Back Lockheed XH-51A Compound

Lockheed XH-51A

The XH-51A's quite impressive performance significantly improved, however, following the second prototype's 1964 conversion into a compound rotorcraft. The conversion of 151263 included the addition of a pod-mounted Pratt & Whitney J60 turbojet engine, short stub wings fixed to the lower fuselage sides, an enlarged horizontal stabilizer, and other detail changes. The reworked XH-51A Compound made its first flight in September 1964, and in June 1967 set an unofficial helicopter world speed record of 487kph.

The XH-51A and XH-51A Compound were extremely valuable technology testbeds, and many of the systems pioneered or refined in these aircraft were later incorporated in such advanced helicopters as the AH-56A Cheyenne. The XH-51As themselves were finally retired from service only in the late 1960s.

S.Harding "U.S.Army Aircraft since 1947", 1990

Lockheed XH-51A

The US Army funded the modification of the second XH-51A as a compound helicopter with mid-mounted 5.18m-span wing and a 1,315kg thrust Pratt & Whitney J60-P-2 turbojet on the port side of the fuselage. These modifications resulted in an increase in gross weight from 1,860 to 2,041kg. First flown in September 1964 without its turbojet, the XH-51A Compound reached a speed of 438km/h in May 1965 after its J60 had been installed. Its performance envelope was then progressively expanded until 29 June 1967, when it set an unofficial speed record for its class of 486.9km/h. Both this compound helicopter and the original XH-51A are now preserved in the collection of the US Army Aviation Museum at Fort Rucker, Alabama.

R.Francillon "Lockheed Aircraft Since 1913", 1987

Technical data for XH-51A Compound

Engine: 1 x Pratt & Whitney of Canada T74 (PT6B) turboshaft, rated at 375kW and 1 x Pratt & Whitney J60-P-2 turbojet, 1170kg of thrust, main rotor diameter: 10.67m, fuselage length: 10.41m, height: 4.88m, take-off weight: 2005kg, empty weight: 1400kg, max speed: 487km/h, cruising speed: 370km/h, service ceiling: 6100m, range: 440km

Bertrand CABARET, e-mail, 15.04.2024reply


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BERCHMAN RICHARD, e-mail, 19.09.2013reply

The pilot who did all the testing on the XH-51A was Don Segner. At one point he was the President on the Experimantal Test Pilot Assoc. (SETP). Never heard of j t rinelli.

Don Hillberg, e-mail, 20.12.2010reply

No Pual E Williams Did not design this Helicopter, Lockheed Did. Did he maintain the patent? and Patents are for a defined period of time, Saw Mr Williams papers Differant configuration, Sorry.

Xavier Norris, e-mail, 24.04.2022 Don Hillberg

It’s ok to be wrong. As it was Mr. Williams.


Xavier Norris, e-mail, 24.04.2022 Don Hillberg

It’s ok to be wrong. As it was Mr. Williams.


Don Hillberg, e-mail, 07.01.2011reply

Looking for data,prints,drawings,reports on this helicopter,call 805-658-8245 Thank you

G Ballard, e-mail, 20.07.2011reply

Fort Rucker Alabama Museum had one. I painted it in 1977.

Don Hillberg, e-mail, 30.03.2012reply

new # 805-832-4248 still looking for data

Rick Koehnen, e-mail, 29.10.2012reply

See comments in XH-51 tab. Both models at Ft Rucker, status unknown.

Rick Koehnen, e-mail, 29.10.2012reply

See comments in XH-51 tab. Both models at Ft Rucker, status unknown.

unknow, e-mail, 07.03.2008reply

paul e.williams made this helicopter

ted, 23.10.2007reply

Paul E. Williams (U.S. patent #3,065,933)
On November 26th, 1962, African American inventor, Paul E. Williams patented a helicopter, Lockheed Model 186 (XH-51). It was a compound experimental helocopter and only 3 units were built.

steve norris, e-mail, 01.07.2007reply

looking for info on lockheed test pilot j.t.rinelli. i believe he was a test pilot on early helicopters,

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