Aviation of World War II
In January 1935, Flettner received a contract from RLM to develop an "experimental gyroplane" ("three-blade rotor gyroplane"). The layout was inspected in June 1935. Only one prototype was built, the Fl 184 V1, which received D-EDVE registration. The gyroplane was destroyed due to a piloting error in December 1934. In appearance, the Fl 184 was very similar to the C 30, the licensed construction of which began at Focke-Wulf around the same time. The Sh 14 engine was used as a power plant, driving a conventional propeller.
The contract for the construction of the Fl 185 was issued by the RLM in February 1937. It was planned to build 2 prototypes. In the "Program for the Development of Aircraft Manufacturing" this device was named "Helicopter Conversion 184", because it was planned to use the unfinished third prototype of the Fl 184 during its construction. The project was financed by insurance received after the accident of the Fl 184 and a grant of about 50,000 Reichsmarks received from RLM. The layout was examined in April 1937.
Fl 185 was a gyroplane with a three-bladed rotor, torque compensation was achieved using variable-pitch pusher propellers driven by beams protruding from the fuselage to the left and right. The right propeller pushed the gyroplane backward, the left propeller forward, so that the moment they created compensated for the turn from the main rotor.
The only prototype was the V1 registered with D-ELFT and flew several flights in 1938. The results were promising, but all tests were conducted at very low altitude.
The next obvious step towards the Fl 282 was the Fl 265, conceived and built in 1938; it differed from previous designs primarily by the use of a new rotor design.
Fl 265 was built for RLM by the joint efforts of engineers from Lucht and Reidenbach with the utmost secrecy.
Professor Tank's first design as CTO at Focke Wulf was the Fw 44 Stieglitz two-seater trainer. The fuselage of this aircraft without wings was used to create the Flettner Fl 265 helicopter. For this, the crankshaft of the 140 hp Siemens-Halske engine. it was necessary to bring it back in flight in order to provide power take-off to the main drive shaft of the main rotor through a gearbox with bevel gears. The blades of both 6.50 m diameter two-bladed main rotor blades were made of seamless drawn steel pipes to which a 25 cm chord profile was attached.
The control was carried out using a control knob, the thrust from which was transmitted deviations to the rotors. Since the propellers rotated towards each other, the propeller turning moments compensated each other, which made it possible to do without the tail rotor. A total of 6 prototypes Fl 265 (serial numbers 1579 to 1584) were built, one of which was tested in a wind tunnel in Meudon (France) in the summer of 1940.
The first time the engine was brought to full power on January 17, 1939, and the first flight to a height of 20 cm was performed on March 14, 1939. The first flights on the Fl 265 V1, registered D-EFLV (E = aircraft with a takeoff weight of up to 1000 kg; FL = Flettner; V = prototype), Captain Richard Perlia performed in a heavily guarded hall (hangar) near Johannisthal airfield. The first flights were carried out on a leash, the cable length was 2 m, which made it possible to understand the basic laws of control of an aircraft of a new type, so to speak "feel" it.
After 3 months, the first free flight in the open air was performed, and the flight altitude did not exceed 5 m A. Flettner promised the tester a prize of 1000 Reichsmarks if he could hang at an altitude of 10 m for 5 minutes. Perla managed to complete this task and received the promised bonus.
After that, the helicopter was demonstrated in Rechlin to Hitler, Goering, Milch, Reidenbach and Lucht.
During flight tests, a vertical take-off was mastered, an altitude of 1200 m and a horizontal speed of 128 km / h were reached.
The main advantage of the Fl 265 over the Fl 185 should have been the ability to land on autorotation, with a stopped and even jammed engine. However, on the first two prototypes, Fl 265 V1 and V2, disconnection of the engine drive from the propellers, allowing the transition to autorotation, was not implemented, so test flights were very dangerous. Failure of at least one spark plug would lead to a drop in engine speed, as a result of which the helicopter would fall from a height like a piano, because the minimum rotational speed of the propellers required for flight is 138 rpm. thus could not be achieved. Perlia, unlike the other two pilots who died later when testing this helicopter, turned out to be quite lucky. The first prototype was decommissioned on April 29, 1940. The third prototype (Fl 265 V3) crashed and burned down on August 21, 1939 due to a pilot error. V5 (decommissioned on November 26, 1941) and V6 (decommissioned on March 25, 1942) were owned by Flettner until November 1942. They tried to re-bring them to flight status, but in the end this idea was abandoned.
The V4 was the first prototype to be able to disconnect the engine shaft from the rotor drive, making autorotation possible. Thanks to the use of a movable joint, the helicopter was able to fly, moving not only forward, but in both directions and back. Any climb or descent maneuvers could be performed at a speed of 20 km / h. It was possible to take off and land on a moving platform, since the control of this aircraft made it possible to very accurately perform any maneuvers.
On the Fl 265 V1, the range and height of the keel were increased to improve directional stability. Even after that, up to a speed of 50 km / h, the Fl 265 V1 was not very stable along the course, but with an increase in speed, stability increased.
The helicopter underwent a series of joint tests (Luftwaffe and Kringsmarine), including landing on the 25 × 25 m cruiser deck area of the Cologne.All prototypes of the Fl 265 flew 126 hours 32 minutes in 1180 flights in total. The total operating time of the engines was 518 hours 44 minutes.
Translation and revision of the text by Petr Klunduk
January 05, 2016
January 05, 2016
January 05, 2016
November 06, 2021