How does a Jet Engine Work?

            A jet engine works on the principle of Newton’s third law of motion, that is, every action has an equal and opposite reaction. Its working can be compared to the action of a boat in which the boatman pushes the water back with his oar, thereby getting a forward thrust which moves the boat forward.

A Jet Engine

            In simple words, according to Newton’s law, the action of pushing the water backwards produces the opposite reaction of the forward movement of the boat. Similarly, a jet engine ejects pushes backward gases to the rear at a high speed, and the resulting opposite reaction gives a forward motion to the aircraft. But how is this gas produced and how is it released with such a great force?

            Jet engines burn fuel to make hot gases. The hot gases blast out form the rear nozzle at high speed, thus pushing the engine forward at an equal speed.

            All jet engines have means of injecting fuel into the combustion chamber. There the burnt fuel produces a great amount of hot gases. It is like an explosion. These hot gases are released from the rear of the engine with great force, which pushes the engine forward. As the engines are fixed to the aircraft, the entire aircraft moves forward. This forward force is called thrust.

            The forward thrust is similar to the motion of an air-filled balloon when the air form it is released suddenly. The balloon moves in the direction, opposite to that of the nozzle from which the air escapes. The force or thrust of air is responsible for pushing the balloon in the opposite direction.

            Rockets also work on the same principle. The main difference between jets and rockets is the source of oxygen. A jet engine takes oxygen form the air through intake nozzles, but a rocket carries its own oxygen supply in the far of liquid oxygen in tank or in the form of solid fuel. Jet engines have compressors to compress the sucked in air before it is mixed with the fuel and burnt in the combustion helps to increase the force of explosion in the engine, thereby producing greater thrust.

How do Planes Take Off and Land Vertically?

            One of the most exciting developments in aircraft technology has been the VTOL aircraft. VTOL means vertical take off and landing planes. The most successful aircraft of this type has been the British made harrier jump jet.

Airplane Take Off 

            Normal twin-jet aircraft have the jet engines fixed horizontally at the sides of the aircraft, or to the wings. Single jet engine aircraft have the engine built into the fuselage of the aircraft. In both, air is sucked in form the front, mixed with fuel in the compression chamber and the exhaust gases are ejected from the rear, thrusting the plane forward. VTOL planes make use of the same process, but their jet engines can be temporarily re-positioned vertically. The exhaust is directed downwards and the resultant thrust is directed upwards.

            Normally the same engines that produce lift are used to propel the aircraft forward. This is done by realigning the engines angle of tilt.

            VTOL aircraft are used mainly for military purposes. Very powerful engines are required for vertical take off, and therefore they produce a lot of noise. Some types of VTOL planes have separate engines to provide lift and for forward propulsion.

            These aircraft do not need long runways for takeoff and landing. They need a small piece of level ground or deck space on an aircraft carrier not much longer than its own length, and once it is in the air, it can fly at supersonic speeds. Since their wings can usually be folded when in storage, they are ideal for use on aircraft carriers where space is limited, and are perfect for reconnaissance or attack roles, as evidenced in their use by the USA in operation Iraqi freedom.