10/31/2007. Remarks by Johan Visschedijk: "This was one of two XH-51A-LOs built to the USN contract NOw 62-0665 of February 1962, for a high-speed research helicopter to be used jointly by the USN and US Army. Built as two-seaters and powered by a 550 shp Pratt & Whitney (Canada) PT6B-9 shaft-turbine, the first flight was made by the first XH-51A, BuNo. 151262 on November 2, 1962. The two helicopters flew an eighteen-month joint Army-Navy evaluation and proved reliable, easy to fly, very stable, and with a top speed of 174 mph (280 kmh), quite fast.

The US Army Aviation Material Laboratories funded the modification of the second helicopter to a compound helicopter. A 17 ft (5.18 m) span wing was added and the helicopter flew again in September 1964, whereafter a 2,900 lb (1,315 kg) st Pratt & Whitney J60-P-2 turbojet was added on the port side. In May 1965 a speed of 272 mph was reached, progressively expanding the performance envelope resulted in an unofficial speed record of 302.6 mph (487.0 kmh) on June 29, 1967.

Both the XH-51A and the XH-51A Compound are preserved at the US Army Aviation Museum at Fort Rucker, Alabama, USA."