The Focke-Wulf Fw 61 (later referred to as Focke-Achgelis Fa 61) was an experimental helicopter built by Henrich Focke in 1932, which marked the beginning of his helicopter career. It quickly became clear that it was the first fully functional helicopter model in the world. It was made in two copies in the years 1935-1936 by the company Focke-Wulf (Focke-Wulf Flugzeugbau AG), founded in 1923 by Henrich Focke and Georg Wulf.
By building Cierva C.19 and Cierva C.30 gyrocopters under license and conducting inconclusive tests with his Fw 186 prototype, Henrich Focke realized in 1932 that their defects could only be eliminated by realizing a real helicopter. Indeed, they lacked maneuverability and stability, and the aircraft could not land safely in case of engine failure or breakage of the driveshaft.
Henrich Focke first made many calculations to build models tested in the wind tunnel. Then he drew on the work of the Spaniard Juan de La Cierva who was working in Great Britain as well as those of Glauert and Lock to improve the characteristics of the rotor.
Focke opted for a concept with two counter-rotating rotors ensuring a perfect symmetry of the controls. In 1934, a first model equipped with a two-stroke engine provides promising first results. She is now exhibited at the Deutsches Museum in Munich. On February 9, 1935, Focke received an order from the Ministry of Aviation (RLM) to make a prototype officially designated Fw 61, but which Focke himself still called F 61. The order for the second specimen was placed on 19 December 1935 by the staff aeronautical engineer (Fl. Hauptstabsing) of the RLM Roluf Lucht.
The first prototype (registered V1 D-EBVU, factory production number 931) was already practically finished and the engineer Ewald Rohlfs, who had joined the Focke-Wulf company on May 1st, 1935, made the first test flights. Apparatus being captive, tied to the ground by ropes in a hall at Hemelingen where Focke had been banned by the "new leaders" of his company. The first completely free flight took place only on June 26, 1936, because Rohlfs had to be repatriated from South America thanks to the insistence of Ernst Udet, where the management of the company - who disapproved the project - had sent on mission in the spring of 1936. Until early August, the tests had progressed sufficiently to allow the official services of the Rechlin Flight Test Center ('' Erprobungsstelle '') to repeat the same tests to verify the performance, which was assigned to engineer Walther Ballerstedt. He had some experience flying Cierva C.30 on autogiro. Focke, who was more than cautious, insisted that his first flight be on captive aircraft. Ballerstedt was enthusiastic about the flying qualities of the aircraft, considering only that the pitch control, controlled by the throttle grip and therefore the rotational speed of the rotors, was very sensitive. Udet, who had in the meantime succeeded General Wilhelm Wimmer, was enthusiastic and pressured to present the helicopter in public as soon as possible. The second prototype (registered V2 D-EKRA, factory number 1789) was able to make its first flight in the spring of 1937, again with Rholfs at the helm. On May 10th, 1937, this one realized the first landing in stopped motor autorotation.
In June 1937, the public learned that Rohlfs had brought all helicopter world records in the German Reich on 25 and 26 June 1937 with this aircraft. The best performances of other helicopters were for years with a flight time of 10 minutes (d'Ascanio) or with no more than 1 km route (Pescara) and 18 m altitude (Œhmichen); It was only in November 1936 that they were increased by Breguet with his helicopter to 1:02 h, 44.69 km in closed track and 158 m. The Fw 61 reached an altitude of 2439 m, a flight time of 1 h 20 min 49 s, a speed of 122.553 km / h over a distance of 20 km and a distance of 80.604 km in closed track. These values exceeded flight captain Dipl.-Ing. Carl Bode (1911-2002) on June 20, 1938 with 230.248 kilometers by a flight from Faßberg to Rangsdorf again considerably; with 3427 m, he also set on January 29, 1939 with the V2 also Rohlfs old altitude record.
Specifications :
crew ; 1
Length ; 7.29 m
Rotor diameter : 2 × 7.0 m
Height : 2.64 m
Max speed : 122 km / h
Service ceiling : 3200 m
Range : 230 km
Power unit Bramo 314 E, 118 kW (160 hp)
0 commentaires :
Post a Comment