Brakes Use

8/10/2019 Brakes Use

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Customer Services

Airbus recommendations for a proper

operation of carbon brakes

by Guy Di Santo


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Airbus recommendations for a proper operation of carbon brakes2

Contents

Protection against high brake temperature and fire

Carbon brakes life

Preferred carbon braking techniques

Optimizing brake temperature

Airbus recommendations

Conclusion



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Regulation requirements

Flammable fluid protection:

in each area where flammablefluids or vapours might escape by

leakage of a fluid system, there

must be means to minimize the

probability of ignition of the fluids

and vapours, and the relevanthazards if ignition does occur


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A BRAKE HOTwarning renders the probability of a fire of

hydraulic origin extremely remote when L/G is retracted

The indicated temperature (e.g. 300C) corresponds to about 400C

in the hottest part of the brake

400C ensures an adequate margin with the auto ignitiontemperature of all hydraulic fluids allowed to be used

The main purpose of the BRAKE HOTwarningis to prevent fire in the L/G bay in case of hydraulic

leakage when L/G is retracted

Airbus design philosophy

Fire protection is ensured by fireprevention


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Getting BRAKE HOTwarning after landing is not an abnormal

situation

The warning is prone to reappear during taxi out if brakes have

not been cooled down enough

Brake fans should be considered as part of thebraking system when short turn around times are

required

Airbus design philosophy (contd)


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Contents


Carbon brakes life




Conclusion

Carbon brakes life


7/24Airbus recommendations for a proper operation of carbon brakes7

Carbon brake life

Carbon brake wear is a very complex physical process

Tests and in-service experience identified two major

parameters affecting carbon brake life

Number of brake applications

Brake temperature



Carbon brake life: Preferred Braking Techniques

Reducing the number of brake applications Do not ride the brakes

Single (two on A340) engine taxi

Alternate left and right braking when taxiing slowly

Use of autobrake at landing


Operate the brakes in temperature ranges where

carbon wear is minimum



Messier-Bugatti

Carbon brake life: Optimizing Brake Temperature

100 200 300 400 500

Disk temperature C

0

80Indicated temperature C

250 500

600

wear

rate



Honeywell - ALS

180 405 630

Disk temperature C

0


315 480

wear

rate




Disk temperature (C)0 100 200 300 400 500

80 165 250 335 420 500

600

Indicated temperature (C)

Wear

rate

Goodrich




Messier - Bugatti

Honeywell-ALS

Goodrich

Wearrate


250150 315 5000




0

0

Time (minutes)

50 100 150 200 250 300 350 400

100

200

300

400

500

600

700

Temperature(C)

Taxi in

landing

Taxi out

parking

Indicated

temperature

Disk

temperature

1st flight 2nd flight 3rd flight


Brake temperature management during taxi

Taxi in

Taxi out



Messier - Bugatti

Honeywell-ALS

Goodrich

Wear

rate

Brake temperature management during taxi

Brake hot

warning

Taxi inTaxi out


250150 315 5000



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Brake manufacturers recommendations

Taxi in: keep the brakes hot

Taxi out:

Messier-Bugatti: below 80C Honeywell-ALS: below 150C

Goodrich: warm or hot

ABS: optimum indicated temperature is 150C

Brake Temperature Management during taxi

Brake temperature management is not easy Up to 150C difference between brakes in normal operation

A good tool: the brake cooling fans


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Hot brakes: setting the limits

Taxi out: Airbus does not promote any procedure that would

intentionally increase brake temperature before takeoff

Ensure max energyis sustained at RTO

Ensure Brake Hot warningwill not appear just prior to takeoff

If no brake fans, on short turnaround, taxi out with hot brakes is

acceptable (Brake Hot warning extinguished at the gate)

Landing/Taxi in: Thermal oxidation accelerated at high

temperature

Brakes should not be repeatedly operated above 500C

Brake fans increase oxidationif brakes are not thermally

stabilized



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Contents

Protection against high brake temperature and fire Carbon brakes life




Conclusion



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Airbus Recommendations

Autobrake at landing

Recommended when need of brake application is

foreseen

On short or evenly contaminated runways: LO or MED

On long and dry runways: LO

Reduces the number of brake applications to one

Increases brake temperature to adequate values for taxi in

Autobrake at takeoff

Use Max to improve safety


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Engine thrust reversers

For safety reasons, select full reverse thrust after main

Landing Gear touches down

If restricted by airport regulations, select idle reverse


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Taxi out: Fans ON when temperature >100C (arc on ECAM)

Before takeoff:

If temperature >150C (fans ON), delay takeoff (except ABS)

Fans OFF when temperature


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Brake temperature > 300C (150C fans ON)

Release parking brake at the gate after chocks are in place

Brake temperature > 500C (350C fans ON)

Avoid parking brake application, unless operationally

necessary

Parking brake

Prolonged parking brake application on hot brakes can bedetrimental to brakes (dragging, oxidation, )


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Some cases have been reported where the parkingbrake has been selected in flight.

Due to a probable freezing of the parking brake selector

valve, it could be released in descent only

Parking brake

Do not pull parking brake in flight...

this does not help slow down the aircraft


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Contents


Carbon brakes life




Conclusion Conclusion


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Conclusion

Braking system design philosophy is based on fireprevention

Airbus takes into account in-service experience and

brake manufacturers data for providing bestoperating procedures

Brake manufacturers do not have all the same views

Some recommendations for carbon brake saving

should be customized

Documents

Brakes Use