Leishman has produced another paper (2012), which is;
Performance Measurements of a 1/6-Scale Model of the 1907 Cornu Rotor.
In it Dr. Gordon Leishman says;
”Engineering challenges to the claims of a successful piloted first flight of the Cornu helicopter in 1907 have been made, first by Boulet (Ref. 8) and then by Leishman (Refs. 9–12). Based on engineering arguments, it has been shown that the power required for Cornu’s machine to have flown successfully would have significantly exceeded the rated power of the 24-hp Antoinette engine that Cornu had installed in his machine.”
Counter Argument:
Boulet provided specifications on the craft but no engineering. In addition, his information on Cornu came from Cornu’s article in
L’Aerophile of 15 April 1908. Therfore Leishman is the sole source of
“engineering challenges”.
Leishman used Boulet's (Cornu's) specifications, which have little information on the airfoil, to build a 1/6th scale approximation of one rotor. This rotor was then placed on a test stand and data was acquired.
The data was then used to give a Power Correction Factor of
2.208. This remarkably high value is in stark contrast with
“For preliminary design, most helicopter manufacturers use their own measurements and experience to estimated values of the Induced Power Correction Factor, a typical value being about 1.15.” Airplane wings and bird wings are also slightly above
1.0.
In contrast to this, Cornu built a complete model helicopter that was 2-1/2 times the size of Leishman's, and then flew it. He then built his full-size craft based on the success of his model. Cornu’s model will obviously be significantly more indicative of the full-size craft then Leishman’s model.
Cornu’s helicopter may, or may not, have lifted a man out of ground effect. However IMO, Leishman’s critique, using questionable data and algorithms that are inappropriate for Cornu's type of rotor, will not revise history.
Leishman's Argument.
A Counter Argument.
Dave