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

  2. 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

  3. 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”

  4. 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

  5. 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

  6. Contents • Protection against high brake temperature and fire • Carbon brakes life • Preferred carbon braking techniques • Optimizing brake temperature • Airbus recommendations • Conclusion • Carbon brakes life

  7. 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

  8. 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

  9. 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

  10. Carbon brake life: Optimizing Brake Temperature wear rate Indicated temperatureC 150 480 315 0 180 405 630 Disk temperatureC Honeywell - ALS

  11. 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

  12. Carbon brake life: Optimizing Brake Temperature Messier - Bugatti Honeywell-ALS Goodrich Wear rate 80 150 250 315 500 0 Indicated temperatureC

  13. 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

  14. 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

  15. 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

  16. 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

  17. Contents • Protection against high brake temperature and fire • Carbon brakes life • Preferred carbon braking techniques • Optimizing brake temperature • Airbus recommendations • Conclusion • Airbus recommendations

  18. 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

  19. 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

  20. 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)

  21. 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, …)

  22. 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

  23. Contents • Protection against high brake temperature and fire • Carbon brakes life • Preferred carbon braking techniques • Optimizing brake temperature • Airbus recommendations • Conclusion • Conclusion

  24. 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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