Focke Wulf Fw 61
The Focke-Wulf Fw 61 is regarded as being the first helicopter of the world which could be deployed for practical use. Developmental work on this experimental helicopter started in 1932 under the direction of Henrich Focke.
In the same year, Focke presented the drafts of the helicopter Fw 61 to the German Ministry of Transport which then gave him an order to design and develop the helicopter.
With a free-flying, five kilogram test model, which can be seen today in the German Museum in Munich (Deutsches Museum), the first experiments and investigations could be accomplished. This test model climbed to an altitude of 18 meters - which back then was the maximum altitude that full-size a gyroplane had reached. The first prototype (which was finished in 1935 and had to undergo several demonstrations tests) took off for its maiden flight on June 26, 1936, in Bremen. After some short test hops, the helicopter flew for 16 minutes at meters in an altitude of 20 meters.
How the public would learn, however, of this historic event only two years later. In the following years the first helicopter in the world to fly beyond the boundaries of an airfield, established internationally acknowledged records. In a world premiere in May 1937, test pilot Rohlfs managed at a height of 400 meters to switch from vertical hovering flight to horizontal flight, and after turning off the motor, gliding for about one minute to a smooth, autoration landing.
In spring 1938, the public could marvel at the pioneer work of Focke during an exhibition in Berlin. The helicopter was presented to the public for the first time in several flights in the "Deutschlandhalle", the largest hall in Berlin in the 1930s.
A year later, on January 29, 1939, the Fw 61 acquired the altitude record for helicopters by reaching a height of 3427 meters. The two rotors the Fw 61 with a diameter of seven meters each were attached to support arms made of steel tubes welded to both sides of the airframe. This type of counter arrangement of the rotors is henceforth known as the "Focke concept".
Even when hovering at a standstill, a manuver not possible at that time by any other rotary-wing aircraft, the Focke concept achieved an outstanding stability for the helicopter. A Siemens aero-engine motor with a starting performance of 110 kW. was mounted in the front of the fuselage. A cooling propeller, which was driven by the engine, and the angled clooling-fins of the cylinders, forced air to the underneath parts of the rotor blades. Friction clutches as well as gearboxes conveyed the power through flexible drive shafts to the two rotors. The steering of the helicopter resulted from changing the angle setting of the blades, which were of a light, mixed-construction design. The movements of the stick and the pedals which shifted the blades were transferred by means of cables, which were mounted along the support struts. Reciprocal, opposed inclining of the rotor disc plane allowed lateral controls, whereby the rudder was moved at the same time. In case of an engine malfunction, the autorotation was set in action automatically which enabled the pilot to land safely in a slwo, smooth glide.
Although the German Ministry of Aviation wanted to start series production of the certified Fw 61, Focke refused to do so. To him, the legendary Fw 61 was solely a testing model that was not to be used as a cargo carrier due to its incapability of lifting useful payloads. Instead, he wanted to focus on a further development of the helicopter, which could not be realized because of the outbreak of the Second World War.
Technical data
Focke Wulf Fw 61
| Power Plant | Siemens Sh 14 B with 110 kW |
Performance
| Top speed | 145 km/h |
| Cruising speed | 125 km/h |
| Climb speed |
1 m/sec (vertical) 3.6 m/sec (inclined) |
| Range | 230 km |
| Fuel | 45 l |
Weight
| Empty Weight | 818 kg |
| Maximum take-off weight | 1024 kg |
Dimensions
| Length | 7.29 m |
| Height | 2.64 m |
| Fuselage width | 0.95 m |
| Diameter main rotor | 7 m |
| Crew | 1 person |
