A320 brake indication on T/O question

[185 585]

Hi,

please excuse a non-pilot chiming in here. This incident note on avherald.com caught my attention recently; apparently, an A320 rejected takeoff due to a locked-up brake and the subsequent indication.

I'd like to know unter which circumstances this indication will pop up. Maybe only at or above a certain speed? What I'd really like to know, is it possible to sense during taxi or at takeoff that one brake is somehow locked up?

Now why am I asking? Sorry to deviate, but two months ago I had tea and biscuits with my operations supervisor because I departed with two handbrakes applied on my freight train. No ECAM there that'll tell you about your mistake. I didn't notice them during the brake test or when starting the train, only some hundred metres after departure due to some unusual drag. That was expensive and unpleasant (and now the supervisor knows my name).

Thanks for your enlightenment.

[compressor stall]

300°C limit for take off (due to exceeding brake energy limits for the RTO).

ECAM warning is inhibited from 80kts to lift off and from touchdown to after shutdown.

[PPRuNeUser0184]

Slightly off topic but....

300°C limit for take off (due to exceeding brake energy limits for the RTO).

This is not correct.

From the A320 FCTM

"The FCOM limits brake temperature to 300deg C before takeoff is started.
This limit ensures that, in the case of hydraulic fluid leakage, any hydraulic fluid, that may come into contact with the brake units, will not be ignited in the wheelwell. This limit does NOT ensure that, in the case of a high energy rejected takeoff, the maximum energy limitation will be respected".

[*Lancer*]

Yep ECAM caution under 80kts, >300 deg.

Would be fairly unusual, as a dragging brake would be noticed taxiing out (asymmetry on taxi, and the brake temp page is automatically displayed). Possible though if the aircraft had the park brake set prior to take off, and the brake failed to release properly or something similar. A fully-locked brake would be immediately obvious, but one partially engaged would be less obvious.

There isn't a specific indication that a brake has failed to release, just an indication of the brake temp. No tea and biscuits.

[compressor stall]

Thanks KZ, brain energy limit was exceeded.

[185 585]

Thanks for all your answers :-) Nice to know that one's able to sense locked-up brakes in an aircraft as well.

May I ask another question, just for the sake of it? Let's take a stationary widebody aircraft at MTOW. Lock up the brakes and go to TOGA. Will it move?

Will a narrowbody aircraft move?

Will any aircraft move under these circumstances?

I'm thinking of cars right now and that Audi-Toyota-unintended-acceleration-debacle. In a car, your brakes will always overpower your engine. Is that also true in airplanes?

In trains? Well, if one in twenty brakes in a loaded twenty-car Jet A1 train (1850 long tons) sticks, you'll need something around 150 kilonewtons of force to get it going from a dead stop, instead of around 25 kilonewtons if everything's all right. Three stuck brakes out of twenty, and you sure won't go anywhere. In my business, brakes will definitely overpower your propulsion.

to repeat myself - thanks for your enlightenment!

[safelife]

Most aircraft will move with a single brake locked, however you will notice the asymmetry while starting the takeoff roll.
Some aircraft do move with ALL brakes applied on T/O power (Q400 i.e.).

[vilas]

185 585
You are not to open TOGA on brakes. Maximum thrust permitted on brakes is given in Flight Manual.

[J.L.Seagull]

Vilas,

You cannot, but engineers can, and do, for various tests! And yes, some types will move.

B777s need ballast, either in the form of fuel, or dead weight in the cargo.

A330/A340s don't, but I think you are allowed to take only one engine at a time to TOGA.

[Goldenrivett]

Let's take a stationary widebody aircraft at MTOW. Lock up the brakes and go to TOGA. Will it move?

From Airbus 340-600 Crash: A Study on HFACS - AviationKnowledge

"Preconditions for unsafe acts - Loss of situational awareness and complacency. The Airbus technician in charge of the engine run test was unaware that the aircraft was moving until the customer representative told him so. He testified to have often carried out this kind of test, but at a higher aircraft weight."
So I guess the tyre friction at MTOW is strong enough to prevent the aircraft from moving.

A330/A340s don't, but I think you are allowed to take only one engine at a time to TOGA.

" Violations - During the test for detecting oil leaks, the procedure to apply thrust on two engines only was not systematically carried out. All four engines were brought to full power, procedures required running up two engines – the one leaking and one on the other wing (to prevent torquing and yawing of the fuselage).The Aircraft Maintenance Manual (AMM) and the CAM (Customer Acceptance Manual) state that the engines tests must be carried out with the use of wheel chocks for the main landing gears."

http://www.flightglobal.com/blogs/ai...-600-incident/

[vilas]

J.L.Seagull
There you go. 340-600 moves a big way. It was 250 million down the drain.

[Metro man]

There is a limit to the temperature difference between brakes on the same side as this could indicate a locked brake or a U/S brake. Hottest brake temp gets an indication above it to draw attention to it.