March 3 1996
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DISPLAYS: Tunnel vision will improve road signs

Amphistar prototype: it can travel at 80mph over any reasonably smooth surface and the inflatable floats can be adjusted to deal with waves up to half a metre high

Flying catamaran gets off the ground

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 metres.

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 amphibious.

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 impacts.

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.

DISPLAYS: Tunnel vision will improve road signs