do airliners employ heated brakes like some king-airs ?

[20DMEYYZ]

having a discussion with someone about whether a heating system exists in airliners to ensure no possible frozen brakes upon touchdown . i remember seeing a hot-brake set-up on a kingair , is that a concern with larger jets ? i.e.- mains still exposed to elements once retracted in 737 types , would they need something of that nature or would some ice-build be neglible ?

[Jastapilot]

never heard of it. for heating the brakes we use what's called 'decelleration'... creates plenty of heat!

[iflyforpie]

Skydrol is good to below -65F. Most large jets actually have heat exchangers in the fuel tanks to cool the fluid (though the stuff going into the brakes doesn't circulate). Turning on the pumps with dry tanks (like during ground checks) will eat up a $30,000 pump in a few minutes.

[c170b53]

I guess this question stems from the latest MOT alert regarding moisture in carbon brakes, where the recommendation is to apply brakes whilst taxing to heat them up and drive out any moisture that might be in a carbon brake prior to take-off. I have not seen a problem on a Boeing, we have had rotor problems in the EMB 190 but not sure as to why. Most airplanes must snub the wheels during retraction by auto applying the brakes which would generate a bit of heat. I read the information but thought it too general in nature and I'll wait for more specific information from the manufacturers for the aircraft I work on.

[pika]

Optional brake fans to cool the brakes is all you will get. Any "airline size" jet has much bigger tires than a KingAir so the brakes are not taxiing through snow and such and the wheels are not hanging out in flight (ie B1900).

[20DMEYYZ]

i suspect i was incorrect from the responses so far , which is fine , was just trying to get some 705 perspective on this topic . the debate arose from talk or a descent thru an inversion or also landing in the soup with cold metal brake parts causing a icing hazard upon touchdown . i guess the velocity ensures all components free up any buildup in a hurry .
going back to the KingAir reference , all that red writing on the mains with the "hot-brakes" must just of been a warning to ground crew of potential hot-parts after the rollout to ramp/hangar . i for some reason suspected it was an option alike some impovement you would see in the panther edition navajo or w/e .
cheers friends .

[ywg9]

It was an option on the 200s i dont think there are to many that have it as it is a very expensive part to change. all it really was is a line with bleed ar in it pointed at the break unit

[Steve Baker]

Heated brakes are an option on the BE20. They are marginally effective. The 737 main gear may not have a door that closes over them but, they are pretty well sealed in when retracted and, certainly out of the elements. I only had problems with the BE20 when warm brakes were exposed to blowing snow or tugged/taxied through snow deep enough to be forced up into the mechanism. They would then subsequently freeze and if the apron surface was contaminated, the tires would skid as you pulled out, instead of rotating. With the gear extended in cold and windy conditions, there wasn't enough heat generated by the brake de-ice to melt anything.

I've never had frozen brakes on the 737. (touch wood)

Steve

[who me ?]

Falcon 900s have carbon brakes, ( cabon brakes are know to hold moisture , which when exposed to cold temps , in cruise flt , cause the brakes to freeze. ) which have caused a few "frozen" brakes on landings.Resulting in , blown tires , and if I recall correctly, at least one runway excurision resulting in airframe damage.

As a result Dassault has had optional "BRAKE HEAT" on the Falcon 900s for the last 10 years or so.

The "Dassault Service Alert" talks about blowing and drifing snow which sticks to the brakes during taxi, and melting and water getting into the carbon brakes, which then freezes in cruise.

Brake heat is turned on after departure , and if "required " ?? prior to gear extension, as well ?

[ahramin]

There was an incident in the UK when a Global Express sat in rain in KTEB for several days and then the moisture laden carbon brakes froze at altitude. Did a great deal of damage on landing.