Hovercraft
T
he ability of hovercraft to cross dry
land as well as water has seen them
employed in the military and
tourism sectors for many years. A lthough
once billed as the next generation of
transportation, they have somewhat
declined in popularit y over the last
decade. Despite this, their usef ulness is
still readily apparent.
The core principle of a hovercraft is that
the hull of the vehicle is suspended on top
of a giant cushion of air, held in place by
fl exible rubber that allows it to traverse
diffi cult terrain or choppy waves w ithout
being torn apart.So how do they work? At the centre of a
hovercraft is a huge fan that fi res air
dow nwards, pushing the hull off the
ground as high as two metres (6.5 feet).
Smaller fans on top of the hull push air
backwards, giving the hovercraft forward
momentum. Rudders direct this fl ow of
horizontal air to allow a hovercraft to
change its direction.
Traditional hovercraft have an entirely
rubber base that allows for travel on land
or sea, but others have rigid sides that,
while suited only to water, can have
propellers or water-jet engines attached
for a quieter craft.How do these incredible machines
traverse both land and sea?
The air
cushion
Plenum chamber
The region of trapped air
underneath the craft is known
as the ‘plenum chamber’, which
controls the escape of air to
create a high-pressure
environment and thus a
circulation of controllable air.Air fl ow
Air is sent down into
the plenum chamber
of the hovercraft from
the main fan.Storage
A ir is stored until it’s
needed to give more lift,
when air escapes through
the hovergap.Lift
Transfer of air into the
plenum chamber
increases pressure and
allows the craft to rise.Hovercraft have been in
use for over 50 yearsCargo
Most modern hovercraft
are used for militar y
purposes, like this
Landing Craft Air Cushion
(LCAC), which can
transport vehicles and
troops with ease.Skirt
This flexible and inflatable
barrier traps the cushion of
pressurised air beneath the
hull, in addition to increasing
the height of the hull to allow
it to move over obstacles.© A lex Pang© Andrew BerridgeSEA