smartt1982 From United Kingdom, joined Nov 2007, 214 posts, RR: 0 Posted (1 year 3 months 1 week 2 days 3 hours ago) and read 3936 times:
I seem to be getting myself confused between the two. From my understanding the "Quick Turnaround Limit" is that if you are over this weight when you land you need to wait a specified time to check the fuse plugs have not melted before commencing another take off.
The "Recommended Brake Cooling Schedule" is to avoid brake overheat and fuse plug problems that could result
from repeated landings at short time intervals or a rejected takeoff.
I think you have assessed the purpose of the two documents correctly, although most new aircraft are equipped with BTMS (brake temp monitoring systems), which make the used of such schedules and limits somewhat outdated. BTMS offers real-time temperatures from the heat stack, which then can be compared to the dispatch limits for brake temp contained in the AFM.
tdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 81 Reply 2, posted (1 year 3 months 1 week 1 day 21 hours ago) and read 3850 times:
Quoting smartt1982 (Thread starter): From my understanding the "Quick Turnaround Limit" is that if you are over this weight when you land you need to wait a specified time to check the fuse plugs have not melted before commencing another take off.
It's not so much that you'll hit fuse plug melt just by landing above the quick turnaround limit. However, if you're above the limit you run the risk of the brakes not cooling down enough during a maximum rate ("quick") turnaround and you'll have to wait extra time to get the brake temperature down to where you've got adequate capacity for the next taxi/takeoff. If you're below the limit then you have reasonable confidence that you're brakes will be ready to go when you are.
boeingfixer From Canada, joined Jul 2005, 519 posts, RR: 0 Reply 4, posted (1 year 3 months 1 week 1 day 8 hours ago) and read 3682 times:
Quoting HAWK21M (Reply 3): Apart from Hard braking,contributer is fast taxying too .....
I've actually found that fast taxiing with intermittent application of the brakes to control your speed results in cooler brakes when compared to slow taxiing when one requires almost constant use of the brakes to keep the speed down. This is based on my experience with the B752 and the B722.
As an example, we have 4 or 5 Captains that love to taxi the B752 ultra slow and on average their brakes are much hotter than most other Captains that use the faster taxi with less brake application method.
boeingfixer From Canada, joined Jul 2005, 519 posts, RR: 0 Reply 6, posted (1 year 3 months 3 days 14 hours ago) and read 3264 times:
Quoting HAWK21M (Reply 5): Fast taxying heat generated is by the tires & not the brakes........Although frequent brake application can raise the temperature too.....
Actually this has more to do with tire sidewall failure than it does with fuse plug integrity. There is no chart for calculating brake cooling times based on taxi speed alone. You would have to taxi quite a ways at high speed to get the brake temps to rise solely on sidewall flex heating without any brake application. I suspect you would get a sidewall failure before registering any temp rise in the heat pack.