RoseFlyer From United States of America, joined Feb 2004, 7619 posts, RR: 51 Reply 1, posted (4 months 3 days 21 hours ago) and read 1678 times:
Quoting captainmeeerkat (Thread starter):
I just wondered if there is a specified time that brakes must be allowed to cool or does it depend totally on temperature?
There are cooling charts. The biggest factor is what the weight of the previous landing was. That indicates how much energy (heat) was absorbed by the brakes. Pressure altitude, outside temperature, and head wind are also factors.
If the airplane was landing at a light weight, quick turn around time procedures can be in place.
Quoting captainmeeerkat (Thread starter):
Does it vary by size, manufacturer etc? And what effect can outside conditions theoretically have on these times?
Yes it does vary. Carbon vs steel and high capacity vs standard capacity influence cooling time. Most planes have carbon brakes, but steel brakes do cool quicker.
If you have never designed an airplane part before, let the real designers do the work!
26point2 From United States of America, joined Mar 2010, 490 posts, RR: 0 Reply 2, posted (4 months 3 days 21 hours ago) and read 1670 times:
Modern carbon brakes are very efficient but actually get hotter before they cool. The process takes some time dependent on how much brake application was applied, outside air temp, etc. but always very slow. After an RTO it could take hours to cool to a suitable temp before another takeoff is made.
The plane I fly does not have a chart to determine how long to wait but each brake assembly has a cockpit temperature indicator and there are max allowable brake temp limits. Brake temp limit is 400C and a requirement to wait 30 minutes after any landing before another takeoff is made.
oldtimer From United Kingdom, joined Aug 2006, 191 posts, RR: 1 Reply 3, posted (4 months 3 days 21 hours ago) and read 1662 times:
Besides the carbon/steel differences it will depend on whether brake cooling fans are fitted as well. As others have said, depending on a/c load, weight etc they all differ. There is no set time or period for all aircraft.
BEG2IAH From United States of America, joined Apr 2004, 699 posts, RR: 11 Reply 4, posted (4 months 3 days 16 hours ago) and read 1544 times:
Quoting oldtimer (Reply 3): Besides the carbon/steel differences it will depend on whether brake cooling fans are fitted as well.
I used to have a client who told me that although this is an option, they installed cooling fans on one aircraft only. How much weight does this system add?
BEG2IAH
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vikkyvik From United States of America, joined Jul 2003, 6516 posts, RR: 29 Reply 5, posted (4 months 3 days 14 hours ago) and read 1469 times:
Quoting RoseFlyer (Reply 1): There are cooling charts. The biggest factor is what the weight of the previous landing was. That indicates how much energy (heat) was absorbed by the brakes. Pressure altitude, outside temperature, and head wind are also factors.
If the airplane was landing at a light weight, quick turn around time procedures can be in place.
Is it strictly by weight? Or do they also look at whether thrust reversers were used, how much of the runway they used (although it wouldn't affect total energy absorbed), autobrake setting if used (same deal), etc.?
Thanks.
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FlyMKG From United States of America, joined Jan 2005, 156 posts, RR: 1 Reply 6, posted (4 months 3 days 13 hours ago) and read 1462 times:
Quoting vikkyvik (Reply 5): Is it strictly by weight? Or do they also look at whether thrust reversers were used, how much of the runway they used (although it wouldn't affect total energy absorbed), autobrake setting if used (same deal), etc.?
On the 727 it is by weight and speed at which brakes were applied. One of the variables on the X axis and one on the Y. Where they meet is the time required to cool the brakes. The only variable is adding or subtracting time based on knots of headwind or tailwind encountered. There does become a point where all the times become the same because the fuse plugs may melt on the tires. That point is hardly ever reached.
FlyMKG
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RoseFlyer From United States of America, joined Feb 2004, 7619 posts, RR: 51 Reply 7, posted (4 months 3 days 13 hours ago) and read 1454 times:
Quoting vikkyvik (Reply 5):
Is it strictly by weight? Or do they also look at whether thrust reversers were used, how much of the runway they used (although it wouldn't affect total energy absorbed), autobrake setting if used (same deal), etc.?
The charts that I have seen do not include thrust reversers. Autobrake is a separate chart from manual brakes.
If you have never designed an airplane part before, let the real designers do the work!
Tristarsteve From Sweden, joined Nov 2005, 3489 posts, RR: 35 Reply 9, posted (4 months 2 days 21 hours ago) and read 1209 times:
Quoting vikkyvik (Reply 5): Is it strictly by weight? Or do they also look at whether thrust reversers were used, how much of the runway they used (although it wouldn't affect total energy absorbed), autobrake setting if used (same deal), etc.?
Many years ago I worked in BAH, and we looked after the transit of the LTU Tristar which went MUC-BAH-Maldives.
They did this with one crew, so we were tasked to perform a quick transit. The aircraft was heavy, nearly 400 pax, but the LTU pilots rolled down the runway with the nose in the air and no brakes. It arrived at the gate with cold brakes. We refuelled it and departed it usually in under 30 mins.
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