04 June 2010
The USAF took delivery of the X-25A and X-25B on 16 February 1968 and immediately embarked on a series of flights to determine the length of a pilot training cycle necessary to master the autogyro controls. The X-25A was used to power itself to an assigned altitude and then shut down its engine and autorotate. This was to determine the glide performance of the aircraft. Twenty pilots all with fixed wing experience and no rotary wing time were then checked out in the X-25B to see how easy it was to operate. All 20 pilots were able to master the X-25B within 30 minutes. The DDV was then used with anthropomorphic test dummies to measure G-loads and glide performance with an incapacitated pilot.
The winding down of the Vietnam War ended interest in the autogyro solution and it was felt that such an aircraft could be packaged to be accommodated in most combat aircraft cockpits with the current technology of the day. The X-25A is currently on display at the National Museum of the US Air Force in Dayton, Ohio, while the X-25B is at the Museum of Aviation at Warner Robbins, Georgia. The final disposition of the DDV is unknown but the X-25 will always be known as the smallest of the X-planes if not one of the most obscure.
Source: The X-Planes- X-1 to X-45 by Jay Miller. Midland Publishing, 2001, p272-275.