Ryan X-13 Vertijet
The Ryan X-13 Vertijet was an experimental pure-jet tailsitter built by Ryan for the U.S. Air Force to test whether a fighter could operate without runways or carriers. Two prototypes were built around a Rolls-Royce Avon turbojet; the aircraft hung from a mobile trailer, took off vertically, transitioned to horizontal flight, and landed by hooking a wire on the trailer. After a first conventional flight in December 1955, Girard made the first vertical takeoff and landing in May 1956, and on 11 April 1957 the second prototype completed the full cycle from the trailer. The Air Force ended development in 1957 for want of an operational requirement, and both prototypes survive in museums.
Why It Mattered
In the 1950s the United States' armed forces wanted combat aircraft that could operate from small, dispersed sites, independent of the airfields and carriers that nuclear weapons had made vulnerable. Ryan's Vertijet, built for the Air Force, was a pure-jet tailsitter: it hung from a mobile trailer, rose vertically on its engine's thrust, pitched over into normal flight, and returned to land on the trailer again. On 11 April 1957 it flew that whole sequence for the first time; the Vertical Flight Society records the flight as the first complete cycle of vertical takeoff, horizontal flight and vertical landing by a jet aircraft. The Smithsonian judges that the Vertijet accomplished every task set for it, yet the concept proved impractical for pilots and the aircraft lacked the performance of an adequate interceptor.
Design Notes
The Vertijet was small even by fighter standards: a single-seat aircraft with a high-mounted delta wing of 21 feet span, wrapped around a Rolls-Royce Avon turbojet delivering 10,000 pounds of thrust, more than the aircraft weighed. It carried no landing gear for vertical operations; a hook at the nose caught a wire on the trailer bed, which tilted upright for launch and recovery and lowered flat to carry the aircraft between sites. In the hover, a swivelling exhaust nozzle controlled pitch and yaw while bleed-air thrusters at the wingtips controlled roll, and a stability augmentation system blended these with the ordinary elevons and rudder. Landing was the hardest part: the airframe blocked the pilot's view of the trailer, so even with his seat pivoted 45 degrees toward the vertical he was talked in by radio, judging his last feet against a graduated pole on the trailer.
Operational History
The idea began just after the Second World War, when Ryan engineers debated whether their FR-1 Fireball, whose thrust roughly equalled its weight at low fuel, could take off vertically. In 1947 the Navy's Bureau of Aeronautics gave Ryan a contract to study a vertically launched jet fighter, and the work advanced through remote-controlled rigs to a manned jet test-bed on which Pete Girard made the first manned hovering flight in a jet aircraft, on 24 November 1953. When Navy funding ran out the Air Force took over, ordering two X-13 demonstrators in July 1954. The first aircraft, serial 54-1619, made its maiden flight on 10 December 1955 as a conventional aeroplane on temporary tricycle gear, so its handling could be explored before vertical flight was risked. Fitted with a temporary tail-sitting truss, Girard made the first vertical takeoff and landing on 28 May 1956; the second X-13 flew for the first time the same day. On 28 November 1956 Girard took the X-13 from level flight up into a hover and back to level flight for the first time, and on 11 April 1957 the second prototype launched from its trailer, flew horizontally, and hooked back onto the trailer's wire. At the end of July 1957 the second X-13 was demonstrated at the Pentagon before more than 3,000 officers and journalists. Competing programmes then drew away the funding, the Vertijet flew for the last time on 30 September 1957, and the Air Force chose not to continue development, judging that no operational requirement existed for it.
Afterlife
Only two X-13s were built, and both survive in museums. In 1960 Ryan donated the first aircraft, together with its launch trailer, to the Smithsonian Institution; the Smithsonian's National Air and Space Museum now lends it to the San Diego Air & Space Museum, whose Gillespie Field Annex displays it. The second prototype, the aircraft that made the full-cycle flight, went in May 1959 to the National Museum of the United States Air Force at Dayton, Ohio. The Smithsonian regards the Vertijet's operating profile as a technological dead end for VTOL aircraft, while noting that the thrust vectoring it pioneered later became an essential component of advanced combat aircraft.