The Flying Flea (Pou du ciel literally "Louse of the Sky" in French) is a large family of light homebuilt aircraft first flown in 1933.
Mignet had failed to be accepted as a military pilot and decided to build his own plane. Between 1931 and 1933 he built prototypes in Paris and tested them in a large field northeast of the city. According to his later book, Le Sport de l'Air, he successfully flew the first successful model, HM-14, in September 10 1933. He publicly demonstrated it in 1934 and published the plans and building instructions in a book
Mignet's original H.M.8 prototype aircraft was powered by a Aubier-Dunne 500 cc two stroke motorcycle engine with a chain drive providing a 2.5:1 reduction ratio. It had a a wingspan of , a length of and a gross weight of . . It had a usable speed range of 25-62 mph (40-100 km/h).
The control system was very unconventional. The aircraft had a standard control stick. Fore and aft movement controlled the front wing's angle of attack, increasing and decreasing the lift of the wing. Because the front wing was located forward of the center of gravity this would pitch the nose up and down.
Side to side movement of the stick controlled the large rudder. This produced a rolling motion because the wings both had substantial dihedral, though yaw-roll coupling. The rudder had to be quite large not only to produce adequate roll but also because the fuselage was very short, reducing the leverage of the rudder.
The Flying Flea, being a two axis aircraft, could not be landed or taken off in substantial crosswinds. This was not a big issue when the aircraft was designed because at that time aircraft were usually flown from large open fields allowing all take-offs and landings into wind.
Mignet claimed that anyone who could build a packing case and drive a car could fly a Flying Flea.
There have more than 300 different models of the Flying Flea. Some of these are:
When on approach to land the pilot would push the stick forward to gain speed for the flare and landing. As speed built up the rear wing, operating at a greater angle of attack would gain lift and pitch the aircraft's nose further downward. The pilot's normal reaction would be to pull back on the stick. This action would increase the angle of attack on the front wing by lowering the trailing edge of the wing. Because the trailing edge of the front wing was close to the leading edge of the rear wing the front wing's downwash would accelerate the air over the rear wing and cause it to gain lift more quickly that the front wing, resulting in an ever increasing nose pitch-down and flight directly into the ground.
Mignet had not encountered this problem during his testing of his prototype because he could not afford a large horsepower engine. When builders started putting larger engines on them and expanding the flight envelope the wing interference problem surfaced.
The Royal Aircraft Establishment in the United Kingdom and the French Air Ministry conducted full-scale wind tunnel tests and discovered the problem. Their investigations resulted in changes to the airfoil used and the spacing of the wings to prevent aerodynamic interference. Later Mignet Flea designs incorporated these changes.
By 1939 there were many improved Flying Fleas in the air but the aircraft never completely overcame its dangerous reputation.
Shortly after the plans appeared in 1934, many enthusiasts in Europe and the USA began to build their own aircraft. In France there were at least 500 completed. The average cost of materials was then $350.
Modern aircraft enthusiasts have continued to build their own aircraft and vary the original design over the years. French enthusiasts hold an annual meeting every June.
The Shuttleworth Collection (UK) has an example in its collection of historic aircraft, powered by a Bristol Cherub engine. There is also an HM.14 Flying Flea, G-AEGV in the Midland Air Museum, Coventry, England. Other sites include the Yorkshire Air Museum, Newark Air Museum.