Originally Posted by
ElNull
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.
Originally Posted by
ElNull
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...