Presentation By-Chirag Solanki

INTRODUCTION HISTORY DESIGN AND OPERATION OTHER APPLICATIONS ADVANCEMENT IN TRANSPORTATION

METHOD FUTURE OF HOVERCRAFT SOME AVAILABLE HOVERCRAFT

Known as Air Cushion Vehicle (ACV). It flies like as an aero plane , float like a boat

,can drive on land like a car. Its engine provides the power to drive large

fans that blows air under the craft, this air is retained by a rubber skirt that helps to move the hovercraft.

Any of the machines characterized by movement in which a significant portion of the weight is supported by forces arising from air pressure developed around the craft, because of which they hover in close proximity to the Earth’s surface can be put under the category of HOVERCRAFT or GROUND EFFECT MACHINE.

First man to introduced the concept of ACV was Sir John Thornycroft in 1870.

First practical use was made in 1929 by German Dornier DO X flying boat.

Work went on its peak during World War -2. In 1960s,American aerodynamicist developed

an experimental craft.Experiment went on many more experimental craft. But they remain experimental.

Finally invented by Christopher Cockerell of UK.

He patented it on Dec. 12, 1955.

If air were pumped under the vessel through a narrow slot running entirely around the circumference, the air would flow toward the centre of the vessel, forming an external curtain that would effectively contain the cushion .This system is known as the Peripheral Jet. Once air has built up below the craft to a pressure equaling the craft weight, incoming air has nowhere to go but outwards and experiences a sharp change of velocity on striking the surface. The momentum of the peripheral jet air keeps the cushion pressure.

Basic elements How a hovercraft

works? Skirt arrangement Power plant Thrust propeller ACV operation

A HULL A SKIRT SYSTEM A PROPULSION

SYSTEM A LIFT SYSTEM

A hover craft is a machine that rides on air under pressure that is continuously supplied by the lift system. A flexible curtain called a skirt is attached to the base. The hovercraft is propelled by a thrust propeller. The steering is applied by using a rudder on the back of the propeller. stopping is achieved with the reduction of power engines or turning 180 degrees and applying full thrust.

The skirt is a shaped, flexible strip fitted below the bottom edges of the plenum chamber slot. As the hovercraft lifts, the skirt extends below it to retain a much deeper cushion of air. The development of the skirt enables a hovercraft to maintain its normal operating speed through large waves and also allows it to pass over rocks, ridges and gullies. It is of semicircular shaped .

Skirt system is beneath the hull .On the skirt system accommodation for passenger, crew and fright is built.

Lift system feeds air into the plenum chamber below the craft in order to provide a cushion.

The propulsion and lift system can be driven by the same power plant or by separate unit.

The power to weight ratio is very critical and it determines not only the payload and performance of the craft but also the ground clearance between the surface and the skirt.

Hull structure are of marine aluminum skin , welded or riveted onto aluminum webs or frames.

The cavity or chamber in which the air is kept is called a ‘plenum’ chamber.

Early crafts used piston type engine. After that gas turbine engines were evolved. The engine has a main shaft having a

compressor and a turbine .A starter motor is connected to one end of the shaft and the other end is to lift fan and propeller gearbox.

These engine creates a lot of noise. Newer engines are made to make engine noise

low and greater fuel efficiency.

Centrifugal lift fan

Usually an aircraft type with variable pitch blades.

The propeller can vary from four-bladed versions and about 9 feet in diameter to the 4 propeller and 19 feet in diameter.

Confined to commercial passenger-carrying ferry service(5 to 40 KM), military operations.

Also used for seismic survey parties, either over shallow-water areas or in deserts, search and rescue operations.

US used these in Vietnam operations. Later used as mine-countermeasure works, antisubmarine works, aircraft carrying and missile launching.

Experiments are going on for hover car and hover train.

This principle is used for moving large or heavy objects.

Air cushion concept was used for passenger carrying trains. In 1970s 235 mile/hr. speed was achieved.

French got 300 mile/hr. Many experiments are going on this project but

now emphasis has diverted to magnetic trains

ACV vehicles have not yet fulfilled their original promise. These hovercrafts are not economical although they are idle in military application.

So research is mainly going on for military purposes.

Surveyor Mk3 Type           Enclosed Cabin, high-class passenger

style hovercraft. Length         10.0metres Width          4.1 meters Capacity      18 passengers or 2,000kg Engine         Duels BF6M-1013ECP Application   Passenger transport, Coast

Guard/Military Patrol, Search & Rescue, Medivac, Freight

Pioneer Mk2Type Enclosed Cabin, high-class passenger style hovercraft. Length 11.6 meters Width 4.8 meters Capacity 30 passengers or 3,000kg Engine Duets BF6M-1015C (330 kW @ 1900rpm)Application Passenger transport, Coast Guard/Military Patrol, Search & Rescue, Medivac, Freight.

Special Purpose Hovercrafts:AIRLIFT 950A (Ambulance)Type Enclosed Cabin. Installed ambulance equipment. Length 9.5 meters Width 4.2 meters Capacity 1 crew + 14 seats, centre 6 seats can be converted to 2 stretcher spaces or operating table. Engine 2 x Cummins 6BTA 5.9 diesel, 2 x 134kW @ 2600rpm Application Ambulance, health services.

AIRLIFT 1060FT (Fire Tender) Type Fire-Fighting and Rescue hovercraft. Length 10.6 meters Width 4.6 meters Capacity 2 to 6 crew plus equipmentEngines 2 x Cummins 6BTA 5.9 diesel, 2 x 134kW @ 2600rpm Application Fire fighting, Pollution control, Dive tender, Rescue.