air-cushion vehicle (ACV), craft designed to travel close to but above ground or water. It is also called a ground-effect machine or Hovercraft. These vehicles are supported in various ways. Some of them have a specially designed wing that will lift them just off the surface over which they travel when they have reached a sufficient horizontal speed (the ground effect). Others are supported by fans that force air down under the vehicle to create lift. In a plenum chamber vehicle the rate of leakage of this air from underneath the vehicle is reduced by placing a skirt around the lower edge of the craft. In an annular jet vehicle the rate of leakage is reduced by directing the air downward and inward from the outer edges of the vehicle. Air propellers, water propellers, or water jets usually provide forward propulsion. Air-cushion vehicles can attain higher speeds than can either ships or most land vehicles and use much less power than helicopters of the same weight. Air-cushion suspension has also been applied to other forms of transportation, in particular trains, such as the French Aerotrain and the British Hovertrain. A relatively smooth land or water surface, however, is a necessity; most of these vehicles cannot clear waves higher than 3 to 5 1/2 ft (1-1.67 m). The first recorded design for an air-cushion vehicle was put forward by Emmanual Swedenborg , a Swedish designer and philosopher, in 1716. The project was short-lived and a craft was never built, for...
air-cushion vehicle (ACV), craft designed to travel close to but above ground or water. It is also called a ground-effect machine or Hovercraft. These vehicles are supported in various ways. Some of them have a specially designed wing that will lift them just off the surface over which they travel when they have reached a sufficient horizontal speed (the ground effect). Others are supported by fans that force air down under the vehicle to create lift. In a plenum chamber vehicle the rate of leakage of this air from underneath the vehicle is reduced by placing a skirt around the lower edge of the craft. In an annular jet vehicle the rate of leakage is reduced by directing the air downward and inward from the outer edges of the vehicle. Air propellers, water propellers, or water jets usually provide forward propulsion. Air-cushion vehicles can attain higher speeds than can either ships or most land vehicles and use much less power than helicopters of the same weight. Air-cushion suspension has also been applied to other forms of transportation, in particular trains, such as the French Aerotrain and the British Hovertrain. A relatively smooth land or water surface, however, is a necessity; most of these vehicles cannot clear waves higher than 3 to 5 1/2 ft (1-1.67 m). The first recorded design for an air-cushion vehicle was put forward by Emmanual Swedenborg , a Swedish designer and philosopher, in 1716. The project was short-lived and a craft was never built, for...
