QRH-brake cooling chart B737-300/400

[stator vane]

Performance Infight-Advisory Information.

737-300 CFM56-3_20K

Brake Cooling Schedule (not pronounced-schwejdule)

for example:

weight 65K brakes on speed 120kts TAT 20C
pressure altitude 0=25.9
2=24.8
4=23.6
whereas
weight 60K brakes on speed 120kts TAT 20C
pressure altitude 0=24.3
2=26.3
4=28.3

i suspect a misprint of some sort, but the charts for the 300-22K, 400-22K, 23.5K have similar abberrations in the 65K 120kts brakes on speed section.

am i missing something obvious?

and no, i didn't find this myself whilst perusing the QRH on my off days!

thanks in advance;

stator vane

[stator vane]

i'll reply to my own message.

any one out there have an idea about this?

this was a serious question.

the bit about schedule was just a harmless recognition that many on here are from the UK and AU.

any ideas would be greatly appreciated.

[mutt]

Stator_Vane,

This is interesting, we don’t operate those models of B737, but I have checked the Brake Cooling chart for the following aircraft, B737-200/B747-400/B777-200.

In these the brake cooling time appears to follow these rules.

Decreasing weight = shorter cooling time.
Increasing Brake On Speed = longer cooling time
Increasing Pressure Altitude = longer cooling time
Increasing OAT = longer cooling time

I have no idea why your charts are different, but it would be worth a quick message to Boeings FLOE department.

Mutt.

[CaptainSandL]

Stator Vane,

The Brake Cooling Schedule is one of the few remaining graphs in our pilot’s performance manual. The JAA are trying to get all pilot data into tables instead of graphs to reduce the scope for errors or “fudging”. If you have ever tried to use this graph in a dark simulator (or worse for real) then you will know how easily misread it is. The joke here is that by the time you have both gone through the graph and agreed between you on a correct answer, then enough time will have elapsed to safely attempt another take-off!

Anyway, the advantage of having a graph is that you can see at a glance which way the corrections work. For all of our 737-3/4/500’s with various combinations of 18.5, 20, 22 and 23.5K engines, the corrections all work in the sense that you would expect, ie the way that Mutt described. I suspect that if you are using tables then the error is in the way that they were constructed because there are no such aberrations in the original Boeing graphs.

I have uploaded a copy of the graph for the 737-300 20K to:
www.b737.org.uk/perf_brakecooling.gif

for your info.

Regards

S & L

[mutt]

CaptainSandl

Thanks for the reference to the B737.org.uk site, it’s extremely interesting.

Mutt

[dolly737]

@stator vane:

It IS a misprint!! (confirmed by Boeing).

[stator vane]

thanks to all.

i put thread on before my days off and received no emails to notify me of any responses.

will be back with another before long.

stator