May 2019

Nicolas Florine Tandem-Rotor Helicopter

Florine II helicopter flight endurance record: 9 minutes 58 seconds – October 25, 1933

Russian-born aeronautical engineer Nicolas Florine (August 1891 – January 1972) fled to Belgium in 1920 and found work at the l'Administration de l'aéronautique in Brussels. By 1926 he had assisted with the creation of Belgium’s first large wind tunnel. His pioneering mathematical studies at Belgium’s Centre d'aérodynamisme on various aerodynamic phenomena — including vortex theory of screw propellers, rotating tandem rotors in the same direction, and control mechanisms of blade pitch for multiple rotors — led to a patent on helicopter torque control by using two rotors. He built his first tandem-rotor helicopter (the Type I) by the end of 1929 with subsidies from the National Society for the Study of Air Transport and the National Funds for Scientific Research. Ground tests revealed drive system issues after a transmission failure. The redesign and rebuilding of the (now Type II) helicopter resulted in a lightened fuselage structure using welded steel tubing. It was powered by a 9-cylinder 200 hp (150 kW) Renard air-cooled radial engine, mounted vertically amidships using a small-diameter cooling propeller, and included flexible shafting using rubber couplings.

By April 1933, the Type II was completed and the aircraft made its first flight on April 12. Like the Type I, to offset the torque effects of the two rotors turning in the same direction, the forward and aft rotor hubs were each canted laterally and differentially by 7 degrees. The rotors were each 4-bladed with wire-braced blades of 23.6 ft (7.2 m) diameter with control by differential collective pitch. The gross weight of the aircraft was 2,094 lb (950 kg).

Although the Type II made over 30 flights between April 1933 and May 1934, the aircraft was destroyed in a crash on May 4 after a clutch failure in the transmission. The pilot, Robert Collin, survived without injury.

A third tandem-rotor machine, the Type III, using two forward-mounted 60 hp (45 kW) Salmson engines, made its first flight on Sept. 15, 1936. This aircraft proved less successful than the Type II and the project was abandoned in 1939.

During World War II in occupied Belgium, Florine studied a single-engine quad-rotor configuration and after the war, this Florine Type IV was displayed as a model at the 1947 Brussels Air Show. This ended Florine’s involvement with rotorcraft, but he continued working at the Aeronautics Technical Department until his retirement in 1956.

Photos: via

Text: Ken Bartie

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