Another version of the paper 'Engineering Analysis of the 1907 Cornu Helicopter' by Gordon Leishman and Bradley Johnson has been published in the July 2009 issue of the 'Journal of the America Helicopter Society.' It attempts to strengthen the 'engineering' side of their argument.
However, the paper's claim that
"the engineering analysis described in this article is unequivocal." is a little over the top, particularly when they make a number of assumptions. My questioning relates to their assumptions of; a Figure of Merit of 0.5, and a Transmission Efficiency of 0.75.
This figure of merit is based on the craft having flat blades, whereas pictures show that the blades are undercambered. Secondly, calculations show that wide-chord, slow turning rotors improve efficiency. Thirdly, Cornu used the side-by-side configuration, which is the most efficient arraignment for hover. IMHO, a meaningfully higher FM is more reasonable.
The power transmission from motor to rotors was by flat-belt. Flat-belt were a well-known and much-used means of transmitting power in machine shops, including Cornu's shop. Today's flat-belts are capable of efficiencies up to 0.98, therefore it could be assumed that the one-minute long eliminations of the belt slippage would have temporarily increased the power at the rotors.
There is nothing to indicate that Paul Cornu did not achieve short-term vertical flight.
Perhaps, his disappointment regarding the Deutsch Archdeacon Grand Prix, and disenchantment with the future potential for his current design caused him to refrain from further promotion, and return to engineering and patenting improvments, such as a continuously variable swashplate system.
Could this be-
_ 'French fries'
_ 
_ 'Freedom fries'
