Brake Cooling Fan
The brake cooling fans are an option to increase heat dissipation and brake cooling. They reduce the cooling time, and therefore prevent takeoff delays on short turnarounds.
In fact, Airbus designs its aircraft so that the brake fans are necessary for short turnarounds. This avoids the extra weight of oversized brakes. Brake cooling fans also help to control brake temperature and therefore increase brake life bringing the brake temperature in the areas where the wear is minimum.
For many aircraft/brake types, the brake temperature indicated in the cockpit when the brake fans are running is significantly lower than the temperature indicated when the brake fans are OFF. This is because the brake fans cool the brake temperature sensor located outside the heat pack. As soon as the brake fans are running, the indicated brake temperature decreases almost immediately. Similarly, when the brake fans are switched off, it takes several minutes for the indicated temperature to increase to the real brake temperature.
As explained in the relevant FCOM, with the fans running, the difference between the indicated brake temperature and the real brake temperature varies from approximately 50 °C (at a real brake temperature of 100 °C) to approximately 150 °C (at a real brake temperature of 300 °C). Therefore, if the BRAKE HOT warning is activated just before takeoff, the ECAM will request the flight crew to select the brake fans, if installed, and to delay the takeoff. When the fans are selected, the warning disappears immediately, but takeoff must be delayed until the indicated temperature is consistently below 150 °C (for a warning set at 300 °C). Then, the brake fans must be switched OFF for takeoff. Refer to the FCOM for more details.
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