L.Opdyke French Aeroplanes Before the Great War (Schiffer)
Deleted by request of (c)Schiffer Publishing
One of the most interesting and productive of the early French aeronautical engineers was Jean Legrand, but today his work is largely forgotten: it exists now in the form of poor postcards of 2 of his achievements, a brief note left by his daughter at the Musee de l'Air, and the texts of various lectures published in La Revue Technique Aeronautique. There is enough left to show clearly his scientific reasoning and brilliance - even though he never designed or built an aeroplane. He modified either one or 2 Voisins to clarify why an aeroplane flies.
In May 1909 he bought de Caters' Voisin, and, associated with Louis Gaudard who brought with him a 50 hp Gnome, made endless modifications designed by Legrand and built by Voisin. It is likely Legrand flew a second Voisin built especially for him: he fitted a dynamometer to the propeller; he also tried a magnetic tachometer, a Bourdon speed indicator, and an incidence meter designed by Arnoux for automobiles. The experimenters broke a lot of wood in the course of their trials. Noticing that oil sprays appeared only on the upper rear surfaces of the wings, he realized that lift was produced by a reduction in pressure above the wings and not by increased pressure below. He recommended ailerons to replace the wing-warping which tended to weaken the structures, and had his own aircraft modified with 4 ailerons on the top wings.
He was granted 3000F on behalf of Major Renard by the Societe d'Encouragement pour lTndustrie Nationale, a group founded by Nadar, alias Felix Tournachon, and used it to have a new set of wings built by Voisin (some say a whole new aeroplane) with a span of 9 m instead of 10.5, a chord of 1.75 m instead of 2: the modified biplane could fly at 62 kmh. He removed the lower tailplane and increased the span of the upper. To improve lateral stability, he shortened the wing curtains, though without apparent effect. He further modified the Voisin as a triplane and as a quintuplane, and then modified it further to carry a crew of 2 with a forward-firing machine gun, and even altered it to can-y 2 push-pull Gnomes. The triplane spanned 7 m with unchanged wing area, and was flown successfully by Camille Guillaume de Mauriac in 1910-13, and by Verrier in April 1911. Legrand is reported to have also modified Wrights, Bleriots, and Voisins by reducing the angle of attack, but found they glided too fast or too steeply. He may have helped with the design of the Gaudard monoplane; eventually he abandoned his aeronautical research for want of money.