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In my company SOP after landing we don’t switch on the brake fans immediately after the HOT annunciation comes on on the BRAKE FANS push button. Instead we are told to wait for a period of 5 mins after landing to allow for thermal equalisation of the brakes and to prevent oxidation of brake surface hotspots.

What exactly does this mean?

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    $\begingroup$ Carbon does always react with oxygen. At room temperature, the rate of that reaction is low, but measurable. If the temperature goes up, the reaction rate goes up too... Big coal piles, for example, use to get warm by slow oxidation, and if not doused with water, may spontaneously catch fire... $\endgroup$ – xxavier Nov 14 '17 at 7:58
  • $\begingroup$ "Furthermore, after heavy braking, use of the brake fans could increase oxidation of the brake surface hot spots, if the brakes are not thermally-equalized." (§4.2.3 of How to properly operate the carbon brakes?). So wait for highest temperatures to decrease before adding oxygen because oxidation is accelerated by temperature. Also (probably) prevent other oxidants and FOD to enter the brakes $\endgroup$ – mins Nov 14 '17 at 8:26
  • $\begingroup$ Did my answer help at all? $\endgroup$ – AirbusLover Nov 20 '17 at 3:55
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Catalytic oxidation of carbon occurs when a catalyst, such as an alkali metal(s), is present. When a catalyst is present, the temperature at which thermal oxidation occurs is lowered. Airplanes equipped with carbon brakes are susceptible to catalytic oxidation caused by exposure to alkali metal runway deicers. - Boeing Aero Magazine

Brake manufacturers produce Oxidation resistant brakes. The effects of can be obtained by using carbon brakes, or using a coating on the brake rotor and friction surfaces.

Best practices for carbon brake application according to Airbus.

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  • $\begingroup$ @fooot I fixed that. Thanks for the comment. $\endgroup$ – AirbusLover Nov 15 '17 at 21:13

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