By DV82XL, Section Commentary Posted on Tue May 22, 2007 at 01:41:26 AM PST
It has long been recognised that flight close to a boundary surface is more aerodynamically efficient than free flight. This has led to the design and construction of craft specifically intended to operate close to the ground and fly 'in ground effect'. A great range of Wing in Ground effect craft (WIG) or Ekranoplans, from the Russan, have been manufactured ranging from 2 seat recreational vehicles to 500 tonne warcraft. Despite this ekranoplans have never enjoyed great commercial or military success.
Ekranoplan vehicles benefit from the peculiarities of aerodynamics close to a surface. The proximity of the surface both compresses the air under the wing, giving it more lift, and reduces the drag from the wing, making it more efficient. This effect increases as the surface gets closer and so is the basis for self-stabilisation in ground effect. There is a relationship between strength of this effect and the wing span and wing cord. From a theoretical perspective the effect is equivalent to adding wingspan under conventional aerodynamics. Hence the ekranoplan requires smaller wings than a conventional aircraft.
Such vehicles can be thought of as a cross between an aircraft and a hovercraft, but unlike the hovercraft which drags its air cushion with it, the ekranoplan generates its cushion as it passes.
In concept, such craft offer a potential form of transport which is faster than boats and slower than aircraft. They also offer greater fuel economy and the potential to carry heavier loads than aircraft. The main issues to be resolved are seaworthiness and safe operation.
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