Lockheed XFV-1 Salmon
The Lockheed XFV-1 Salmon was an experimental tailsitter built for a U.S. Navy programme that sought a vertical takeoff and landing (VTOL) fighter able to operate from the afterdecks of conventional ships and protect convoys. Two prototypes were ordered in 1951, but only one was completed and flown; because the more powerful Allison T54 engine the design was drawn around never became available, it flew on a temporary conventional undercarriage and made 32 flights in 1954-55, transitioning between horizontal and vertical flight in the air but never taking off or landing vertically. The Navy cancelled the project in June 1955, and the flying prototype is now displayed at the Florida Air Museum in Lakeland, Florida.
Why It Mattered
In 1948 the U.S. Navy asked for an aircraft able to take off and land vertically from platforms mounted on the afterdecks of conventional ships, a step towards a VTOL fighter that could protect convoys. Lockheed's answer was a tailsitter, an aircraft that sat upright on its tail and was meant to rise vertically before levelling off into forward flight, and it competed in the programme against Convair's rival design. The XFV-1's test career showed that a tailsitter could be flown, and could change between horizontal and vertical flight in the air, but also that it asked for more power and more pilot skill than the Navy had to give.
Design Notes
The XFV-1 was a single-seat aircraft whose tail surfaces formed a reflected cruciform, an X of fins extending above and below the fuselage, so that it could rest upright on its tail. Its Allison XT40-A-14 turboprop produced 5,100 shaft horsepower and drove three-bladed contra-rotating propellers. Full VTOL testing was to wait for the 7,100-shaft-horsepower Allison T54, but that engine never materialised, and the prototype kept the interim XT40. It was to be armed either with four cannon of 20 mm or with 48 rockets, each of 2.75-inch calibre. Because it could not yet fly from its tail, the aircraft was fitted for testing with a temporary, non-retractable undercarriage of long braced V-legs, with fixed wheels on the lower fins. Lockheed employees nicknamed it the "pogo stick", after the rival Convair aircraft, while the name Salmon came from its chief test pilot, Herman "Fish" Salmon.
Operational History
On 19 April 1951 the Navy ordered two prototypes from Lockheed, under the designation XFO-1, which was changed to XFV-1 soon afterwards when the Navy's code for Lockheed changed from O to V. Only one of the two was ever completed and flown; the second prototype was never finished. In November 1953 the aircraft went by road to Edwards Air Force Base, where ground testing and taxi trials began. During a taxi test on 22 December 1953, chief test pilot Herman "Fish" Salmon took it past liftoff speed and the aircraft made a brief hop, its first time in the air. The official first flight followed on 16 June 1954, a conventional takeoff on the temporary undercarriage. In 32 flights the XFV-1 never took off or landed vertically; what vertical flying it did was a few transitions in flight between the conventional and vertical modes, and brief hovers at altitude. The Navy cancelled the project in June 1955, concluding that contemporary fighters would soon outclass it in speed and that it took an exceptionally experienced pilot to fly.
Afterlife
The single flying prototype survives at the Florida Air Museum, on the SUN 'n FUN campus in Lakeland, Florida, which obtained it on loan from the National Naval Aviation Museum in Pensacola. For many years it stood on its tail near the museum's main office, where long-time SUN 'n FUN fly-in attendees may recall seeing it. Dedicated volunteers restored it over several years, and visitors can now find it beside the Guest Hospitality Center in Southeast Exhibits. The aircraft was assigned Bureau Number 138657, but it is marked as 658 following its restoration. The unfinished second prototype is on display at Los Alamitos Army Airfield in California.