Carbon Brake Cooling Rates
Join Date: Oct 2010
Location: 5° above the Equator, 75° left of Greenwich
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Couple of things. First, bear in mind that in the A320, there are different carbon brakes manufacturers. They all make their brakes slightly different, so their composition, and hence their cooling qualities differ slightly. This is particularly noticeable with the BF Goodrich brakes, if I'm not mistaken.
Second: Again in the A320, the FCOM states that the brakes do cool off faster with the parking brake off, and it advises you to do so if operationally viable. Not only that, but it also states that this action also prevents exposing critical surfaces to higher temperatures thus preventing possible damage, or at least, faster degradation of these components due to heat.
And while we're talking about degradation, since (again) the brake manufacturers and their respective brake composition is different, the one action to reduce brake degradation that applies to all brands of brakes is to reduce brake applications. Some of you have discussed temperatures from a braking efficiency point of view, however, Airbus documentation discusses the use of brakes (actions, techniques, temperatures, etc) from a brake degradation point of view. Outofsynch mentioned 150 - 200°C; if I'm not mistaken, this is the worst temperature range for ANY brake manufacturer as far degradation goes, since the recommendation is to taxi with either cold brakes (below 80) or "warm" brakes (over 300, if memory serves me right). Let's face it, degradation is a far more usable and impactful factor in day to day operations than the low chance of an RTO.
By the way, these are bites of info contained in the link that FlightDetent has kindly put up for all of us to improve our knowledge.
Follow your SOP
Second: Again in the A320, the FCOM states that the brakes do cool off faster with the parking brake off, and it advises you to do so if operationally viable. Not only that, but it also states that this action also prevents exposing critical surfaces to higher temperatures thus preventing possible damage, or at least, faster degradation of these components due to heat.
And while we're talking about degradation, since (again) the brake manufacturers and their respective brake composition is different, the one action to reduce brake degradation that applies to all brands of brakes is to reduce brake applications. Some of you have discussed temperatures from a braking efficiency point of view, however, Airbus documentation discusses the use of brakes (actions, techniques, temperatures, etc) from a brake degradation point of view. Outofsynch mentioned 150 - 200°C; if I'm not mistaken, this is the worst temperature range for ANY brake manufacturer as far degradation goes, since the recommendation is to taxi with either cold brakes (below 80) or "warm" brakes (over 300, if memory serves me right). Let's face it, degradation is a far more usable and impactful factor in day to day operations than the low chance of an RTO.
By the way, these are bites of info contained in the link that FlightDetent has kindly put up for all of us to improve our knowledge.
Follow your SOP
Only half a speed-brake
Unfortunately the main article got lost somewhere inside the drive, perhaps it was from Boeing's AERO.
Mileage may vary.
a) the brake-pad material is supposed to behave in a similar fashion
b) the location of the brake temp sensors is different and creates most of the varying effect observed on the flightdeck. INDICATED brake temperature.
c) my only primary concern is the brake energy capacity before RTO. Same as Airbus says. Exactly as expected from a Performance / EFB geek.
I have a plan now to organize a Brake*pad*a*looza festival and celebrate the idea of keeping the brakes hot for better stopping action, with like-minded fellows - somewhere within the HIMARS range. Seriously, tungsten pellets are what that logic deserves.
The only recommendation Airbus delivers is to reach the holding point with the brakes cooled down as much as possible.
For longevity of the hardware, two suggestions are made
- reduce the number of applications (from rather fast to quite slow in one squeeze, instead of riding; using alternating action on left and right pedals independently; ...)
- hot temps after lading are not such a big deal as they seem to be
Mileage may vary.
a) the brake-pad material is supposed to behave in a similar fashion
b) the location of the brake temp sensors is different and creates most of the varying effect observed on the flightdeck. INDICATED brake temperature.
c) my only primary concern is the brake energy capacity before RTO. Same as Airbus says. Exactly as expected from a Performance / EFB geek.
I have a plan now to organize a Brake*pad*a*looza festival and celebrate the idea of keeping the brakes hot for better stopping action, with like-minded fellows - somewhere within the HIMARS range. Seriously, tungsten pellets are what that logic deserves.
The only recommendation Airbus delivers is to reach the holding point with the brakes cooled down as much as possible.
For longevity of the hardware, two suggestions are made
- reduce the number of applications (from rather fast to quite slow in one squeeze, instead of riding; using alternating action on left and right pedals independently; ...)
- hot temps after lading are not such a big deal as they seem to be
OK, I did say I was happy to be corrected. There are far too many opinions out there, and far too few facts/training.
Your explanation FD is accepted, and appreciated.
Cheers!
Your explanation FD is accepted, and appreciated.
Cheers!
Only half a speed-brake
goeasy Not sure you were invited. 
Honest, there's nothing wrong with your posts, being disoriented in a noisy environment is not a sin.
Unnecessary brake wear is an ugly beast and with carbons great much of it can be avoided by operating them well. Still and ever, they are energy reservoirs with limited capacity. Start with the bucket not emptied properly - find out you're overfilling earlier than expected. The videos with the brakes meltin' red show an undesirable state where the assemblies are at their edge limit to contain the braked energy.
When unable to avoid departing with the brakes heated up there are limits of what's reasonable, not very strict. Sure, (fanless) indication of 300 is accepted and that is not the 'starting energy' limit even.
But showing up warm at the threshold deliberately, convinced it is the right thing to do .... ?
Honest, there's nothing wrong with your posts, being disoriented in a noisy environment is not a sin.Unnecessary brake wear is an ugly beast and with carbons great much of it can be avoided by operating them well. Still and ever, they are energy reservoirs with limited capacity. Start with the bucket not emptied properly - find out you're overfilling earlier than expected. The videos with the brakes meltin' red show an undesirable state where the assemblies are at their edge limit to contain the braked energy.
When unable to avoid departing with the brakes heated up there are limits of what's reasonable, not very strict. Sure, (fanless) indication of 300 is accepted and that is not the 'starting energy' limit even.
But showing up warm at the threshold deliberately, convinced it is the right thing to do .... ?
SR lost a Caravelle from a undercarriage bay fire caused by their technique of using a high thrust/speed runway fog clearance technique followed by a U-turn and take off. The gear was retracted without cooling and the subsequent fire was augmented by the hydraulic fluid.
The Trident had brake fans in the 60s.
IIRC Twas Dubai where a relatively new 747 captain tried to bump start an engine with a full load of fuel and pax. It took several days to fly out a full set of wheels as he blew the fusible plugs after the take off abortion..there but for the grace of dog…
The Trident had brake fans in the 60s.
IIRC Twas Dubai where a relatively new 747 captain tried to bump start an engine with a full load of fuel and pax. It took several days to fly out a full set of wheels as he blew the fusible plugs after the take off abortion..there but for the grace of dog…
