As a result of German research by Focke-Wulf on VTOL fighter design during latter days of the Second World War, the US Air Force and Navy initiated Hummingbird project 1947. Fears of Russian effort to move into western Europe and deny Allies use of coventional airfields led to search for aircraft that could operate from limited space. Similarly, Navy interested in VTOL capability to permit operations from small carriers or even merchant ships.
The Navy received design proposals from Lockheed and Convair in 1950. In May 1951 Convair was awarded a contract for the XFY-1, and in June 1951 was Lockheed awarded similar contract for the XFV-1. The tail-sitting Lockheed XFV-1 was the prototype for a proposed U.S. Navy vertical take-off and landing (VTOL) point-defense interceptor. The Lockheed XFV-1 used F-104-like wings and an X shaped tail. Lockheed's own VTOL never received an official nickname but, oddly enough, both aircraft soon came to be known interchangeably as Pogo, by public and insiders alike.
The airplane was powered by a 5,850 horsepower turboprop engine driving a pair of huge, three-bladed contra-rotating propellers. Fitted with a temporary undercarriage, the XFV-1 was first flown in a conventional mode at Edwards on 16 June 1954. Although, while in flight, it did demonstrate successful transitions from conventional into the vertical mode and back, its engine lacked sufficient power to guarantee safe VTOL operations and the whole concept of tail-sitting aircraft was soon abandoned in favor of designs employing vectored jet thrust.
Lockheed assigned the design project to its chief designer, Clarence L. "Kelly" Johnson and his Skunk Works team, the legendary group which produced a series of brilliant aircraft for Lockheed for more than a generation. The vertical take-off and landing (VTOL) project would prove to be one of the most unusual--and in many ways the most frustrating--of Johnson's experience.
The new aircraft would normally rest in a vertical stance, literally sitting upon its cruciform tail. At takeoff the pilot, lying on his back, would lift the thundering fighter into the air. At a safe altitude he would ease it over into horizontal flight, whereupon the plane could be maneuvered like a conventional fighter, supported by a pair of thin, straight, F-104-like wings. At landing, once more on his back, the pilot would hang the XFV-1 on its propellers and ease it slowly backward and down until contact was made with the ground.
As development continued, it became obvious that both the aircraft and pilot would be operating at the very limits of their capabilities. Lockheed's problem was compounded by the fact that only one YT-40 engine suitably configured for vertical flight was immediately available. As the first contract signer, Convair received the engine and was able to proceed directly to vertical flight testing.
In the interim, Lockheed designed a girder-like temporary landing gear which would allow its aircraft to take off and land in the conventional manner. The XFV-1 made only conventional takeoffs and landings, beginning in December 1953. In this way, the aircraft could make its first flight (23 December 1953) and some of its flight characteristics could be studied until such time as the designed engine was delivered.
Unfortunately, this never took place. Famed Lockheed test pilot Herman "Fish" Salmon continued to fly the revolutionary aircraft with its temporary landing gear, making numerous successful in-the-air transitions between vertical to horizontal flight. With the proper engine configuration, the XFV-1 could indeed fulfill its design.
By that point, however, Navy interest in the VTOL project had begun to cool. Rapid advances in turbojet technology were yielding engines and aircraft with twice the speed which the tailsitters could ever hope to achieve. Even the promise of a more powerful derivative of the YT-40 engine, the YT-40-A-14 rated at 7,100 horsepower, could not significantly improve the performance of either aircraft. More fundamentally, it was also becoming obvious to all that vertical-landing turboprops would always be too tricky to land--a difficult task for a highly skilled test pilot would be well-nigh impossible for a line pilot, especially under combat conditions. Putting a tailsitter down on a concrete ramp in full daylight was one thing; an uneven pasture or a heaving deck at sea would be quite another.
After making 32 flights, none involving actual vertical takeoffs or landings, the Lockheed project was cancelled in June 1955.
The design was not successful for several reasons, including the lack of power and reliability from current turboprops, and the very high amount of pilot skill required to successfully land a tail-sitting aircraft. The brief era of tail-sitting VTOL gave way to jet-propelled, fixed- wing, thrust-vectored Harrier made in UK by Hawker-Siddeley.
The unique aircraft thereafter was displayed at Lockheed's Burbank facility for a number of years. After San Diego's Aerospace Museum proved unable to accept it, the XFV-1 was donated in 1981 to the U.S. Naval Air Museum at Pensacola, Florida. There it remains as an everlasting tribute to the imagination and ingenuity of America's aerospace designers.
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