Did the Wright brothers discover the three-axis control system for airplanes/gliders and the adverse yaw? 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?


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.
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.