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PSX - Brake Temperature

Started by 1stOfficer, Mon, 11 Aug 2014 09:56

1stOfficer

Hi guys,

as a new member and owner of this artwork of Simulation, first I wanted to say, that I'm very impressed of this.

This Simulation gives a feeling like sitting in a professional full flight simulator of professional airlines or even in the real plane.

My first question is technically applied - I've made some experiments for causing different damages, like overheating the wheels or the wheel-brakes.

I started the departure with the full loaded 747 and aborted the start with 180 knots.
So I've fully depressed the brake pedals, without reverser and speedbrakes to stop the plane.
After that I've taken a look on the "wheels"-EICAS page and realized that the brake-temperature is still at '0'.

After making several starts and braking the plane with maximal wheel-brakes, the brake-temperature rises very slightly.

Is this behavior correct and similarly to the real plane?

Best Regards,

Michael
Best Regards,

Michael

Hardy Heinlin

#1
Hi Michael,

thanks!

You need to wait 10 to 20 minutes or so until the heat reaches the sensor system. That's normal.

You can use the Time Acceleration to demo it.


Cheers,

|-|ardy

1stOfficer

Thank you very much  :) !
Best Regards,

Michael

David Palmer

Quote from: 1stOfficerI started the departure with the full loaded 747 and aborted the start with 180 knots.
How did you keep it on the ground?
A fully loaded 747-8 on its maximum brake energy test reached 173kts before rejecting the run with later brake temps reaching 1,400 degs Celsius.
Regards,
David.
a.k.a. 'The Commodore'

luxair_ca

hi...i just wanted to ask the same question...

but i do have another question then...

if the brake temperature goes up to much on lets say taxi-out for takeoff, and you put the gear up after liftoff, how should the Pilot now, that he has overheated Brakes if the sensor only reacts after 10 minutes or so... (could be that one brake locks up during taxi and takeoff) so he has a probable fire before the break heat sensor reacts?

many thanks

Marc

Lasse

#5
Hi,

The Brake topic is very complex.
The delay between peak temperature in the brake rotor, on the BTMS and the fuse plug is offset due to certification requirements.
Its not an safe and acceptable design if the tires blow right away and catches fire... Therefore the wheels are designed this way to fulfill the requirements of FAR 25 and the associated AMC's.
So when doing a RTO, coming to a complete stop. Do not set the parking brake, unless evacuation has to be done. Then consult the Recommended Brake Cooling Schedule. As seen in the notes it takes 10-15 min before BTMS is providing reliable data do to wheel design and heat transfer.
Same for landing, after landing look at the BTMS or then consult the QRH for cooling. Remember the MQTLW limitation as well..
For the taxi out and airborne problem. Well the MQTLW should protect you against leaving the gate and taxi out with a potential fuse plug melt down. However there are no direct informations about having enough energy left in the brakes for a new RTO after a short turnaround. Even if recommended cooling schedule has been kept!
If brakes become so hot that you will get hot brakes in the air then its not something that is coming sneaking as such. (In the real word that is. ) However if you will get too hot brakes then just perform the associated non-normal checklist. As seen cooling in air gear down is about 10 times better than on the ground. Some short haul operators even delay and extend gear to cool them down when having short turn arounds combined with short sectors and many of them...
/Lasse

Martin Baker

Quote from: Hardy HeinlinYou need to wait 10 to 20 minutes or so until the heat reaches the sensor system. That's normal.

You can use the Time Acceleration to demo it.


Cheers,

|-|ardy

Hi - I loaded the default Sydney-LAX situ, aborted the take-off at V1, let the plane stop using max autobrakes then watched the brake temp display. After many minutes it increased to 1, then 2, then decreased again to 1. Wouldn't one expect the brakes in this situation to reach a much higher temperature?

Hardy Heinlin

No, just add a few more brake actions during taxi or after landing, then it will rise into the amber range.


Cheers,

|-|ardy

Sylle

Hi Hardy,

Could you further expand on the reason why a few brake applications in taxi would make the brake temp rise into the amber range according to you? I fail to see the logic behind that...

Brake wear is in relation to the number of brake applications (for carbon brakes).
Brake temp is in relation to the amount of energy that has been absorbed by the brakes.

Did the test decried two posts above myself, using only idle reverse and RTO autobrakes at V1 until full stop. Brake temp did not exceed 1 unit and all temps were back to 0 after 15min. That can't be correct...
A rejected takeoff in the Sydney-LAX situ at V1 should result in high temp values on the BTMS when taking into consideration how much kinetic energy has been absorbed by the brakes via friction.

Regards,
Sylvain

Hardy Heinlin

#9
Hi Sylvain,

in the past years I read various opinions about how the brake temp behaviour is supposed to be. I don't claim that the current model is the only correct one. It is just a compromise of multiple opinions. I may modify it if enough experts ask for it.

Usually, when users ask, the first unknown fact is the delay of the temp distribution to the sensors. So pointing at this effect often solves the initial questions :-)

As for the plain physical plausibility: -- (By the way, I heard of incidents where a wheel well fire occured after takeoff because the crew used continuous braking during taxi; there was no RTO before.) -- Power involves energy and time. You can put a paper on fire by holding a cigarette lighter on it for a second, or by rotating a wooden stick on a wooden plank for 5 minutes.

The function is exponentional. Some knots more or less cause a huge temp difference at the end of the RTO. So any modifications in the model must be done very carefully. Instead of an RTO, try some landings with max autobrake: make test landings at 140 kt, 170 kt, 200 kt (very heavy emergency landing). At full stop, slide the time acceleration to x64.

Also note: ground speed, not airspeed. 30 kt headwind makes a difference.


Cheers,

|-|ardy


E.g. use ...

03 Approach 017 - Thessaloniki - Moderate turbulence.situ

Set wind calm, set flaps 20, 197 KIAS. I get an amber 5. Maybe it should be 9?