An aircraft is a machine that flies in the Earth’s atmosphere. Most aircraft have wings to keep them up and engines to make them move along. Aircraft do dozens of different jobs. Some are commercial aircraft, such as airliners and cargo aeroplanes. Some are military aircraft, such as fighters and transport helicopters. Private aircraft carry just a few passengers. Sports aircraft such as gliders and hot-air balloons are for flying fun.
THE PARTS OF AN AEROPLANE
The fuselage is the main part of an aeroplane. This is where the passengers and cargo are carried. An aeroplane’s wings and engines are attached to its fuselage. The tail is made up of a tailplane (or horizontal stabilizer) and a fin (or vertical stabilizer). These keep the plane flying in a straight line. An aeroplane’s undercarriage allows it to roll along on the ground for take-off and landing. It is normally retractable, which means it folds up into the fuselage when the aeroplane is flying.
If you could cut off an aeroplane’s wing and look at its end you would see a shape called an aerofoil. It has a rounded front, a thick middle and a thin, pointed back. When the wing is moving forwards, air flows over and under the wing. The aerofoil shape makes the air flow faster over the top of the wing than underneath it. This makes the air push the wing upwards. The push is called the lift and it keeps the aeroplane up in the air.
The slower an aeroplane flies, the less lift its wings make. An aeroplane must fly slowly during take-off and landing. To make sure that there is enough lift to keep it in the air, the wings are made bigger temporarily by wing extensions called flaps.
Most aeroplanes have one pair of wings. They are called monoplanes. Biplanes have two pairs of wings, one above the other. Triplanes have three pairs of wings. Small, fast aeroplanes such as fighter jets normally have small, short wings. Large, slow aircraft normally have long, thin wings.
As an aeroplane flies, the air it flies through tries to slow it down. The slowing force is called drag. Engines make a force called thrust that overcomes drag. Some aeroplanes have engines with propellers. A propeller bites into the air as it spins, pulling the aeroplane forwards. Propellers do not work very well at speeds over about 650 kilometres an hour. Fast planes have jet engines instead. A jet engine sends a jet of hot gas backwards that pushes the aeroplane forwards.
Some aeroplanes can take off and land vertically. These are called vertical take-off and landing (VTOL) aeroplanes. They do not need a runway, as normal aeroplanes do. During take-off and landing their engines push them vertically upwards. During normal flight, their engines push forwards and their wings keep them up.
CONTROLS AND INSTRUMENTS
A pilot steers an aeroplane through the air. The pilot operates controls in the cockpit that make parts of the wings and tail called control surfaces tilt up and down or move left and right. Elevators on the tailplane make the aeroplane climb or dive. Ailerons on the wings and a rudder on the tail make the aeroplane bank and turn to the left or right.
Instruments in the cockpit give the pilot information. They show the aeroplane’s speed, how quickly it is climbing or descending, its altitude and which way it is going. They also show if the engines are working correctly. Radar shows other aircraft in the sky ahead.
An autopilot is a device that flies aircraft automatically so the pilot can rest. It keeps the aeroplane flying straight and level, and can even land it automatically. Some aeroplanes are controlled by computers. The computer makes sure that the pilot does not fly the aeroplane dangerously. A few aeroplanes are pilotless. They fly under remote control or completely automatically.
A helicopter is an aircraft with a spinning rotor instead of wings. The rotor has blades that create lift as they spin through the air. A helicopter can take off and land vertically and also hover in one place in the air. The rotor also makes the helicopter move forwards, backwards or sideways. A single-rotor helicopter has a small rotor on its tail that stops the fuselage spinning in the opposite direction to the main rotor. A twin-rotor helicopter has two main rotors that spin in opposite directions.
Helicopters can land in tiny spaces and on the roofs of buildings. They are useful for transport in places where there are no runways, such as city centres. They are also used to rescue people at sea and in the mountains, and as air ambulances.
BALLOONS AND AIRSHIPS
Balloons and airships are aircraft that are so light that they float in the air. They are huge bags filled with hydrogen or helium gas—both gases are lighter than air. The pilot of a balloon can make it rise and fall, but it is mostly blown along by the wind. An airship also has engines so that it can be steered through the air.
THE HISTORY OF FLIGHT
People first tried to fly by copying birds. They strapped wings to their arms and jumped from towers. Most were badly injured or killed. The first manned flight took place in 1783 in a hot-air balloon built in France by two brothers, Joseph Michel and Jacques Étienne Montgolfier. The first successful airship flew in 1852, powered by a small steam engine.
During the 19th century, several aviators experimented with gliders. They gradually began to understand how wings could create lift. These experiments helped the Wright brothers, from the United States. Orville and Wilbur Wright made thousands of test flights in kites and gliders. Then in 1903 they built and flew the first successful aeroplane. During the following decade, many aviators built their own simple aeroplanes.
By the time World War I ended in 1918 air forces had fighter and bomber planes. After the war, the bombers were converted into the first airliners. During the 1920s and 1930s, passengers flew in new all-metal airliners and giant airships across the Atlantic.
By the end of World War II in 1945 aeroplanes had become bigger and faster. The first practical helicopter, the Sikorsky VS-300, was also invented during World War II. The jet engine was invented in the 1930s and by the 1940s it was used to power jet fighters and airliners. Supersonic jet fighters were developed in the 1950s. In 1969 the first supersonic airliner, the Concorde, took off for the first time. A year later the first Boeing 747 made its first commercial flight. This huge aircraft is still being built today.
Did you know?
• The fastest aircraft ever built was the Lockheed SR-71 Blackbird spy plane. In 1976 it reached 3,509 kilometres per hour.
• In 1986 the Rutan Voyager became the first aircraft to fly around the world non-stop without refuelling. The flight took just over 9 days.
• The Hughes H4 Hercules, known as the Spruce Goose, has a world-record wingspan of 98 metres. The aircraft only flew once, in 1947.