My Science School

BOEING 747

All Modern aeroplanes have similar features, although those of airliners such as the Boeing 747 are larger and more complex than those of smaller aeroplanes. The fuselage is a strong tube inside which the passengers, crew and their baggage travel. Wings support the aeroplane in the air by creating a force called lift. Engines provide a forward force called thrust, which pushes the aeroplane forwards against the resistance of the air (which is called drag). The fin and tail-plane keep the plane flying straight and level. Hinged sections called control surfaces (the rudder, elevators, and ailerons) steer the aircraft through the air.

The 747 is 70.7 m long. Its wingspan is 64.3 m. Take-off weight is 400 tonnes, including 150 tonnes of fuel, stored in tanks in the wings.

The Boeing 747-400 is the latest model of the world’s largest airliner, known as the “Jumbo Jet”. It can carry up to 569 passengers (but normally carries 420 in first, business and economy cabins), and cruises at up to 985 kilometres per hour, at an altitude of 10 kilometres. Its maximum range is 14,100 kilometres - more than a third of the way round the world.

As an aeroplane moves forwards through the air, air hitting the leading edge of the wing separates above and below the wing. Because of the curved shape of a wing, called an aerofoil, the air that flows over it is faster than that flowing underneath. This creates higher air pressure under the wing than above it. The difference in pressure pushes the wing upwards with a force called lift.

CONTROLLING LIFT

The amount of lift from a wing increases with the aero-plane’s speed and also with the angle of attack, the angle at which the wing hits the air. At lower speeds, the pilot maintains lift by raising the nose of the plane to increase the angle of attack. But if the angle becomes too great, air cannot flow smoothly over the top of the wing and lift is lost. This is called a stall.

At low speed during take-off and landing, flaps extend from the trailing (rear) edge of the wing. On the 747, each set of flaps has three sections. There are also small flaps on the leading edge of the wing. Flaps increase the size of the wing, and so create extra lift. For take-off, flaps are partly extended. For landing they are fully extended. Spoilers flip up from the upper surface of the wing. They break the flow of air over the wing, reducing lift.

Picture Credit : Google