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Let suppose an emergency aircraft has made an overweight landing. The brakes are white hot, and the fire crews are requested to be on scene.

What can be done about the hot brakes? Can they just shoot water at the gear assembly? If flames are visible, would they shoot foam instead?

This related question asks how do fire crew inspect the brakes, but not what they do when the brakes are known to be very hot.

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enter image description here
(Airbus) A320 landing gear approach paths.

It's important to approach the landing gear from the right angle, because an explosion could throw deadly debris at the firefighters.

Cooling

According to Airbus, water-mist is to be used to cool the brakes.

Water, CO2, or foam, are not to be used. All those cause sudden cooling that can lead to wheel cracks or rim burst.

Fire

If there is fire, then large amounts of water or water-mist is to be used. Foam is to be used if fuel tanks are at risk.

enter image description here
(YouTube) Fire crew attending to 1400°C brakes.


Not an emergency, but interesting:

enter image description here
(airliners.net)

Upon deplaning back in Pyongyang, we noticed the brakes of the main gear were being cooled down with water. Naturally, this led to a mass gathering downstairs, as everyone wanted to take a photo of this event. We learned that this is actually standard procedure, which seemed legit as I remembered seeing water on the apron after our [Ilyushin Il-62] flight as well.


Related: When the brakes are checked, what do the firemen actually do?

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    $\begingroup$ I guess not just the sudden cooling, but also heterogeneous cooling, i.e. "cold spots" might be a problem if you hit the brakes directly with water (the side that is facing the fire crew gets hit directly and cools out faster, causing the material to contract unevenly, and thus warp). $\endgroup$ – Jörg W Mittag Apr 17 '17 at 12:17
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    $\begingroup$ That guy didn't read the warning. He's right in the tire hazard area $\endgroup$ – TomMcW Apr 17 '17 at 17:31
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    $\begingroup$ @TomMcW: The diagram is for overheat hazard situations. Those tires probably aren't hot enough to be an overheat hazard. $\endgroup$ – user2357112 Apr 17 '17 at 18:55
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    $\begingroup$ I'm impressed that a rim burst on an A320 can throw shrapnel up to 80 m, or twice the length of the plane itself. $\endgroup$ – Michael Seifert Apr 17 '17 at 20:47
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    $\begingroup$ @MichaelSeifert I suspect 80m is a very paranoid safety radius because it's of the same order of magnitude as a 500lb bomb (~40-50% HE the remainder steel casing to generate fragments) which can throw dangerous fragments 60-100m. The odds of an 80m fragment are probably very low, but catching a one in a million fragment in the wrong part of your body would leave you just as dead as if you were standing right next to it. $\endgroup$ – Dan Neely Apr 17 '17 at 23:31
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I'm working on B747 cl. Here they used to use water when the temperature is close to 700°F, almost every time there is a wheel change the maintenance crew found the rotor brakes shattered like a crystal, but they continue doing it as a mean to not generate any cargo delay due to deflated wheel. Unsafe condition? Yes very much unsafe, a risk of a stuck wheel on takeoff or landing can occur.

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    $\begingroup$ Welcome to Aviation.SE. You say "they used to use" What do they do now? And who's "they"? $\endgroup$ – Federico Apr 4 '18 at 11:59

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