A pilot is taxiing out for take-off on a very hot day and his/her aircraft is equipped with carbon brakes. The pilot is aware that it is going to be a long taxi and wants to maximise the brakes' ability to absorb energy in case of a rejected take-off. To control the taxi speed, he/she decides to use:
Frequent light brake applications, as carbon-brake wear is determined by the number of times the brakes are applied.
Firm brake applications, as carbon-brake wear is determined by the number of times the brakes are applied.
Frequent light brake applications, as carbon-brake wear is determined by the brakes' temperature.
Firm brake applications, as carbon-brake wear is determined by the brakes' temperature.
Because the wear mechanisms are different between carbon and steel brakes, different taxi braking techniques are recommended for carbon brakes in order to maximize brake life.
- Steel brake wear is directly proportional to the kinetic energy absorbed by the brakes. Maximum steel brake life can be achieved during taxi by using a large number of small, light brake applications, allowing some time for brake cooling between applications. High airplane gross weights and high brake application speeds tend to reduce steel brake life because they require the brakes to absorb a large amount of kinetic energy.
- Carbon brake wear is primarily dependent on the total number of brake applications — one firm brake application causes less wear than several light applications. Maximum carbon brake life can be achieved during taxi by using a small number of long, moderately firm brake applications instead of numerous light brake applications. This can be achieved by allowing taxi speed to increase from below target speed to above target speed, then using a single firm brake application to reduce speed below the target and repeating if required, rather than maintaining a constant taxi speed using numerous brake applications. Carbon brake wear is much less sensitive to airplane weight and speed than steel brake wear.
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