Boeing's Recommended Brake Cooling Schedule

[ElNull]

The schedules have Inflight Gear Down Cooling. I've always thought that this part was solely for after-takeoff gear cooling. However, the FCTM states: Extending the gear a few minutes early in the approach normally provides sufficient cooling for a landing. Total in-flight cooling time can be determined from the PI chapter of the QRH which lead to the confusion. which lead to the confusion.

The only example I can find in the book suggesting early gear extension is for overweight landings. Perhaps this practice should be considered during hot days and high elevation as well? Nonetheless, if the Brake Cooling Schedule is indeed applicable in this scenario, I'm still perplexed as to how I'm expected to determine the million foot-pounds (the brake energy absorbed) before landing, in order to calculate the required cooling time.

I've contemplated whether Vref could serve as a reference point, but I'm hesitant to proceed without solid confirmation/reference.

[Fursty Ferret]

Brakes don’t really cool when tucked safely away with the gear up. So if you take off with them scorching, they’re still going to be hot an hour later.

[ElNull]

Fursty Ferret (https://www.pprune.org/members/370749-fursty-ferret) True, but this doesn't answer my question.

[bigduke6]

Landed MEX and had very warm brakes that did not fully cool, but were at 2 and below, so OK for take-off. Did normal gear retraction for climb, etc. Short leg over to GDL so extended the gear early on the approach to let it cool down some more prior to another heavy weight ldg.

[Fursty Ferret]

Fursty Ferret (https://www.pprune.org/members/370749-fursty-ferret) True, but this doesn't answer my question.

I assume the point the FCTM is making is that if the brakes are hot at the point of take off, you don’t need to leave the gear extended to cool them but instead lower it early on approach.

[BraceBrace]

Brake cooling schedule is a calculation for turnarounds, to give an indication of the minimum turnaround time - or leave the gear down for takeoff (performance penalty). On days with multiple sectors and short turnarounds, the overall temperature can still slowly rise as there isn't really time to let the brakes cool down. As the day progresses, every time you do a turnaround, the risk of running into a "minimum turnaround time" (or takeoff performance penalty due to gear down requirement) is bigger and bigger. Think hot 4/5 sector day with very short flights, extended taxi time, high payloads,....

In order to provide extra cooling to the brakes, Boeing proposes to lower the gear earlier on the sectors. The advantage is that your starting point in the brake cooling schedule calculation will be lower, hence less chance to end up with a turnaround time requirement (or gear down required after takeoff) after sector 3/4/....

[ElNull]

Brake cooling schedule is a calculation for turnarounds, to give an indication of the minimum turnaround time - or leave the gear down for takeoff (performance penalty). On days with multiple sectors and short turnarounds, the overall temperature can still slowly rise as there isn't really time to let the brakes cool down. As the day progresses, every time you do a turnaround, the risk of running into a "minimum turnaround time" (or takeoff performance penalty due to gear down requirement) is bigger and bigger. Think hot 4/5 sector day with very short flights, extended taxi time, high payloads,....

In order to provide extra cooling to the brakes, Boeing proposes to lower the gear earlier on the sectors. The advantage is that your starting point in the brake cooling schedule calculation will be lower, hence less chance to end up with a turnaround time requirement (or gear down required after takeoff) after sector 3/4/....

Thanks for the response! However I still have 2 questions:

1) I understood that extending the landing gear early in approach contribute to brake cooling, but from what I understood from your reply is that we can’t determine the required time the gear needs to be extended during the approach from the schedules. Hence the schedule is not usable in this case. Correct?

2) During an RTO when recognize the rejected speed so we can obtain the brake cooling time from the schedule, I have read somewhere that if we couldn’t identify the RTO speed we can use V1. My question is how to determine the braking speed _after landing_ so we can see the minimum turnaround time (to cool the brake). Do we use Vref?

[Fursty Ferret]

You either go into the tables with Vref, which will give a correction for altitude / temperature, or use the ground speed at touchdown directly on the sea level and 15C line.

[BraceBrace]

Thanks for the response! However I still have 2 questions:

1) I understood that extending the landing gear early in approach contribute to brake cooling, but from what I understood from your reply is that we can’t determine the required time the gear needs to be extended during the approach from the schedules. Hence the schedule is not usable in this case. Correct?

The main thing to remember is that brake cooling schedules are advisory information. It does refer to a quick turnaround _limit_ (in the AFM) which is based on landing weight and density altitude. That IS a hard limit in time to check the brakes temps.

The brake cooling schedule on the other hand is _advisory_ to prevent problems (it does however refer to the quick turnaround limit for safety reasons to make sure you check it). The brake cooling schedule itself does not really "stop" you from doing anything, and if you would compare brake cooling schedule tables in QRH and different AFM's, you might find them to give different results.

There are too many variables involved. The biggest one from my experience is actually taxi time and the use of the brakes during taxi. My experience is the awareness is a lot bigger on widebody fleets, much less on narrowbody fleets. As mentioned before, you might taxi out and notice hotter than expected brakes prior to takeoff. It is up to you as a pilot to decide on how to handle the issue; leave the gear down if able on takeoff, however you are not "required" to do so. If however you would end up with a warning after takeoff, there is a note to put the gear back down for an certain amount of time. If nothing happens, you continue on but in order to create some safety when running the "advisory" brake cooling tables shows you might heat the brakes too much on landing and taxi, you might decide to put the gear down early on the approach. It is all about awareness.


2) During an RTO when recognize the rejected speed so we can obtain the brake cooling time from the schedule, I have read somewhere that if we couldn’t identify the RTO speed we can use V1. My question is how to determine the braking speed _after landing_ so we can see the minimum turnaround time (to cool the brake). Do we use Vref?

You can actually use groundspeed on touchdown if you manage to read it. Or Vref and "recalculate" the GS based on actual wind (don't know the details anymore, but it's in the AFM).

Hope this helps, and always comments welcome to correct...

[High Energy]

My company uses a generic minimum turnaround (waiting) time IF you detemined you have landed at a weight above your OPT Quick turnaround weight on your OPT Landing Dispatch page. We do not have brake temp monitors /scales hence we have a time and weight SOP. How you use the nbrs after RTO is a bit vague and as they are all 'advisory' it is recommended to assume worst case scenario of V1, add 10 minutes after stopping to decide what to do wrtmove or not after stopping due to het build up and then apply good airmanship when it. omes to using the tables. The 'in-flight' cooling is useless without the monitor/scales as you have no way of telling.