Military working dogs train to ensure they’re ready for action at a moments’ notice.
Army's Experimental Jet Helicopter
The Lockheed XH-51 (Model 186) was a three-bladed, single-engine experimental helicopter designed by Lockheed-California, a division of Lockheed Aircraft, utilizing a rigid rotor and retractable skid landing gear . The XH-51 was selected as the test vehicle for a joint research program conducted by the United States Army and United States Navy to explore rigid rotor technology. 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)