Lift jet

Lift jet

A lift jet is a jet engine angled to provide an aircraft with "aerostatic" (i.e., not requiring the movement of air over an airfoil) lift instead of (or in addition to) thrust. On a fixed-wing aircraft, lift jets may be installed as auxiliary engines, with a separate engine to provide forward thrust, or, as in the Harrier jump jet, may be vectored in flight to provide both.

Lift jets were first designed by German engineers during World War II, but none saw operational service. Many nations had experimental programs involving such engines by the early 1950s: one typical example was Rolls-Royce's Thrust Measuring Rig (TMR), nicknamed the "Flying Bedstead," which took its lift solely from engine thrust. An early dedicated lift jet was the Rolls-Royce RB108, first run in 1955.

In the early 1960s both the USSR and western nations considered the possibility of lift engines as a way of providing STOL or even VTOL capability to combat aircraft. The Soviets did side-by-side testing of versions of combat aircraft using variable geometry wings and lift jets (the results became the Mikoyan MiG-23 and Sukhoi Su-24). The problems with the auxiliary lift engine are high fuel consumption, extra weight (which is simply dead weight when the engines are not needed for lift), and taking up fuselage volume that could be used for fuel or other systems. The Soviets decided that variable-geometry wings provided comparable advantages in take-off performance without as many penalties.

One of the few operational military aircraft with auxiliary lift engines was the Soviet Yakovlev Yak-38, a VTOL fighter used by the AVMF's small aircraft carriers, which were not large enough to support conventional fixed-wing aircraft. The Yak-38 proved disappointing in service for most of the above reasons, having limited payload and range as well as dismal handling.

A novel alternative to the lift jet for auxiliary vertical thrust is to be employed by the VTOL Lockheed F-35B version of the U.S. Joint Strike Fighter program. This does not have a jet lift engine, but a central lift fan that is powered by the main engine via a driveshaft. When not needed, it is declutched from the engine so that it does not consume power (analogous to the transfer case of a four-wheel drive vehicle). The operational viability of this system remains to be seen. It has, however, in pre-operational testing proven the ability to take off vertically and go supersonic in level flight in the same mission, a first for a combat aircraft.

Wikimedia Foundation. 2010.

Игры ⚽ Поможем сделать НИР

Look at other dictionaries:

  • Lift (force) — For other uses, see Lift. Boeing 747 8F landing A fluid flowing past the surface of a body exerts a surface force on it. Lift is the component of this force that is perpendicular to the …   Wikipedia

  • Jet pack — For other meanings see Jetpack (disambiguation). : The Martin Jetpack, despite its name, has no jets or rockets, but is a small helicopter, and is discussed as such. Jet pack, rocket belt, rocket pack, and similar names, are various types of… …   Wikipedia

  • jet engine — an engine, as an aircraft engine, that produces forward motion by the rearward exhaust of a jet of fluid or heated air and gases. Also called jet, jet motor. [1940 45] * * * Any of a class of internal combustion engines that propel aircraft by… …   Universalium

  • Jet engine — For a general overview of aircraft engines, see Aircraft engine. A Pratt Whitney F100 turbofan engine for the …   Wikipedia

  • Lift-induced drag — In aerodynamics, lift induced drag, induced drag, vortex drag, or sometimes drag due to lift, is a drag force that occurs whenever a moving object redirects the airflow coming at it. This drag force occurs in airplanes due to wings or a lifting… …   Wikipedia

  • Jet aircraft — A jet aircraft is an aircraft propelled by jet engines. Jet aircraft fly much faster than propeller powered aircraft and at higher altitudes as high as 10,000 to 15,000 meters, about 33,000 to convert|49000|ft|m| 2. At these altitudes, jet… …   Wikipedia

  • Jet airliner — A jet airliner, sometimes contracted to jetliner, is a passenger airplane (passenger aeroplane) that is powered by jet engines. In contrast to today s long distance quiet, fuel efficient, and modern turbofan powered air travel, first generation… …   Wikipedia

  • Jet Star (Särkänniemi roller coaster) — Infobox roller coaster name= Jet Star caption= Jet Star roller coaster at Särkänniemi. location= Särkänniemi section= type= Steel type2= type3= status= Open opened= 1980 manufacturer= Anton Schwarzkopf designer= Ingenieur Büro Stengel GmbH model …   Wikipedia

  • Jet Star (roller coaster) — Infobox roller coaster name= Jet Star caption= location= Knoebels section= type= Steel type2= type3= Family status= Removed in 1992 opened= 1977 manufacturer= Anton Schwarzkopf designer= Ingenieur Büro Stengel GmbH model= Jet Star track= lift=… …   Wikipedia

  • jet flaps — An arrangement in which the efflux of air or a jet stream in the form of a sheet of air is ejected under pressure at or near the trailing edge of the airfoil. This helps to control the boundary layer, and if this sheet of air can be deflected,… …   Aviation dictionary

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”