"Brake temp" message in flight?

[Guest JTH]

Hi everyone, I was flying the 744 today and a yellow "brake temp" message was displayed on the EICAS during flight. Just wondering why this would be seeing as the gear was up and locked and, as far as I understand it, the brake temp message refers to the temperature of the tires and occurs when you brake the plane while travelling too fast on the ground?Thanks for any help on this one. Regards, Paul.

[mburkhard 23]

Paul,when exactly "in flight" did you see that message? Be aware that carbon brakes' temperature can increase for quite some time after you have stopped using them. Meaning you'd use them for landing and their temperature can still be increasing when you've reached the parking position!Now if your brakes were heavily used during taxi before take off it could very well be that you'd get that message AFTER lift-off. However you'd have to have had long and curvy taxiways for that to happen.Regards,Markus

[Guest JTH]

It's possible that that was the reason, because I did have to turn a lot to taxi to the runway. As an aside, what speed should I be taxiing at? I must be going too fast if I get these "brake temp" messages.

[cowpatz 243]

The company I fly for has the following taxy speed lmits:Right angle turns max 10 kts less is very heavy or wet. The 747 really rolls when full of fuel and this is not modelled so well with PMDG 747. 25 kts max taxy speed but reducing to 20 kts for a long taxy ie. departing 25L at LAX after taxying from the North side or taxying to the Reef runway at HNL.Some areas of airports have limits as low as 5 kts in some places when manoeuvering close to other aircraft on certain taxiways ie SFO.Not only does the application of brakes heat up the tires but the sidewall flexing of the tyre itself causes heat build up. We have a limit of 2 on the EICAS brake temps prior to take off. This ensures that adequate braking will be available in the event of a rejected TO.Brake temps do not indicate straight away and as has been mentioned in the previous post it can take some time. In fact the indication system can take up to 15 min to indicate the peak temperature. This can be very dangerous for ground personel as after a heavy braked landing the brake temps can paek just as you are parking at the gate.CheersSteve

[mburkhard 23]

>It's possible that that was the reason, because I did have to>turn a lot to taxi to the runway. As an aside, what speed>should I be taxiing at? I must be going too fast if I get>these "brake temp" messages.It does not necessarily mean that you were too fast, maybe you are just using your brakes in not the best way. Be aware that continuous but slight braking is deadly for those carbon brakes. If you must use them, use them for short instances only but with somehwat more pressure. I think it helps if you just keep thinking about your brakes while taxiing. Go to idle thrust earlier before a turn and let gravity slow your aircraft down before you start applying brakes. Braking on an airliner is a delicate task but if you have enough experience you'll be able to use full braking on a landing without overheadting anything.Regards,Markus

[Guest JTH]

Thanks for the replies, very interesting.

[Guest keiron]

Is it possible for them to heat up as well when applying the brakes on climb out before retracting gears?

[mburkhard 23]

>Is it possible for them to heat up as well when applying the>brakes on climb out before retracting gears?No not really. Applying brakes on climbout does nothing else but to slow down the wheels, there's no mass to it. Also there is the airflow around the landing gear which would cool any of that little heat anyway.Now the important thing:You DO NOT apply brakes manually on climbout before retracting the gear on an airliner, this is done automatically.However there is the option to leave the gear extended for some time for better cooling of the brakes should they have gotten warm during taxi. But be aware that this can ruin your climb out performance...Regards,Markus