Of dozens of V/STOL designs tried from the 1950s to 1980s, only the subsonic Hawker Siddeley Harrier and Yak-38 Forger reached operational status, with the Forger being withdrawn after the fall of the
Soviet Union.
Props, proprotors, and advanced rotorcraft The idea of vertical flight has been around for thousands of years, and sketches for a VTOL (helicopter) show up in
Leonardo da Vinci's sketch book. Manned VTOL aircraft, in the form of primitive helicopters, first flew in 1907, but would take until after World War Two to be perfected. In addition to
helicopter development, many approaches have been tried to develop practical aircraft with vertical take-off and landing capabilities, including
Henry Berliner's 1922–1925 experimental horizontal-rotor fixed-wing aircraft, and
Nikola Tesla's 1928 patent, and George Lehberger's 1930 patent for relatively impractical VTOL fixed wing airplanes with tilting engines. In the late 1930s, British aircraft designer
Leslie Everett Baynes was issued a patent for the
Baynes Heliplane, another tiltrotor aircraft. In 1941, German designer
Heinrich Focke's began work on the
Focke-Achgelis Fa 269, which had two rotors that tilted downward for vertical takeoff, but wartime bombing halted development. Similarly, the
Ryan X-13 Vertijet flew a series of test flights between 1955 and 1957, but also suffered the same fate. In 1962, Lockheed built the
XV-4 Hummingbird for the
U.S. Army. It sought to "augment" available thrust by injecting the engine exhaust into an ejector pump in the fuselage. First flying vertically in 1963, it suffered a fatal crash in 1964. It was converted into the XV-4B Hummingbird for the
U.S. Air Force as a testbed for separate, vertically mounted lift engines, similar to those used in the
Yakovlev Yak-38 'Forger'. That plane flew and later crashed in 1969. The
Ryan XV-5 Vertifan, which was also built for the U.S. Army at the same time as the Hummingbird, experimented with gas-driven lift fans. That plane used fans in the nose and each wing, covered by doors which resembled half garbage can lids when raised. However, it crashed twice, and proved to generate a disappointing amount of lift, and was difficult to transition to horizontal flight.
Rockwell International built, and then abandoned, the
Rockwell XFV-12 supersonic fighter which had an unusual wing which opened up like
window blinds to create an ejector pump for vertical flight. It never generated enough lift to get off the ground despite developing 20,000
lbf of thrust. The French had a nominally Mach 2
Dassault Mirage IIIV fitted with no less than 8 lift engines that flew (and crashed), but did not have enough space for fuel or payload for combat missions. The German
EWR VJ 101 used swiveling engines mounted on the wingtips with fuselage mounted lift engines, and the VJ 101C X1 reached supersonic flight (Mach 1.08) on 29 July 1964. The supersonic
Hawker Siddeley P.1154, which competed with the Mirage IIIV for use in NATO, was cancelled even as the aircraft were being built.
NASA has flown other VTOL craft such as the
Bell XV-15 research craft (1977), as have the
Soviet Navy and
Luftwaffe.
Sikorsky tested an aircraft dubbed the
X-Wing, which took off in the manner of a helicopter. The rotors would become stationary in mid-flight, and function as wings, providing lift in addition to the static wings.
Boeing X-50 is a
Canard Rotor/Wing prototype that utilizes a similar concept. A different British VTOL project was the
gyrodyne, where a rotor is powered during take-off and landing but which then freewheels during flight, with separate propulsion engines providing forward thrust. Starting with the
Fairey Gyrodyne, this type of aircraft later evolved into the much larger twin-engined
Fairey Rotodyne, that used
tipjets to power the rotor on take-off and landing but which then used two
Napier Eland turboprops driving conventional propellers mounted on substantial wings to provide propulsion, the wings serving to unload the rotor during horizontal flight. The Rotodyne was developed to combine the efficiency of a fixed-wing aircraft at cruise with the VTOL capability of a helicopter to provide short-haul airliner service from city centres to airports. , the first production
tiltrotor aircraft CL-84-1 (
CX8402) on display at the
Canada Aviation and Space Museum in Ottawa, Ontario The
CL-84 Dynavert was a Canadian V/STOL turbine tilt-wing monoplane designed and manufactured by
Canadair between 1964 and 1972. The Canadian government ordered three updated CL-84s for military evaluation in 1968, designated the CL-84-1. From 1972 to 1974, this version was demonstrated and evaluated in the United States aboard the aircraft carriers USS
Guam and USS
Guadalcanal, and at various other centres. These trials involved military pilots from the United States, the United Kingdom, and Canada. During testing, two of the CL-84s crashed due to mechanical failures, but no loss of life occurred as a result of these accidents. No production contracts resulted. Although tiltrotors such as the
Focke-Achgelis Fa 269 of the mid-1940s and the Centro Técnico Aeroespacial "Convertiplano" of the 1950s reached testing or mock-up stages, the
Bell-Boeing V-22 Osprey is considered the world's first production
tiltrotor aircraft. It has one three-bladed
proprotor,
turboprop engine, and transmission
nacelle mounted on each wingtip. The Osprey is a multi-mission aircraft with both a vertical takeoff and landing (VTOL) and short takeoff and landing capability (
STOL). It is designed to perform missions like a conventional
helicopter with the long-range, high-speed cruise performance of a
turboprop aircraft. The FAA classifies the Osprey as a model of
powered lift aircraft. Attempts were made in the 1960s to develop a commercial passenger aircraft with VTOL capability. The
Hawker Siddeley Inter-City Vertical-Lift proposal had two rows of lifting fans on either side. However, none of these aircraft made it to production after they were dismissed as too heavy and expensive to operate. In 1983, the Defense Advanced Research Projects Agency (
DARPA) initiated the Advanced STOVL (ASTOVL) program to develop a supersonic STOVL fighter (SSF) to replace the Harrier for the U.S. Marine Corps and the U.K. Royal Navy. Several propulsion methods were explored under ASTOVL and assigned to different contractors for research and development. These include the Shaft-Driven Lift Fan (SDLF) by
Lockheed which had a forward
lift fan powered by a shaft connected to the main engine's low-pressure spool and engaged by a clutch, the Lift-Plus-Lift/Cruise (LPLC) by
Northrop (later
Northrop Grumman) which had a separate dedicated lift engine alongside the main engine, and the Gas-Driven Lift Fan (GDLF) by
McDonnell Douglas that used the main engine bleed air to power a lift fan; all methods had an aft vectoring nozzle for the main engine. ASTOVL would continue under the
Common Affordable Lightweight Fighter (CALF) program, which eventually became part of the
Joint Strike Fighter program; the
Lockheed Martin X-35B with the SDLF was eventually selected for full-scale development in 2001, with the production aircraft for operational service becoming the F-35B with the
F135-PW-600 engine.
NASA uses the
abbreviation SSTOVL for Supersonic Short Take-Off / Vertical Landing, and as of 2012, the X-35B/F-35B are the only aircraft to conform with this combination within one flight. In 2018, Opener Aero demonstrated an electrically powered fixed-wing VTOL aircraft, the
Blackfly, which the manufacturer claims is the world's first ultralight fixed-wing, all-electric, VTOL aircraft. , a modern VTOL
unmanned aerial vehicle In the 21st century, unmanned drones are becoming increasingly commonplace. Many of these have VTOL capability, especially the
quadcopter type.
Jet lift Tail-sitters In 1947, the
Ryan X-13 Vertijet, a
tailsitter design, was ordered by the US Navy, who then further issued a proposal in 1948 for an aircraft capable of VTOL aboard platforms mounted on the afterdecks of conventional ships. Both
Convair and
Lockheed competed for the contract but in 1950, the requirement was revised, with a call for a research aircraft capable of eventually evolving into a VTOL ship-based convoy escort fighter. At the end of 1958, the French
SNECMA Coléoptère, a tailsitter
annular wing design, performed its maiden flight. However the sole prototype was destroyed on its ninth flight in 1959, and financing was never sourced for a second prototype.
Conventional design Another more influential early functional 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), Short Brothers and Harland, Belfast which used four vertical lift engines with a horizontal one for forward thrust. The
Short SC.1 was the first British fixed-wing VTOL aircraft. The SC.1 was designed to study the problems with VTOL flight and the transition to and from forward flight. The SC.1 was designed to meet a Ministry of Supply (MoS) request for tender (ER.143T) for a vertical take-off research aircraft issued in September 1953. The design was accepted by the ministry and a contract was placed for two aircraft (XG900 and XG905) to meet Specification ER.143D dated 15 October 1954. The SC.1 was also equipped with the first "fly-by-wire" control system for a VTOL aircraft. This permitted three modes of control of the aerodynamic surfaces or the nozzle controls. The
Republic Aviation AP-100 was a prototype VTOL 6x
General Electric J85 turbojet-engined nuclear-capable strike fighter concept designed by
Alexander Kartveli that had three ducted fans in the centre of its fuselage and tail as a possible contender for the
TFX Program. Another design was the A400 AVS that used variable-geometry wings but was found too complicated; however, it led to the development of the
AFVG, which in turn helped the development of the
Panavia Tornado. 's VTOL aircraft, the
Yakovlev Yak-38 The
Yakovlev Yak-38 was a
Soviet Navy VTOL aircraft intended for use aboard their light carriers, cargoships, and capital ships. It was developed from the
Yakovlev Yak-36 experimental aircraft in the 1970s. Before the Soviet Union broke up, a supersonic VTOL aircraft was developed as the Yak-38's successor, the
Yak-141, which never went into production.
VJ101 on display at the
Deutsches Museum,
Munich, Germany on display at the
Deutsches Museum, Germany In the 1960s and early 1970s, Germany planned three different VTOL aircraft. One used the
Lockheed F-104 Starfighter as a basis for research for a V/STOL aircraft. Although two models (X1 and X2) were built, the project was canceled due to high costs and political problems as well as changed needs in the
German Air Force and NATO. The
EWR VJ 101C did perform free VTOL take-offs and landings, as well as test flights beyond mach 1 in the mid- and late 60s. One of the test aircraft is preserved in the
Deutsches Museum in Munich, Germany, another outside Friedrichshafen Airport. The others were the VFW-Fokker
VAK 191B light fighter and reconnaissance aircraft, and the
Dornier Do 31E-3 (troop) transport. The
LLRV was a
spacecraft simulator for the Apollo lunar lander. It was designed to mimic the flight characteristics of the
lunar exploration module (LEM), which had to rely on a reaction engine to land on the Moon. The idea of using the same engine for vertical and horizontal flight by altering the path of the thrust was conceived by
Michel Wibault. It led to the
Bristol Siddeley Pegasus engine which used four rotating
nozzles 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.
V/STOL with
Indian Naval Air Arm The Harrier is usually flown in STOVL mode, which enables it to carry a higher fuel or weapon load over a given distance. The March 1981 cover of
Popular Science showed three illustrations for its "Tilt-engine V/STOL – speeds like a plane, lands like a copter" front-page feature story; a followup story was part of the April 2006 issue that mentioned "the fuel-consumption and stability problems that plagued earlier plane/copter." Retired from the British
Royal Navy in 2006, the
Indian Navy continued to operate
Sea Harriers until 2016, mainly from its
aircraft carrier . The latest version of the Harrier, the
BAE Harrier II, was retired in December 2010 after being operated by the British
Royal Air Force and Royal Navy. The
United States Marine Corps and the Italian and Spanish navies all continue to use the
AV-8B Harrier II, an American-British variant. Replacing the Harrier II/AV-8B in the air arms of the US and UK is the STOVL variant of the
Lockheed Martin F-35 Lightning II, the F-35B.
Convertiplanes and gyrodynes prepares to land A
tiltrotor is a
rotorcraft that generates lift and propulsion by way of one or more powered
rotors (sometimes called
proprotors) mounted on rotating
shafts or
nacelles usually at the ends of a fixed wing. Tiltrotor design combines the VTOL capability of a helicopter with the speed and range of a conventional
fixed-wing aircraft. A
tiltwing is similar to a tiltrotor, except that the rotor mountings are fixed to the wing and the whole assembly tilts between vertical and horizontal positions. A
gyrodyne is a type of VTOL aircraft with a helicopter rotor-like system that needs to be driven by its engine only for takeoff and landing, and includes one or more conventional propeller or jet engines to provide thrust during cruising flight.
Rockets SpaceX developed
several prototypes of Falcon 9 to validate various low-altitude, low-velocity engineering aspects of its
reusable launch system development program. The first prototype, Grasshopper, made eight successful test flights in 2012–2013. It made its eighth, and final, test flight on October 7, 2013, flying to an altitude of before making its eighth successful VTVL landing. This was the last scheduled test for the Grasshopper rig; next up will be low altitude tests of the Falcon 9 Reusable (F9R) development vehicle in Texas followed by high altitude testing in New Mexico. On November 23, 2015,
Blue Origin's New Shepard booster rocket made the first successful vertical landing following an uncrewed suborbital test flight that reached space. On December 21, 2015,
SpaceX Falcon 9 first stage made a successful landing after boosting 11 commercial satellites to
low Earth orbit on
Falcon 9 Flight 20. These demonstrations opened the way for substantial reductions in space flight costs. ==Lists of V/STOL aircraft==