Nature devised the rotary wing as a way to disperse tree seeds on the wind. Generations of daydreamers, observing the spiraling flight of maple or ash seeds, imagined riding just as effortlessly through the air. Around 400 BC a Chinese tinkerer devised a bamboo toy – a propeller on a stick – that could rise up into the air when twirled rapidly between the hands. In 1480, Leonardo da Vinci sketched a flying machine with a hand-cranked spiral rotor. Never built, it could not have generated enough lift to fly, and would have been uncontrollable.
A British scientist, Sir George Cayley (1773-1857), worked out the basic principles of rotary wing flight, but without a sufficiently light and powerful engine, his ideas remained theoretical. The pre-history of the helicopter is littered with wrecked prototypes that almost worked, and the broken dreams of inventors who almost solved the difficult technical challenges of stability and control.
By the 1930s Spanish (Cierva), French (Breguet), Soviet (the TsAGI research institute) and American (Sikorsky) engineers were making progress toward solving these problems. Then the war came.
The military potential of a flying machine that could take off and land without a runway seems obvious to us today, familiar as we are with troop carrier, attack, medevac and other helicopters. But it was less obvious to military aviators struggling to get conventional fighters and bombers into mass production, while being bombarded with new concepts and competing technologies.
Fa 61: The First Practical Helicopter
On Feb. 19, 1938, Berlin’s vast Deutschlandhalle arena was packed with an expectant crowd attending a Motor Show. Down on the floor, Hanna Reitsch, only 25 years old, climbed into the open cockpit of a strange looking machine, with great three-bladed rotors mounted on spindly struts where its wings should have been. The little aircraft rose straight up, gracefully pivoted in place, and circled the arena before landing gently.
It was the public debut of the Focke-Achgelis Fa 61 (also known as the Focke-Wulf Fw 61). It was the world’s first practical, controllable helicopter. Reitsch repeated the performance on 14 successive evenings. Propaganda newsreel footage of the demonstration was widely distributed.
The Fa 61 was based on the fuselage of the Fw 44 Steiglitz (“Goldfinch”) biplane basic trainer. It had a cut-down wooden propeller in the nose, but it served only to cool the engine. The rotors rotated in opposite directions, cancelling out the torque that would otherwise tend to spin the aircraft in flight. Like modern helicopters, the Fw 61 could vary the pitch of the blades for directional control, but vertical control depended on using the throttle to vary the rotor rotation speed (most helicopters maintain relatively constant rotor speed).
Only two prototypes of the Fa 61, registered as experimental civil aircraft, were built. They set early world records for rotary-wing altitude, speed, endurance and distance. Neither survived the war, but the German helicopter museum in Bückeburg displays a full-scale replica of the historic aircraft.
Dr. Henrich (not Heinrich!) Focke was born in Bremen in 1890. A heart condition kept him out of the trenches in the First World War. In 1936 Focke lost control of the company he had founded with George Wulf in 1923. (Wulf died in the crash of an experimental aircraft in 1927.) The Nazis reportedly considered Focke “politically unreliable” and wanted to take over his factory in order to increase production of Bf 109 fighters. The most famous aircraft that bears Focke’s name, the Fw 190 fighter, was actually designed by the brilliant aeronautical engineer Kurt Tank (1898-1983).
In 1937, Focke formed a new company in partnership with Gerd Achgelis, a talented test pilot. Before the final collapse of the Third Reich, the Focke-Achgelis company would go on to build some of the first operational military helicopters, and to design some surprisingly advanced projects.
Focke-Achgelis Fa 61
- Crew: 1
- Length: 7.3 meters (m)/23 feet, 11 inches (fuselage only)
- Height: 2.65 m (8 ft. 8 in.)
- Empty weight: 800 kilograms (kg)/ 1,764 pounds (lb.)
- Max takeoff weight: 950 kg (2,094 lb.)
- Powerplant: 1 × Bramo Sh.14A 7-cyl. air-cooled radial piston engine, 119 kW (160 hp)
- Diameter of main rotors: 2× 7 m/23 ft.
- Maximum speed: 112 km/h (70 mph; 60 knots) at sea level
- Cruising speed: 90 kph (56 mph; 49 knots)
- Range: 230 kilometers (143 miles; 124 nautical miles)
- Service ceiling: 3,427 m (11,243 ft.)