The Bell X-14 was a jet powered VTOL aircraft that was used extensively for tests and experiments between 1957 and 1981.
Bell's first attempt at a jet powered VTOL aircraft had been the Model 65 ATV, a private venture aircraft powered by jet engines mounted on the sides of the fuselage. The idea was that the entire engine would rotate to make the transition from vertical to horizontal flight. The ATV flew for four and half hours in 1954-55, and flew both horizontally and vertically, but never made the transition between the two.
In July 1955 Bell received a new Air Force contract for research into VTOL aircraft. This allowed them to build the X-14, or Bell Model 68. Some work had clearly already been done, as construction of the prototype began three months later.
The X-14 was a fairly odd looking aircraft. It used the wings and part of the undercarriage and ailerons from a Beechcraft Model 35 Bonanza and the tail from a Beechcraft T-34A Mento. It had a open cockpit with what looked like an car windscreen. Two jet engines were mounted in the nose, with their air intakes side by side. The engines had their tailpipes replaced with thrust diverters. The idea was for all of the power to be directed down for take off. Once the aircraft had reached a safe height the thrust would slowly move from the vertical to the horizontal. At first most of the lift would still come from the jets, but once the aircraft was travelling at speed the wings would take over, and all of the thrust would be directly horizontally. The process could be reversed to allow the aircraft to hover or land. When the aircraft was hovering, control was provided by compressed air nozzles in the wingtips and tail.
During its lifetime the X-14 used several different sets of engines. It was originally built with two 1,560lb Armstrong Siddeley Viper 8 axial flow turbojets. Early tests showed that these weren't powerful enough, so during 1960 it was given two 2,680lb st General Electric J85-GE-5s. In 1970 it was given 3,015lb st J85-GE-19s (becoming the X-14B)
Ground tests began in October 1956. The engines were then installed, and the aircraft made its first hover test on 17 February 1957. In June it made a partial transition, and on 24 May 1958 its first full transition from vertical to horizontal flight. The aircraft was then taken over by the Air Force, but early tests revealed the lack of power.
The test programme resumed in 1961 after the aircraft had been given the J85-GE-5 engines, and the new designation X-14A. For the next eleven years it was used to test V/STOL handling and controls, helping several other research programmes.
In 1970 it was given the GE-19 engines, as well as a programmable computer that allowed it to replicate the flight characteristics of other VTOL aircraft. It was then known as the X-14B. The test programme resumed in February 1971. During this period 25 test pilots used it as part of other programmes.
On 29 May 1981 the X-14B suffered a very hard landing that caused damage to the main undercarriage, ruptured a fuel tank and caused a fire that damaged the tail. By now the aircraft was 25 years old, and it was never repaired. Even so, during its quarter century of operations it had provided a great deal of valuable data for other VTOL programmes.
Engine: Two General Electric J85-GE-19s
Power: 3,015lb static thrust each
Span: 33ft 9.5in
Height: 8ft 9.5in
Empty Weight: 3,173lb
Loaded Weight: 4,269lb
Maximum Speed: 172mph
Range: 300 miles