Herrick HV-2
| Herrick HV-2 | |
|---|---|
| Type: | Experimental airplane |
| Design country: | |
| Manufacturer: |
Gerard Herrick (construction) |
| First flight: |
October 31, 1936 (as a fixed wing biplane) |
| Number of pieces: |
1 |
The Herrick HV-2 (Herrick Vertoplane-2) was one of the first convertible aircraft in the world and was designed by Gerard P. Herrick , a pioneer in the field in the 1930s. Herrick's concept envisaged an aircraft that had a fixed lower wing and an upper wing that could rotate about the vertical axis. The upper rotor wing could be stopped or started both on the ground and in the air. The HV-2 was the first aircraft with a stop rotor in which this combined system for generating lift and propulsion was actually used in a large number of test flights and a transition was carried out in flight.
Modern counterparts that use a similar propulsion concept are the Sikorsky X-wing and the Boeing X-50 .
history
The main reason for the development of the convertible aircraft was the construction of a stall-proof aircraft. Herrick saw the rotating wing as a kind of parachute that should be used in an emergency during the critical take-off and landing phases. For this purpose, the rotor wing should be able to be started or stopped both in flight and on the ground. His projects, carried out between 1931 and 1937, differed from the modern stop protor concepts in that the rotor was not actively driven, but operated in autogyromode .
During the development phase, Herrick changed the name of his aircraft several times, using the names Vertoplane, Vertaplane, Convertoplane and Convertaplane. The Convertible Aircraft Congress also named him the father of the Convertiplane when it was awarded a plaque for his life's work .
HV-1
The HV-1 was the first aircraft designed by Herrick. The single-seater had a 40 horsepower Ployer engine and was equipped with a short wing lower wing and a Teeter-type upper rotor wing 11.00 m in diameter on a pylon above the cockpit. The prototype of the HV-1 had its first flight as a fixed-wing aircraft on November 6, 1931 in Niles (Michigan) . Later there were also starts with a rotating rotor as autogyro, but when the upper wing was started in flight, it hit the rudder unit and remained in the position parallel to the fuselage. The pilot was able to jump off, but the altitude was so low that his parachute no longer opened. The HV-1 was destroyed in the accident.
HV-2A
Herrick then began, with the help of aeronautical engineer Ralph McLaren, designing a revised variant called the HV-2A. The prototype, like the HV-1, was built by Heath Aircraft, a small manufacturer of self-designed sports aircraft. The upper wing only had a wingspan of 7.32 m to prevent contact with the vertical stabilizer.
The test flights with the HV-2A were carried out by the 22-year-old George Townson, who had no previous experience with autogyros. He received US $ 25 for every hour of flight, US $ 12.50 for taxiying hours and US $ 1.50 for consultation hours. The first flight as a fixed wing aircraft was carried out on October 31, 1936, the subsequent testing at Boulevard Airport in the outskirts of Philadelphia. Then the first attempts at taxiing and flights in autogyro mode were made. The flights were carried out in such a way that the rotor was set in motion by briefly pushing it at a standstill, the aircraft then rolled along the periphery of the field in order to increase the speed of the rotor, finally rolled to the start of the runway and took off against the wind. The flights all took place in a straight flight path at a maximum height of only about 15 m. The demolition speed in the fixed wing mode was 64 km / h and in the autogyromode 56 km / h, so that it could be proven that the rotor could take on a lift function. Below 56 km / h there was a vertical sink without tipping effects.
Flights at a higher altitude of 400 m and the first turns took place between the Boulevard Airport and a smaller airfield about 1.6 kilometers away. The first transition between fixed wing and autogyro configuration took place on July 26, 1937. To do this, the procedure was that the rubber rope in the upper wing was tensioned with two rotations of the rotor and, after take-off at 80 km / h at a height of 45 m, the locking of the upper wing was released. In the first such attempt, Townson fought with strong vibrations around all three axes, which only subsided when the rotor speed reached 250 / min. This flight is considered to be the first successful transition of a convertible aircraft. There was a second successful attempt on July 30, 1937, this time under observation by the media and members of the NACA and military staff.
Between 1937 and 1939, the year the aircraft was decommissioned, around 100 more transitions were made in the air. The machine was then handed over to the National Air and Space Museum , where it was exhibited from the ceiling of Building 23 in Silver Hill, Maryland .
construction
The concept of the HV-1 and HV-2 differed from later designs in that Herrick's rotor was not driven but only operated in autogyro mode. The HV-2A was powered by a 5-cylinder Kinner radial engine. The lower wing had a Clark-Y-profile, a structure made of wood with a plywood planking. The upper surface, also made of wood with a Herrick M-7-II profile, had double planking. The symmetrical profile with a curved top and a flat bottom had a depth of 1.20 m in the middle, which ended at the wing tips to 0.60 m. The fuselage and tail unit were fabric-covered and conventionally constructed from welded tubes. The cost of construction is said to have been $ 1500.
The rotating surface had no control device and was only equipped with an unlocking lever. In the locked position, the upper wing was aligned parallel to the lower, after unlocking the upper wing began to rotate as a rotor. As with the HV-1, this was mounted on a pivot. A hinge joint allowed a "rocking movement", i. H. the rotor moved up when turning towards the bow and down when moving backward. A hydraulic damping system limited the deflections.
The HV-2A had a special Bendix ignition system in order to set the rotor turning after the rotor lock was released, even in emergencies in which the rotation was not started automatically. This consisted of a small turbine, a drive shaft and a cap that contained a cartridge with an igniter. After opening the lock, the detonator was triggered electrically. The cartridge's gases, which were led through a pipe, drove the turbine, which acted on the drive shaft. This brought the rotor to a speed of around 60 per minute within a few revolutions. The wind then ensured that a stable speed of around 250 rpm was finally set. However, this emergency system was never used during testing.
If the rotor was already set in rotation on the ground, this was done according to the following procedure: With the help of four people (two at each rotor tip), a rubber rope was tensioned by turning the rotor backwards with two turns, which was located in a tube inside the wing. The rope was connected to another cable that was wound around a drum on the rotor head. After releasing the cable, the rotor accelerated to about 60 revolutions / min.
Technical specifications
| Parameter | Data |
|---|---|
| crew | 1 |
| length | 6.46 m |
| Wingspan upper wing (rotor diameter) |
7.32 m |
| height | 3.18 m |
| Rotor area | 6.50 m² |
| Rotor profile | Herrick-M-7-II |
| Area of the lower wing | 9.29 m² |
| Empty mass | 468 kg |
| Takeoff mass | 686 kg |
| Engines | 1 × five-cylinder radial engine Kinner B-5 with 125 hp (92 kW) |
Further development of the stop rotor concept
Corresponding concepts for stop rotor aircraft experienced a renaissance in the 1960s, when Hughes Aircraft introduced the rotor / wing concept. Here, the rotor should be shut down after take-off and act as a lift surface, with the propulsion being taken over by two jet engines. Bell and Sikorsky as well as Lockheed also presented corresponding designs, but these were also not realized. With these concepts, the rotors were folded after stopping for cruising flight and stowed in gondolas (Bell) or in the fuselage (Sikorsky, Lockheed). This configuration was also known as the Controlled Circulation Rotor .
See also
literature
- Howard Levy: Mr. Herrick's Convertiplanes . In: Airplane Monthly . February 1991, ISSN 0143-7240 , p. 90-93 .
Individual evidence
- ↑ George Townson's biography
- ^ Günther Molter: The rotor / wing concept from Hughes Tool. In: Flug Revue April 1967, pp. 21–24.
- ↑ V / STOL development in the USA. In: Flug Revue February 1971, pp. 26, 31.
- ^ Günther Molter: Lockheed-California Folding Rotor Concept. In: Flug Revue May 1967, p. 26 f.
- ↑ VTOL airliners. In: Flug Revue September 1970, p. 54 f.