Hammondsport, N. Y. Nov. 11, '08.
Dear Mr. Bell,
Received your communication concerning the Wright disaster at Fort Meyers O. K. You Casy and Gardiner ha ve certainly gone over the probable caused from all sides and I don't see that there is much left for me to say.
As you state in your article, the immediate cause of this accident was loss of headway, but how was this brought about? Certainly the breaking of a propeller would not cause sudden stoppage in the air and consequently leave the machine without motion of translation.
A {Begin deleted text}re{End deleted text} ll the eye witnesses of the accident you talked with agreed that the machine first started on a gentle glide and as she gained speed, her course was diverted into an upward glide. Then the machine having lost her motion of translation turned upon end and dove.
The reason for her diving is of course, quite obvious — the center of pressure at the traveling speed comes far in advance of the geometrical center of the surface and the machine is balanced for its speed by having the center of g ravity of the machine as a whole coincident with thi s point. (center of presure).
As the machine looses head way of c o use the C. of P. recedes till when the machine has no motion of translation the center of presure coincides with the geometrical center of surface.
When the Aerodrome is flying in a normal manner the front {Begin deleted text}c{End deleted text} control no matter how large or ow powerful has no effect on the position of the center of presure loc a ted in the main plane because t the angle of incidence of the control v a ries ; at one moment it presents a negative angle of attack and the nest moment it presents perhaps a positive angle of attack. But when the Aerodrome has lost its {Begin deleted text}medium{End deleted text} motion of translation the front control comes into play and influence s the geometrical center of surface of the machine as whole. It has been found by Mr. Chanute and others that two supperposed plans separated from each other two thirds or a distance equivalent to the depth of the planes, and falling so that {Begin deleted text}the{End deleted text} the planes of the surfaces are at right angles to the line of {Begin deleted text}distance{End deleted text} decent — the top lane has 0.7 times the supporting part of the bottom plane. On this basis I have figured out the effect which would be produced in the Silver Dart. Suppose that for some reason or other motion of translation should be entirely lost while in the air. The machine would turn on end as the Wright flyer did unless the front control was dropping relatively to the air at the rate of Twenty to Thirty miles per hour. In that case the moment produced by the eccentric loading would be entirely compensated for.
