Forty Years of Aeronautical Researcli 



J5y J. C. HUNSAKER 



Chairman, National Advisory Committee for Aeronautics 

 Regent, Smithsonian Institution 



[With 10 plates] 



Before the Wriguts' airplane flew, all the elements of the airplane 

 were known: wings, rudders, engine, and propeller. The Wrights 

 showed how to combine a man's senses and reflexes with the controls of 

 a flying machine to make the machine both controllable about its atti- 

 tude of equilibrium and steerable as desired. The secret of flight was 

 manual control, in a three-dimensional fluid medium, in accordance 

 with visual signals (the pilot's view of the gi'ound and observation of 

 his attitude relative to it — fixed axes of reference), and monitored by 

 visual observation of the response to his control actions (feedback). 

 The Wrights' airplane w^as, however, like the Wrights' bicycles, in- 

 herently unstable and was controllable only when it had sufficient for- 

 ward speed. Controlled by the sight, brain, nerves, and muscles of man, 

 the Wrights' unstable vehicle was the first practical flying machine in 

 the history of the world ! 



The Wriglit airplane was quick to respond to control action because 

 it had no righting tendency if disturbed. The pilot was expected to 

 act at once to recover from any disturbance of equilibrium. There was 

 no fixed tail to push it into a safe glide if the engine stopped. 



The early pioneers of flight worked with gliders and with self-pro- 

 pelled models. They strove for inherent stability and conceived the 

 ideal to be an inherently stable flying platform on which the pilot 

 need do no more than steer. Penaud's model gliders of the 1870's, with 

 long tails, w^ere stable; Lanchester developed prior to 1908 a theory 

 of dynamical stability for his model "aerodromes" ; Langley flew stable 

 steam-powered models in 1896, and Bryan in 1903 published the dy- 

 namical equations of motion for a glider, and criteria for inherent 

 stability. In all cases, stability was found to require a tail and slightly 

 elevated wing tips. 



As might be expected from complete and constant dependence on one 

 man's sometimes defective judgments and reactions, the Wright air- 



241 



