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Hot Brakes Delays Departure - Preventable?  
User currently offlineGOT From Sweden, joined Dec 2000, 1912 posts, RR: 1
Posted (3 years 1 month 1 week 6 days 16 hours ago) and read 10609 times:

Hi all!

Pardon my ignorance if I missed something obvious, but here goes: I was on AF347 YUL-CDG on the A380 last Friday, August 6th. After being delayed due to late incoming aircraft we finally left gate about an hour late. After taxiing out to runway 24L and waiting for what seemed like a pretty long time, we lined up, waited some more and finally started rolling. However, we never really gained speed and leisurely rolled down the runway, exiting about half way down, then parking somewhere along the crosswind runway. The captain came on the PA, announcing that the brakes were hot from the arrival and hadn't cooled of properly in the heat of Montreal, so we would have to wait another 25 minutes for them to cool off before another attempt. Second time around, all went well and we left around 2 hrs late.

What got me thinking though: How common is this? Would the brakes have been excessively used during landing, or can this result from a 'normal' landing? Why wasn't this noticed earlier? Why did we have to go all the way to the runway and delay planes behind us? Where pilots hoping that they would cool enough on the way? I don't know the exact temperature in Montreal that day, but the plane spent well over 2 hours at gate, wouldn't this usually be enough?

Anything that enlighten the chain of things behind this is appreciated!

Best regards,
Robert


Just like birdwatching - without having to be so damned quiet!
41 replies: All unread, showing first 25:
 
User currently offlineshamrock137 From United States of America, joined Jul 2005, 144 posts, RR: 0
Reply 1, posted (3 years 1 month 1 week 6 days 11 hours ago) and read 10545 times:

The issue of brake temperature is an important concern to pilots. Hot brakes can severely decrease braking performance in the event of a rejected takeoff. It is quite possible that even though the aircraft was on the ground for 2 hours, the brakes were not able to completely cool off. In addition, a long taxi time as you mentioned could easily heat up the brakes. When the aircraft is taxiing for takeoff, it is at its heaviest, and a long taxi can be tough on the brakes. Sometimes the pilots can request fans to be placed on the landing gear while the aircraft is at the gate to speed up the cooling process. In your case, perhaps the airport did not have the proper equipment for the A380, or other aircraft were already using it.


Time to spare? Go by air!
User currently offlinecontrails15 From United States of America, joined Oct 2008, 1181 posts, RR: 0
Reply 2, posted (3 years 1 month 1 week 6 days 11 hours ago) and read 10511 times:

Brake fans being on at the gate wouldn't be enough to decrease the temp of the brakes enough? 2 hour ground time seems like a lot of time.


Giants football!!!!!!!!!!!!!!!!!!!!!!!!
User currently offlineMaverick623 From United States of America, joined Nov 2006, 5648 posts, RR: 6
Reply 3, posted (3 years 1 month 1 week 6 days 10 hours ago) and read 10471 times:

Quoting GOT (Thread starter):
heat of Montreal

     

Sorry, but being from PHX....  
Quoting GOT (Thread starter):
How common is this?

Not common, but certainly not unheard of.

Quoting GOT (Thread starter):
Would the brakes have been excessively used during landing, or can this result from a 'normal' landing?

Both.

Quoting GOT (Thread starter):
Why wasn't this noticed earlier?

Who says it wasn't?

Quoting GOT (Thread starter):
Why did we have to go all the way to the runway and delay planes behind us?

I'm sure you only delayed the planes behind you a few minutes. Besides, maybe the temp was borderline and the pilots thought they'd cool off during taxi.

Quoting GOT (Thread starter):
the plane spent well over 2 hours at gate, wouldn't this usually be enough?

It depends. It's not just about how hot the brakes are, but how quickly they can dissipate the heat. Being parked in a warm area with little air flow can increase the cool-down time. Maybe they forgot to turn on the brake fans (it happens).

Also, as said, taxiing with a fully loaded plane can be hard on the brakes.



"PHX is Phoenix, PDX is the other city" -777Way
User currently offline26point2 From United States of America, joined Mar 2010, 825 posts, RR: 0
Reply 4, posted (3 years 1 month 1 week 6 days 8 hours ago) and read 10435 times:

Carbon brakes such as these continue to heat up after brake use is discontinued.

As mentioned hot brakes are not as effective but also putting hot brakes into the wheel-well is not a great idea either.

We are prohibited from taking off if brake temp exceeds 425C on the type I fly.


User currently offlineALTF4 From United States of America, joined Jul 2010, 1212 posts, RR: 4
Reply 5, posted (3 years 1 month 1 week 5 days 14 hours ago) and read 10225 times:

Quoting 26point2 (Reply 4):
We are prohibited from taking off if brake temp exceeds 425C on the type I fly.

Thinking about it, it is only logical that the brakes heat up that hot... but... dang that is pretty hot! In cold months, do ramp rats volunteer to do duties in the vicinity of the wheels so they get some radiant heat?  



The above post is my opinion. Don't like it? Don't read it.
User currently offlinecontrails15 From United States of America, joined Oct 2008, 1181 posts, RR: 0
Reply 6, posted (3 years 1 month 1 week 5 days 14 hours ago) and read 10200 times:

Quoting ALTF4 (Reply 5):
In cold months, do ramp rats volunteer to do duties in the vicinity of the wheels so they get some radiant heat?  

We hang out by the heat exhaust vents under the belly. Brake blowers when the vents aren't pumping out hot air. Great way to dry off too.



Giants football!!!!!!!!!!!!!!!!!!!!!!!!
User currently offlineGOT From Sweden, joined Dec 2000, 1912 posts, RR: 1
Reply 7, posted (3 years 1 month 1 week 4 days 19 hours ago) and read 10061 times:

Thanks for all the answers, guess I'll never know exactly what happend...

Quoting Maverick623 (Reply 3):
Quoting GOT (Thread starter):
heat of Montreal



Sorry, but being from PHX....

Pilot's word, not mine  
Quoting Maverick623 (Reply 3):
Quoting GOT (Thread starter):
Why wasn't this noticed earlier?

Who says it wasn't?

Quoting GOT (Thread starter):
Why did we have to go all the way to the runway and delay planes behind us?

I'm sure you only delayed the planes behind you a few minutes. Besides, maybe the temp was borderline and the pilots thought they'd cool off during taxi.

The way I see it, if it was borderline it shouldn't have taken another 25 minutes to cool off. But what do I know really :-P

The point about the plane being heavy during taxi is good though, thanks everyone!

/Robert



Just like birdwatching - without having to be so damned quiet!
User currently offlinerfields5421 From United States of America, joined Jul 2007, 7607 posts, RR: 31
Reply 8, posted (3 years 1 month 1 week 4 days 18 hours ago) and read 10047 times:

Quoting GOT (Reply 7):
The way I see it, if it was borderline it shouldn't have taken another 25 minutes to cool off.

It was probably not over the limit when the taxi started, but the temps increased during the taxi. The pilots thought it would cool off enough when they got into the line for takeoff, but if the temps went up a couple degrees over the limit, the plane could not do a legal takeoff and could not block access to the runway for other aircraft ready to takeoff.

The short taxi down the runway, braking again and turning off would heat the brakes again.

25 minutes was probably needed for the brakes to cool enough below the go/no go temp - so the pilots could be sure the additional braking necessary to get to and lined up on the runway did not raise the temps too high.

They had already tried to go with the temps closer to the borderline and been wrong, so they would probably want the brakes cooler than the last taxi attempt so they did not repeat the failure to takeoff again.


User currently offlinelonghauler From Canada, joined Mar 2004, 4990 posts, RR: 42
Reply 9, posted (3 years 1 month 1 week 4 days 17 hours ago) and read 10023 times:

Quoting Maverick623 (Reply 3):
Sorry, but being from PHX....

I flew a YYZ-PHX-YYZ flight a few weeks ago. The temperature in eastern Canada YYZ/YOW/YUL was hotter at 41C than PHX, which was 36C when we left. It does happen! And trust me, it sure as hell wasn't a "dry heat".

Quoting 26point2 (Reply 4):
Carbon brakes such as these continue to heat up after brake use is discontinued.

As mentioned hot brakes are not as effective but also putting hot brakes into the wheel-well is not a great idea either.

Airbus recently issued some new directives on this issue. As, in fact carbon brakes are MORE effective when they are hot, unlike steel brakes. The bigger issue, is as you state that, you don't really want to put very hot brakes into the wheel well.

While the max brake temp for take-off still stands, it would appear that the issue is not the performance for a rejected take-off. The "hot brake" ECAM warning is inhibited during take-off, so Airbus now suggests if the warning appears after take-off, AND the gear is still down AND if performance requirements permit ... leave the gear down to cool. Then .. they state "retract the gear with an engine failure".

My guess therefore is the max brake temperature for takeoff is a performance restriction after take-off, not for a rejected take-off.



Never gonna grow up, never gonna slow down .... Barefoot Blue Jean Night
User currently offlineHAWK21M From India, joined Jan 2001, 31684 posts, RR: 56
Reply 10, posted (3 years 3 weeks 3 days 12 hours ago) and read 9318 times:

I've noticed an IL62 heated MLG wheels being sprayed with Steam/water......Is that normal on such a type?.


Think of the brighter side!
User currently offlineqslinger From India, joined Apr 2006, 261 posts, RR: 0
Reply 11, posted (3 years 2 weeks 3 days 10 hours ago) and read 8830 times:

What about hosing the brakes down with cold water for quicker cool down...or even using a fire engine to come to a remote stand to spray water to cool them down? Beats having to go back to the gates for brake cooling?


Raj Koona
User currently offlineRoseFlyer From United States of America, joined Feb 2004, 9642 posts, RR: 52
Reply 12, posted (3 years 2 weeks 3 days 10 hours ago) and read 8819 times:

Carbon fiber brakes have an interesting characteristic. They wear faster during taxi and light application then when on hard application during landing. Taxiing will heat them up and cause material to wear. When at high temps the brakes weld particles that flake off back together. Steel brakes are the opposite, but the only new build large jets with steel brakes are 737s for airlines not taking the carbon brake option.

Quoting GOT (Reply 7):
The way I see it, if it was borderline it shouldn't have taken another 25 minutes to cool off. But what do I know really :-P

Airplanes don't operate on borderlines. It's either ok or not. The same is true for visibility, crosswinds, MTOW, etc. Sure there isn't a big change in a few degrees, but if it is certified for a certain temp, then that is the max.



If you have never designed an airplane part before, let the real designers do the work!
User currently offlineMax Q From United States of America, joined May 2001, 4522 posts, RR: 18
Reply 13, posted (3 years 2 weeks 3 days 9 hours ago) and read 8811 times:

Quoting longhauler (Reply 9):

Airbus recently issued some new directives on this issue. As, in fact carbon brakes are MORE effective when they are hot, unlike steel brakes. The bigger issue, is as you state that, you don't really want to put very hot brakes into the wheel well.

This is a common misconception about Carbon Brakes.



The reality is that Carbon Brakes WEAR better / less when they are hot. They work just fine at lower temperatures.




This is one of the reasons that the use of idle reverse has been so widely promoted and Pilots have misunderstood why, it is to optimally heat the carbon Brakes so they last longer.




And while we are on the subject of hot brakes, if the A380 in question had four reversers and used max on the previous landing you most likely would not have had that delay !



The best contribution to safety is a competent Pilot.
User currently offlinerfields5421 From United States of America, joined Jul 2007, 7607 posts, RR: 31
Reply 14, posted (3 years 2 weeks 2 days 20 hours ago) and read 8704 times:

Quoting qslinger (Reply 11):
What about hosing the brakes down with cold water for quicker cool down...or even using a fire engine to come to a remote stand to spray water to cool them down? Beats having to go back to the gates for brake cooling?

At the temps involved and the way the parts around the brakes and wheels are constructed - spraying cold water on overheated systems can possibly cause fractures of the metal parts due to unequal cooling.

So rather than waiting for a while for the brakes to cool, the passengers could easily have to wait several hours while a wheel is replaced, or a landing gear part is examined for fractures.

Pooring water on hot parts of various different metals and other materials to cool it is a last resort.


User currently offlineViscount724 From Switzerland, joined Oct 2006, 25338 posts, RR: 22
Reply 15, posted (3 years 2 weeks 2 days 14 hours ago) and read 8623 times:

Noted following recent (August 31) "hot brakes" item involving two departing aircraft at YYC, from the Transport Canada daily incident reports. Departing from runway 34 at YYC involves an approximate 2 mile taxi from the terminal.

JZA 316, Air Canada Jazz CRJ-200 was overshot by Calgary Tower at 2 NM final for Runway 34 due to KLM 678, a KLM A330-200, in position unable to depart due to hot brakes. KLM 678 taxied ahead and exited right on Runway 25. Subsequently, the crew of ACA 140, an Air Canada A320, advised on reaching Runway 34 that they were also unable to depart due to hot brakes. WJA 255 and JZA 555 were both caught behind ACA 140 and KLM 678 blocking Taxiway Charlie and were delayed approximately 15 minutes until they could get past ACA 140 and KLM 678 at the holding bay.

[Edited 2011-09-04 12:51:36]

User currently offlineHAWK21M From India, joined Jan 2001, 31684 posts, RR: 56
Reply 16, posted (3 years 2 weeks 2 days 14 hours ago) and read 8617 times:

Quoting qslinger (Reply 11):
What about hosing the brakes down with cold water for quicker cool down...or even using a fire engine to come to a remote stand to spray water to cool them down? Beats having to go back to the gates for brake cooling?

Would that not cause a shock cooling to the brake housing & crack it?.



Think of the brighter side!
User currently offlineMD11Engineer From Germany, joined Oct 2003, 14026 posts, RR: 62
Reply 17, posted (3 years 2 weeks 20 hours ago) and read 8406 times:

Quoting HAWK21M (Reply 16):
Quoting qslinger (Reply 11):
What about hosing the brakes down with cold water for quicker cool down...or even using a fire engine to come to a remote stand to spray water to cool them down? Beats having to go back to the gates for brake cooling?

Would that not cause a shock cooling to the brake housing & crack it?.

Yes. It is the last resort by the firefighters to prevent a tyre fire, but afterwards you can remove the brake and wheel and send it for inspection / overhaul. You´d also have to inspect the axle for damage.

BTW, we had a lot of issues with carbon brakes due to catalytic oxydation, materials like anti-icing fluid (both for runways and aircraft) seem to interact with the hot carbon brakes that the brake discs go soft and literally crumble apart. We had to change a lot of brakes due to this on our airline alone and the brake overhaul shop we are working with had issues getting enough new brake discs from the manufacturers, because other airlines had the same issues.

Jan

[Edited 2011-09-06 06:54:24]

User currently offlineHAWK21M From India, joined Jan 2001, 31684 posts, RR: 56
Reply 18, posted (3 years 2 weeks 17 hours ago) and read 8362 times:

Quoting MD11Engineer (Reply 17):
Yes. It is the last resort by the firefighters to prevent a tyre fire, but afterwards you can remove the brake and wheel and send it for inspection / overhaul. You´d also have to inspect the axle for damage.

Water on the hot tire could be more serious than on a hot brake for obvious reasons.....



Think of the brighter side!
User currently offlineMD11Engineer From Germany, joined Oct 2003, 14026 posts, RR: 62
Reply 19, posted (3 years 2 weeks 15 hours ago) and read 8333 times:

Quoting HAWK21M (Reply 18):
Quoting MD11Engineer (Reply 17):
Yes. It is the last resort by the firefighters to prevent a tyre fire, but afterwards you can remove the brake and wheel and send it for inspection / overhaul. You´d also have to inspect the axle for damage.

Water on the hot tire could be more serious than on a hot brake for obvious reasons.....

The firefighters will approach the overheated wheel from either front or back, never from the side and will use a spray nozzle, not a sharp jet of water.

Jan


User currently offlinebuckfifty From Canada, joined Oct 2001, 1316 posts, RR: 19
Reply 20, posted (3 years 2 weeks ago) and read 8253 times:

The other solution is to install brake fans. Wonderful devices these are, and are great for aircraft that are constantly doing short turnarounds. Not sure how much they weigh, but they are especially useful going to ports where they don't have any (or have poor) brake cooling equipment.

Which reminds me, sometimes when we go to India, they use ground air conditioning carts to cool the brakes for us.


User currently offlineShnoob940 From Australia, joined Sep 2008, 185 posts, RR: 0
Reply 21, posted (3 years 1 week 6 days 23 hours ago) and read 8243 times:

Quoting Viscount724 (Reply 15):
unable to depart due to hot brakes

Excuse me for being stupid, but couldn't they just leave the gear down for a minute or two after takeoff, and the wind rushing past would cool down the brakes?



A319 A320 A321 A332 A333 A343 A388 733 734 735 737 738 739 743 744 762 763 773 788 E170 E190 Q400
User currently offlinezeke From Hong Kong, joined Dec 2006, 9104 posts, RR: 75
Reply 22, posted (3 years 1 week 6 days 23 hours ago) and read 8238 times:

Quoting GOT (Thread starter):
What got me thinking though: How common is this?

Very, almost every landing I will have hot brakes, i.e. indicating above 300 deg C after I get to the gate. That is the limit for us to takeoff.

Quoting GOT (Thread starter):
Would the brakes have been excessively used during landing, or can this result from a 'normal' landing?

Normal.

Quoting GOT (Thread starter):
Why wasn't this noticed earlier? Why did we have to go all the way to the runway and delay planes behind us?

As a rule of thumb, the brakes will cool in excess of 1 degree per minute, if I see the brakes at 400 deg C and 40 minutes to pushback I know in most cases I will be okay.

Quoting GOT (Thread starter):
I don't know the exact temperature in Montreal that day, but the plane spent well over 2 hours at gate, wouldn't this usually be enough?

If you have a downhill taxi to takeoff, or need numerous brake applications while taxiing, the temps will go up. For departure the aircraft is at a higher weight than landing.

Quoting buckfifty (Reply 20):
The other solution is to install brake fans.

Not practical on a long haul aircraft, the fuel cost would be too high.

Quoting Shnoob940 (Reply 21):
Excuse me for being stupid, but couldn't they just leave the gear down for a minute or two after takeoff, and the wind rushing past would cool down the brakes?

Need the brake temps to be low enough to meet the performance requirements on takeoff.



We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
User currently offlinerfields5421 From United States of America, joined Jul 2007, 7607 posts, RR: 31
Reply 23, posted (3 years 1 week 6 days 20 hours ago) and read 8196 times:

Quoting Shnoob940 (Reply 21):
Excuse me for being stupid, but couldn't they just leave the gear down for a minute or two after takeoff, and the wind rushing past would cool down the brakes?

Excessively hot brakes won't stop the aircraft in normal distances if the takeoff has to be aborted. If the brakes exceed the maximum operating temp, then all the takeoff distance and speed calculations are wrong. The aircraft probably would not be legal for takeoff at all on many airports, or near maximum weights.


User currently offlineCitationJet From United States of America, joined Mar 2003, 2438 posts, RR: 3
Reply 24, posted (3 years 1 week 6 days 15 hours ago) and read 8157 times:

Quoting Shnoob940 (Reply 21):
Excuse me for being stupid, but couldn't they just leave the gear down for a minute or two after takeoff, and the wind rushing past would cool down the brakes?

You will need the brakes to work in case you DON'T takeoff; in other words if the takeoff is aborted.



Boeing Flown: 701,702,703;717;720;721,722;731,732,733,734,735,737,738,739;741,742,743,744,747SP;752,753;762,763;772,773.
25 Shnoob940 : Ok, I see now.
26 HAWK21M : Wouldn't Wheel shattering create uneeded FOD & Aircraft damage.
27 C172Akula : I was looking over the CADOR reports today and that one caught my eye, then I come across this thread and new the answer right away. That long taxi c
28 bonusonus : Yes, this would definitely be bad for the components, and likely risk damaging them. However, spraying a fine mist of water along with the cooling ai
29 HAWK21M : On the B737/757s the use of water is def not permitted for cooling purposes......
30 Ward86IND : Earlier this summer I was on a DAL A320 out of IND and we actually extended the gear in the middle of the climb for about 2 minutes to cool the brakes
31 Starlionblue : Performance reasons?
32 tdscanuck : The climb calculations for the takeoff assume gear up shortly after liftoff. If you leave the gear down there is no guarantee that you can achieve th
33 blueflyer : There's been a lot of taxiway work at YUL over the summer, with various taxiways closed at one time or another, sometimes with serious consequences on
34 Kaiarahi : 1. I know from other threads that you think T/Rs are the answer to everything, including a maiden's prayer, but I'm wondering if you have the landing
35 HAWK21M : Another contributer is those hurrying Crew that taxi way beyond the required speeds.
36 DrEsteban : Interesting fact; one brake application on an A320 equals approx $80 in brake wear. Hence the importance of correct braking technique, ie don't 'ride'
37 rfields5421 : Uh? This was a delay at takeoff. If the aircraft had excessively hot brakes from the previous landing - it would not have left the gate. The issue in
38 Post contains images don : JAL uses these external brake cooling fans, especially on the freighters on which you always land with heavy landing weights.
39 HAWK21M : Some types have cooling fans as a customer option built into the Wheel.
40 longhauler : Wow, that is a great rig. I have copied the picture and forwarded it to our Flight Ops managers. I could see that being very useful. We had cooling f
41 HAWK21M : Exactly the reason....Reliability of the fans & costs due to the added weight.
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