page_title: Harrier Jump Jet
section_title: Operation
hierarchical_section_title: Harrier Jump Jet / Operation
caption_attribution_description: Rolls-Royce Pegasus engine on display, sections have been cut out to provide an internal view.
context_page_description: The Harrier, informally referred to as the Harrier Jump Jet, is a family of jet-powered attack aircraft capable of vertical/short takeoff and landing operations. Named after a bird of prey, it was originally developed by British manufacturer Hawker Siddeley in the 1960s. The Harrier emerged as the only truly successful V/STOL design of the many attempted during that era. It was a subsonic aircraft, unlike most of its competitors. It was conceived to operate from improvised bases, such as car parks or forest clearings, without requiring large and vulnerable air bases. Later, the design was adapted for use from aircraft carriers.
  There are two generations and four main variants of the Harrier family, developed by both UK and US manufacturers:
  Hawker Siddeley Harrier
  British Aerospace Sea Harrier
  McDonnell Douglas AV-8B Harrier II
  British Aerospace Harrier II
  The Hawker Siddeley Harrier is the first generation-version and is also known as the AV-8A Harrier; it was used by multiple air forces, including the Royal Air Force and the United States Marine Corps.
context_section_description: The Harrier Jump Jet, capable of taking off vertically, can only do so at less than its maximum loaded weight. In most cases, a short take off is needed to lift the required amount of fuel and weapons needed for a training sortie/mission, using forward speed to supplement the jet lift with aerodynamic lift. A short takeoff also uses less fuel than a vertical take off. On aircraft carriers, a ski-jump ramp is used at the bow of the carrier to help the aircraft become airborne. Landings are not usually done in a conventional manner because the range of speeds at which this is advisable is narrow due to the relatively vulnerable outrigger undercarriage. Operationally, a near-vertical landing with some forward speed is preferred, and this technique called Shipborne rolling vertical landing (SRVL). Rotating the vectored thrust nozzles to some angle other than rearwards during normal flight (to a maximum of 8-degree forward of vertical, i.e. 98 deg.) is called vectoring in forward flight, or "VIFFing". This is a dog-fighting tactic, allowing for more sudden braking and higher turn rates. Braking could cause a chasing aircraft to overshoot and present itself as a target for the Harrier, a technique formally developed by the USMC for the Harrier in the early 1970s.  This technique was much discussed in the Media before the Falklands War in 1982, but ultimately not used by British pilots in that conflict. However, the ability to rotate the nozzles slightly forwards did allow the aircraft to fly slowly backwards in the hover, which was widely used in British and American airshows.
  The wind direction is critical during VTOL manoeuvres because unless it enters the intake from straight ahead it will push the nose sideways as it turns to enter the intake (known as intake momentum drag). If not corrected immediately the aircraft will roll out of control. The pilot has a wind vane in front of the windscreen to help him keep pointing into the wind. The procedure for vertical takeoff involves facing the aircraft into the wind. The swivelling nozzles are pointed vertically downwards (thrust vector 90°) and the throttle is pushed to its maximum stop, at which point the aircraft leaves the ground. The throttle is adjusted until hovering is achieved at the desired altitude.  The short-takeoff procedure involves proceeding with a normal takeoff and then rotating the nozzles partially downwards (a thrust vector less than 90°) at a speed below the normal takeoff speed; usually this is done at about 65 knots (120 km/h). For a shorter takeoff run the thrust vector is greater for more jet lift. The reaction control system uses thrusters at the aircraft extremeties, nose, tail and wingtips. Thrust from the engine can be temporarily syphoned to control the aircraft's pitch, roll and yaw before it is going fast enough for the elevators, rudder and ailerons to become effective.
  The Harrier has been described by pilots as "unforgiving" to fly. The aircraft is capable of both forward flight (where it behaves like a fixed-wing aircraft above its stall speed), as well as VTOL (where the conventional lift and control surfaces are ineffective) and STOL. Accelerating and decelerating transitions between hovering and conventional flight required considerable skill and concentration on the part of the pilot, especially in crosswind conditions. Pilots for the combined UK/US/Germany trials on the Kestrel were first given several hours helicopter tuition Royal Air Force pilots destined for Harrier squadrons were usually selected from those with single-seat fast-jet experience. On two occasions the Royal Air Force explored whether experienced helicopter pilots, with their ability to hover and transition to forward flight, would be a better source for Harrier squadrons. In both cases the pilots were completely out of their depth with conventional flight, navigation, orientation and weapons delivery at the high speeds of a fast jet. With the introduction of two-seat Harriers less experienced pilots were introduced. The United States Marine Corps also started with ver
caption: Rolls-Royce Pegasus engine on display, sections have been cut out to provide an internal view
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