|A FLYING CATAMARAN that
can take off vertically from the surface of the sea like a Harrier
jump jet has been built by Russian scientists in a bid to create the
world's most efficient form of transport, writes Dag Pike.
It was designed during the cold war and its owners are
now looking for commercial applications. The craft, called the
Amphistar has been developed by a Moscow aviation company, Pacific
Technique Development. It combines many of the virtues of an
aeroplane and hovercraft.
Standard ground-effect craft use short, wide wings to generate
good lift at low speed. The Amphistar has wings like this built into
the lower part of the fuselage where they are close to the ground to
give maximum lift.
These wings terminate in floats that have a rigid top and an
inflatable lower section. The aircraft sits on these floats, making
it similar to a wide catamaran with an overall length of 10.4
The unique part of the design is the propulsion system based on a
220hp Subaru car engine. This is linked to the two air propellers
installed each side of the centre nacelle at the front.
Unlike conventional ground-effect craft, the Amphistar's
propellers can be tilted so that their thrust can be directed from
the horizontal downwards and under the leading edge of the wing.
This generates air pressure under the wing that is contained by
the side floats and a flap across the aft end of the wing. The
effect is to lift the craft like a hovercraft, allow ing the
Amphistar to take off at virtually zero speed.
For higher speeds, the propellers are tilted towards the
horizontal. As the speed rises, the propeller-generated lift is
replaced by the ground-effect lift generated by the forward motion.
The big advantage of this system is that the craft can be
"parked" on any reasonably flat piece of ground. It does not need a
water surface for take-off and landing. This makes it truly
At high speed, the steering is managed by twin air rudders on the
high tailplane. To help manoeuvring when operating over water at low
speed, a retractable water rudder is fitted.
The Amphistar has a top speed of 80mph and it can operate over
any reasonably smooth surface water, ice, snow and sandbanks.
At sea it can operate in waves up to half a metre high. The air
pressure in the inflatable floats can be varied to suit the terrain
over which the craft is travelling. Low pressure in these floats
when operating over waves helps to absorb the shock from wave
The prototype Amphistar has had many hundreds of hours of trials,
and the design has been refined so that a production version made in
advanced composites is now becoming available. The prototype has a
cabin with seating for the pilot and five passengers, but other
versions can be developed for police, ambulance and rescue work. The
existing version is priced at about £350,000 and it is likely ot be
used first as a water taxi or for leisure.
Plans are already well advanced for a version that could take 70
passengers and offer very economical travel on rivers and lakes at
speeds of up to 100mph.
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