A hovercraft is an amphibious vehicle that is supported by a cushion of slightly pressurized air. Although often seen as a mysterious, even bizarre mode of transportation, it is conceptually quite simple. To understand how hovercraft work, it is necessary to understand that the dynamics are more closely related to aircraft than to boats or automobiles. As a member of the family of air cushion vehicles (ACVs) or ground effect machines, which includes wing-in-ground-effect or ram wings, surface effect ships, sidewall hovercraft, and surface skimmers, hovercraft, are the amphibious member of the air cushion vehicle family. They are the most novel among vehicles that are supported by pressurized air. Refer to the illustration below as you read about how hovercraft actually function.
Hovercraft float on a cushion of air that has been forced under the craft by a fan. This causes the craft to rise or lift. The amount of lift can range from 6" to 108" (152mm to 2,743mm) depending on the size of the craft. The amount of total weight that a hovercraft can raise is equal to cushion pressure multiplied by the area of the hovercraft. To make the craft function more efficiently, it is essential to limit the cushion air from escaping, so the air is contained by the use of what is called a skirt. Fashioned from fabric, which allows a deep cushion or clearance of obstacles, hovercraft skirts vary in style ranging from bags to cells (jupes) to separate fingered sections called segments. Most HTI hovercraft utilize the segmented skirt system because each segment can deflect individually when passing over bumps so that very little lift air is lost on uneven terrain.
Once "lifted" or "on cushion", thrust must be created to move the hovercraft forward. With many craft, this is generated by a separate engine from the one used to create the lift, but with some, the same engine is used for both. As the diagram below indicates, the fan-generated air stream is split so that part of the air is directed under the hull for lift, while most of it is used for thrust.
Now that the hovercraft has lift and thrust, it must be steered safely. This is achieved through the use of a system of rudders behind the fan, controlled by handlebars up front. Steering can also be controlled by the use of body weight displacement...a skill which is achieved after practice. As an option, HTI hovercraft offer patented, reverse thrust buckets as another means of control. This is the only system available today that enables the driver to reverse at speed, to maintain cushion at speed, to regulate speed going downwind, to hover while stationary and to brake (a must on ice).