Ground effect vehicle

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This article is about aircraft, for cars based on a related effect, see Ground effect in cars.

See also: Ground effect

A Russian cold war ekranoplan in flight

A Ground effect vehicle (GEV) refers to an aircraft that takes advantage of the aerodynamic principle of the Wing-in-ground effect (a form of ground effect). GEVs were originally called Ekranoplans, after the original vehicles created in the former Soviet Union pioneered by Rostislav Alexeev; this name is now used to describe the Russian designed vehicles and their variants, with GEV being used as the more generic term for this class of vehicle.^[1]

The development of the ekranoplans slowed towards the end of the Soviet Union. However some development is still ongoing into the vehicle. Other GEVs are being currently developed such as the Boeing Pelican,^[2] and the French supported 'Aéroptère' (also being referred to as a 'wingboat') built by the company Focus 21.^[3]

1 Wing configurations of Ground Effect Vehicles
2 Advantages and Disadvantages
3 References

[edit] Wing configurations of Ground Effect Vehicles

[edit] Inverse Delta

These are based upon research done by the German physicist Alexander Lippisch and use a property of the delta wing shape that allows stable flight in ground effect. These have the advantage of being self stabilising. This is the main Class B form of ground effect craft.

[edit] Ekranoplan Wing

This was the profile adopted by the Russian craft such as the Caspian Sea Monster (shown above), designed by Rostislav Alexeyev. The wings are normally significantly shorter than comparative aircraft due to the addition lift from ground effect. This configuration is pitch and altitude self stabilized thanks to a high aft placed horizontal tail, out of ground effect. Pitch stability comes from front-aft wings lift slopes differential. Flying at very low altitude above the sea may be dangerous if the craft is too much banked to achieve a small radius turn.

[edit] Tandem Wings

[edit] Ram-wing

[edit] Advantages and Disadvantages

A ground effect craft may have better fuel efficiency than an equivalent aircraft flying at low level due to the close proximity of the ground reducing Lift-induced drag. There are also safety benefits in flying close to the water as an engine failure will not result in the craft falling a great distance. Despite this, the Russian Ekranoplan program had a series of disasters due mostly to pilot error showing how difficult that particular wing configuration is to fly even with computer assistance. Another problem is the difficultly of taking off from the water as the small wings of most ground effect craft do not provide as much lift as highly flapped wings. A take off must also be into the wind which, in the case of a water launch means into the waves. Two main solutions to this problem have been implemented. This first was used by the Russian Ekranoplan program which placed engines in front of the wings to provide more lift. The Caspian Sea Monster had eight such engines which were not used once the craft was airborne. A more elegant approach was used by Hanno Fischer in some of the Airfisch ground effect craft which used some of the air from the engines to inflate a skirt under craft in the style of Hovercraft to raise it most of the way out of the water making take-off easier. Note : thanks to the square-cube law to allow this easier solution.