Airbus recommendations for a proper operation of carbon brakes
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Airbus recommendations for a proper operation of carbon brakes. by Guy Di Santo. 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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Airbus recommendations for a proper operation of carbon brakes

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Airbus recommendations for a proper operation of carbon brakes

Airbus recommendations for a proper operation of carbon brakes

by Guy Di Santo


Contents

Contents

  • Protection against high brake temperature and fire

  • Carbon brakes life

    • Preferred carbon braking techniques

    • Optimizing brake temperature

  • Airbus recommendations

  • Conclusion

  • Protection against high brake temperature and fire


Protection against high brake temperature and fire

Protection against high brake temperature and fire

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”


Protection against high brake temperature and fire1

Protection against high brake temperature and fire

Airbus design philosophy

  • 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 brake

    • 400°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

 Fire protection is ensured by fire prevention


Protection against high brake temperature and fire2

Protection against high brake temperature and fire

Airbus design philosophy (cont’d)

  • 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


Contents1

Contents

  • Protection against high brake temperature and fire

  • Carbon brakes life

    • Preferred carbon braking techniques

    • Optimizing brake temperature

  • Airbus recommendations

  • Conclusion

  • Carbon brakes life


Carbon brake 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 applications

    • Brake temperature


Carbon brake life preferred braking techniques

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

  • Optimizing brake temperature

    • Operate the brakes in temperature ranges where carbon wear is minimum


Carbon brake life optimizing brake temperature

Carbon brake life: Optimizing Brake Temperature

wear rate

Indicated temperatureC

80

500

250

0

100

200

300

400

500

600

Disk temperatureC

Messier-Bugatti


Carbon brake life optimizing brake temperature1

Carbon brake life: Optimizing Brake Temperature

wear rate

Indicated temperatureC

150

480

315

0

180

405

630

Disk temperatureC

Honeywell - ALS


Carbon brake life optimizing brake temperature2

Carbon brake life: Optimizing Brake Temperature

Wear rate

Indicated temperature (°C)

80

165

250

335

420

500

0

100

200

300

400

500

600

Disk temperature (°C)

Goodrich


Carbon brake life optimizing brake temperature3

Carbon brake life: Optimizing Brake Temperature

Messier - Bugatti

Honeywell-ALS

Goodrich

Wear rate

80

150

250

315

500

0

Indicated temperatureC


Carbon brake life optimizing brake temperature4

Carbon brake life: Optimizing Brake Temperature

700

Taxi in

600

Temperature (°C)

Disk temperature

500

landing

Indicated temperature

Taxi out

400

300

200

parking

100

1st flight

2nd flight

3rd flight

0

50

100

150

200

250

300

350

400

0

Time (minutes)

Brake temperature management during taxi

Taxi in

Taxi out


Carbon brake life optimizing brake temperature5

Carbon brake life: Optimizing Brake Temperature

Messier - Bugatti

Honeywell-ALS

Goodrich

Wear rate

80

150

250

315

500

0

Indicated temperatureC

Brake temperature management during taxi

Taxi out

Taxi in

Brake hot warning


Carbon brake life optimizing brake temperature6

Carbon brake life: Optimizing Brake Temperature

Brake Temperature Management during taxi

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 is not easy

    • Up to 150°C difference between brakes in normal operation

  • A good tool: the brake cooling fans


Carbon brake life optimizing brake temperature7

Carbon brake life: Optimizing Brake Temperature

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 RTO

    • Ensure Brake Hot warning will 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 500°C

    • Brake fans increase oxidation if brakes are not thermally stabilized


Contents2

Contents

  • Protection against high brake temperature and fire

  • Carbon brakes life

    • Preferred carbon braking techniques

    • Optimizing brake temperature

  • Airbus recommendations

  • Conclusion

  • Airbus recommendations


Airbus recommendations

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


Airbus recommendations1

Airbus Recommendations

Engine thrust reversers

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

    • If restricted by airport regulations, select idle reverse


Airbus recommendations2

Airbus Recommendations

Brake cooling fans (if installed)

  • 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 gate

    • Short turnaround or temperature likely to exceed 500°C

      • Select fans (forget oxidation)

  • Parking:

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


Airbus recommendations3

Airbus Recommendations

Parking brake

  • 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

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


Airbus recommendations4

Airbus Recommendations

Parking brake

  • 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

  • Do not pull parking brake in flight...

…this does not help slow down the aircraft


Contents3

Contents

  • Protection against high brake temperature and fire

  • Carbon brakes life

    • Preferred carbon braking techniques

    • Optimizing brake temperature

  • Airbus recommendations

  • Conclusion

  • Conclusion


Conclusion

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 views

    • Some recommendations for carbon brake saving should be customized


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