Kellett KD-1
| Kellett KD-1 | |
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| Type: | Gyroplane |
| Design country: | |
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| First flight: |
1934 |
The Kellett KD-1 is a gyroplane made by the US manufacturer Kellett Autogiro Corporation . It was tested in 1935 as the YG-1 by the United States Army Air Corps , making it the first rotary wing aircraft in the American armed forces .
history
development
The KD-1 was developed in the mid-1930s and was the first Kellett gyroplane to use direct control. The "D" in KD therefore stands for direct control . In contrast to the first four types K-1X, K-2, K-3 and K-4 developed by Kellett, the KD-1 used a tiltable rotor for control. The previously preferred control with the help of a conventional tail unit and wings had proven to be inadequate, especially at low speeds. Wallace Kellet and his chief engineer went on a study trip to England to see Cierva in advance to inspect his new C.30 model .
Use of airmail
The prototype had the aircraft registration NX14742. The KD-1 demonstrated its short take-off capabilities by hauling mailbags about 10 km from the roof of the ten-story post office building on Philadelphia's 30th Street across the Delaware River to Camden Airport . The KD-1 was the first gyroplane in the world to carry airmail. Following a tender by the postal authority, Eastern Air Lines was awarded the contract to operate the line and purchased a KD-1B from Kellett. The difference to the KD-1A was that the front passenger compartment for mail transport could be closed with a flap and the pilot's rear cockpit was fitted with a sliding hood.
Eastern Air Lines operated the airmail service five times a day from July 1939 to July 1940. A total of over 2,300 take-offs and landings were carried out on the roof of the office building, with the mail carried on each flight weighing about 135 kg. During the entire period of use there was only one notable incident when a gust of wind rolled the machine on its side on the roof. However, the KD-1B could be repaired.
Military use
The US Army Air Corps (USAAC) procured a KD-1 in 1935 to evaluate its military usability. It was given the military designation YG-1 (USAAC serial no. 35-278), with the code letter "G" standing for gyroplane from 1935 to 1939 . During this time, Kellett made efforts to improve the design in the form of the KD-1A, which received an electric starter and other minor modifications. The USAAC received a KD-1A with additional radio equipment and then procured seven more machines as YG-1B (37-377 to 37-382, 37-635) in 1937. In these, the fuel capacity was reduced from 44 to 30 gal. Five of the seven copies were then used in a training program for airborne artillery observers and for liaison duties. The other two were returned to Kellett for the further development of the gyroplane concept. After their military use, the US Border Patrol initially deployed the five YG-1B on the Texas border, after which they ultimately remained in private hands. One of them made it to Canada to Leavens Brothers in Toronto, where it was destroyed in a startup accident.
The two YG-1B returned to Kellett were given the new designation XR-2 and XR-3 by the USAAC , although the letter "R" was actually only intended for helicopters. With the XR-2 an attempt was made to further develop the jump start capabilities of the gyroplane. In addition, systems have already been installed that should be used later in the planned XO-60 variant. The XR-2 was equipped with a 285 hp seven-cylinder Jacobs R-915 and a Hamilton standard - constant speed propeller . However, the XR-2 never flew because the undercarriage was too weakly dampened and the entire machine started to resonate during roll attempts and was destroyed in the process. The XR-3 was used to develop the rotor system for the planned XR-8 . After completing the test program, General Electric bought the XR-3 to use for its rotorcraft research at the then new research center in Schenectady, New York. It was then passed on to the Teterboro School of Aeronautics in New Jersey for technical training purposes, and finally it was bought by a private individual from Harrisburg, Pennsylvania .
The XO-60 , commissioned by the USAAC in 1940, was a further development of the KD-1A / YG-1B and arose from the demand for higher engine power, greater payload and better vertical take-off properties. The single XO-60 was followed by six more YO-60s for field testing. In these machines, the pilot sat in the front seat for the first time, while the observer behind was accommodated on a swivel seat and had a small work table behind him. Both cockpits were covered with a hinged canopy, and the pilot could also see down through a transparent floor section. In addition, the side walls were flattened at the rear and the cockpit hood was bulged in order to give the observer a better view of the ground.
The machines were subjected to intensive military suitability testing, after which it was concluded that the procurement and maintenance costs were too high compared to light fixed-wing aircraft that could perform the same tasks. In addition, the development of helicopters had progressed so far that they were also in direct competition with gyroscopes.
NASA
The NASA later received a YO-60 from the USAAC, which was destroyed during flight testing.
Replica in Japan
In Japan, too, the Imperial Japanese Army was interested in developing gyrocopter in the USA. A KD-1A was imported, but it was severely damaged during testing. At the Kabaya Industrial Company , the construction was examined and a replica was carried out as the Kabaya Ka-1 . The Ka-1 used as an observation, liaison and patrol aircraft used an Argus As 10 C engine built under license as a drive . After the first flight on May 26, 1941, a series of around 240 machines was produced. Some of them were stationed on board the light aircraft carrier Akitsu Maru and with two 60 kg depth charges were the first armed gyrocopter outside the USSR. One with a Jacobs L-4MA-7 radial engine was named Ka-2.
construction
Like the Cierva C.30, the KD-1 had a wingless design with two tandem seats. The drive consisted of a Jacobs L-4 MA seven-cylinder radial engine with an output of 225 HP (165 kW) and a 101-inch (2.57 m) Curtiss Reed fixed propeller . The rotor blades, whose depth of 12 inches was reduced by almost half compared to the previous designs, had a Göttingen 606 profile. The rotor blades had a tubular steel spar with steel ribs and three-layer wooden planking. The rotor arm made of steel tubes and the vertical drive shaft between the motor and the rotor (to accelerate the rotor before the start) were provided with an aluminum cladding. A rotor brake was located under the engine cover, and a clutch enabled the engine and rotor to be connected quickly and smoothly, and the connection to be released before take-off.
The fuselage was a conventional welded tubular space construction with an aluminum-clad front fuselage and a fabric-covered rear fuselage section. The horizontal surfaces of the tail unit - the surface on the right had an inverted profile - could be adjusted on the ground. The vertical surfaces were arranged below the horizontal in order to prevent contact with the rotor.
Whereabouts
The only example still preserved today comes from the YO-60 series and was rebuilt after an accident before it came to its current location in the Smithsonian Air and Space Museum .
Technical specifications
| Parameter | Data of the KD-1 |
|---|---|
| crew | 1 to 2 |
| length | 6.41 m (21 ft.) YO-60: 6.33 m (20 ft. 9 in.) |
| Rotor diameter | 12.20 m (40 ft.) YO-60: 13.17 m (43 ft. 2 in.) |
| height | 3.13 m (10 ft. 3 in.) (All variants) |
| Empty mass | 597 kg (1315 lb) KD-1B: 726 kg (1600 lb) |
| Max. Takeoff mass | 1022 kg (2250 lb) KD-1B: 1090 kg (2400 lb) YO-60: 1200 kg (2640 lb) |
| Cruising speed | 160 km / h (100 mph) (KD-1 and KD-1B) |
| Top speed | 192 km / h (120 mph) YO-60: 200 km / h (125 mph) |
| Minimum speed | 26 km / h (16 mph) |
| Climb performance | 305 m / min (1000 ft./min) KD-1B: 244 m / min (800 ft./min) |
| Engines | a Jacobs L-4 MA seven-cylinder radial engine with 225 hp |
See also
literature
- Howard Levy: Kellett Gyrations Part 1 . In: Airplane Monthly November 1995, pp. 24-29
- Howard Levy: Kellett Gyrations Part 2 . In: Airplane Monthly December 1995, pp. 36-39
- Airplanes from A – Z. In: AERO - The illustrated compilation of aviation. No. 100, p. 2795, Cavendish.
Web links
- History of the KD-1
- The First Air Mail Flight from the roof of 30th Street Station in Philadelphia youtube video from minute 2:20