Flettner Fl 282
| Fl 282 | |
|---|---|
 |
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| Flettner Fl 282 during flight trials after World War II, with US markings. | |
| Role | Helicopter |
| Manufacturer | Anton Flettner, Flugzeugbau GmbH |
| Introduction | 1942 |
| Retired | 1945 |
| Primary user | Luftwaffe |
| Number built | 24 |
The Flettner Fl 282 Kolibri ("Hummingbird") is a single-seat intermeshing rotor helicopter, or synchropter, produced by Anton Flettner of Germany. According to Yves Le Bec, the Flettner Fl 282 was the world's first series production helicopter.
The Fl 282 Kolibri was an improved version of the Flettner Fl 265 announced in July 1940, which pioneered the same intermeshing rotor configuration that the Kolibri used. It had a 7.7 litre displacement, seven-cylinder Siemens-Halske Sh 14 radial engine of 150-160 hp mounted in the center of the fuselage, with a transmission mounted on the front of the engine from which a drive shaft ran to an upper gearbox, which then split the power to a pair of opposite-rotation drive shafts to turn the rotors.
The Sh 14 engine was a tried-and-true design that only required servicing every 400 hours, as opposed to the nearly 27 litre displacement, nine-cylinder BMW/Bramo Fafnir 750 hp radial engine powering the larger Focke Achgelis Fa 223 helicopter, whose outdated design required maintenance every 25 hours. The Fl 282's fuselage was constructed from steel tube covered with doped fabric, and it was fitted with a fixed undercarriage.
The German Navy was impressed with the Kolibri and wanted to evaluate it for submarine spotting duties, ordering an initial 15 examples, to be followed by 30 production models. Flight testing of the first two prototypes was carried out through 1941, including repeated takeoffs and landings from a pad mounted on the German cruiser Köln.
The first two "A" series prototypes had enclosed cockpits; all subsequent examples had open cockpits and were designated "B" series.
In case of an engine failure, the switch from helicopter to autorotation was automatic.
Three-bladed rotors were installed on a test bed and found smoother than the vibrating 2-blade rotor, but the concept was not pursued further. The hover efficiency ("Figure of Merit") was 0.72 whereas for modern helicopters it is around 60%.
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