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AIRCRAFT

Both aeroplanes and HELICOPTERS are aircraft. These machines use engines and aerofoil wings to lift off the ground and move through the air. Aeroplanes use either conventional engines with propellers or jet engines. Jets burn lots of fuel to generate huge forward thrust and go very fast. The faster an aeroplane moves, the more lift its wings produce.

WOODEN PROPELLER

A propeller is a twisted aerofoil, driven by an engine, that spins around at high speed. As a propeller turns, it generates a backward draft of air that moves the aeroplane forwards. Aircraft propellers spin faster than ships’ propellers. This is because aeroplanes need to move forwards more quickly to generate the lift that keeps them in the air.

AIRLINERS

Airliners can carry hundreds of passengers and huge amounts of cargo, so they are extremely heavy. They need to have very wide wings to generate enough lift to overcome the force of gravity and get them into the air. The huge wings also contain fuel tanks. The liquid fuel is piped directly to the jet engines under the wings.

HELICOPTERS

This type of aircraft generates lift and thrust using a huge overhead propeller or rotor. The rotor has several blades shaped like aerofoils. As the blades spin, they generate lift that overcomes the helicopter’s weight and lifts it into the air. The pilot can move a helicopter forwards, backwards, or from side to side by tilting the rotor blades slightly as they spin around.

HOVERING HELICOPTER

When a helicopter hovers above the ground without moving, the lift from its rotors is exactly equal and opposite to its weight. Although a normal aeroplane can fly along at a steady height, it cannot hover. It must move forwards all the time to generate the lift that keeps it flying.

Copyright © 2007 Dorling Kindersley

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