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1) Various sites like this one: Orville and Wilbur Wright, The Inventors of the 3-axis Flight Control System, 9 Months before their powered flight at Kitty Hawk say that the two brothers invented the three-axis control system.

Is it true?

This is what they wrote in the beginning of their British patent: 1904-03-19 – 1904-05-12, Orville and Wilbur Wright, “GB Patent No. 6732, A.D. 1904 – Improvements in Aeronautical Machines”, Date of Application: 19th Mar., 1904, Accepted: 12th May, 1904, 5 pages, the first that was granted to them.

"Our invention relates to improvements in that class of aeronautical machines in which the weight is sustained by the reactions resulting when thin surfaces, or wings, are moved horizontally almost edgewise through the air at a small angle of incidence, either by the application of mechanical power, or by the utilization of the force of gravity.

The objects of our invention are, first, to provide a structure combining lightness, strength, convenience of construction, and the least possible edge resistance; second, to provide means for maintaining or restoring the equilibrium of the apparatus; and third, to provide efficient means of guiding the machine in both vertical and horizontal directions."

The expression "three-axis control" does not appear in the patent.

Regarding this patent, more precisely its German version, filed on March 23, 1904, (four days after the British text) the fact that the wing twisting and the vertical rudder had nothing to do with steering the machine was clearly explained by Harry Aubrey Toulmin (the Wright brothers’ patent lawyer) to Carl Pieper (his German correspondent) in a letter dated April 11, 1905. Here is the relevant excerpt of this document:

“It is evident from the action of the German Patent Office that the invention is not yet understood by them. The entire purpose of the structure on which the application is based, excepting the front rudder, which is for another purpose, is to maintain the body of the structure level or parallel with the horizon. It has nothing whatever to do with steering, neither has it anything to do with the raising and lowering of the plane of flight. The setting of the two parallel edges of the supporting planes at different angles is solely for the purpose of maintaining the wide body of the machine parallel with the horizon. The rear rudder is solely for the purpose of overcoming the tendency to turn around a vertical axis which naturally results from setting the two edges of the planes at different angles. … We shall trust to you to place these matters before the German Office in the best way possible and hope that you will be successful in obtaining the allowance of the application.”

H. A. Toulmin, “Letter to the Carl Pieper”, Springfield, Ohio, April 11, 1905

The explanation above is puzzling and seems to nullify any kind of pretentious that the Wrights invented the three-axis control system as long as their patent application had “nothing whatever to do with steering”.

2) Regarding the adverse yaw, the description given in the patent and the explanation of Toulmin are quite clear. The Wrights proposed a method for counteracting this unwanted effect but where they the first who noticed it?

enter image description here The Wright brothers glider as it appeared in the US patent granted on May 22, 1906, which is a bit more detailed than the drawing in the British patent, granted two years before.

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The patent lawyer is explaining things quite correctly and this applies to modern aircraft. The rudder does in fact have nothing to do with steering the airplane. Its job is to keep the tail lined up behind the nose (or to move the tail out of alignment with the nose if you wish) mainly overcoming adverse yaw caused by warping (or later, ailerons).

The bolded text in the paragraph you quoted describes the wing warping being for roll control, and the rudder for controlling for the adverse yaw that results from the wing warping (same as aileron displacement in modern aircraft), just like any modern aircraft. He is describing how a modern airplane flies in other words, and this was a pretty radical idea at the time so it didn't make sense to a lot of people.

The Wrights discovered adverse yaw as they were developing their totally new wing warping system concept, as it was abundantly obvious from the way the nose would slew the opposite direction to the wing warp input and a rudder control was the obvious solution. They didn't get it from anybody else because nobody else had thought of the concept of differential lift to control bank in order to turn. Lillienthal, from whom the Wrights based a lot of their work in the beginning, used weight shift to control his gliders.

I recall from books I read on the Wrights years ago that they proceeded originally from from Otto Lillienthal's aerodynamic theories, and as they tested their glider machines, they started to discover that Otto had a lot of things wrong, prompting them to build their home made wind tunnel and start development from scratch.

So I would say for (1) yes, they invented the 3 axis control system, that is, all 3 being used together to make coordinated banked turns, because they developed and patented wing warping (ailerons coming later and leading to a long patent legal battle with Glenn Curtiss). Up until then, and for some time after, developers were controlling turns by skidding using rudders (helped by dihedral effect to achieve banking in some cases) or by weight shift, or in Bleriot's case trying to achive roll control with differential elevator movement like an F-15 to get around the Wrights' wing warp patent (which they defended furiously, leading to the long patent battle with Curtiss, who ironically ended up taking them over in later years and becoming Curtiss-Wright, a running concern to this day).

The proof of this is obvious if you read of the various accounts describing the Flyer's demonstrations through the mid 00s. The Flyer's contemporaries, such as they were, would slither about the sky, whereas the Flyer flew around making coordinated banked turns like a modern aircraft. This astounded observers, especially the French when the Wrights demonstrated the Flyer in France. The French reaction to the Flyer was really something else, one of awe, admiration, and a bit of jealousy, that those two American yahoos brought a flying machine that could literally fly circles around machines like 14-bis.

So for (2) I would say the answer is also yes because they invented differential lift for roll control in order to turn, which quickly indicated the need for a rudder to counteract adverse yaw and which followed on naturally.

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  • $\begingroup$ If the vertical rudder plus ailerons (wing warping) are not used for steering, then they are just for stabilizing the flying machine in roll, which would be one-axis stability. The patent would by about the stability about the longitudinal axis and control/stability about the transverse axis (pitch). The yaw control (steering the plane to the left and to the right) is not covered and in consequence the patent is not about 3-axis control. It appears that the Wrights were simply not allowed to claim steering (in pitch and mainly yaw) because the two movements were covered by other patents. $\endgroup$ – Simplex11 Jan 2 at 22:54
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    $\begingroup$ The July 15, 1908, issue of L’Aérophile (gallica.bnf.fr/ark:/12148/bpt6k6550620m/f284), after saying that a Blériot VIII had flown for 8 min and 24 sec on July 6, 1908, a notable performance for a monoplane, noticed the impressive manœuvrability of the apparatus, due, in part, to its ailerons (not based on wing warping). This flight took place more than 1 month before August 8, 1908, when the Wrights first showed their machine on the ground and in flight. That day Wilbur flew for 1 min and 45 sec. As a remark, on July 6, 1908, Farman flew for 20 min 20 sec without ailerons. $\endgroup$ – Simplex11 Jan 2 at 23:10
  • $\begingroup$ Wright's patent was only for wing warping for roll. I never said they patented 3 axis control; I just said they were first to apply it in the modern sense insofar as they introduced the 3rd element, roll control, and they used the rudder for it's correct purpose in the modern sense, to keep the tail lined up behind the nose. $\endgroup$ – John K Jan 2 at 23:34
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    $\begingroup$ You said: "they [the Wrights] used the rudder for it's correct purpose in the modern sense, to keep the tail lined up behind the nose". I do not really get the meaning of this statement (I do not say it is wrong, I just say I do not understand it). On January 13, 1908, Henri Farman made turns, without ailerons, and flew 1 km in a circuit at a stable altitude. He steered the airplane, in the horizontal plane, just with its tail (vertical rudder). $\endgroup$ – Simplex11 Jan 3 at 5:28
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    $\begingroup$ But they MANEUVERED like a modern aircraft, which was unprecidented. Stability is not the issue. You're not really getting it. $\endgroup$ – John K Jan 3 at 22:11
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The Wright brothers were not aware a glider or plane could be steered to the left or to right by rolling it to the left or to the right

The two inventors did not discover the method of turning a plane by banking it to one side or the other.

In their patents, what they had in mind was the classical steering with the vertical tail rudder (not invented by them) while the wings of the airplane were maintained as parallel to the ground as possible by stabilizing the flying apparatus in roll using the Wing Warping method.

It is a myth that the two brothers from Dayton realized a plane could be made to take turns by banking it.

They have two more patents, filed on February 17, 1908, (see the drawings below) in which the tail rudder is disconnected from the wing warping mechanism, the tail being free to move independently of the twist of the wings. The adverse yaw, unlike in the May 12, 1904, British patent, is corrected with two vertical vanes placed close to the wing tips in the US Patent No. 1,122,348 and with another mobile vertical rudder placed in front of the main wings in No. 987,662.

None of these two patents nor the May 12, 1904 British patent talk about steering by banking.

enter image description here

enter image description here

Orville and Wilbur Wright, “US Patent No. 1,122,348 – Flying-Machine”, Filed: February 17, 1908, Patented: December 29, 1914

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Orville and Wilbur Wright, “US Patent No. 987,662 – Flying-Machine”, Filed: February 17, 1908, Patented: March 21, 1911.

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  • $\begingroup$ Well they sure are banking it to turn in this 1909 film youtube.com/watch?v=dtZ8MxuePno. $\endgroup$ – John K Jan 9 at 4:18
  • $\begingroup$ I read through the patent linked and nowhere does it say they turn by skidding. The vertical vanes described are for control of "secondary effects" of the wing warp - adverse yaw. They also turned their 1902 glider by banking. They had to; a glider with no thrust source beside gravity and no side area to speak of will simply not change heading fast enough to be useful if you skid it. It will just carry on more or less in the same direction with maybe a painfully slow heading change. Here is a pic of the glider turning britannica.com/topic/Wright-glider-of-1902. $\endgroup$ – John K Jan 9 at 4:40
  • $\begingroup$ That 1909 plane had dihedral stability. The gliders in the 1904 British patent and the two US patents of February 17, 1908, did not have automatic stability in roll. If the airplane is naturally stable, and it also possesses ailerons, just moving the ailerons in opposite directions will determine it to start steering by banking. The Wright brothers might have noticed this effect starting with August 1908. $\endgroup$ – Simplex11 Jan 9 at 4:50
  • $\begingroup$ In their patents, nowhere it is written that the Wrights intended to turn their airplane by skidding or banking. In the Feb 17, 1908, US patents both steering by skidding and banking are possible but the two inventors do not say how the machine could take turns. There is no word about the lateral force that appears when the plane banks. $\endgroup$ – Simplex11 Jan 9 at 7:44
  • $\begingroup$ It is clear now that the Wright brothers had in mind skidding not banking because this is what they said in their Feb. 10, 1908, patent about automatic stabilization (see: docs.google.com/viewer?url=patentimages.storage.googleapis.com/…): “If it is desired to drive the machine in a circle ... set the vertical rudder at an angle to its normal position, and, with the parts thus reset, the automatic-controlling mechanism will operate then in exactly the same manner as when the machine is being driven forward in a straight line”. $\endgroup$ – Simplex11 Jan 9 at 8:01
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No, the Wright brothers did not invent the three-axis control, at least in their Patent No. 6732, A.D. 1904 (They might have other patents which cover: roll, pith, and yaw control together. I do not speak for them if they exist.)

In No. 6732 the two brothers do not have a clear explanation about steering the glider in the horizontal plane. The Wrights do not say how they control the yaw rotation (except the adverse yaw) and in consequence the patent does not make them the inventors of the three-axis control system.

What the patent explains well is:

1) the stability in pitch and also to a lesser degree but still understandable the control of the pitch angle (the steering in the vertical plane).

2) the stability in roll and how the adverse yaw is compensated.

Their claim:

to provide efficient means of guiding the machine in both vertical and horizontal directions.

is not sustained, regarding the horizontal direction, by the explanations they gave.

With reference to the image below, we will assume that at moment t0 the plane was flying horizontally with its wings parallel to the ground and the pilot attempts to steer it to the right by rising the tips of the left wings and lowering those of the right wings. As the rear vertical rudder is interconnected with the wing warping mechanism and the angle it makes, to the neutral position, can not be independently adjusted regardless the level of the twist, the rear rudder will automatically turn to the right to compensate for the adverse yaw that rotates the plane to the left. If the pilot forces the configuration "Left wing tip up, Right wing tip down, vertical tail to the right" he can no longer control the roll stability. The plane will turn to the right only assuming that during this maneuver it does not have any tendency to roll chaotically due to its inherent instability in roll, which is not the case.

The Wright brother's glider How the two brothers maintained their glider stable while taking a turn remains an unexplained thing.

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  • $\begingroup$ While taking a turn to the right, the Wright brothers might have thought of keeping the vertical rudder at a reference angle, say 45 deg, to the right and balancing the plane by moving the rudder a few degree above or below this reference angle. However they do not say this. They do not detail how the vertical rudder in synchronization with the wing twist can steer the plane. $\endgroup$ – Simplex11 Jan 5 at 0:18
  • $\begingroup$ What they had was the Ercoupe's no-rudder-pedal control system, where the rudder was geared directly to the ailerons and worked only to compensate for adverse yaw induced by wing warp. It's blindingly obvious to anybody who flies that they could not have turned their glider without banking it. A glider with no side area and no engine will simple slither sideways if you tried to "steer" it with rudder (you are actually skidding it). If you get any turn rate out of it, it will be too slow to be of any utility. $\endgroup$ – John K Jan 9 at 4:47
  • $\begingroup$ In their Feb. 10, 1908, patent they explain how the plane could be steered by skidding just by turning the vertical rudder to one side (applying a shift, setting a new zero for its position) and then working the rudder and ailerons exactly like during a flight in a straight line. $\endgroup$ – Simplex11 Jan 9 at 11:00
  • $\begingroup$ The vertical rudder appears to be interconnected to the wing warp mechanism so a rudder input results in a roll not just a skid sideways. That kind of machine skidding sideways will take a week to effect a change in direction. If the film of it you can see it is banking in all its turns. Don't put too much into the patent language. The patent also describes a pendulum/air cylinder driven servo contraption for creating artificial stability which wasn't implemented. $\endgroup$ – John K Jan 9 at 20:16
  • $\begingroup$ 1) In the Feb 10 patent the Wrights imagined a special mechanism that allowed them to set by hand the initial position of the vertical rudder, independently of the wing twist, and then they coupled the rudder to the automatic mechanism which moved it relative to its new position. Read my previous comment that contains the text "If it is desired to drive the machine in a circle" for more explanations. 2) Orville said in 1913/14 the Feb 10 patent had been implemented and it worked!!? (see: aviation.stackexchange.com/questions/71934/…). $\endgroup$ – Simplex11 Jan 10 at 20:25
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"1) Various sites like this one: Orville and Wilbur Wright, The Inventors of the 3-axis Flight Control System, 9 Months before their powered flight at Kitty Hawk say that the two brothers invented the three-axis control system.

Is it true?"

Matthew Piers Boulton proposed the combined use of ailerons, a pitch control surface, and a rudder well before the Wrights began their experiments.

However, the Wrights were the first to actually demonstrate a working 3-axis control system, and came up with their control system largely through their own independent thought plus actual trial and error. They also appear to have been the first to combine an understanding that banking was the most efficient way to turn an aircraft, with the design of an effective system to accomplish a change in bank angle, with an understanding that a movable rudder was an effective way to counteract adverse yaw but should not be used as the primary "turning" control. So if you are asking if the Wrights were the first to come up with something resembling the modern understanding of how a three-axis control system should be used to maneuver an aircraft in flight, I would say "yes". In aswering this one shouldn't rely too heavily on what the Wrights did or did not choose to include in any given patent application, and one certainly shouldn't rely on a lawyer's attempted "explanation" of the content of any given patent application.

On the other hand if you are asking if the Wrights were the first to ever consider the combined use of pitch, yaw, and roll controls on an aircraft, the answer must be "no". Note however that Boulton appeared to envision using ailerons primarily to keep the wings level, while using the rudder as the primary turning control. Note also that Boulton's patent application suggested that either the ailerons could either be manually operated, or a pendulum hanging below the aircraft could be used to pull on cords to activate the ailerons to automatically return the aircraft to wings-level whenever it entered a bank. The latter concept would not have worked very well to keep the wings level, but might have had the unintended side effect of making the aircraft roll nicely into a bank whenever the pilot applied the rudder to try to turn, because the rudder would skid the aircraft and throw the pendulum off to one side!

"2) Regarding the adverse yaw, the description given in the patent and the explanation of Toulmin are quite clear. The Wrights proposed a method for counteracting this unwanted effect but were they the first who noticed it?"

Yes, as far as I know no one is on record as having noticed adverse yaw before the Wrights. Note that even weight-shift roll control can create adverse yaw, but Lilienthal's weight shift roll inputs probably involved too little cg displacement, and created too low a roll rate, to make enough adverse yaw to be easily noticed.

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  • $\begingroup$ Matthew Piers Watt Boulton was aware of the notion of three-axis control as long as in his 1868 (see: commons.wikimedia.org/wiki/Category:Matthew_Piers_Watt_Boulton) patent he wrote about "a controlling power to direct the horizontal and vertical course of aerial vessels and to prevent their turning over by rotating on the longitudinal axis." (I quoted his words exactly.) $\endgroup$ – Simplex11 Jan 6 at 7:13

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