Lockheed XN-51 ( model 186 ) is an American single-engine experimental helicopter developed by Lockheed using a rigid rotor and retractable landing gear . The XH-51 was selected as a test vehicle for a joint research program conducted by the U.S. Army and U.S. Navy to study the technology of the hard rotor.
| Lockheed XH-51 | |
|---|---|
| English Lockheed xh-51 | |
 XH-51A after conversion to a composite rotorcraft test bench. | |
| Type of | Experimental |
| Manufacturer | Lockheed corporation |
| First flight | November 2, 1962 |
| Status | Out of production |
| Operator | U.S. Army NASA |
| Base model | Lockheed XH-51 |
| Options | XH-51A, connected XH-51A, XH-51N, Model 286 |
Content
Design and Development
In 1959, Lockheed began to develop his concept of a rigid rotor with the design of the CL-475 helicopter. The choice of a rigid rotor meant that the helicopter was more maneuverable than it would be with a fly rotor . Performance CL-475 encouraged Lockheed to strive for further development. Lockheed introduced the CL-475 Army as a candidate to replace the Bell OH-13 Sioux and Hiller OH-23 Raven observation helicopters. Lockheed also unsuccessfully tested the waters of the commercial market. However, in February 1962, the Lockheed 186th model, a new design based on the CL-475 solid rotor, was selected as the winner for a joint Navy Army program to evaluate the solid rotor for high-speed flight capabilities. [one]
Operational History
For the program, two four-seater three-bladed XH-51As were ordered and built. Pratt & Whitney Canada PT6B-9 , XH-51A (serial number 61-51262) equipped with 550 shp (410 kW ) turboprops first flew on November 2, 1962. During flight tests, the original rigid three-blade rotor system with three blades demonstrated instability at higher speed ranges. Lockheed engineers solved the problem by modifying the aircraft with a four-blade rotor system. In 1963, the Army Technology Research and Assessment Command (TRECOM) entered into a contract with Lockheed to modify one of the XH-51 aircraft in a mixed helicopter. [2]
The second XH-51A (serial number 61-51263) was subsequently converted by adding wings with a span of 16.1 feet (4.9 m) and 2900 pounds (12.9 kn) of a Pratt & Whitney J60-2 turbojet engine mounted on the left wing to increase productivity. The XH-51A blend flew for the first time without turning on a turbojet engine on September 21, 1964, [2] while tests were performed for balance and handling. The first flight of the aircraft as a real complex helicopter took place on April 10, 1965. [3] And on November 29, 1967, it reached a speed of 263 knots (302.6 km / h, 486.9 km / h) [4] during shallow descent. The highest level of flight speed was 223 knots (413 km / h; 257 mph. [5]
In June 1964, NASA ordered a five-seater three-bladed version of the XH-51N (NASA 531) as a test helicopter. [four]
Lockheed built two demonstration aircraft, designated Lockheed Model 286, for sale to the public (registration numbers N286L and N265LC ). These aircraft had a five-seat configuration XH-51N with a four-blade rotor system XH-51A. Model 286 was certified for civilian use by the FAA on June 30, 1966, but Lockheed never sold any aircraft. Lockheed used the plane for several years as an executive vehicle. The aircraft was eventually sold to a collector, and then destroyed by fire in 1988. [6]
In order to complete the US Army’s Advanced Air Fire Support System for a strike helicopter, Lockheed designed a rigid rotor with a pusher tail rotor, which was commissioned as a Lockheed AH-56 Cheyenne attack helicopter. However, technical problems led first to delays, and then to the suspension of production. Compounded by rivalry between services and political issues, Cheyenne was completely canceled in 1972, and this was Lockheed's last helicopter
Options
- XH-51A
- four places, three-blade rotor
- United KhN-51A
- modified with a four-blade rotor, dead-end wings and an auxiliary engine of 2,900 lbs / force (12.9 kN) Pratt & Whitney J60-2.
- XH-51N
- five seats, three-blade rotor for test purposes by NASA .
- Model 286
- Five local civilian or military light helicopters are for sale, but not one is sold.
Surviving Helicopters
Two examples of the KhN-51A (serial numbers 61-51262 and 61-51263) are stored at the US Army Aviation Museum , Fort Racker . [7]
Specifications (XH-51A)
Data from Jane's “All Airplanes of the World 1969-70.” [eight]
Key Features
- Length: 40 ft 9 in (12.40 m)
- Rotor Diameter: 35 ft 0 in (10.67 m)
- Height: 8 ft 2½ in. (2.50 m)
- Disc area: 962 ft² (89.4 m²)
- Empty weight: 2.790 libre (1.265 kg)
- Max. take-off weight: 4,100 lib (1,864 kg)
- Engine: 1 × Pratt & Whitney Canada PT6 B-9 turboshaft , 550 hp (410 kW)
Flight characteristics
- Top speed: 151 knots (174 mph, 280 km / h)
- Cruising speed: 139 knots (160 mph, 257 km / h)
- Range: 226 Nm (260 mi, 418 km)
- Climbing speed: 16,000 ft (4,876 m) (maximum altitude (taking into account the influence of the earth))
- Climb speed: 2,000 ft / min (10 m / s)
- Disc load: 4.26 lib / ft² (20.9 kg / m²)
- Strength / mass: 0.27 hp / libr (0.44 kW / kg)
See also
Development related
- Lockheed CL-475
- Lockheed AH-56 Cheyenne
Notes
- ↑ Connor, R. Lockheed HL-475 . Smithsonian National Air And Space Museum. Changes as of August 15, 2002. Get access on September 3, 2007.
- ↑ 1 2 Robb, Raymond L. “Hybrid helicopters: Compounding the quest for speed” Archived on September 27, 2006. , Vertiflite . Summer 2006. American Helicopter Society. Accessed on 8 November 2008.
- ↑ Hirschberg, Michael J. and David K. Daley. Lockheed, US and Russian Helicopter Development In the 20th Century Archived October 4, 2006. . American Helicopter Society, International. Accessed on November 16, 2007.
- ↑ 1 2 Badrocke and Gunston (1998)
- ↑ Lentine, F.P.; Grotto, V.P .; Oglesby, T. N. " Research on the maneuverability of the XH-51A helicopter connection " Lockheed , June 1968. Date of Appeal: August 27, 2014.
- ↑ Landis and Jenkins 2000, pp. 29-31, 34.
- ↑ Rotary Wing Collection . United States Army Aviation Museum . Archived July 13, 2012.
- ↑ Jane. Janes's All The World's Aircraft 1969-70. - Jane. - London, 1969 .-- S. 359-360.
Bibliography
- Landis, Tony and Jenkins, Dennis R. Lockheed AH-56A Cheyenne - WarbirdTech Volume 27 , Specialty Press, 2000. ISBN 1-58007-027-2 .