VTOL is an abbreviation for
Vertical Take-Off and Landing aircraft. See also
V/STOL. This classification includes
fixed-wing aircraft that can hover, take off and land vertically as well as
helicopters and other aircraft with powered rotors, such as
tiltrotors.
[1][2][3][4] Autogyros,
balloons,
airships and
rockets are not normally considered VTOL, but may be termed VTVL (Vertical Takeoff with Vertical Landing).
[citation needed] Some VTOL aircraft can operate in other modes as well, such as
CTOL (Conventional Take-off and Landing),
STOL (Short Take-Off and Landing), and/or
STOVL (Short Take-Off and Vertical Landing) mode. Others, such as some helicopters, can only operate by VTOL, due to the aircraft lacking
landing gear that can handle horizontal motion. VTOL is a subset of
V/STOL.
Besides the ubiquitous helicopter, there are currently two types of VTOL aircraft in military service craft using a tiltrotor, such as the Bell Boeing V-22 Osprey, and aircraft using directed jet thrust such as the Harrier family.
In addition to the helicopter, many approaches have been tried to develop practical aircraft with vertical take-off and landing capabilities. An early contribution to VTOL was Rolls-Royce's Thrust Measuring Rig ("flying bedstead") of 1953. This led to the first VTOL engines as used in the first British VTOL aircraft, the Short SC.1 (1957) which used 4 vertical lift engines with a horizontal one for forward thrust.
The idea of using the same engine for vertical and horizontal flight by altering the path of the thrust led to the Bristol Siddeley Pegasus engine which used rotating ducts to direct thrust over a range of angles. This was developed side by side with an airframe, the Hawker P.1127, which became subsequently the Kestrel and then entered production as the Hawker Siddeley Harrier, though the supersonic Hawker Siddeley P.1154 was canceled in 1965. The French in competition with the P.1154 had developed a version of the Dassault Mirage III capable of attaining Mach 1. The Dassault Mirage IIIV achieved transition from vertical to horizontal flight in March 1966, reaching Mach 1.3 in level flight a short time later.
