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Surface skimming vehicles

 Surface skimming vehicles

  • The hovercraft can reasonably be counted as a type of airplane, as it does fly, albeit just above the ground. The hovercraft is lifted above the ground or water surface by means of a fan, which produces a raised pressure under the vehicle. Leakage of the air from the underside is restricted by a peripheral ‘curtain’ of high-speed air, normally supplemented by a flexible ‘skirt’.
  •  At one time, the hovercraft was seen as a major new type of transport vehicle, and for many years hovercraft operated a ferry service across the English Channel. In fine weather, this provided a much faster alternative to the conventional ferries.
  • However, the hovercraft was expensive to run and maintain. Also, they could not be operated in very heavy seas and were prone to generate nausea amongst the passengers even in moderate seas.  
  • Nowadays hovercraft are mostly used for very specialized operations, for example in swampy areas, and for recreational and competition use. For ferry duties, they have been largely superseded by various types of catamaran and hydrofoil.
  • Another type of vehicle that flies just above the surface is the surface skimmer or ekranoplane. These aircraft resemble a conventional aircraft, but by flying just above the surface, take advantage of the ‘ground effect’ which greatly reduces the wing downwash, and consequently reduces the accompanying trailing vortex drag.
  •   Some extremely large and very fast aircraft of this type were under development in the old Soviet Union just before its collapse, but subsequent economic difficulties brought further development to a virtual standstill.
  • The engines can be rotated to provide conventional forward flight after take-off. ensuring the correct ground clearance at all times, and the very large amount of engine power needed to get the aircraft to lift off from the water. Several large turbojets were needed on the larger experimental aircraft, and once liftoff had been achieved, most of them became redundant for the rest of the journey.

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