Aircraft brakes and tyres

The high weights and speeds at which many aircraft land mean that the braking system must be capable of absorbing and dissipating the very large amounts of heat created as the energy of motion is converted. There are two main types of brake - drum brakes and disc brakes. The drum brake is rarely used, because it suffers from poor heat dissipation, causing the brakes to overheat and, fade - lose their braking effectiveness at high temperature.

Disc brakes are much more effective at dispersing the heat produced, maintaining their effectiveness during long periods of heavy braking. They consist of a disc or series of discs of aluminium alloy, steel, carbon or other material, gripped between pads of friction material. These pads are forced against the discs by pistons under hydraulic pressure. Control is usually achieved by placing a toe pedal for each brake on its respective rudder pedal.

These can then be operated differentially by the pilot, giving the ability to steer the aircraft by applying different amounts of braking on each main wheel. Applying the brakes equally on both main units causes the aircraft to be braked smoothly in a straight line. Large aircraft may have quite a number of discs in each brake, to get the required braking forces and heat dissipation. The combination of carbon discs and carbon pads, known as the carbon-carbon brake, is widely favoured, because it combines light weight and the ability to operate effectively at extremely high temperatures.

Braking effectiveness is reduced if a wheel locks (stops rotating), perhaps leading to loss of control of the aircraft. In some instances, the wheel may lock but the tyre may continue to rotate. If this occurs for even a few seconds, the heat generated will cause a tyre burst, or possibly a fire. Locking of the wheels is prevented by an anti-skid unit detecting when the wheel or wheels on any unit stop turning, and momentarily releasing brake pressure on that unit only. This gives the aircraft the ability to stop in the shortest possible distance without loss of control, particularly when surfaces are wet or icy. The unit works in a similar way to the anti-lock braking system (ABS) fitted to many cars.

If the wheel and tyre overheat, the pressures generated may cause tyre bursts. Excessive tyre pressure may be prevented by a fusible plug fitted in the wheel. This melts before the tyre becomes hot enough to blow out, and allows the tyre to deflate slowly, easing the steering problems caused by the tyre bursting.

The braking of an aircraft can be supplemented by other forms of braking, which are not part of the undercarriage system. However, it is worth mentioning these systems briefly here, since they are relevant to the complete braking system of the aircraft. Used both in flight and during the landing, air brakes consist of large plates fitted to the fuselage or wings that can be moved so they project into the air flow. They cause a large increase in drag to slow the aircraft. After touch-down, reverse thrust of jet engines can be deployed by moving doors into the jet exhaust to deflect the flow forwards. Turbo-prop engines can achieve a similar effect by changing the pitch of the propeller to reverse the air flow.

NASCO brakes acquired by MABS brakes

Aircraft braking systems industry re-alignment... Since January 2008, Meggitt Aircraft Braking Systems MABS has been the trade name of the two Meggitt businesses supplying aircraft wheels and aircraft brakes, Aircraft Braking Systems Corporation (ABSC) and Dunlop Aerospace Braking Systems (DABS).

They are now one of the leading aircraft wheels and brakes suppliers in the world, and have facilities on both sides of the Atlantic, as well as in Europe and Asia.

Only a year before ABSC had acquired Nasco Aircraft Brake Inc., forming K&F Industries, now a wholly owned subsidiary of Meggitt Aircraft Braking Systems and Meggitt PLC supplying aircraft wheel and brake components for the military and commercial aircraft markets.