HOVERCRAFT

Introduction A hovercraft (air-cushion vehicle,

ACV) is a vehicle that travels over land or water on a cushion of pressurized air. This works on the principle of "surface effect“. Although supported by air, a hovercraft is not considered an aircraft.

Principle

The basic principle

The basic principle of an air cushion is that if you lift an object off the ground using air you reduce the force needed to move the object. Because the object is no longer in contact with the ground the friction this causes (surface friction) is reduced, making it easier to move the object.

This also implies that the smoother the surface the less the friction. This is also true. Uneven surfaces with rocks and other obstacles can significantly slow down or even stop and damage an air cushion vehicle if the chamber containing the air cushion (the plenum chamber) was made of rigid materials.

Applications Hovercraft are used throughout the

world as specialized transports. They can also be used after a natural disaster for emergency purposes. Because they are supported by a cushion of air, hovercraft are unique among all other forms of ground transportation in their ability to travel equally well over land, ice, and water. Small hovercraft are used for sport, or passenger service, while giant hovercraft have civilian and military applications

History The first mention in the historical record

of the principles behind hovering and hoverboats was by Swedish scientist Emanuel Swedenborg in 1716.

In 1915 Austrian Dagobert Müller built the world's first air-cushion vehicle.

The first design that would be recognized as a true hovercraft was designed by Finnish aero engineer Toivo J. Kaario in 1931. Kaario's design included the modern features of a lift engine blowing air into a flexible envelop for lift

Modern Hovercrafts

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