Reynolds number aerodynamics	202
Similitude, dynamic scaling and subscale flight testing	155
Wing and configuration aerodynamics	155
Slender bodies, fuselages and apparent mass	144
Thrust vectoring, drag rudders and yaw effectors	140
Directional stability and lateral-directional dynamics	137
Time delay, latency and delay compensation	135
Stability margins and robust control	105
Control allocation and redundant effectors	90
Flight dynamics, stability derivatives and unstable modes	83
Turbofan performance, thrust and fuel consumption	80
Computational aerodynamics, surrogate models and uncertainty	77
Radar signature and low observability	66
Turn performance, agility and manoeuvre	51
Flight simulation and simulators	29
Mass properties and moments of inertia	23
The X-36, X-29 and X-31 demonstrators	21
The viscosity of air and Sutherland’s law	18
Fighter and technology demonstrator programmes	12
Total	3,712

This section surveys the current literature on the subjects the aircraft touched as well as on the aircraft itself. This subject is unusual in that its centre of gravity moved instead of growing. Tailless fighters remained a research topic. Subscale dynamically scaled flight testing became a routine method. The cluster table above gives the shape of the survey, the review subsections that follow read the literature against the aircraft, and the clusters themselves close the section.

The Method Outlived the Aeroplane

In 1997 a 28 percent remotely piloted research aeroplane was an expensive and unusual thing to build, at about 21 million dollars for two aircraft and their flight testing in the programme account. It is now ordinary. Cheap airframes, cheap autopilots and cheap radio links turned the dynamically scaled free-flight model from a specialist technique into a routine one, and much of the modern literature applies the scaling relations set out above. Sobron et al 2021 review the current practice of subscale flight testing and its practical difficulties, Raju Kulkarni et al 2019 estimate how closely a subscale aircraft reproduces its original, Wang et al 2020 set out an analytical scaling method and its scale effects, and Hakim and Choukri 2023 and Ananda et al 2017 design small aircraft to Froude similarity from the start.

The Froude choice is still the right one and for the same reason, so the modern work inherits the same Reynolds penalty and the same time compression the X-36 carried. What has changed is that the latency is now measured and compensated rather than assumed, because the people building these vehicles are also building their links, as in the real-time latency compensation of Ostermann et al 2024 for the remote control of an unmanned aircraft and the study of latency in drone control by Singh 2025.

The research records on this subject are gathered below in the cluster on similitude, dynamic scaling and subscale flight testing and the cluster on unmanned aircraft, ground stations and remote piloting.

The Reynolds Penalty Has a Modern Name and a Large Literature

The article’s Reynolds penalty was a caveat in 1997 and is a field now. What the period called scale effects the present calls low Reynolds number aerodynamics, and the small unmanned aircraft is now one of its principal applications, as in Aditya and Srinivas 2019 on low Reynolds number flyers, Somashekar and Immanuel Selwyn Raj 2018 on an aerofoil for a micro aerial vehicle and Feng et al 2017 on a solar unmanned aircraft.

That literature is directly about the middle rows of this article’s comparison table. Laminar separation bubbles, transition location and their sensitivity to Reynolds number decide whether a subscale model’s separation onset resembles its original’s, and they are reviewed in Benny Thompson and Gunasekaran 2021 and modelled in Catalano et al 2024.

The X-36 sits at the top of that regime rather than inside it. At 8.40 million on the mean chord it is far above the millions-and-below range where the low Reynolds literature concentrates, and the placement helps, because it means the penalty this article computes is real but the model is not in the difficult part of the curve.

The cluster below on Reynolds number effects and low Reynolds number aerodynamics contains these records.

Tailless Control Became an Unmanned Subject

The configuration this aircraft tested became a subject of unmanned aircraft design. The tailless and flying-wing planform recurs throughout the literature on low-observable unmanned combat aircraft, as in Sepulveda Palacios and Smith 2019 on the effect of mission requirements on low-observable configurations, Cummings et al 2018 on the aerodynamics of an unmanned combat aircraft configuration and Li et al 2017 on the distribution of effectors on a flying wing optimised for low observability. The control problem the X-36 explored is the control problem those vehicles have, and yaw control without a fin is studied directly in Shearwood et al 2020.

Below, the cluster on tailless aircraft and flying wings and the cluster on radar signature and low observability collect the records on this subject.

Control Allocation Became General

An aircraft with more effectors than axes was a speciality in 1997 and is now a standard problem. The literature moved from ad hoc mixing and daisy chaining to constrained optimisation, set out in Enns 1998, Durham 1999 and Bodson 2000, with the tailless case in Buffington and Buffington 1997 and Matamoros and de Visser 2018. Multirotor and tilt-rotor vehicles, which have nothing but redundant effectors, now carry much of the subject, as in Vepa 2021.

The records for this subsection are in the cluster on control allocation and redundant effectors.

The Reynolds Penalty Is Now Quantified

The contemporary work does something the period could not. It computes what the penalty costs. High-fidelity simulation can run the same configuration at different Reynolds numbers and compare, as Yamazaki et al 2018 do for the indirect Reynolds number effect and Wang et al 2021 do for a transport aircraft, with the high angle of attack case in Rist 1996 and a double-delta wing measured in Verhaagen 1999. That turns the argument in this article’s comparison section from a caveat into a measurement.

The research records on this subject are gathered below in the cluster on Reynolds number effects and low Reynolds number aerodynamics and the cluster on computational aerodynamics, surrogate models and uncertainty.

Latency Spread to Every Remote Vehicle

The delay argument in this article was a niche concern for one aircraft and is now a general one. Every remotely operated vehicle has it. The aircraft-side evidence is older, in Smith and Sarrafian 1986 on time delay and flying qualities and King 1993 on display latency. The teleoperation literature has grown around it since, with predictive displays in Brudnak 2016, explicit delay compensation in Abidi et al 2016, and the measured effect of communication latency on operators in Storms and Tilbury 2015 and Black et al 2024.

Records on latency appear below in the cluster on time delay, latency and delay compensation and the cluster on handling qualities, pilot-induced oscillation and the pilot model.

Adaptive, neural and reconfigurable flight control

Adaptive, neural, fault-tolerant and reconfigurable flight control, including dynamic inversion and its incremental form, and the reinforcement learning controllers that now extend them.

433 records. [122 Neural networks applied to optimal flight control 1993] [Abouheaf et al 2020] [Accommodation of failures in the F-16 aircraft using adaptive control 1991] [Acquatella et al 2017] [Adams and Banda 1993] [Adams and Banda 1993] [Agarwal et al 2021] [Agarwal 1988] [Ahmadi Dastgerdi et al 2022] [Ahmed-Zaid et al 1990] [Alag and Kaufman 1974] [Andrianantara et al 2025] [Andropov et al 2017] [Annaswamy 2005] [Applications of Fuzzy Logic and Neural Network Technology to Flight Control System Design: an Overview 2004] [Atmaca and Van Kampen 2025] [Atmaca et al 2025] [Bacon and Ostroff 2000] [Bajodah et al 2018] [Balakrishnan 1972] [Balas et al 1992] [Banerjee 2019] [Bao et al 2025] [Berens and Biezad 1988] [Berra et al 2017] [Beyer et al 2018] [Binz and Moormann 2020] [Binz et al 2019] [Bodson and Groszkiewicz 1997] [Bodson and Pohlchuck 1996] [Bodson and Pohlchuck 1998] [Bodson et al 1997] [Bodur et al 2025] [Bomben et al 2006] [Boskovic and Mehra 1999] [Boskovic and Mehra 2000] [Boskovic and Mehra 2001] [Boskovic and Mehra 2002] [Bosworth 2008] [Bosworth 2010] [Bouaiss et al 2023] [Bradshaw and Huber 1982] [Brandin 1990] [Braun et al 2025] [Brinker and Wise 1996] [Buffington and Sparks 1998] [Buffington et al 1998] [Bukov 1989] [Burken et al 1999] [Burken 2005] [Burken and Larson 2009] [Burken et al 2006] [Burken et al 2010] [Buschbacher and Bosworth 2006] [Cakiroglu et al 2018] [Calise 2001] [Calise et al 1997] [Calise et al 1998] [Calise et al 2000] [Cao and Lu 2024] [Cao et al 2026] [Caverly et al 2016] [Chaikalis et al 2020] [Chakravarty and Mahanta 2015] [Chang et al 2022] [Chao and Yingmin 2015] [Chen et al 2017] [Chen et al 2020] [Chen et al 2024] [Cheng et al 2019] [Cheng et al 2020] [Cho and Cho 1995] [Chowdhury and Keshmiri 2024] [Chu et al 2001] [Chun-Liang Lin et al 2004] [Clarke and Hwang 2020] [Cotting and Burken 2001] [Crespo et al 2010] [Cunningham et al 2011] [d’Apolito and Sulzbachner 2021] [Dally and Van Kampen 2022] [Daskiran et al 2017] [Deng et al 2024] [Dethomas and Goel 1982] [Di Francesco and Mattei 2016] [Diget et al 2022] [Digirolamo 1992] [Dillon and Speyer 1996] [Dillon and Speyer 2000] [Dong xinmin et al 2003] [Duggan and Bhandari 2021] [Eberhardt and Ward 1999] [Ehlers and Smyth 1968] [Emami et al 2022] [Enns and Si 2002] [Enns et al 1994] [Ermeydan and Kiyak 2017] [Eva Wu et al 2000] [Fan et al 2026] [Fault Tolerant Control for Aircraft Flaperon Faults Using Nonlinear Dynamic Inversion 2025] [Fei et al 2023] [Feng et al 2022] [Fernandes and Cardoso-Ribeiro 2025] [Ferrari and Stengel 2004] [Gadient and Weltz 2004] [Gaither et al 1989] [Gavra and van Kampen 2024] [Gavra and Van Kampen 2024] [Ghiglino et al 2015] [Ghorawat et al 2015] [Goman and Kolesnikov 1998] [Gong et al 2019] [Gou et al 2023] [Gregory 1998] [Gregory 2001] [Grondman et al 2018] [Guan and Shi 2019] [Guo et al 2026] [Guoqiang and Jinkun 2015] [Gursoy and Yavrucuk 2015] [Gäßler and Robens 2025] [Gümüşboğa and İftar 2021] [Ha 1990] [Hageman et al 2003] [Hajiyevt and Caliskan 2001] [Hamza and Samir 2020] [Han and Zhang 2019] [Han et al 2023] [Han et al 2024] [Harris et al 2019] [He et al 2020] [He Mingyi et al 1998] [Henkenjohann et al 2023] [Henkenjohann et al 2024] [Hess and Wells 2002] [Hess and Wells 2003] [Hess and McLean 2000] [Heyer et al 2020] [Ho and Zhou 2023] [Hofsäβ and Holzapfel 2024] [Homola et al 2025] [Horowitz 1964] [Horowitz 1965] [Huang et al 1992] [Huang et al 1999] [Huzmezan 1998] [Huzmezan and Maciejowski 1999] [Ignatyev 2018] [Imran et al 2021] [Inanc et al 2025] [Jafari et al 2017] [Jayaraman and Ghosh 2021] [Jayaraman et al 2021] [Jeong et al 2024] [Ji et al 2021] [Ji et al 2022] [Jianmin Wang et al 2016] [Johnson 1986] [Juliana et al 2004] [Kamel et al 2015] [Kamel et al 2016] [Kanai et al 1990] [Kaneba et al 2022] [Kaufman and Berry 1976] [Kim 1995] [Kim et al 2003] [Kiyak and Ermeydan 2018] [Klein et al 2016] [Ko et al 2019] [Kocurek et al 1997] [Konatala et al 2021] [Konatala et al 2024] [Koopman and Zammit-Mangion 2024] [Kumar et al 2018] [Kumtepe et al 2022] [L’Afflitto et al 2018] [Lamperski 2022] [Lang et al 2024] [Larson et al 2009] [Lee and Kim 2001] [Lee and Van Kampen 2021] [Lee et al 2020] [Lee et al 2021] [Lee et al 2021] [Leonard and Arnett 1980] [Li and van Kampen 2024] [Li and Wang 2017] [Li et al 1994] [Li et al 2018] [Li et al 2021] [Li Yan et al 2000] [Linear and neural network feedback for flight control decoupling 1996] [Littleboy et al 1997] [Liu and Jiang 2024] [Liu and Zhu 2021] [Liu et al 2016] [Liu et al 2018] [Liu et al 2019] [Liu et al 2022] [Liu et al 2022] [Liu et al 2024] [Lu et al 2016] [Lu et al 2024] [Lubing et al 2017] [Lungu and Lungu 2016] [Luo et al 2019] [Luo et al 2022] [Ly and Ho 1986] [Ma and Peng 2021] [Ma et al 2019] [Ma et al 2023] [Ma et al 2025] [Mahulkar 2010] [Mallavalli and Fekih 2018] [Mallavalli and Fekih 2019] [Mallery and Neebe 1965] [Malloy and Chang 1998] [Mansur and Lanteigne 2020] [Matthews and Yi 2019] [Matthews and Yi 2021] [Maybeck and Stevens 1990] [Maybeck and Stevens 1991] [Mayhew and Gleason 1988] [McFarland and D’Souza 1994] [McLean 1994] [McLean and Aslam-Mir 1992] [McLean and Aslam-Mir 1994] [McLean and Aslam-Mir 1994] [Miller 2011] [Miller 2011] [Model Following Reconfigurable Flight Control System Design Using Direct Adaptive Scheme 2003] [Moerder et al 1989] [Mohammadi et al 2025] [Mokhtar and El-Badawy 2023] [Monaco et al 1997] [Montgomery and Caglayan 1976] [Montgomery and Price 1976] [Morse and Ossman 1989] [Morse and Ossman 1990] [Morton et al 1996] [Moses et al 1965] [Mueller et al 2026] [Mulgund and Stengel 1993] [Mulgund and Stengel 1995] [Nadell et al 2023] [Napolitano et al 1997] [Napolitano et al 2001] [Niewoehner and Carter 2001] [Nihtilä 1989] [Nikiforuk and Gupta 1977] [Nikiforuk et al 1979] [Nivison and Khargonekar 2017] [Nivison and Khargonekar 2017] [Nivison and Khargonekar 2018] [Nonlinear adaptive flight control using neural networks 1998] [Nonlinear Discrete-Time Reconfigurable Flight Control Systems Using Neural Networks 2004] [Oktay and Kose 2021] [Oliva 2001] [Oppenheimer and Doman 2004] [Optimum neural network control 1993] [Orozco et al 2026] [Ortiz-Torres et al 2018] [Ostroff and Bacon 2002] [Ouyang and Lin 2017] [Ouyang et al 2022] [Padhi and Balakrishnan 2003] [Palkin and Zenchenko 2025] [Pan et al 2016] [Pan et al 2017] [Panish et al 2023] [Papageorgiou and Glover 2002] [Park et al 2024] [Park et al 2025] [Park et al 2025] [Patel and Smith 1998] [Pfeifle and Fichter 2022] [PI control of a tailless fighter aircraft with dynamic inversion and neural networks 1999] [Pollack et al 2026] [Qian et al 2022] [Qian et al 2024] [Ransquin and Chatelain 2021] [Reconfigurable Flight Control Law Using Adaptive Neural Networks and Backstepping Technique 2003] [Reiner et al 1994] [Reiner et al 1995] [Reiner et al 1996] [Ren and Wang 2026] [Richter et al 2024] [Ronfle-Nadaud 2009] [Rubertus 1983] [Rysdyk and Calise 1998] [Rysdyk and Calise 1999] [Sabra et al 2025] [Sadeghi 1984] [Safwat et al 2018] [Saini et al 2024] [Salahudden et al 2024] [Sancı and Öke Günel 2024] [Saraf et al 1998] [Sayyed et al 2025] [Schaff and Prazenica 2025] [Schierman et al 2015] [Schnetter et al 2015] [Schuck 1959] [Schuck 1960] [Schumacher 1999] [Semmelhack and Hoppe 1967] [Seo and Kim 2019] [Seres et al 2023] [Sever et al 2025] [Shankar et al 2004] [Shao et al 2019] [Shen and Xu 2021] [Shen et al 2023] [Shin and Kim 2004] [Shin et al 2003] [Shore and Bodson 2004] [Shtessel et al 1999] [Shukla et al 2025] [Singh and Steinberg 1996] [Singh et al 1999] [Siwakosit and Hess 2001] [Siwakosit et al 2000] [Smit and Craig 1998] [Smit et al 2022] [Smith 1994] [Smith 1998] [Smith and Berry 2000] [Smith and Patel 1995] [Smith et al 1998] [Snell 1992] [Snell and Stout 1994] [Snell and Stout 1998] [Snell et al 1998] [Soloway and Haley 2000] [Song 2008] [Song and Huang 2026] [Stable multiple model adaptive flight control for accommodation of a large class of control effector failures 1999] [Stein et al 1975] [Stein et al 1977] [Steinberg 1999] [Steinberg 2001] [Steinberg and DiGirolamo 1991] [Steinberg and Page 1998] [Steinberg and Page 1999] [Steinleitner et al 2022] [Stewart and Shuck 1990] [Stolarik 2007] [Stougie et al 2024] [Sun and van Kampen 2021] [Sun et al 2020] [Taherinezhad and Ramirez-Serrano 2023] [Tamaskani et al 2026] [Tang and Lai 2020] [Tang et al 2024] [Tantrairatn and Veres 2015] [Terrell and Zein-Sabatto 2017] [Tian and Zhou 2021] [Toloei and Ghaderi 2026] [Torres et al 2022] [Totah and Totah 1997] [Tranchero and Latorre 2001] [Unal 2021] [Urnes et al 2001] [Urnes et al 1990] [Urnes et al 1993] [van Overeem et al 2023] [Vankadari et al 2018] [Vieira dos Santos and Van Kampen 2025] [Wang and Wang 2020] [Wang and Zhang 2021] [Wang et al 2016] [Wang et al 2016] [Wang et al 2017] [Wang et al 2018] [Wang et al 2018] [Wang et al 2018] [Wang et al 2018] [Wang et al 2019] [Wang et al 2020] [Wang et al 2026] [Ward et al 1998] [Weinstein et al 1986] [Wells 2002] [Wen and Tian 2020] [Werbos 2001] [Williams 2004] [Wilson and Riccardi 2022] [Wise 1992] [Wise and Sedwick 1998] [Wu and Zhu 2024] [Xia and Zhang 2019] [Xiao et al 2018] [Xiao et al 2025] [Xie et al 2022] [Xu et al 2017] [Xu et al 2024] [Yan et al 2019] [Yan et al 2025] [Yang and Xiong 2023] [Yang et al 2023] [Yang et al 2026] [Yoo et al 2021] [Yu and Wang 2024] [Yu et al 2017] [Yu et al 2017] [Yu et al 2019] [Yu et al 2019] [Yu et al 2024] [Yuan and Zhou 2024] [Yuksek and Inalhan 2020] [Zha and Li 2025] [Zhang 2026] [Zhang and Ran 2023] [Zhang et al 2016] [Zhang et al 2017] [Zhang et al 2018] [Zhang et al 2019] [Zhang et al 2020] [Zhang et al 2021] [Zhang et al 2023] [Zhang et al 2023] [Zhang et al 2026] [Zhao and Zhu 2016] [Zhao et al 2024] [Zhen and Hao 2020] [Zheng and Horn 2015] [Zheng and Li 2019] [Zhou et al 2019] [Zhou et al 2021] [Zhou et al 2022] [Zou et al 2026] [Zuhri 2025] [Żugaj 2017]

Handling qualities, pilot-induced oscillation and the pilot model

Handling and flying qualities criteria, pilot-induced oscillation and the models of the human pilot, for fixed-wing aircraft, rotorcraft and unmanned aircraft.

Unmanned aircraft, ground stations and remote piloting

Unmanned aircraft and remotely piloted vehicles as flying machines, their design, flight control, ground control stations, operators and the programmes that flew them.

Flight test method, instrumentation and system identification

Flight test method, parameter estimation and system identification from flight and wind tunnel data, and the correlation of the tunnel with flight.

250 records. [Advisory Group for Aerospace Research and Development 1999] [Air Force Flight Test Center Edwards Afb Ca 1974] [Air Force Flight Test Center Edwards Afb Ca 1974] [Air Force Test Pilot School Edwards Afb Ca 1990] [Air Force Test Pilot School Edwards Afb Ca 1990] [Aircraft performance monitoring from flight data 2015] [Aksteter et al 1994] [AlAbsi and Fields 2017] [Alexander 1991] [Alford and Knarr 1999] [AlShabi et al 2024] [American Institute of Aeronautics and Astronautics 1992] [An et al 2025] [Anderson and Vincent 1985] [Araujo-Estrada and Windsor 2019] [Armstrong 1977] [Asher and Hyland 1965] [Bach and McNally 1988] [Badwan and Tutunji 2018] [Balatti et al 2021] [Bayoğlu et al 2016] [Simmons 2023] [Bennett 1984] [Benyamen and Keshmiri 2022] [Benyamen et al 2024] [Bergmann et al 2021] [Beyers 1986] [Beyers and Ericsson 2002] [Billingsley 1976] [Bliss 1980] [Bousson and Paglione 2001] [Brandon and Morelli 2016] [Bronz and Hattenberger 2016] [Buffington et al 1999] [Burner et al 2000] [Burton and Bischoff 1976] [Butler 1976] [Che et al 2021] [Chen and Xiao 2015] [Chen et al 2019] [Cheney 1988] [Clarke and Roskam 1982] [Cosentino 2007] [Cosentino 2008] [Danowsky et al 2017] [Dantsker et al 2019] [Dantsker et al 2020] [Dantsker et al 2023] [de Visser and Pool 2023] [Denton et al 2025] [Dias 2023] [Dogan Kuzey and Yıldırım Dalkıran 2026] [Domino et al 2023] [Donovan and Allison 2017] [Dwyer 1994] [Estlow and Kovacevic 1990] [Eulrich and Rynaski 1980] [Eulrich et al 1978] [Farhadi 2017] [Fegely et al 2016] [Flight Test Programme 1970] [Flight-test evaluation of engine power effects on lift and drag 1985] [Friehmelt 1997] [Fry and Sage 1974] [Fry and Sage 1974] [Fukami et al 2004] [Gandhi et al 2019] [Gao et al 2021] [Ge and Zhan 2024] [Gebert et al 2000] [Geng and Li 2023] [Ghazi 1993] [Ghosh and Raisinghani 2000] [Ghosh and Raisinghani 2002] [Ghosh Roy and Peyada 2016] [Ghosh Roy and Peyada 2017] [Grauer 2015] [Grauer 2016] [Grauer 2020] [Grauer 2021] [Grauer and Boucher 2018] [Grauer and Morelli 2015] [Gres et al 2025] [Gresham et al 2023] [Guenther et al 2026] [Göttlicher et al 2016] [Hale et al 2015] [Hale et al 2017] [Halefom et al 2022] [Hamel and Jategaonkar 1996] [Han et al 2025] [Harris et al 2016] [Herrlinger 1991] [Hoffer et al 2015] [Hofmann et al 2025] [Hosseini et al 2025] [Hull and Roger 1975] [Hutt and East 1985] [Ibuka and Ishiguro 2023] [Iliff 1987] [Iliff and Maine 1983] [Irwanto and Artono 2018] [Ishola et al 2024] [Jaganraj and Velu 2019] [Jain et al 2025] [Jategaonkar et al 1997] [Jones 1995] [Jordan 1974] [Juhasz et al 2020] [Klein 1978] [Klein 1989] [Klein and Murphy 2001] [Knighton 1992] [Kohlman 1977] [Kohlman 1979] [Kokolios 1994] [Korsun and Moung Htang 2023] [Korsun et al 2018] [Kraft 2018] [Kumar and Ghosh 2017] [Kumar and Ghosh 2018] [Kumar and Ghosh 2018] [Kumar and Ghosh 2018] [Kumar and Ghosh 2023] [Kumar and Rao 2004] [Kumar et al 2015] [Lawrence and Mills 2002] [Lebacqz 1974] [Legowo et al 2019] [Lerro et al 2020] [Leshikar et al 2021] [Leung et al 2019] [Li and Gao 2025] [Li et al 2026] [Lichota 2016] [Lichota 2023] [Lichota et al 2016] [Liu et al 2018] [Lu and Van Kampen 2015] [Mamou and Broughton 2023] [Margason and Hoad 1980] [Matt et al 2025] [Maunder 1979] [McCrink and Gregory 2017] [Mehra and Eupta 1975] [Mehra and Tyler 1973] [Metodiev 2024] [Miller 1973] [Moes and Iliff 2002] [Moes et al 2003] [Mohamed et al 2019] [Molusis 1973] [Molusis 1973] [Molusis and Briczinski 1974] [Morelli 2021] [Morelli and Cooper 2015] [Morelli and Klein 1995] [Morelli and DeLoach 2003] [Morris 1964] [Morris 1966] [Moszczynski and Grant 2017] [Moszczynski et al 2019] [Moua et al 2007] [Moua et al 2012] [Mulder 1985] [Murphy et al 2004] [Neves et al 2020] [Neville and Stephens 1993] [Nicola et al 2025] [Nicolosi et al 2015] [Niewald and Parker 2000] [O’Donnell and Mohseni 2018] [Ovcharenko and Poplavsky 2021] [Parameter estimation techniques and 1974] [Park 1977] [Pfifer and Danowsky 2016] [Plaetschke et al 1982] [Pounds and Walker 1980] [Dhayalan et al 2018] [Raisinghani and Adak 1983] [Ratcliff et al 2016] [Rhew and Parker 2017] [Rodzewicz 2024] [Saderla et al 2016] [Saderla et al 2017] [Saraswathi 2000] [Schaff and Prazenica 2024] [Schumacher 1952] [Schwanz and Grimes 1980] [Sharpe and Hansman 2024] [Shi et al 2023] [Simmons 2022] [Simmons 2023] [Simmons and Murphy 2021] [Simmons et al 2019] [Simmons et al 2023] [Simmons et al 2023] [Simpson 1972] [Simpson 1979] [Smetana et al 1972] [Smith et al 2003] [Sokolov et al 2017] [Soltmann and Hall 2017] [Song et al 2002] [Song et al 2022] [Souza et al 2019] [Speyer and Crues 1985] [Speyer and Crues 1987] [Srinathkumar et al 1995] [Steinmetz et al 1972] [Stouder 1981] [Strader et al 2016] [Sun et al 2019] [Szymanski et al 2025] [Tavoularis 1999] [Taylor et al 1992] [Thompson et al 2017] [Tomaine et al 1978] [Travassos and Kaufman 1979] [Traven and Whitley 1995] [Venkataraman and Seiler 2019] [Verhaegen 1988] [Verma and Peyada 2018] [Wang and Iliff 2004] [Wang et al 1986] [Wang et al 2015] [Wang et al 2021] [Wang et al 2022] [Wang et al 2023] [Ward 1968] [Wei and Renliang 2015] [Weinstein et al 2018] [Weiss and Thielecke 2000] [Wells et al 1979] [Wells et al 1982] [Whitefield et al 1981] [Wingrove 1978] [Wisbacher et al 2025] [Woodbury et al 2015] [Woodruff 2009] [Yasue 2020] [Yavuztürk and Topbas 2020] [Yavuztürk et al 2017] [Yeager 1997] [Yechout 1988] [Yechout and Schweikhard 1984] [Yeo et al 2015] [Yu et al 2017] [Zhou and Wang 2026] [Zhou et al 2023]

High angle of attack, vortex flow and departure

High angle of attack aerodynamics and control, vortex flow and vortex breakdown, departure and spin.

227 records. [Adams 1993] [Air Force Test Pilot School Edwards Afb Ca 1991] [Alferov et al 1982] [Anderson 1984] [Anderson 1985] [Arena and Nelson 1989] [Axelson 1975] [Ayoub and McLachlan 1988] [Ayoub and McLachlan 1987] [Bagherzadeh et al 2025] [Banks 1988] [Bay and Kara 2026] [Bennett et al 2017] [Bigler 1986] [Bihrle and Barnhart 1982] [Bihrle and Billy 1980] [Bihrle 1970] [Bihrle and Bowman 1980] [Boyden 1970] [Boyden 1971] [Brody and Fagley 2024] [Bruns and Smith 1992] [Bui 2016] [Canin 2019] [Carine Viola Dsouza and Dr. Basawaraj 2015] [Cornelius and Lucius 1993] [Cornelius and Lucius 1994] [Cunis et al 2018] [Debry et al 1992] [Dias 2015] [Durston and Schreiner 1983] [Ekaterinaris and Schiff 1990] [Elmiligui et al 2015] [Elmiligui et al 2017] [Erickson and Brandon 1987] [Erickson 1991] [Ericsson 1996] [Ericsson 1996] [Ericsson 1997] [Ericsson and Hanff 1994] [Farcy et al 2020] [Faure and Leogrande 2020] [Feng et al 2024] [Fischenberg 1995] [François et al 2021] [Gee et al 1992] [Go and Maqsood 2015] [Gordnier 1995] [Grafton et al 1982] [Greenwell 2003] [Gursul and Yang 1994] [Gursul and Yang 1995] [Gursul et al 1995] [Hadidoolabi and Ansarian 2017] [Hadidoolabi and Ansarian 2018] [Hall et al 1998] [Heald and Brassell 1976] [Hebbar et al 1991] [Hitzel 1988] [Hitzel 2017] [Hollingsworth and Cohen 1971] [Hreha and Lutze 1983] [Hreha and Lutze 1984] [Huang et al 2026] [Innocenti 1989] [Ishibashi and Miyaji 2015] [Jarrah 1989] [Johnson et al 1980] [Johnston and Hogge 1974] [Johnston and Hogge 1976] [Kapuscinski et al 2020] [Kofman and Becus 1996] [Kramer and Smith 1994] [Kurade et al 2021] [Lackey and Hadfield 1992] [Landa et al 2018] [Lanser and Meyn 1992] [Lee and Han 2019] [Lee and Ko 2017] [Lee and Marnineau-Mes 1996] [Lee and Libbey 1961] [Li and Yang 2017] [Liberatori et al 2023] [Lin and Rockwell 1995] [Liu et al 2016] [Liu et al 2018] [Lofthouse and Cummings 2015] [Lofthouse and Cummings 2017] [Lowson and Riley 1994] [Lowson and Riley 1995] [Nguyen et al 1980] [Luckring et al 2022] [Ma et al 2020] [Malik et al 2020] [Malik et al 2021] [Marchman 1981] [Mayya et al 2022] [McKeehen and Cord 1997] [Mello and Agnew 1979] [Menke and Gursul 1999] [Meyer et al 1989] [Milillo 1972] [Mitchell et al 1980] [Mitrut et al 2021] [Moore et al 1980] [Morton 2003] [Morton et al 2002] [Murri et al 1983] [Naigle et al 2022] [Nelson 1985] [Nelson and Mouch 1978] [Nguyen 1979] [Numerical Analysis of the Flow Pattern and Vortex Breakdown over a Pitching Delta wing at Supersonic Speeds 2017] [Ogburn et al 1993] [Osipov 2019] [Ostroff 1998] [Ozgören et al 2002] [Patel and Smith 1996] [Patel et al 2002] [Patten 1988] [Pedreiro et al 1998] [Pelikan 1974] [Pelletier and Nelson 2000] [Pfnür and Breitsamter 2019] [Pitts et al 1974] [Planeaux and Barth 1988] [Prediction of vortex breakdown effects on a rolling delta wing 1994] [Probst et al 2019] [Qi and Zhongke 2015] [Rainbird et al 2015] [Ransom 1983] [Rao 1989] [Rao and Murri 1986] [Rao et al 1987] [Rao et al 1986] [Rhodeside 1986] [Biedron and Whitaker 1994] [Li and Yang 2017] [Rohith and Sinha 2017] [Rom et al 1987] [Roos 1996] [Roos 2001] [Roy et al 2023] [Russell et al 2022] [Saderla et al 2016] [Sahin et al 2026] [Salahudden 2024] [Salahudden 2025] [Salahudden and Ghosh 2021] [Salahudden et al 2020] [Salahudden et al 2022] [Salahudden et al 2024] [Salahudden et al 2025] [Salehian et al 2022] [Salehian et al 2024] [Salehian et al 2025] [Schaeffler and Rediniotis 1995] [Schmidt et al 2025] [Schrader et al 1988] [Sedlacek et al 2022] [Sellers et al 1988] [Sellers et al 2004] [Seraj and Martins 2022] [Shah 1991] [Shivam and Verma 2019] [Shojae et al 2025] [Silva and Wolf 2024] [Silva and Wolf 2026] [Singh and Jategaonkar 1996] [Skow et al 1982] [Skow and Peake 1983] [Son et al 2015] [Son et al 2015] [Stoll and Koenig 1983] [Strickland et al 1996] [Suarez et al 1992] [Suarez et al 1992] [Suarez et al 1993] [Symposium on Advanced Flow 2003] [Taylor and Skow 1988] [Tinger 1987] [Tinoco 2020] [Towfighi and Rockwell 1993] [Uhlig and Selig 2017] [Valasek and Walchli 1998] [Van Dommelen 1995] [Vauchel and Caro 2026] [Venkateswara Rao and Go 2019] [Visbal 1993] [Visbal 1993] [Visbal 1994] [Visbal 1995] [Visbal 1997] [Visonneau et al 2022] [Vlahostergios et al 2018] [Vorobieff and Rockwell 1996] [Walchli et al 1992] [Waldmann 2015] [Wan et al 2023] [Wang et al 2016] [Wang et al 2017] [Wang et al 2021] [Wang et al 2023] [Wang et al 2025] [Webster and Shang 1989] [Wei et al 2017] [Weissman 1972] [Weissman 1973] [Weissman 1974] [Weissman 1975] [Wendel et al 1991] [Werner et al 2022] [Werner et al 2024] [Witkowski et al 2022] [Wu et al 2017] [Xiong and Nguyen 2023] [Xiong et al 2026] [Xu et al 2016] [Yang et al 2015] [Yoo 2018] [York and Anderson 1994] [Zhang and Samtaney 2016] [Zhang et al 2017] [Zhou et al 2019] [Zhu et al 2019] [Zohar and Er-El 1988] [Zwerger et al 2015]

Tailless aircraft and flying wings

Tailless aircraft and flying wings, their stability, control and design, from the wartime tailless gliders to the unmanned combat aircraft.

214 records. [Addington and Myatt 2000] [Ahmed et al 2024] [Aleisa et al 2023] [Asaro and Vos 2025] [Asaro and Vos 2026] [Ashkenas and Klyde 1989] [Atmaca et al 2026] [Balasubramanian et al 2024] [Banerjee 1988] [Barker and Balas 1999] [Bishop 1961] [Bliamis et al 2021] [Boskovic et al] [Bowlus et al 1997] [Brewer 1946] [Brinker and Wise 1998] [Brinker and Wise 1999] [Buffington 1999] [Buffington 1999] [Calise et al 2001] [Campos and Marques 2021] [Chaudhuri et al 2018] [Colgren and Loschke 2008] [Cong et al 2023] [Cook and Hauser 2018] [Coppin et al 2018] [Cosentino 2007] [Cox et al 1949] [Cusher and Gopalarathnam 2006] [Cusher and Gopalarathnam 2012] [de Becdelievre and Kroo 2021] [DeLaurier 2022] [Deslich et al 2021] [Development of Neo-Ptero Tailless Micro Aircraft 2018] [Eberhardt and Ward 1999] [Ericsson and Beyers 2002] [Esfandabadi and Djavareshkian 2026] [Experimental investigation of synthetic jet control of wing rock for a flying wing aircraft 2023] [Flanagan et al 2020] [Flow Control and High-Lift Performance for Flying-Wing Unmanned Combat Air Vehicle Configurations by inserting slots 2016] [Friehmelt 1996] [Gamble and Inman 2016] [Gan and Zha 2015] [Gillard 1998] [Gillard et al 1997] [Grismer et al 1997] [Guiler] [Guiler and Huebsch 2005] [Hall et al 2006] [Hauser 1999] [He et al 2022] [He et al 2022] [Hoffler et al 1988] [Hong and Ma 2016] [Hu et al 2024] [Hu et al 2025] [Huang and Zhang 2020] [Huber 2022] [Jentzsch et al 2017] [Jentzsch et al 2019] [Jiang et al 2019] [Jiang et al 2025] [Jiguang Li et al 2016] [Jo et al 2015] [Jo et al 2016] [Kalyankar et al 2024] [Karimi Kelayeh and Djavareshkian 2024] [Keidel et al 2019] [Keidel et al 2020] [Kim et al 2025] [Kwiek 2019] [Lee 1946] [Lee 1947] [Leishman 2026] [Lesalli and Cahyono 2020] [Li and Cai 2026] [Li et al 2017] [Li et al 2018] [Li et al 2022] [Lim et al 2025] [Liu and Hu 2014] [Liu and Jiao 2017] [Liu and Zhang 2022] [Liu et al 2021] [Liu et al 2025] [Loechert et al 2018] [Lyu et al 2023] [Ma et al 2008] [Ma et al 2019] [Marques 2013] [McKeehen 1998] [Meckstroth and Blake 2015] [Meckstroth and Ordóñez 2020] [Meckstroth and Ordóñez 2020] [Metin et al 2023] [Mirosław et al 2022] [Mohammadi Farhadi et al 2018] [Mohan and Kumar 2025] [Molinari et al 2015] [Molinari et al 2018] [Morris 1992] [Morris et al 2014] [Myatt et al 1998] [Nae 2026] [Nedilko et al 2026] [Ngo et al 1996] [Nie et al 2021] [Niestroy 2025] [Niestroy et al 2017] [Niestroy et al 2019] [Nieto-Wire and Sobel 2007] [Nieto-Wire and Sobel 2009] [Nieto-Wire and Sobel 2011] [Nieto-Wire and Sobel 2013] [Nieto-Wire and Sobel 2014] [Oosterom and Vos 2022] [Orhan and Subbarao 2021] [Owashi et al 2017] [Pan and Huang 2018] [Pan and Huang 2019] [Pan and Huang 2019] [Paranjape and Chung 2010] [Paranjape et al 2011] [Park et al 2015] [Park et al 2016] [Park et al 2016] [Park et al 2017] [Park et al 2017] [Paul et al 1997] [Pena and Voulgaris 2001] [Pepelea et al 2016] [Petrenko and Gašparovič 2025] [Phillips et al 2019] [Protz and Sparks 1998] [Qu et al 2011] [Rajput et al 2015] [Reist and Zingg 2015] [Reist and Zingg 2016] [Riethausen 2026] [Rojas Carvajal and Amitay 2023] [Rossetti and Beblo 2022] [Sudhakar et al 2025] [Saeed and Graham 2015] [Saephan and van Dam 2006] [Saephan and van Dam 2006] [Seacord and Campbell 1945] [Shayan and Van Kampen 2021] [Shearwood et al 2019] [Shi and Wu 2022] [Shtessel et al 1999] [Shtessel et al 2002] [Shuang et al 2016] [Simon et al 1993] [Song et al 2016] [Sparks] [Sparks and Sparks 1997] [Stenfelt and Ringertz 2009] [Stenfelt and Ringertz 2010] [Stenfelt and Ringertz 2013] [Tal and Karaman 2021] [Tal and Karaman 2022] [Teel 1999] [Teel 1999] [Tipton and Smith 1995] [Tipton et al 1996] [Tournes and Johnson 1999] [Tournes et al 1997] [Traas et al 2026] [Vale J 2013] [van den Aarssen et al 2019] [Veismann et al 2023] [Vicroy et al 2018] [Vos et al 2002] [Wang and Qi 2021] [Wang et al 2020] [Wang et al 2023] [Wang et al 2025] [Weil 1981] [Wells and Hess 2002] [Wells and Hess 2003] [Weyl 1944] [Weyl 1945] [Weyl 1945] [Weyl 1945] [Weyl 1945] [Weyl 1945] [White and Innis 1959] [Williams et al 2025] [Wise et al 1999] [Xi and Zhao 2017] [Xie et al 2011] [Xin et al 2024] [Xu and Feng 2025] [Xu and Yu 2025] [Xu and Zhou 2015] [Yazdi et al 2026] [Yazdi et al 2026] [Yu et al 2022] [Yu et al 2023] [Yu et al 2023] [Yu et al 2023] [Yue et al 2009] [Yue et al 2013] [Yuzawa and Ogami 2002] [Zhang and He 2026] [Zhang and He 2026] [Zhang and Meng 2019] [Zhang et al 2018] [Zhang et al 2023] [Zhang et al 2024] [Zhao et al 2023] [Zhu et al 2016] [Zhu et al 2022] [Zou et al 2026]

Of the 214 records, 11 date from 1950 or earlier and 130 from 2015 or later.

Flight control law design and fly-by-wire systems

Flight control law design and fly-by-wire flight control systems, their redundancy, actuation and robustness.

204 records. [213 Development of a robust flight control law for a VSTOL aircraft 1994] [A multi microprocessor flight control system design principles 1979] [A Novel Sliding Mode Controller for Underactuated Vertical Takeoff and Landing Aircraft 2020] [Ackerman et al 2019] [Akbari and Greeff 2024] [Akmeliawati and Mareels 1999] [Aldosari and Feron 2025] [Allen et al 2002] [Amato et al 2022] [Automatic Landing 1964] [Barret and Barret 1997] [Beasley 1984] [Belmont 1983] [Berg 1991] [Bodur and Ucun 2023] [Bolting et al 2017] [Bosch and Kuehl 1976] [Bosch and Kuehl 1977] [Bouzid et al 2018] [Burris 1969] [Burris and Bender 1969] [Burton and Kneeland 1981] [Carino et al 2015] [Carpenter and Jenny 1964] [Caverly and Forbes 2018] [Chakravarty 1987] [Chen and Zhao 2017] [Cheng and Xin 2019] [Chu and Bryson 1987] [Chunrong and Yunhong 2025] [Cliff and Lutze 1972] [Colgren and Martin 2000] [Combined flight control/utility system 1974] [Comer et al 2026] [Cotton 1974] [Cox and Cotting 2005] [Craig 1965] [Czyba and Blachuta 2001] [Czyba and Blachuta 2003] [Czyba and Stajer 2019] [de Oca and Flores 2020] [Demarchi and Haning 1978] [Digital model-reference flight control of aircraft with unstable sampling zeros 1994] [Dobos-Bubno and Hartsook 1977] [Du 2024] [Dukes 1970] [Duran 2026] [Duran et al 2019] [Ebner and Mark 1977] [Enns 2003] [Forkun et al 2020] [Fosdick 1970] [Franklin et al 1985] [Friedland 1982] [Fujimori and Nikiforuk 1999] [Fujimori et al 1997] [Fujimori et al 1998] [Funk 1975] [Gain Scheduled Fuzzy Control on Aircraft Flight Control 2004] [Gainer 1963] [Gaudet and Furfaro 2023] [Gaylor 1984] [Goldberger 1966] [Govindaraj et al 1979] [Gregory et al 1994] [Grossman 1957] [Guerrero-Bonilla et al 2017] [Guo 2021] [Guy 1976] [Harris and Rickard 1979] [Hart 1956] [Hart 1968] [Henn and Boronow 1959] [Herrmann and Ben-Asher 2016] [Hess and Peng 2018] [Hill 1987] [Hogan and Rinde 1978] [Hongyan and Xiaoyong 2026] [Hueschen 1984] [Hübener and Luckner 2026] [Inertially augmented approach and landing systems 1971] [Stewart 1992] [Stewart et al 1992] [Jeffrie and Rolston 1972] [Jenney 1979] [Jenney 1980] [Jenney et al 1982] [Jianhong and Yanxiang 2026] [Jianliang Wang and Sundararajan 1994] [Kanai and Nikiforuk 1982] [Kazarin et al 2016] [Khamvilai et al 2024] [Kisslinger and Wendl 1971] [Kistyarev and Wang 2025] [Kohlman and Brainerd 1974] [Kohnhorst and Magnacca 1980] [Konar et al 1974] [Kouvaritakis et al 1979] [Kuchar and Looye 2018] [Kus and Ergazi 2025] [Larson 1986] [Lateral Control of a Hypersonic Aircraft 2025] [Lavretsky 2019] [Lee and Hedrick 1994] [Lee et al 2001] [Liang 2025] [Liu et al 2018] [Liu et al 2023] [Liu et al 2024] [Lorenzetti et al 1969] [Lu and Martos 2021] [Ma 2019] [Mao et al 2022] [Martorella et al 1981] [Masaoka and Hashimoto 2024] [Masubuchi et al 2004] [Mattern et al 1989] [McDonald and Farris 1964] [McGough et al 1974] [McKenzie 1973] [McMaster and Schenk 1974] [Melekhin and Khachumov 2021] [Mineck 1976] [Mohamed 2024] [Mueller 1965] [Muir 1993] [Muir and Bradshaw 1996] [Muller 1967] [Muravyev 2022] [Napolitano et al 1998] [Nardi 1970] [Neal and Smith 1970] [Negre 1975] [Nguyen and Tran 2021] [Nield 1981] [Northrop Aircraft Inc Hawthorne Ca 1952] [Ogren et al 1974] [Onken and Stuckenberg 1978] [Oosterom et al 2000] [Oosterom et al 2002] [Ossmann et al 2019] [Ostheimer and Giguere 1963] [Patience and Nahon 2020] [Payne 1968] [Peng et al 2018] [Petrie 1968] [Porter and Swaim 1975] [Posingies 1979] [Qian et al 2025] [Rabenberg and Palarz 1983] [Research and Design of Automatic Flight Control System Test System 2022] [Rickard 1978] [Robinson 1968] [Robinson 1969] [Rogalski 2018] [Rogalski et al 2020] [Rogalski et al 2021] [Rosa and Belo 2021] [Rynaski 1994] [Schierman and Schmidt 1991] [Schreadley 1977] [Scott 1977] [Sedlmair et al 2022] [Servo-control device for aircraft flight control 1984] [Sklaroff et al 1973] [Smith 1991] [Smith and Meyer 1984] [Smith and Meyer 1987] [Smith et al 1991] [Snell et al 1990] [Snell et al 1992] [Sobel and Shapiro 1984] [Sparks 2003] [Stephan et al 2023] [Sugino et al 2019] [Thompson 1965] [Thompson and Chiang 1990] [Tribuno et al 1976] [Venkataraman et al 2017] [Verma and Junkins 1999] [Vieten 1992] [Voting software for fault-tolerant aircraft flight control systems 1993] [Wagdi 1984] [Walker 1960] [Walker 1961] [Wang et al 2020] [Wang et al 2022] [Warren 1989] [Watson and Komechak 1977] [Weiser et al 2020] [Weiser et al 2024] [Wise et al 1999] [Wolf 1978] [Wu et al 2015] [Xiao et al 2018] [Yang et al 2025] [Yijie et al 2023] [Yonke et al 1985] [Yue et al 2017] [Zhang et al 2017] [Zhishuai and Lingling 2022] [Zhou and Deng 2024] [Zhu and Qin 2023] [Zipperer et al 1975]

Reynolds number effects and low Reynolds number aerodynamics

Reynolds number effects, laminar separation bubbles and the aerodynamics of wings and aerofoils at low Reynolds number.

202 records. [Adak et al 2024] [Adeyi et al 2024] [Aditya and Srinivas 2019] [Ahmad and Li 2022] [Albrecht et al 2019] [Albrecht et al 2022] [Alford and Altman 2004] [Algozino et al 2015] [Anyoji 2019] [Aono et al 2018] [Arshad et al 2022] [Ashish Kumar Gupta et al 2023] [Aulehia 1987] [Avirovic et al 2023] [Avirovic et al 2024] [Badrya and Baeder 2019] [Badrya et al 2018] [Bagade et al 2015] [Balaji et al 2025] [Bansal and Lavoie 2025] [Benny Thompson and Gunasekaran 2021] [Bernal and Yu 2015] [Bernardos et al 2019] [Boschetti et al 2004] [Brunelli et al 2026] [Bucci et al 1997] [Catalano and D’Aniello 2025] [Catalano et al 2024] [Chandan et al 2023] [Chandra 2020] [Chen and Yang 2022] [Chitsaz et al 2021] [Cho et al 2018] [Ciobaca and Dandois 2017] [Collison et al 2017] [De Almeida and Dias 2024] [de Paula et al 2017] [de Rosa et al 2024] [Dellacasagrande et al 2020] [Dias Pires de Souza et al 2017] [Drela 1991] [Drela and Giles 1986] [Durgesh et al 2019] [Dwivedi et al 2022] [Désert et al 2019] [Eftekhari and Al-Obaidi 2019] [Esmaeili et al 2018] [Evangelista et al 1987] [Evans 1964] [Fayaz et al 2022] [Feng et al 2017] [Ferrand et al 2026] [Fujita et al 2019] [Geng et al 2018] [Genç et al 2022] [Giacomini and Westerberg 2025] [Gnatowska and Gajewska 2024] [Gopalarathnam et al 2001] [Gopalarothnam and McGowan 2008] [Greer et al 1999] [Gungordu and Tayfuner 2026] [Gupta et al 2025] [Güler et al 2021] [Hall and Kern 1996] [Hammer and Shumway 2026] [Hammer and Shumway 2026] [Hart et al 2016] [Herbst et al 2018] [Hoxey et al 1997] [Hsiao 1988] [Hsiao et al 2004] [Ikeda et al 2015] [Inoue et al 2019] [Itsariyapinyo and Sharma 2016] [Jabbari et al 2021] [Jacob et al 2026] [Jain et al 2015] [Jones et al 2017] [Joy et al 2016] [Karthikeyan et al 2024] [Kase et al 2021] [Kase et al 2023] [Khan 2023] [Khan et al 2022] [Klose et al 2018] [Korkischko and Konrath 2017] [Kouser et al 2024] [Kouser et al 2024] [Kuester et al 2016] [Kumar et al 2015] [Kumar and Mukherjee 2024] [Kumar Gupta et al 2018] [Kurtulus 2019] [Kurtulus 2021] [Lee et al 2015] [Lee et al 2015] [Lee et al 2015] [Lee et al 2015] [Lei et al 2017] [Leung and Redonnet 2022] [Li and Liu 2016] [Li et al 2022] [Li et al 2023] [Liang et al 2022] [Lim et al 2026] [Lin et al 1992] [Linehan and Mohseni 2016] [Liu and Luo 2022] [Liu and Xiao 2020] [Liu and Yang 2024] [Liu et al 2021] [Liu et al 2024] [Mahns and Amitay 2025] [Maji et al 2024] [Malik et al 2018] [Manar et al 2016] [Marchman 1987] [Matías-García et al 2025] [Maughmer and Somers 1987] [Maughmer et al 2021] [Maughmer et al 2023] [Meng et al 2015] [Meng et al 2026] [Metkowski et al 2022] [Michelsen and Mueller 1987] [Michna and Rogowski 2022] [Michna et al 2025] [Mohamed et al 2021] [Mohamed Ibren et al 2021] [Moreschi and Guardone 2024] [Mueller and Torres 2001] [Muhammed and Virk 2024] [Mukohara and Anyoji 2021] [Munday et al 2015] [Varsha et al 2023] [Neuwerth et al 1998] [Nik Mohd 2017] [Nudson et al 2025] [Oh and Choi 2018] [Ol 2007] [Pandi and Mittal 2025] [Park et al 2019] [Parra et al 2026] [Passive Flow Control over an Airfoil by Control Rod at Low Reynolds Number 2020] [Pelletier and Mueller 1999] [Peng et al 2016] [Peristy et al 2016] [Perry and Mueller 1986] [Petrović et al 2016] [Pfenninger and Vemuru 1988] [Potter and Whitfield 1957] [Poudel et al 2021] [Priyanka and Sivapragasam 2021] [Rahal and Dutta 2024] [Reaser et al 1983] [Reed 1990] [Ren and Zha 2025] [Ren et al 2026] [Rist 1996] [Robinson and Wissler 1988] [Rocha Ribeiro and Wolf 2025] [Rolston 2001] [Roy and Mukherjee 2021] [Ruifeng 2015] [Saunders 1996] [Shah 2017] [Shams et al 2018] [Somashekar and Immanuel Selwyn Raj 2018] [Sreejith and Sathyabhama 2020] [Steinhoff 2002] [Stremel 1994] [Sun and Boyd 2004] [Tamura and Oyama 2019] [Tokugawa et al 2026] [Toppings and Yarusevych 2021] [Tran 2025] [Traub 2021] [Traub 2024] [Traub and Coffman 2019] [Traub et al 1998] [Traub et al 2015] [Uthra and Antony 2020] [Somashekar and Immanuel Selwynraj 2022] [Verhaagen 1999] [Waldmann et al 2023] [Wang et al 2021] [White et al 2025] [Wrist and Hubner 2017] [Xi et al 2025] [Xiao et al 2016] [Yamazaki et al 2017] [Yamazaki et al 2018] [Yang and Agarwal 2019] [Yang et al 2016] [You et al 2013] [Yu et al 2024] [Zhang et al 2017] [Zhao et al 2024] [Zhou et al 2021] [Zhu and Guo 2019] [Zilli et al 2017] [Zilstra and Johnson 2026]

Of the 202 records, 164 date from 2015 or later, which is the shape of a literature that grew with the small unmanned aircraft.

Similitude, dynamic scaling and subscale flight testing

Similitude, dynamic scaling and the subscale and free-flight model testing of aircraft, from the free-spinning tunnel to the radio-controlled research aircraft.

155 records. [Akaryildiz et al 2024] [Ananda et al 2017] [Anderson et al 1954] [Axelson and Emerson 1949] [Bantscheff and Breitsamter 2023] [Baumann and Gal-Or 1992] [Baylen et al 1967] [Beeman 1972] [Berman 1947] [Berman 1949] [Berman and Pumphrey 1950] [Bertrand-Noël et al 2022] [Betin 2026] [Bowman 1957] [Brown and Duhon 1965] [Bunge et al 2015] [Burk and Wilson 1975] [Byrdsong and Brooks 1980] [Byrdsong and Brooks 1983] [Byrdsong and Hallissy 1979] [Chedrik et al 2004] [Comer et al 2024] [Comer et al 2026] [Comer et al 2026] [Courtin et al 2020] [Cox et al 2012] [Crites et al 1992] [Croom et al 2000] [Cumming and Kramer 1966] [Dantsker 2024] [Dantsker and Mancuso 2019] [Dantsker and Selig 2015] [Dantsker et al 2022] [Dantsker et al 2023] [DeBoer et al 2026] [Deets and Brown 1986] [Degenne et al 1973] [Denham and Owens 2016] [Doll et al 2024] [Eilertson 1975] [Ericsson 1985] [Ericsson 1985] [Fitzgerald and Gingras 1996] [Foster et al 2020] [Fratello and Shearin 1975] [Fremaux 1995] [Gee 1978] [Genito et al 2024] [Geuther et al 2024] [Ghanchi and Gururajan 2026] [Gingrich et al 1977] [Grafton et al 1974] [Gray 1964] [Guo et al 2017] [Hakim and Choukri 2023] [Hammer et al 2026] [Hastedt et al 2022] [Head 1962] [Healy 1958] [Hitzel and Zimper 2018] [Hoe et al 2012] [Holmes and Woehr 1971] [Howard and Bray 1992] [Hwang et al 2024] [Hyde and Massie 1993] [Harasani 2015] [Iliff 1980] [Jaffe 1972] [Jayaraman et al 2022] [Johnson 1949] [Jordan et al 2004] [Jordan et al 2005] [Chambers 1988] [Keller et al 2026] [Klinar and Healy 1955] [Kotsabasis 1981] [Krause et al 2024] [Kunwar and Chakraborty 2025] [Kunwar et al 2026] [Laiosa 1985] [Lallemand 2000] [Larsen 1975] [Larsson 2025] [Laughter 2012] [Layton 1974] [Lee 1952] [Lee 1963] [Lockenour and Layton 1976] [Long 1968] [Lorincz 1980] [Lovell 1954] [Lu et al 2015] [Lu et al 2016] [Lu et al 2019] [MacAllister 1955] [Mandal and Gu 2016] [McClinton et al 1998] [Mineck et al 1976] [Motter and High 2009] [Murri et al 1984] [Nagel and Thomas 1965] [Napolitano 2002] [Nepomuceno and Annes Da Silva 2021] [Nepomuceno et al 2022] [Obermark 2004] [Oblique Wing Remotely Piloted 1974] [Olejnik et al 2019] [Olejnik et al 2022] [Owens et al 2006] [Pallister et al 1992] [Pan et al 2025] [Pan et al 2026] [Park et al 2025] [Petersen 1976] [Petersen 1976] [Peterson et al 2016] [Pieper et al 2018] [Platou 1968] [Pusztai et al 2024] [Raju Kulkarni et al 2019] [Rayleigh 1915] [Reed 1974] [Richardson 1976] [Ruan and Aagren 2025] [Sadovnitchii et al 1997] [Sadovnychiy et al 1998] [Sakata 2002] [Burk and Libbey 1961] [Sarker et al 2026] [Silvers et al 1958] [Simmons and Ackerman 2026] [Simon et al 2023] [Simon et al 2024] [Sobron et al 2021] [Solies 1994] [Spurlin and Lueck 1984] [Stephens 1931] [Tai et al 2026] [Tenhave et al 2026] [Traub 2024] [Tsushima et al 2024] [Uppoor et al 2026] [Vigh 1977] [Wang et al 2019] [Wang et al 2020] [Ward et al 2025] [Ward et al 2026] [Weiland 2021] [Winchenbach et al 1982] [Winchenbach et al 1984] [Wolowicz et al 1979] [Yarlett et al 2000] [Yip et al 1990] [Yip et al 1990] [Yip et al 1991]

Of the 155 records, 73 date from 1997 or earlier, the free-spinning and free-flight model tradition the X-36 descends from, and 66 from 2015 or later.

Wing and configuration aerodynamics

The aerodynamics of wings, fuselages and complete configurations, and the estimation of aerodynamic coefficients for design.

155 records. [Abu Salem et al 2023] [Addoms 1977] [Adiwidodo and Wijaya 2022] [AERODYNAMIC ANALYSIS OF EAGLE WINGLETS ON AIRCRAFT 2017] [Aerodynamic Performance of Swayasa Aircraft Wing Model against the Effect of Airfoil Flap Angle Configuration 2025] [Aircraft design optimization with multidisciplinary performance criteria 1989] [Akgumus Gok 2024] [Aleisa et al 2023] [Ali et al 2024] [Allen 2017] [Aprovitola et al 2021] [Aryasomayajula et al 2001] [Asztalos et al 2025] [Ban et al 2018] [Bissonnette and Bramesfeld 2015] [Black 1968] [Boschetti et al 2020] [Boschetti et al 2022] [Bosnyakov et al 2024] [Bui 2018] [Bushnell 1990] [Caap and Elemeland 1986] [Casadei et al 2019] [Cavallo and Dash 2000] [Chau and Zingg 2017] [Chau and Zingg 2022] [Chau et al 2026] [Chen et al 2025] [Coder and Ortiz-Melendez 2018] [Cui et al 2019] [Cummings et al 2018] [Czyz and Karpinski 2020] [de Vries and Vos 2023] [Deere et al 2017] [Della Corte et al 2021] [Della Corte et al 2022] [Deng et al 2017] [Dickinson 1953] [Dizdarevic and Dizdarevic 2022] [Dovi and Wrenn 1989] [Duong Nguyen et al 2022] [Durston and Stonum 1987] [Erhard et al 2021] [Evans et al 1949] [Filippoli et al 2026] [Gagnon and Zingg 2016] [Gallay and Laurendeau 2016] [Gardner and Downey 1950] [Gerhardt and Chen 1978] [Ghasemzadeh and Banazadeh 2025] [Goerttler 2025] [Gopalarathnam and McAvoy 2002] [Goparaju et al 2015] [Grauer and Morelli 2015] [Xuan and Cheng 2016] [Hall et al 1999] [Hantla and Wang 2025] [Harry and Trobaugh 1966] [Hassan et al 1997] [Huntley et al 2019] [Ishikawa and Yamazaki 2021] [Ito et al 2017] [Jaffrezic et al 2015] [Jentys and Breitsamter 2023] [Jesudasan et al 2026] [Jin et al 2020] [Jones 1979] [Kamiyama and Yamazaki 2020] [Katz 2017] [Kaygan and Ulusoy 2018] [Keshmiri et al 2017] [Kim et al 2022] [Konishi et al 2023] [Kästner et al 2021] [Lam and Stollenwerk 1966] [Lee 2016] [Lee and Ko 2018] [Lee et al 2024] [Li et al 2019] [Li et al 2022] [Li et al 2024] [Liu et al 2020] [Liu et al 2024] [Lucas 1978] [Luckring et al 1989] [Ma 2025] [Mahesh et al 2023] [Mahgoub and Cortelezzi 2020] [Makgantai et al 2021] [Mason 1991] [Matos and Marta 2025] [McInville and Moore 1994] [Mestriner et al 2018] [Morra and Nicolosi 2025] [Moëns 2022] [Murugappa and Kazerani 2025] [Nasuhbeyoglu and Akça 2024] [Navaratna and Pontillo 2022] [Neuwerth et al 1999] [Nguyen et al 2016] [Nguyen et al 2018] [Odendaal et al 2024] [Okolo et al 2015] [Olson and Selberg 1976] [Parlange 1968] [Paulson et al 1979] [Peng et al 2019] [Ptitsin 2017] [Rakshith et al 2015] [Reel and Baltadjiev 2018] [Reinbold et al 2026] [Reist and Zingg 2017] [Reist et al 2022] [Ren et al 2022] [Reuther and Jameson 1995] [Ribeiro and Resende 1993] [Rios and Tamayo 2017] [Rivers et al 2001] [Rohani and Jahangirian 2022] [Rong 2026] [Rs et al 2018] [Sabo and Bugaj 2021] [Samoylovitch and Strelets 2000] [Shahjahan et al 2026] [Simon et al 2025] [Sinha 2004] [Sirbaugh 1983] [Sluis et al 2023] [Smith et al 1992] [Soinne 1999] [Stoldt et al 2020] [Sundaram and Wu 1983] [Takarics et al 2020] [Terry 1964] [Tu 1992] [Uribe et al 2017] [Utsumi 2025] [van Rooij and Cummings 2018] [van Sluis et al 2026] [Veresnikov and Goncharenko 2025] [Wang et al 2018] [Weisshaar 1977] [Wendorff et al 2016] [Whoric 1974] [Wood 2003] [Wu 1981] [Wu and Sankar 1980] [Yang 2024] [Yoo and Duensing 2019] [Yu 2021] [Yuan 2026] [Zannetti and Onofri 1984] [Zastawny 2016] [Zhu 2024] [Zimper and Hummel 2018]

Slender bodies, fuselages and apparent mass

Slender bodies and bodies of revolution, fuselage aerodynamics, apparent mass and the cross-flow on inclined bodies, which carry the article’s fuselage instability.

144 records. [Abdelhamid 1985] [Adams and John C. 1968] [Aerodynamic Characteristics of Bodies 1951] [Aerodynamics of arbitrary wing body combinations with vortex latticeand slender body theory 1976] [Allee 1973] [Allen and Perkins 1951] [Almosnino 1983] [Almosnino 1985] [AlQadi and Eljack 2016] [Atli 1988] [Atta and Nayfeh 1978] [Bai et al 2025] [Baker 1978] [Beall 1986] [Benedikt 1953] [Bond and Packard 1961] [Borisova and Silantiev 2022] [Calarese 1981] [Campbell 1959] [Catani et al 1982] [Cebeci et al 1983] [Champigny 1984] [Chaudhuri and Praharaj 1971] [Cleary 1969] [Clevenson et al 1953] [Cohen 1951] [Cox 1957] [Deffenbaugh and Jacoby 1980] [DeJarnette and Jones 1978] [Desai and Pant 2026] [Devan 1989] [Dexter and Hunt 1981] [Doyle and Rosema 2015] [Dress 1988] [Dress 1989] [Ehret et al 1950] [Ericsson 1989] [Ericsson and Reding 1985] [Est and Nelson 1992] [Fediaevsky 1935] [Fleeman and Nelson 1974] [Froning 1981] [Gorski 1998] [Grimminger et al 1950] [Hall 1987] [Han and Patel 1977] [Heller and Clemente 1973] [Hemsch 1985] [Hemsch 1987] [Hemsch 1988] [Hemsch 1989] [Hsieh and Wang 1976] [Hung 1979] [Hung 1980] [Influence of interference of the wing and fuselage on aerodynamic characteristics 2018] [Jack 1951] [Jorgensen 1977] [Jorgensen 1979] [Kao 1975] [Karn et al 2021] [Keldysh 1958] [Kellock and Miller 1971] [Kerney and White 1975] [Kirk 1961] [Klimas and Kilikevičius 2024] [Koh 1968] [Lai and Kamaruddin 2018] [Laitone 1947] [Lee et al 2021] [Lee et al 2021] [Levy 2003] [Levy and Tobak 1970] [Li et al 2026] [Lijewski 1986] [Loposer and Rumsey 1954] [Luckert 1973] [Malmuth et al 1983] [Martin et al 1976] [Mateescu 1986] [Mateescu 1987] [Matveev and Wheeler 2022] [Miles 1952] [Miles 1953] [Moretti 1965] [Munk 1979] [Munk 1924] [Murphy 1966] [Murphy and Schmidt 1953] [Newman 1965] [Nicolosi et al 2015] [Nicolosi et al 2016] [Nielsen 1985] [Obeid et al 2019] [Osawa and Hewitt 1986] [Owen and Johnson 1978] [Paranjape et al 1966] [Patel and Ramaprian 1978] [Peterson 1968] [Pinebrook and Dalton 1983] [Pinebrook and Dalton 1983] [Platzer and Hoffman 1966] [Plyashechnik et al 1999] [Prizirembel and Wen 1978] [Rajagopal et al 1988] [Rakich and Cleary 1970] [Rakich and Cleary 2003] [Reklis 1980] [Rodden et al 1962] [Rodgers 1963] [Rubin and Mummolo 1973] [Sacks 1954] [Schoombie et al 2017] [Schuman 1981] [Seiff and Sandahl 1951] [Sharma et al 1998] [Shekarriz et al 1991] [Sheridan 1968] [Smith 1960] [Spreiter and Stahara 1970] [Stanek and Visbal 1991] [Starr and Varner 1976] [Thomas 1991] [Transonic theory for flow past slender fuselages and afterbodies 1970] [Tsien 1938] [Tsutsui et al 2021] [Tuckerman 1923] [Van Tuyl 1988] [Vendemia 1965] [Venkatachari et al 2015] [Wang 1971] [Wang 1972] [Ward and Katz 1987] [Ward and Katz 1987] [Ward and Katz 1989] [Ward and Katz 1989] [Wardlaw et al 1975] [Wei 1964] [White 1977] [White 1977] [White 1995] [Wolfe and Oberkampf 1982] [Wood and Murphy 1955] [Yamaoka 1963] [Zilliac et al 1990]

Thrust vectoring, drag rudders and yaw effectors

Thrust vectoring, drag rudders, spoilers and other yaw effectors that replace or supplement a fin.

140 records. [Ahmed et al 2025] [Alexander 1993] [Anna and Kidman 1994] [APPLICATION OF FLUIDIC THRUST VECTORING IN V/STOL AIRCRAFT 2024] [Bacon et al 1996] [Baldini et al 2026] [Barnhouse et al 2025] [Bazuhair 2018] [Beard and Foley 1983] [Behm 1973] [Berens 2019] [Bergman 1979] [Brandt et al 2019] [Buffington et al 1993] [Buffington et al 1994] [Capello et al 2019] [Capone 1979] [Capone and Mason 1986] [Chawla and Van Dalsem 1992] [Cheatham et al 1991] [Chudoba and Cook 2003] [Cohn et al 1985] [Collins et al 2004] [Collins Jr 2005] [Cornelius and Lucius 1993] [Cornelius and Lucius 1995] [Crowther and Wood 1993] [Das et al 2024] [Davis and Hines 1976] [Erwin et al 1964] [Esker and McArdle 1993] [Esker and Sedrick 1972] [Ferlauto and Marsilio 2016] [Friend 1964] [Gal-Or 1994] [Gal-Or 2001] [Gal-Or et al 1995] [Gill 1974] [Glezer and Leonard 2012] [Goetz et al 1976] [Granasy 1995] [Ha et al 2025] [Hall 1965] [Helicopter Yaw Control 1990] [Herrick 1992] [Hienz and Vedova 1984] [Hirano et al 2019] [Hoholis et al 2016] [Hollmeier et al 1999] [Hu et al 2025] [Hunter et al 2001] [Isaac et al 2024] [Jeong et al 2015] [Jeong et al 2024] [Jiméneze and Icaza 2000] [Jyothy and John Wessley 2023] [Kazarin et al 2017] [Kentfield 1975] [Kentfield 1975] [Kigotho et al 2022] [Kikkawa and Uchiyama 2017] [Kou et al 2021] [Kowal 2002] [Kuang and Zhu 2015] [Kumar et al 2020] [Lampard 1978] [Lee et al 2018] [Li and Ma 2014] [Li et al 2018] [Li et al 2022] [Liu et al 2022] [Liu et al 2024] [Luo et al 2025] [Lyu et al 2023] [Mace et al 1989] [Malcolm and Ng 1990] [Margetts et al 2015] [Mason and Crowther 2004] [Maughmer et al 1990] [Miller 1983] [Miller 1986] [Miwa 2021] [Miwa and Maruhashi 2016] [Murri and Rao 1987] [Murri et al 1994] [Natarajan et al 2004] [Nguyen et al 2025] [O’Rourke 1995] [O’Rourke and Sedor 1995] [Oosedo et al 2022] [Pahle et al 1996] [Pedreiro 1997] [Pulk and Stolarik 1977] [Raney et al 2000] [Resta et al 2021] [Rolls and Aoyagi 1977] [Roseberg 1982] [Ruetten 2018] [Salagame et al 2025] [Schirmer and Capone 1989] [Shearwood et al 2021] [Shendge 2021] [Sherbaum and Lichtsinder 1998] [Shi et al 2024] [Shmilovich and Princen 2026] [Shukla et al 2026] [Silva et al 2018] [Snow 1990] [Soundararajan 2022] [Soundararajan and Sridhar 2024] [Steer 2000] [Steer 2000] [Syed et al 1990] [Syed et al 1992] [Tanveer and Ahmad 2023] [Tanveer and Ahmad 2023] [Tavella et al 1986] [Tavella et al 1987] [Taylor 1988] [Thomas et al 1977] [Ulizar 1997] [Vechtel and Buch 2022] [Vieira and Maughmer 2017] [Visser 1999] [Wang et al 2020] [Wang et al 2025] [Warsop and Crowther 2019] [Warsop et al 2019] [Whitaker and Gowadia 1994] [Wilcox 1913] [Wood and Bauer 1999] [Wornom 1960] [Xu and Zhang 2025] [Xue et al 2021] [Yi et al 1979] [Yong et al 2020] [Yu and Kim 2024] [Yu et al 2023] [Zhou et al 2022] [Zwerneman and Eller 1994]

Directional stability and lateral-directional dynamics

Directional and lateral-directional stability and dynamics, the subject a missing fin makes primary.

137 records. [Air Force Test Pilot School Edwards Afb Ca 1990] [Air Force Test Pilot School Edwards Afb Ca 1990] [Alaian et al 2016] [Albostan and Gökaşan 2018] [Alston 1936] [Ananthkrishnan and Sinha 2023] [Anderson et al 2004] [Ashraf and Van Kampen 2020] [Atzhorn and Stengel 1981] [Bachmaier and Anderson 2021] [Balas et al 1996] [Balas et al 1997] [Balas et al 1998] [Banerjee et al 2017] [Bielat and Wiley 1959] [Bischoff and Palmer 1982] [Bischoff and Palmer 1983] [Bischoff et al 1974] [Bloy and Lea 1995] [Brandeau 1978] [Bryson 1954] [Campbell and Abramovitz 1975] [Cavanaugh 2003] [Chambers and Hall 2004] [Chavez and Vogel 2003] [Chen and Xie 2024] [Chen et al 2026] [Chowdhury et al 2021] [Chuan et al 2016] [Ciliberti and Nicolosi 2025] [Coe et al 1975] [Connors and Swaim 1968] [Corona-Sanchez and Rodriguez-Cortes 2015] [Costigan and Calico 1989] [Davidson et al 1998] [De et al 2015] [de Paula et al 2017] [Della Vecchia et al 2015] [Dolan 1964] [El Mobaraky et al 2026] [Enns 1990] [Fahmi and Woolsey 2018] [Fialho et al 1997] [Foster et al 1993] [Frazier 1991] [Garrard 1998] [Ghosh et al 1998] [Gilyard et al 1972] [Goodwin and Kaattari 1958] [Goud and Dwivedi 2022] [Hall and Boothe 1972] [Hart and Picha 1979] [Hegde et al 2019] [Hougui et al 1995] [Huang 2016] [Johnson 1940] [Kanneganti et al 2022] [Kojima et al 2024] [Kostić et al 2024] [Kuhn 1981] [Kumar and Prakash 2022] [Liang et al 2026] [Lin et al 1998] [Liu 2024] [Livneh 1995] [Livneh 1995] [Long Lu and Turkoglu 2015] [Lu and Turkoglu 2016] [Lu and Turkoglu 2018] [Lungu and Lungu 2015] [Lungu and Lungu 2016] [Luu and Ochi 2023] [Lyu et al 2022] [Lyu et al 2023] [Ma et al 2019] [Mann et al 1987] [Marino and Mastrocola 1952] [Martínez-Ramírez and Rodríguez-Cortés 2022] [Mason and Ravi 1994] [Mengali 2003] [Mineck 1977] [Mohamed and Joy 2021] [Mohan and Kumar 2024] [Napolitano and Kincheloe 1996] [Nicolosi et al 2020] [Nie et al 2020] [Park et al 2001] [Peristy et al 2019] [Peterson 2024] [Peterson 2025] [Peterson 1961] [Phillips 2000] [Phillips 2000] [Poojari 2022] [Price 1943] [Putman 1969] [Raul Azinheira et al 2001] [Ravi and Mason 1994] [Reigelsperger et al 1995] [Robinson 1958] [Sachan et al 2025] [Sanfilippo 1970] [Seaver et al 2023] [Shah and Granda 1998] [Shankar and Yathisha 2023] [Silva et al 2022] [Singh and Jategaonkar 1996] [Singh and Raol 2000] [Sinha and Ananthkrishnan 2002] [Sivan 1971] [Snell 1993] [Snell et al 1991] [Sparks et al 1994] [Stalford 1979] [Stengel 1975] [Stengel 1980] [Stengel and Miller 1978] [Swaim and Connor 1968] [Swarnkar and Kothari 2016] [Sánchez et al 2024] [Tai et al 2023] [Thacker and Lan 1993] [Thompson and Gilruth 1940] [Tournes and Landrum 2003] [van Rooyen and Eshelby 1981] [Wandini et al 2016] [Wang et al 1999] [Wang et al 2016] [Wang et al 2022] [Wu et al 2018] [Xiuming Liu et al 2016] [Yanagihara et al 1991] [Yang et al 2026] [Zanette and Almeida 2015] [Zhang et al 2017] [Zhao et al 2022] [Öznurlu et al 2023]

Time delay, latency and delay compensation

Time delay and its compensation in control systems and teleoperation, the stability of delayed systems, and the effect of delay on the pilot.

135 records. [Abidi et al 2016] [Alsolami et al 2025] [Alvarez-Munoz et al 2019] [Azarmi and Tavakoli-Kakhki 2020] [Baker and Batavia 2016] [Bellamri et al 2024] [Bing et al 2015] [Black et al 2024] [Blanken and Pausder 1994] [Bordei and Halanay 2025] [Breitung 2001] [Brudnak 2016] [Brudnak 2020] [Brueckner et al 2023] [Caradima and Wang 2000] [Carter 1976] [Chao et al 2017] [Chen and Liu 2021] [Chen et al 2022] [Crane 1983] [King 1993] [Delay-dependent stability criteria for discrete-time delay systems 1999] [Ding and Eskandarian 2024] [Du 2019] [Ellis and Christofides 2015] [Gamal et al 2016] [González et al 2017] [Gu and Lee 1988] [Han et al 2026] [Hashemipour et al 2017] [Hashemzadeh et al 2016] [He et al 2021] [Herrera et al 2018] [Heryana et al 2022] [Hirai and Satoh 1980] [Huang et al 2022] [Ionita 1996] [Jafari and Spong 2017] [Ji et al 2025] [Armah 2018] [Katsanikakis and Bekiaris-Liberis 2025] [Katsuyama et al 2023] [Kharitonov 1999] [Kharrat 2024] [Kumar 2015] [Kumar and Hote 2022] [Kumar et al 2018] [Kumar et al 2022] [Kuzu et al 2015] [Lane et al 2001] [Lee and Chang 1998] [Levison and Papazian 1987] [Li et al 2017] [Li et al 2026] [Liu 2023] [Liu and Brandel 2004] [Liu et al 2026] [Lloyds Raja and Ali 2017] [Loo 1969] [Luz et al 2023] [Ma et al 2015] [Ma et al 2024] [Mazenc and Malisoff 2020] [Mirzal 2017] [Mitchell et al 1991] [Moniruzzaman et al 2021] [Moniruzzaman et al 2022] [N-Nagy and Al-Tikriti 1970] [Nasiri et al 2021] [Nenadic et al 1997] [Optimized PI-PD Control for Varying Time Delay Systems Based on Modified Smith Predictor 2024] [Orlosky et al 2018] [Ostermann et al 2024] [Ozturk 1986] [Ozturk 1991] [Pacheco-Gutierrez et al 2021] [Pakzad 2021] [Piccinelli and Muradore 2021] [Popescu et al 2003] [Prakash et al 2019] [Provost et al 2026] [Provost et al 2026] [Pryor et al 2020] [Qi et al 2016] [Rajarajan et al 2024] [Rakita et al 2020] [Ramírez et al 2021] [Rao and Srinath 1965] [Roy et al 2017] [Salinas et al 2015] [Sato et al 2021] [Scholcover and Gillan 2017] [Sharma and Rajamani 2024] [Shen et al 2025] [Shinoda et al 1998] [Shinoda et al 1999] [Singh 2025] [Smith and Sarrafian 1986] [SS networked control and teleoperation 2017] [Stojanovic and Debeljkovic 2004] [Stojanovic and Debeljkovic 2004] [Storms and Tilbury 2015] [Su et al 1993] [Sun et al 2025] [Tavakoli 2024] [Thompson 1970] [Tian 2021] [Tian et al 2015] [Ting et al 2016] [Tissir and Hmamed 1994] [Tokutake et al 1999] [Tumerdem and Yilmaz 2021] [Uddin and Ryu 2016] [Vite and Mondie 2022] [Webb et al 2016] [Wu et al 2018] [Xing and Zhang 2017] [Yang et al 2019] [Yeg̃in and Özbay 2023] [Yongming and Yuanqing 2015] [Youcef-Toumi and Bobbett 1991] [Youcef-Toumi and Wu 1992] [Yue et al 2003] [Zahedi and Haeri 2017] [Zennir et al 2017] [Zennir et al 2017] [Zhang 2023] [Zhang and Bradley 2022] [Zhang et al 1992] [Zhang et al 2015] [Zhang et al 2019] [Zhao et al 2024] [Zhong et al 2023] [Zhou 2023] [Zhu and Zhang 2018]

Stability margins and robust control

Gain, phase and delay margins, robustness analysis and the fundamental limitations of feedback, which fix the article’s delay budget.

105 records. [088 Stability margin of a feedback system with structured and unstructured uncertainties 1994] [A simple link between pole shifting and phase margin 1994] [Ahmadi and Haeri 2017] [Ahmadi and Haeri 2018] [Amato et al 1996] [Amaya et al 2026] [Analytic constraints in feedback control of linear time-varying systems: Bode’s sensitivity integral 1999] [Balcan et al 2026] [Bar-On and Jonckheere 1991] [Begum et al 2020] [Bennett and Baras 1985] [Bercovici et al 1990] [Bhusal and Subbarao 2022] [Bosworth and Stachowiak 2005] [Brimelow 1970] [Cao et al 2017] [Chand and Chiu 1991] [Chandra et al 2025] [Chen 1992] [Chen 1993] [Clements 2016] [Clements 2017] [Czarkowski 2004] [Dorato et al 1999] [Elia 2004] [Emirler 2018] [Famularo et al 1999] [Freudenberg and Looze 1985] [Galeani et al 2004] [Glad 1982] [Glad 1984] [Ho et al 1993] [Ho et al 1995] [Ho et al 1998] [Huang and Wang 2001] [Jie Chen 1995] [Jie Chen 1998] [Jin et al 2018] [Jugo 2001] [Junnarkar et al 2026] [Kammer 2025] [Katayanagi 2001] [Kellett 1996] [Kellett et al 1996] [Khouloud and Ali 2023] [Kiefer et al 2016] [Kim 2023] [Koduri et al 2016] [Koduri et al 2016] [Kubo 1999] [Le Yi Wang and Ji-Feng Zhang 2001] [Lei et al 2025] [Liang et al 2025] [Lin and Han 1986] [Lindberg and Pates 2023] [Lucarini et al 2025] [Luhanga and Mwandosya 1986] [Ly 2002] [Maeda and Vidyasagar 1985] [Mao and Chen 2026] [Mazenc and Malisoff 2022] [Molander and Willems 1980] [Mori 1988] [Nataraj and Sardar 1999] [Nogami et al 1986] [Noury and Yang 2020] [Palframan et al 2019] [Patel et al 2002] [Perng et al 2004] [Pfifer and Seiler 2015] [Power 1969] [Prabhakar et al 2019] [Quenzer et al 2018] [Ren and Quan 2016] [Robertson 1997] [Rossi and Miller 1999] [Roy and Bhasin 2019] [Ryan 1990] [Safonov and Athans 1976] [Safonov and Athans 1977] [Sariyildiz et al 2018] [Satoh and Sugimoto 2002] [Schmidt and Newman 1990] [Sezer and Siljak 1980] [Sezer and Siljak 1981] [Shi et al 2021] [Shin and Belcastro 2008] [Singh and Padhy 2017] [Sobel et al 1983] [Sobhani and Jayasuriya 1994] [Srazhidinov et al 2023] [Surmann et al 2024] [Tan 2004] [Tsu-Tian Lee and Shiow-Harn Lee 1988] [Uchida et al 1986] [Viola and Angel 2015] [Wang et al 2017] [Woolcock and Schmid 2026] [Yamaguchi et al 2000] [Yamaguchi et al 2001] [Yang and Kabamba 1991] [Yaniv 1992] [Yue Zhao et al 2016] [Zhang et al 2024] [Zhong and Huang 2023]

Control allocation and redundant effectors

Control allocation among redundant effectors, for aircraft and for the multirotor and tilt-rotor vehicles that have only redundant effectors.

90 records. [Akram et al 2020] [Antonakis and Biannic 2024] [Asghari and Tayefi 2026] [Atay et al 2021] [Baggi et al 2020] [Baggi et al 2022] [Battipede et al 2004] [Bernhard and Adamy 2017] [Bezerra and Santos 2022] [Bodson 2000] [Bolling et al 1997] [Buffington and Buffington 1997] [Bugliari Armenio et al 2024] [Burken et al 2001] [Cao et al 2022] [Chen et al 2026] [Cong et al 2023] [Cui et al 2021] [de Castro and Brembeck 2019] [de Vries and Van Kampen 2019] [Derrouaoui et al 2023] [Doman and Sparks 2002] [Dong et al 2016] [Dong et al 2025] [Duan and Okwudire 2018] [Durham 1999] [Durham and Nelson 2001] [Enenakpogbe et al 2025] [Enns 1998] [Fan et al 2006] [Frost et al 2009] [Goodrich and Sliwa 1987] [Grogan et al 1994] [Harkegard 2003] [Jafari et al 2022] [Jothiraj et al 2020] [Kamath et al 2025] [Krimphove et al 2023] [Li et al 2023] [Li et al 2025] [Libório et al 2025] [Lin et al 2019] [Liu et al 2015] [Liu et al 2018] [Maadani et al 2023] [Martin 2025] [Matamoros and de Visser 2018] [Miles and Broughton 2017] [Montgomery and Hunsaker 2022] [Nelson and Durham 2002] [Page and Steinberg 1999] [Park et al 2019] [Pfeifle and Fichter 2023] [Pose et al 2017] [Prochazka and Stomberg 2020] [Prochazka et al 2018] [Raza and Silverthorn 1985] [Sagan et al 2021] [Santos et al 2022] [Scordamaglia et al 2025] [Shearwood et al 2020] [Shearwood et al 2020] [Shearwood et al 2021] [Shuo et al 2025] [Singh et al 2024] [Sisson and Dogan 2025] [Sisson et al 2024] [Spaans et al 2024] [Stam and de Visser 2025] [Su et al 2022] [Theilliol et al 2015] [Tohidi et al 2017] [Tohidi et al 2021] [Tsagkaris et al 2026] [Venkataraman and Doman 2001] [Vepa 2021] [Vernyi et al 2026] [Vile et al 2020] [Virnig and Bodden 1994] [Wahler et al 2023] [Wang and Zhang 2022] [Wang et al 2020] [Wang Fawei 2016] [Wu et al 2026] [Yan and Shi 2024] [Yiming et al 2019] [Yin et al 2019] [Yılmaz and German 2024] [Zhou et al 2015] [Zhou et al 2016]

Of the 90 records, 6 date from 1997 or earlier and 71 from 2015 or later. Among their titles, 18 name a multirotor, tilt-rotor or vertical take-off vehicle and 9 name a tailless aircraft or flying wing.

Flight dynamics, stability derivatives and unstable modes

Flight dynamics, stability derivatives and the modes of motion, including the unstable and inertia-coupled ones.

83 records. [Addington 2000] [Ajaj 2021] [Ananthkrishnan and Sudhakar 1994] [Ananthkrishnan and Sudhakar 1995] [Beaufrere 1986] [Been et al 2018] [Biber 2015] [Bird 1970] [Campos 1989] [Coulter and Marquart 1982] [Curtiss and Zhao 1988] [Czaykowski 1958] [Dat et al 2018] [Dhiman et al 2022] [Dr. Olivia Davis 2021] [Elliott et al 2025] [Ericsson 1980] [Ferguson and Thomson 2015] [Foster and Hartman 2017] [Gan et al 2021] [Gao et al 2020] [Gao et al 2022] [Goetzendorf-Grabowski and Kwiek 2023] [Hacker 1977] [Horst et al 2017] [Humphreys and Watkinson 1972] [Hyde et al 2014] [Foster and Hartman 2017] [Juhasz et al 2022] [Junior Kuitche et al 2024] [Klauck and Keßler 2025] [Klein 1977] [Klein et al 1982] [Kogler and Quam 1983] [Koryanov and Kukharenko 2023] [Krishnamurthy and Luckner 2017] [Laitone and Lin 1972] [Laitone and Lin 1973] [Lapins et al 1982] [Laudeman 1972] [Lee et al 2021] [Lessing and Butler 1959] [Leylek and Costello 2015] [Liu et al 2026] [Lueckhof and Stumpf 2018] [Lytovchenko 2026] [Masak 1965] [Montalvo and Costello 2015] [Mukai and Hunter 1996] [Mukherjee and Sinha 2016] [Munk 1922] [Pagliuca and Timme 2016] [Perry 1976] [Phillips and Santana 2002] [Potvin and Grant 2026] [Qiu and Gourishankar 1984] [Quitter et al 2021] [Rampy 1966] [Rising et al 1984] [Roberts et al 1977] [Rodden and Giesing 1970] [Rooney et al 1982] [Rosario-Gabriel and Cortes 2018] [Schiff 1971] [Schwanz 1972] [Shayak et al 2024] [Shi and Wan 2015] [Shrivastava and Stengel 1989] [Sizlo et al 1979] [Sliwa 1980] [Sparavalo 2021] [Spearman 1979] [Suryakumar et al 2016] [Swaim 1977] [Theodore and Celi 2002] [Tran and Sawan 1983] [Tzafestas 1975] [Uribe Quintero et al 2024] [Wang et al 2019] [Wilhelm and Schafranek 1986] [Wu et al 2016] [Yedavalli 2024] [Yuan et al 2020]

Turbofan performance, thrust and fuel consumption

Turbofan and small gas turbine performance, thrust and fuel consumption, and engine control.

80 records. [Akagi et al 1997] [Andersen and Bagby 1965] [Bartlett and Turner 1975] [Bennett et al 2024] [Burnell et al 1973] [Campbell 1973] [Campbell 1974] [Chamberlain 1968] [Chamberlin and Miller 1979] [Coalson 1968] [Coalson 1982] [Coalson and Csavina 1975] [Collins 1982] [Connolly et al 2017] [Connolly et al 2016] [Csavina 1976] [Cui et al 2024] [Dean 1978] [Dik et al 2017] [Drell 1965] [Effects of Reynolds number and other parameters on the throttle-dependent, nozzle/afterbody drag of an 0.11 scale single-engine aircraft model 1979] [Evans and Chamblee 1966] [Evans 1991] [Filinov and Ostapyuk 2019] [Filinov et al 2020] [Gagg 1937] [Guo et al 2024] [Hines and Gaffin 1976] [Hunt and Gowadia 1981] [Identification method of temperature corrections to aircraft engine thrust in flight tests 2023] [Jameson 2009] [Kadosh and Cukurel 2016] [Kashikawa et al 1995] [Kauser and Burcham 2001] [Kc et al 2019] [Khalid 2016] [Khalid 2017] [Kingcombe and Dunning 1980] [Lacaille and Loro 2016] [Lecuyer 1970] [Liew et al 2005] [Liew et al 2005] [Liew et al 2005] [Lin and Yeh 1999] [Lind and Protopapas 1977] [Ling 1983] [Liu and Sirignano 2000] [Loro and Lacaille 2017] [Magrini et al 2021] [Mattingly 1998] [McGuigan 1970] [Mehalic and Ziemianski 1980] [Miao et al 2020] [Tong 2020] [Miller and Hackney 1976] [Motycka and Skowronek 1968] [Neal and Sengupta 1989] [Olsson 1982] [Palacios et al 1998] [Price and Glidewell 1981] [Ramdin et al 2023] [Roth and Mavris 2001] [Schmidt 1985] [Sens 1978] [Shmelоv et al 2019] [Shufan et al 2017] [Singh 1986] [Sowers and Tabakoff 1983] [Srivastava and Duraisamy 2018] [Subagyo 2019] [Tate and Gillard 1975] [Tich et al 1987] [Van Der Hoeven 1981] [Wills and Wise 1976] [Xu 2025] [Zagranski et al 1974] [Zeller et al 1982] [Zhai et al 2025] [Ziemianski 1981] [Zimbelman and Rouser 2025]

Computational aerodynamics, surrogate models and uncertainty

Computational aerodynamics, surrogate models, machine learning of aerodynamic data and uncertainty quantification.

77 records. [Abe 1993] [Abras et al 2023] [Alhazmi et al 2021] [Ashton 2017] [Asouti et al 2023] [Asztalos et al 2026] [Atmaja et al 2023] [Bidar et al 2024] [Bobrowski et al 2016] [Brown 2025] [Burchett 2023] [Burchett and Bryson 2025] [Burrows and Allaire 2019] [Cai et al 2026] [Cakici and Yörük 2022] [Campbell et al 2026] [Chen 2026] [Chen et al 2026] [Dupuis et al 2018] [Eldredge and Mousavi 2026] [Eriş et al 2026] [Feldwisch 2026] [Gao et al 2015] [Hasan et al 2025] [Iyengar and Mavris 2025] [Jo et al 2018] [Jung and Baeder 2023] [Karali et al 2020] [Kiely and Agarwal 2023] [Kikuchi et al 2016] [Kirsch et al 2025] [Lakkur et al 2025] [Liem et al 2015] [Lin 2025] [Liu et al 2017] [Liu et al 2023] [Liu et al 2025] [Liu et al 2026] [Long 2016] [Long 2016] [Lyu et al 2024] [Mar Aye et al 2020] [Michal 1998] [Ni et al 2024] [Nieto-Centenero et al 2024] [Nikolaou et al 2025] [Ong and Chan 2016] [Othman and Kanazaki 2015] [Othman and Kanazaki 2015] [Pagliuca and Timme 2017] [Papoutsis-Kiachagias et al 2021] [Qin 2026] [Renard and Deck 2015] [Rosić and Diekmann 2015] [Schaefer et al 2019] [Schaefer et al 2024] [Schnell 2023] [Sharma and Hosder 2021] [Song et al 2016] [Stoldt et al 2021] [Stradtner and Bekemeyer 2025] [Suga and Yamazaki 2015] [Sun et al 2022] [Sung et al 2025] [Taylor 2015] [Valasek and Chakravorty 2015] [Wang 2025] [Wang 2025] [Wang et al 2024] [Way et al 2026] [West and Phillips 2020] [West et al 2017] [Yan and Shi 2025] [Yang and Yee 2022] [Yondo et al 2018] [Zhang et al 2024] [Zimmnau et al 2025]

Radar signature and low observability

Radar cross section and low observability of aircraft and unmanned aircraft, the consideration that made the vertical tail a liability.

66 records. [Abdullah and Miao 2026] [Abdullah et al 2025] [Altman 2008] [Aronstein 1996] [Ashraf et al 2018] [Brown 1993] [Chen et al 2015] [Chung and Tuan 2021] [Correa et al 1981] [Dybdal 1987] [Edefur and Tormalm 2018] [Fry 2008] [Garretson 1986] [Guay et al 2017] [Guo et al 2018] [Jeong et al 2018] [Kao and Anderson 1981] [Kurbanismailov et al 2021] [Lee 2024] [Liu et al 2017] [Lowry et al 1978] [Mahulikar et al 2022] [Mammadova et al 2025] [Marvasti and Boutayeb 2024] [Nam 2026] [Norsell 2003] [Ozdemir et al 2024] [Papageorgiou et al 2018] [Persson 2017] [Persson and Bull 2016] [Piccirillo 1996] [Queen 1976] [Radar cross section fundamentals for the aircraft designer 1979] [Sai Teja et al 2017] [Sepulveda Palacios and Smith 2019] [Siegel 1961] [Sijabat and Indriyanto 2021] [Silva et al 2026] [Steinberg et al 1989] [Taj et al 2023] [Tarlanov and Kurbanismailov 2021] [Trueman et al 1993] [Tsai et al 2016] [Tusa et al 2015] [van Schalkwyk and Smit 2017] [Vogel 2016] [Vogel and Junqueira 2017] [Wang et al 2022] [Wang et al 2025] [Wang et al 2025] [Wang et al 2026] [Woods et al 1996] [Wright 1975] [Xiaofeng Ai et al 2016] [Xu et al 2020] [Yang 2024] [Zhang et al 2023] [Zhang et al 2026] [Zhou and Huang 2021] [Zhou and Huang 2021] [Zhou and Huang 2022] [Zhou and Huang 2022] [Zhou and Huang 2023] [Zhou and Huang 2023] [Zhou et al 2021] [Özdemi̇r 2020]

Turn performance, agility and manoeuvre

Turn performance, agility, energy manoeuvrability and the manoeuvre performance that thrust vectoring changes.

51 records. [Altunkaya and Özkol 2025] [Beck and Cord 1995] [Boppe and Martorella 1992] [Bryson et al 1969] [Bryson and Desai 1968] [Caddy and Arnold 1988] [Denham et al 2022] [Cecen 2021] [Chakraborty and Mishra 2021] [Costes 1988] [Cramer 1995] [Dwyer and Lutze 1993] [Foss 1944] [Gal-Or 1992] [Gal-Or and Baumann 1993] [Gomes and Suleman 2004] [Hoffman and Stalford 1991] [Incorporating agility flight test metrics concurrently into the aircraft preliminary design process 1994] [Johnson 1972] [Kimberlin 2001] [Kutschera and Render 1999] [Landgraf 1964] [Landgraf 1965] [Langan and Samuels 1995] [Lee and Lan 1992] [Loh and Lusty 1974] [Manolescu 1994] [Mazza 1992] [Montgomery et al 1998] [Moroney et al 1979] [Morris and Kroo 1990] [Papadales and Basil S. 1979] [Paranjape and Ananthkrishnan 2023] [Rajeswari and Prabhu 1987] [Rutowski 1954] [Ryan and Downing 1993] [Sanders 1997] [Schairer 1964] [Schrage 1990] [Schultz and Zagalsky 1972] [Stalford and Hoffman 1989] [Stanley 1980] [Tamboli 1956] [Tamrat 1988] [Tomczyk 1998] [Valasek and Downing 1993] [Wang et al 2020] [Warren 1990] [Wilson et al 1993] [Wittenberg 2001] [Yajnik 1977]

Flight simulation and simulators

Flight simulation and simulators, ground-based and in flight, including the visual and motion cues a ground pilot receives.

29 records. [Aume et al 1976] [Benyamen et al 2023] [Bezdek 1995] [Carter 1988] [Chetty and Henschel 1987] [Cooksey et al 1964] [Ebeling 1969] [Fuad et al 2024] [Gu 2025] [Gundry 1977] [Huang et al 2017] [Huguenin 1981] [Ivan 1985] [Jansen 1980] [Litt et al 2012] [Liu et al 2015] [Morlang and Strassburger 2025] [Motyka 1975] [Motyka and Reynolds 1971] [Nonlinear model following control application to a flight simulator control loader 1989] [Research and Analysis on Development and Flight Test of Military Aircraft Flight Simulator 2022] [Roganov et al 2017] [Sarathy and Murthy 1993] [Sarrafian 1984] [Sarrafian 1986] [Shlien 1991] [Stortz and ODonoghue 1995] [Wortman et al 1975] [Yifei et al 2015]

Mass properties and moments of inertia

Mass properties and the measurement and estimation of moments of inertia of aircraft, missiles and test articles.

23 records. [Aircraft moments of inertia 1996] [Alyshev et al 2016] [Chai et al 1995] [Chin et al 2015] [Chin et al 2015] [Dantsker et al 2018] [Green 1958] [Hou et al 2011] [Jardin and Mueller 2009] [Malaek and Soltan-Mohammed 2001] [Martin and Lind 2025] [Morelli 2021] [Morelli 2022] [Napolitano et al 2024] [Pal and Gaberson 1973] [Patera 1981] [Peterson 2004] [Schwartz et al 1957] [Setati et al 2022] [Simmons et al 2023] [Simmons et al 2023] [Swank 2012] [Wickman 1953]

The X-36, X-29 and X-31 demonstrators

The aircraft’s own record, and that of the X-29 and X-31, the two flight-control demonstrators this article sets beside it.

21 records. [Bosworth and Cox 1989] [Bosworth and Stoliker 1996] [Brinker and Wise 2000] [Brinker and Wise 2001] [Calise 2000] [Fratello et al 1987] [Harris and Harris 1997] [Hicks and Matheny 1989] [Huber 1995] [Huber and Schellenger 1994] [Ishmael and Wierzbanowski 1985] [Kaletka and Fu 1993] [Klafin 1988] [Putnam et al 1986] [Smith and Schroeder 1986] [Tamrat 2004] [Trippensee 1991] [Voracek and Clarke 1994] [Walker 1997] [Whiting 1996] [X-29 Research Aircraft 1991]

Of the 21 records, 5 titles name the X-36, published from 1997 to 2001, and one of them is a report primary.

The viscosity of air and Sutherland’s law

The viscosity of air and other gases and its variation with temperature, which Sutherland’s law expresses and the Reynolds number computation uses.

18 records. [Bond 1936] [Edwards and Rankine 1927] [Gupta et al 1991] [Hansen 1959] [Harrington 1939] [Holman 1876] [Holman 1885] [Houston 1937] [Kellström 1936] [Keyes 1927] [McInally 1963] [Nadi and Zeid 1955] [Palmer and Wright 2002] [Rigden 1938] [Sutherland and Maass 1932] [Viegas and Howe 1962] [Williams 1926] [Williamson 1951]

None of the 18 records is later than 2002, which is the shape a settled subject takes.

Fighter and technology demonstrator programmes

Fighter and technology demonstrator programmes, their conduct, flight testing and lessons.

12 records. [Andrews et al 1980] [Aulehla and Kissel 1981] [Aulehla and Kissel 1982] [Bailey et al 2020] [Borer et al 2019] [Borer et al 2024] [Brown et al 2026] [Filippoli et al 2026] [Kramer et al 2018] [Lorell 1989] [Nicholson 1985] [Veletas 2026]

Where the Framing Breaks Down

The Article Leans Hard on Idealised Similitude

The scaling argument in this article assumes idealised similitude, and real models depart from it. Matching the mass ratio exactly requires matching the inertia ratio too, which means placing the mass correctly in three axes and not merely getting the total right. Whether the X-36 did so is not in the public record. If its inertias were not scaled, the doubling times computed above are wrong by whatever factor the inertia is wrong by, and the article’s bracket across radius of gyration is an admission of that rather than a resolution of it.

The Latency Argument Has No Measurement Behind It

The structure of the latency argument is sound and its magnitude is unknown. The amplification factor of 1.8898 is exact and follows from the scale factor alone. The thing being amplified is not published. If the link delay was very small then the handicap was small, and the article’s claim reduces to a statement about a multiplier rather than about a difficulty.

The claim is therefore made in that weaker form, and no assertion is made that the pilot found the delay hard, because the published ratings do not isolate it. Walker 1997 reports Cooper-Harper ratings of 4 for pitch attitude capture and 3 for bank angle capture in the first phase, Level 1 handling qualities in all axes in the second, and that considerable pilot attention was required.

The Instability May Have Been Milder Than Assumed

The directional derivative used above is assumed rather than measured, at a value typical of a tailless configuration. A less unstable aircraft would double more slowly and the whole argument would soften. The bracket across radius of gyration does not cover this, because a different derivative scales the growth rate rather than the inertia, and the article flags it as the assumption its sharpest number is most exposed to.

The Comparison With the Previous Article Is Neat and Should Be Distrusted for It

Two consecutive demonstrators, one flown easier than the real thing and one flown harder, is a pleasing symmetry. It is also the kind of pattern that appears when one goes looking for it. The X-35 comparison rests on weights and an ordering, which are published. The X-36 comparison rests on a scaling law, which is exact, applied to a latency that is not published. Those are not equally solid, and they are not presented here as though they were.

The Source Base

The aircraft’s own record is thin and the record of its methods is deep. The vehicle facts come from the programme account, the published specification, the inventory of American X-vehicles and the programme’s flight-test paper Walker 1997, which gives the weights, thrust, speeds and control effectors. The first three disagree on the size of the programme and are reported side by side where they do. The flight-control literature of the programme, the papers on the reconfigurable control law flown in 1998, and the subsystems and test-pilot papers of 1997 are surveyed in the cluster on the X-36, X-29 and X-31 demonstrators.

No latency figure for the command and video link is public, which is the quantity the article’s sharpest argument would most like to have. Only envelope maxima of angle of attack are public, 40 degrees in the programme account and 35 degrees for turning and rolling manoeuvres in the inventory of American X-vehicles, and what is public from high angles of attack is pilot ratings and a normalised roll-time plot reaching a little above 30 degrees in Walker 1997, with no time history, though that is what the tailless argument turns on. No moment of inertia, no stability derivative and no wing area is public, so three of the numbers in the sizing section are inversions or brackets rather than readings, and each says so where it stands. The fuselage volume the slender-body derivation needs is not public either, and neither is the drag increment of the split ailerons, which is why the conclusion about them flips inside its own bracket.

The following books and monographs supplied the standing theory, and almost none of them concerns this aircraft, covering stability and control, flight dynamics, similitude, flight test method and the control literature the adaptive work drew on.

The research survey holds 3,712 research records drawn from the National Aeronautics and Space Administration’s Technical Reports Server, the Defense Technical Information Center and the journal literature indexed by Crossref, of which 520 are report primaries, being 14.0 percent, by the identifier rule set out under The Definition of Primary. The median publication year is 2015. Of the 3,709 dated records, 1,517 were published in 2001 or earlier, the period of the aircraft’s design, flight programmes and reports, being 40.9 percent, and 1,973 were published in 2015 or later, being 53.2 percent. The count and the fraction are reported together, because adding sources on one side lowers the other’s share without removing anything.

The Definition of Primary

Primary means the reports and papers written during the programme and the technology base it drew on, which for this subject reaches back to the free-flight model work of the 1950s and to the flying-wing stability literature that is older still. Primacy is a property of the document, and this survey derives it from the identifier. A record is a report primary when its address is on the NASA Technical Reports Server or it carries a digital object identifier under the 10.21236 prefix, which Crossref registers for Defense Technical Information Center reports. Of the five titles that name the X-36, one is a report primary, so most of the aircraft’s own record is journal and conference literature under this rule. The rule does not reach the journal papers among the foundational sources, such as the slender-body papers of the period and the viscosity measurements, so 14.0 percent is a lower bound on how much of the survey is first-hand.

Thin Subjects

Five research records carry this aircraft’s designation in their titles. The X-33, X-34 and X-35 show the same shape for different reasons. The X-33 and X-34 were cancelled and stopped generating literature under their own names. The X-35 won and never had a documentary trace at all, because contractor demonstrators flown for a source selection do not produce reports.

The X-36 is a fourth case and its reason is different again. The programme was neither cancelled nor a competition. It ran to completion, met its objectives, and produced a technique rather than a vehicle. What it contributed is in the literature under the names of its methods rather than under its own, which is why the scaling, control allocation and adaptive control clusters are large while the vehicle’s own record is not. Four vehicles, four different reasons for the same thin record, and the pattern is a finding about the series of aircraft rather than about any one of them.

Six 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. Where a row joins two groups of terms with the word together, a title must carry a term from each group.

Subject	Title terms counted	Records
the drag increment of a split aileron or drag rudder	split aileron, split ailerons, drag rudder, drag rudders, deceleron, decelerons, clamshell	1
the time to double of an unstable mode	time to double, doubling time, doubling times, time to half	0
the link delay of a remotely piloted aircraft	latency, time delay, time delays, transport delay, video delay together with remotely piloted, unmanned aircraft, unmanned aerial, UAV, UAVs, RPV, drone, drones	6
the moments of inertia of an aircraft	moment of inertia, moments of inertia, radius of gyration, radii of gyration, inertia measurement together with aircraft, airplane, aeroplane, UAV, unmanned, hexacopter, quadcopter	7
turn rate and corner speed	turn rate, turn performance, corner speed, corner velocity, sustained turn, instantaneous turn	3
the Froude number of a free-flight model	Froude	2

The drag increment of a split surface is the quantity the yaw argument most needs and the least studied. One title names a split aileron, a drag rudder, a deceleron or a clamshell surface, and the bracket on the increment stands on the relation derived above rather than on a measured value for this aircraft.

The time to double is a textbook quantity rather than a research subject. No title names the time to double or a doubling time, so the distinction drawn above between the modal time and the time from rest is the article’s own.

The delay of a remotely piloted aircraft’s link is studied far less than delay in general. Six titles name a delay together with a remotely piloted or unmanned aircraft, against 135 records in the cluster on time delay, latency and delay compensation, of which 23 titles name an aircraft, a pilot, flight or an unmanned aircraft and the rest concern teleoperated robots and ground vehicles or the theory of delayed systems. The delay that the article’s amplification multiplies is therefore not available from this literature either.

The inertia of a whole aircraft is rarely the subject of a title. Seven titles name the moments of inertia of an aircraft or an unmanned aircraft, so the bracket across radius of gyration above cannot be narrowed from the literature.

Turn rate and corner speed are named in three titles, while the manoeuvre literature itself sits under agility and energy manoeuvrability in the cluster on turn performance, agility and manoeuvre.

Froude scaling is used far more than it is named. Two titles carry the word Froude, while the cluster on similitude, dynamic scaling and subscale flight testing holds 155 records on the scaling and testing of models.

What the Survey Admits

A record is admitted only when a person reading its title finds it on this article’s subject, which is the flight dynamics, control, aerodynamics, scaling, testing and remote operation of a tailless subscale research aircraft, together with the theory its derivations use. Many words this subject depends on also name something else, and a record that shares only such a word is excluded. Restore names a military laundry, a cancer gene and an operation in Somalia as well as a control law. Departure names a flight leaving its gate, so airport scheduling and departure noise are excluded. Similitude and dynamic scaling also belong to soils, beams, crash testing and mooring cables, and dynamic scaling is a term of control theory. Moment of inertia also names a property of servo drives, classroom pendulums, internal-friction apparatus and spacecraft. Viscosity also names liquids, aerosols and the artificial viscosity of numerical methods, and apparent mass also belongs to bodies in water and gas-particle flows. Control allocation also serves underwater vehicles, ships, electric cars, robots and satellites, rudder also names the rudders of ships and sailboats, and thrust vectoring also steers rockets and missiles. Reynolds number effects also govern turbine and compressor cascades, circular cylinders and buildings, and teleoperation also names the control of robotic manipulators with no delay in the loop. Records whose only link to the article is a distant application of the same aircraft class are excluded as well, among them drones used for mapping, surveying, wildfire watch and radio measurement, aircraft noise, icing, landing gear and tyres, crash survival, flutter and structures, rotorcraft rotors, launch vehicles, re-entry vehicles, projectiles and missiles, and electric propulsion and batteries. Correction notices, conference reports and announcements, trade news and supplementary-material records are excluded, because a survey counts research works and those are notices attached to works or parts of works. A signed comment on a paper and the authors’ reply to it argue about a result and are research works, as are a signed discussion and a signed letter, so each is admitted when its subject is this article’s, while an unsigned item of these kinds and a referee’s report on a manuscript are not. Reviews of books, reference entries of two pages or fewer, and the abstracts of papers and patents reprinted in the abstract sections of other journals are excluded on the same ground, while a signed encyclopedia article and a textbook chapter are research works and stay. Where the same paper is deposited twice, as a digest and as the paper, one record is kept, while a conference paper and the journal article that followed it are kept as two documents.

Some records of doubtful relevance are kept. Teleoperation of ground vehicles and robots through a delayed link, the general theory of time-delay systems and of stability margins, control allocation for multirotor vehicles, the slender-body aerodynamics of missiles, rotorcraft handling qualities, and the correspondence of William Froude on ship models each share the delay, the margin, the redundant effectors, the fuselage or the scaling law with this subject, so each is kept and a reader may weigh it accordingly. No residual cluster is needed, because every admitted record falls within one of the named clusters.

Every research title has been read for relevance, so the off-topic share that remains is a matter of reading judgement. A reading of titles cannot show that a work is relevant in substance, so this is a statement about titles only.

Epistemic State

Historical Fact

The X-36 was a 28 percent scale, remotely piloted, tailless research aircraft built by McDonnell Douglas in partnership with the National Aeronautics and Space Administration. Two were built. It was 18 feet 2.5 inches long with a span of 10 feet 5 inches, weighed 1,083 pounds empty and 1,245 pounds at takeoff, carried 162 pounds of usable fuel, and was powered by a Williams F112 turbofan of 700 pounds force. Its approach speed was 112 knots, its test envelope was held at first to 160 knots under a dynamic pressure limit of 200 pounds per square foot, its ceiling was 20,500 feet and its load factor limit was 5 g. The weights, fuel, approach speed and limits are those of Walker 1997, the test pilot’s report, and the dimensions and ceiling those of one published specification, which gives 1,270 pounds maximum, 1,090 pounds empty, 180 pounds of fuel and a 110 knot approach instead. It reached 206 knots, 20,200 feet and an angle of attack of 40 degrees. It first flew on 17 May 1997 and completed 31 research flights and 15 hours 38 minutes of flight time by 12 November 1997, a period of 25 weeks. One inventory of American X-vehicles gives 25 flights ending on 24 September 1997 instead. In December 1998 it flew twice more carrying the Air Force Research Laboratory’s Reconfigurable Control for Tailless Fighter Aircraft software. It had no vertical or horizontal tail and used a canard, split ailerons and a thrust-vectoring nozzle, commanded by a digital flight control system, with the pilot in a ground station viewing through a camera on the forward fuselage.

Engineering Analysis

Every scaling ratio follows from the scale factor alone once Froude matching is chosen, and each is an identity that holds at every scale factor. The velocity and time ratios are 0.5292, the frequency ratio 1.8898, the angular acceleration ratio 3.571, the inertia ratio 0.001721 and the Reynolds ratio 0.1482, a penalty of 6.749. The implied full-scale weight of 56,715 pounds follows from cube scaling, and the length of 19.82 metres and span of 11.34 metres from the length ratio. The wing area of 3.117 square metres and aspect ratio of 3.235 are inverted from the published approach speed. The model Reynolds number of 8.40 million and Mach number of 0.367 at maximum speed follow from the standard atmosphere and Sutherland’s law. The yaw moment from thrust vectoring of 2,364 newton metres and the authority crossover at 350.5 knots follow from the moment balance. The identity that a disturbance released from rest doubles in 1.900 times the modal time is exact and depends on nothing. Every figure in this section can be reproduced from the published figures and the stated assumptions with the relations the article displays, and the doubling times can also be reproduced by integrating the yaw equation under its two initial conditions.

Inference

That the scale factor is the interesting quantity, and not the missing tail, is a judgement about what is worth explaining and not a fact. That the demonstration was harder than the thing it demonstrated is an inference with an exact multiplier and an unmeasured multiplicand, and the article states it in that form. Whether the split ailerons were margin or necessity is not determined by public information, since the drag increment that decides it is unpublished and across its plausible range the split surfaces run from 21.0 to 126.2 percent of the nozzle’s moment, so the answer flips inside the bracket. What is settled is the structural claim, that the nozzle’s authority is flat with speed while the drag rudder’s rises as its square, and that needs no increment at all. That the vehicle cluster is thin for a fourth distinct reason is an inference from four cases and is offered as a pattern rather than a law.

What the Record Does Not Settle

Whether the aircraft’s inertias were correctly scaled is not settled, and if they were not then the doubling times are wrong by that factor.

The size of the link delay is unpublished, so the amplification factor is exact and what it amplified is unknown.

The aircraft’s behaviour at its highest angles of attack remains open, since the public record gives the maximum of 40 degrees but no time history there, only pilot ratings and a normalised roll-time plot from lower angles, which limits what can be said about the question the programme existed to answer.

Whether a tailless manned fighter is practical is not settled by this aeroplane and was never going to be, because the binding constraints on that question are certification and signature rather than control.

Out of Scope

The radar cross section of tailless configurations is outside this article, which has no access to the measurements and no way to compute them. The production unmanned aircraft that adopted the planform are outside it. The detailed architecture of the neural-network control law flown in 1998 is touched on only as a programme fact. The X-31 and X-29, which are the series’ other flight-control demonstrators, are covered in their own articles, which this one cites without re-examining.

Conclusion

The X-36 asked whether a fighter can fly without a tail, and answered yes at 28 percent scale. The substance lies in that qualification.

Matching the Froude number is the only choice that makes a free-flight model move like an aeroplane, and it fixes everything else. The model’s motions run 1.8898 times faster than the full-scale aircraft’s, its angular accelerations are 3.571 times larger, and its Reynolds number is lower by a factor of 6.749. The first of those is a handicap on the demonstration, because a delay in a video link and the reaction time of a human being do not compress to match. The third is a limit on what the demonstration can measure, and it falls precisely on the separated flow at high angle of attack that the experiment was about.

The aircraft’s own weight confirms the choice. At 1,245 pounds and 28 percent it stands for a fifty-seven thousand pound fighter, sixty-five feet long, which matches a real class of aeroplane.

And the missing fin turns out to be the least interesting part of the story, because the arithmetic says the vectoring nozzle alone could hold ten degrees of sideslip at every speed the aircraft ever flew. Public information cannot say whether the split ailerons were carrying most of the yaw at high speed or almost none of it, and the article says so where it computes them. A nozzle can replace a fin because a fin’s authority and the instability it opposes both scale with dynamic pressure, so their ratio never improves, while a nozzle’s authority does not scale with anything. The nozzle is strongest where the fin is weakest, in the condition a tailless aircraft most fears.

The previous article found a demonstration flown easier than the thing it stood for. This one was flown harder. The X-36’s divergence doubled in well under a second, nearly twice as fast as its full-scale equivalent would have, and a pilot on the ground held it there through a delay that counted for nearly twice its length in clock time. That is a better result than the programme claimed for itself, and nobody said so because the factor is hidden inside the scale.