A hovercraft is a vehicle that is supported
on a cushion of air. It is able to traverse many different types
of terrain on land and can also travel on water.
The hovercraft was invented in 1952 by the British inventor Sir
Christopher Cockerell, who was knighted for his services to
engineering in 1969. By simple experiments involving a vacuum
cleaner motor and two cylindrical cans he proved the workable
principle of a vehicle suspended on a cushion of air blown out
under pressure, making the vehicle easily mobile over any surface.
This would enable it to operate over soft mud, water, and marshes
and swamps as well as on firm ground.
The British aircraft manufacturer Saunders Roe developed the first
practical man-carrying hovercraft, the SR-N1, which carried out
several test programmes in 1959 to 1961 (the first public
demonstration in 1959), including a cross-channel run. It was
found that the craft's lift was improved by the addition of a
'skirt' of flexible fabric or rubber around the hovering surface,
to contain the air.
The SR-N1 was powered by one [piston] engine, driven by expelled
air, and could carry little more than its own weight and two men.
The first true passenger-carrying hovercraft was the Vickers VA-3,
which in the summer of 1961 carried passengers regularly along the
North Wales Coast from Wallasey to Rhyl. It was powered by two
turboprop aero-engines and driven by propellers. During the 1960s
Saunders Roe developed several larger designs which could carry
passengers, including the SR-N6, which operated across the Solent
to Ryde on the Isle of Wight for many years.
By 1970 the largest British hovercraft were in service, the
'Mountbatten class' SR-N4, regularly carrying cars and passengers
across the English Channel from Dover to Calais. This service
ceased in 2002 when the Channel tunnel took over the fast transit
of cross-channel traffic.
The commercial success of hovercraft suffered from rapid rises in
fuel prices during the late 1960s and 1970s following conflict in
the Middle East. Alternative over-water vehicles such as
hydrofoils (marketed as the Seacat in Britain) use less fuel and
can perform most of the hovercraft's marine tasks. Today
hovercraft are manufactured all over the world for both civil
purposes as well as small pleasure craft. While hovercraft service
in Britain has declined in recent years (especially since the
channel service was dropped in 2002) there still are some
AP188-100 services running regularly to the Isle of Wight, as
well as a range of Griffon Hovercraft used by the Royal
National Lifeboat Institution.
There are an increasing number of small homebuilt and kit-built
hovercraft used for fun and racing purposes, mainly on inland
lakes but also in marshy areas and in some estuaries.
Hovercraft typically have two (or more) separate engines. One
engine - called the impeller - is responsible for lifting the
vehicle by forcing air into the skirt. One or more additional
engines are used to provide thrust in order to propel the craft in
the desired direction.