Engineering Analysis of Nicolas Florine's Helicopters (1926-1948)

Nicolas Florine (1891–1972) was a Russian-born aeronautical engineer who developed three prototype helicopters in Belgium during the period 1926–1938. Under the auspices of the Service Technique de l'Aérotechnique at Rhode St. Genese, he was the first to design a successful tandem rotor helicopter, with twin rotors arranged in a fore-and-aft disposition. Florine's helicopter designs were innovative in that both rotors turned in the same direction, with the torque-reaction on the airframe being countered by differential lateral tilts of the two rotor disks, a concept that he formally patented in 1928. While the rotor of Florine's first prototype helicopter suffered from a catastrophic failure resulting from an aeroelastic instability, his second helicopter design was flying by early 1933. While this second aircraft was underpowered and suffered from relatively high levels of vibration, Robert Collin piloted the machine for 30 flights and clearly demonstrated stable hovering capabilities under positive flight control. On 25 October 1933, Collin flew Florine's helicopter to set a flight endurance record of 9 minutes and 58 seconds, sustaining continuously an altitude of between 5 and 6 meters, and beating the duration record previously set in 1930 by Marinello Nelli in the Italian d'Ascanio–Trojani D'A.T.3 helicopter. On another flight, Florine's helicopter was to reach an altitude of 21 meters (69 feet). These modest flight records would stand for nearly two years until being swept away by the French Breguet-Dorand "Gyroplane No.1" and the German Focke-Wulf Fw-61. Florine's third helicopter prototype of 1936 was unsuccessful, the aircraft suffering from a susceptibility to ground and air resonance instabilities. Florine designed two other helicopter concepts, including an innovative 2-seater concept with four rotors arranged in two lateral pairs. However, with the outbreak of the Second World War in Europe neither aircraft was built and Florine's work soon faded from the aeronautical limelight.