Lockheed XH-51A High Speed Jet Helicopter 240 MPH (210 Knots) 1965

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From Wikipedia, the free encyclopedia http://en.wikipedia.org/wiki/Lockheed_XH-51

Lockheed began developing its rigid rotor concept with the CL-475 helicopter design in 1959. The choice of a rigid rotor meant that the helicopter was more agile than it would have been with a flapping rotor. The performance of the CL-475 encouraged Lockheed to seek further development. Lockheed submitted the CL-475 to the Army as a candidate to replace the OH-13 Sioux and OH-23 Raven helicopters. Lockheed also tested the commercial market waters without success. However, in February 1962, Lockheed's Model 186, a new design based on the CL-475 rigid rotor, was selected as the winner for a joint Army-Navy program to evaluate the rigid rotor for high-speed flight capability.

Two four-seat, three-bladed XH-51As were ordered and built for the program. Powered by the 550 shp (410 kW) Pratt & Whitney Canada PT6B-9 turboshaft engine, XH-51A (serial number 61-51262) first flew on 2 November 1962. As flight testing progressed, the original three-bladed, rigid rotor system demonstrated instability at higher speed ranges. Lockheed engineers solved the problem by modifying the aircraft with a four-bladed rotor system. In 1963, the Army's Technology Research and Evaluation Command (TRECOM) contracted with Lockheed to modify one of the XH-51 aircraft into a compound helicopter.

The second XH-51A (serial number 61-51263) was subsequently converted by adding wings with a span of 16.1 ft (4.9 m), and a 2,500 hp (1,864 kW) Pratt & Whitney J60-2 turbojet engine mounted on the left wing to increase performance. The XH-51A Compound first flew without powering up the turbojet on 21 September 1964, while tests were conducted for balance and handling. The aircraft's first flight as a true compound helicopter took place on 10 April 1965. and on 29 November 1967 achieved a speed of 263 knots (302.6 mph, 486.9 km/h).

In June 1964, NASA ordered a five-seat, three-bladed variant, the XH-51N (NASA 531) as a helicopter test vehicle.

Lockheed built two demonstrator aircraft, designated the Lockheed Model 286, to market to the public (registration numbers N286L and N265LC). These aircraft had the five-seat configuration of the XH-51N with the four-bladed rotor system of the XH-51A. The Model 286 was certificated for civil operation by the FAA on 30 June 1966 but Lockheed never sold any aircraft. The Model 286s were used as executive transports by the Lockheed for years. In non-flying condition, they were sold to a collector and later destroyed by fire in 1988.

Category:

Science & Technology

Tags:

• Lockheed
• XH-51A
• Jet
• Helicopter
• Reaches
• 240
• MPH
• 1965
• CL-475
• Army
• 61-51263
• 15263
• Pratt
• Whitney
• J60-2
• Sikorsky
• x-2
• airboyd
• airboyd.tv
• #airboydtv
• yt:quality=high

[losttribe3001]

This just needs the Airwolf theme music..

[strassj]

Retractable Skid!!!!

[MrZhilvinas]

' Once was helicopter viewed as a slow and reliable workhorse... Well, no more!'

I bet this thing is unreliable :D

[Bravo21]

The new move in this direction is the Sikorsky X-2 helicopter, its a twin rotor design with a pusher prop for nigh speed maneuvers and can do 250kts...all fly by wire. Unlike the Lockheed XH-51A, the X-2 looks like something that will lead to a production model aircraft.

[CrazyHeliDude]

@losttribe3001 - True. I'd be willing to bet dollars to donuts that this is where Bellisario got the primary concept for Airwolf.

[fezzin1992]

jet helicopter....  Jellycopter

[krbosak]

@CorrectiveAction What we see on the vid is not helicopter either. But Osprey is also a VTOL using blades, this is what sets the class. What is see on the vid is not helicopter eiter.

Wiki Gyrodyne, It's alll muddy terrain this classification. I would agree most on FAI designation, whatever it is.

[CorrectiveAction]

@krbosak Osprey is hardly a helicopter...

[hotrod4you2]

where all the gas go? 

[Korvan1993]

It seems that the military videos from the old days where way cooler. Today you just got an uber excited announcer who tells you that THIS BULLETS SOMETHING IS OVAR 9000!!!!!!!!!!!!!!!!!!!!!!

[grreeknick]

@gaberth Google, "retreating blade stall."

[gaberth]

1965 Helicopter gets 272 mph... today a commercial Helicopter Maker is proud to create a 240 mph model ? come on... the same happens with cars AUDI got a 250 mph car in 1941