The Probert Encyclopaedia of Aircraft

LOCKHEED MODEL 186

The Lockheed Model 186 was an American high-performance research helicopter built in 1962 for the US Army and Navy under the designation XH-51. The Lockheed Model 186 was a two-seater research helicopter powered by a United Aircraft of Canada T74 (PT6) shaft-turbine providing a top speed of 280 kmh and a range of 388 km.
Research Lockheed Model 186