Airbus Recommendations for a Proper Operation of Carbon Brakes

Customer Services

Airbus recommendations for a proper operation of carbon brakes

by Guy Di Santo

Airbus recommendations for a proper operation of carbon brakes2

Contents

Protection against high brake temperature and fire

Carbon brakes life Preferred carbon braking techniquesOptimizing brake temperature

Airbus recommendations

Conclusion




Regulation requirements

Flammable fluid protection:

“in each area where flammable fluids 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 relevant hazards if ignition does occur”



A BRAKE HOT warning renders the probability of a fire of hydraulic origin extremely remote when L/G is retracted

The indicated temperature (e.g. 300°C) corresponds to about 400°C in the hottest part of the brake400°C ensures an adequate margin with the auto ignition temperature of all hydraulic fluids allowed to be used

The main purpose of the BRAKE HOT warning is 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 fire prevention



Getting BRAKE HOT warning 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 the braking system when short turn around times are

required

Airbus design philosophy (cont’d)


Contents




Conclusion

Carbon brakes life


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 applicationsBrake temperature


Carbon brake life: Preferred Braking Techniques

Reducing the number of brake applicationsDo not ”ride” the brakes Single (two on A340) engine taxiAlternate left and right braking when taxiing slowlyUse of autobrake at landing

Optimizing brake temperatureOperate the brakes in temperature ranges where carbon wear is minimum


Messier-Bugatti

Carbon brake life: Optimizing Brake Temperature

100 200 300 400 500Disk temperature ° C

080

Indicated temperature ° C250 500

600

wear rate


Honeywell - ALS

180 405 630Disk temperature ° C

0150

Indicated temperature ° C315 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

Wear rate

80Indicated temperature ° C

250150 315 5000



00

Time (minutes)50 100 150 200 250 300 350 400

100

200

300

400

500

600

700

Tem

pera

ture

(°C

)

Taxi in

landingTaxi 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

GoodrichWear rate

Brake temperature management during taxi

Brake hot warning

Taxi inTaxi out

80Indicated temperature ° C

250150 315 5000




Brake manufacturers recommendations

Taxi in: keep the brakes hot

Taxi out:Messier-Bugatti: “below 80°C”Honeywell-ALS: “below 150°C”Goodrich: “warm or hot”ABS: “optimum indicated temperature is 150°C”

Brake Temperature Management during taxi

Brake temperature management is not easyUp to 150°C difference between brakes in normal operation

A good tool: the brake cooling fans


Hot brakes: setting the limits

Taxi out: Airbus does not promote any procedure that would intentionally increase brake temperature before takeoff

Ensure max energy is sustained at RTOEnsure Brake Hot warning will not appear just prior to takeoffIf 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 500°CBrake fans increase oxidation if brakes are not thermally stabilized



Contents




Conclusion



Airbus Recommendations

Autobrake at landing

Recommended when need of brake application is foreseen

On short or evenly contaminated runways: LO or MEDOn 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



Engine thrust reversers

For safety reasons, select full reverse thrust after main Landing Gear touches down

If restricted by airport regulations, select idle reverse



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

Before takeoff:If temperature >150°C (fans ON), delay takeoff (except ABS)Fans OFF when temperature <150°C

Taxi in:Normal operation:

• Fans selection delayed for 5 minutes or at the gateShort turnaround or temperature likely to exceed 500°C

• Select fans (forget oxidation)

Parking:Fans OFF if temperature < 100°C (no arc on ECAM)

Brake cooling fans (if installed)



Brake temperature > 300°C (150°C fans ON)Release parking brake at the gate after chocks are in place

Brake temperature > 500°C (350°C fans ON)Avoid parking brake application, unless operationally necessary

Parking brake

Prolonged parking brake application on hot brakes can be detrimental to brakes (dragging, oxidation, …)



Some cases have been reported where the parking brake 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


Contents




ConclusionConclusion


Conclusion

Braking system design philosophy is based on fire prevention

Airbus takes into account in-service experience and brake manufacturers’ data for providing best operating procedures

Brake manufacturers do not have all the same viewsSome recommendations for carbon brake saving should be customized

Airbus Recommendations for a Proper Operation of Carbon Brakes

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