BRAKE SYSTEM OVERHEAT CONDITION

A braking system works by converting the kinetic energy of a moving aircraft into heat. To prevent damage to the tyres and undercarriage structure, the heat energy must be dissipated rapidly into the surrounding air. If this does not happen and the amount of heat generated becomes excessive, as can be the case after an aborted take off or following a landing at an excessive mass and/or speed, the tyres can overheat and burst. Consequently, brake and/or wheel fires are likely to occur. To prevent tyres bursting due to overheating, wheels are fitted with fusible plugs which melt at a preset temperature. This allows the tyre to deflate at a steady controlled rate.

Should a fire develop, more direct intervention is required. Responders must exercise caution when approaching burning or overheated wheel assemblies as, so long as the wheels remain inflated, there is a risk of explosive failure of the wheel assembly laterally. Any approach to the wheel should therefore be conducted from the front or back.

When extinguishing a wheel fire, sand or dry powder should be used to cover the fire and cut the oxygen supply. Some extinguishers will cool the landing gear too quickly and the wheel may explode.