B757-Taxing with Carbon brakes

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B757-Taxing_with_Carbon_brakes

 

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BOEING
Flight Operations REVIEW
A MESSAGE TO FLIGHT CREWS FROM THE BOEING COMMERCIAL AIRPLANE GROUP
727-09
737-10
747-09
757-08
767-08
August 1, 1990
TAXIING WITH CARBON BRAKES
Introduction
Carbon brakes are now standard equipment on the Boeing 747-400,
757, 767-200 (increased gross weight models), and the 767-300.
The use of these brakes provides a substantial reduction in
airplane operating empty weight, but in-service experience has
generally shown lower brake life than originally expected.
Analysis has revealed a difference between the wear
characteristics of carbon versus steel brakes. It is believed
that improvements in carbon brake life can be achieved through
better understanding of the operational factors affecting carbon
brake life.
Discussion
The majority of airplanes currently in service are fitted with
steel brakes. Most pilots are familiar with the fact that steel
brake life is primarily dependent upon the severity of brake
application during the landing rollout. For steel brakes, heavy
braking and/or high speed braking will normally result in greater
brake wear than light and/or low speed braking. Carbon brakes do
not exhibit the same wear characteristics in this regard. For
carbon brakes, the number of brake applications largely
determines brake life.
Dynamometer tests have confirmed that the severity of brake
application has less of an effect on the life of carbon brakes
than the cumulative number of brake applications. It is therefore
not surprising that the majority of carbon brake wear occurs
during taxi to and from the ramp where frequent brake
applications are typically required. For carbon brake equipped
aircraft, it becomes more critical to observe recommended taxi
braking techniques to extend brake life.
From the pilots perspective, there should be no difference in
braking techniques during taxi for carbon or steel brake equipped
airplanes. The techniques noted in all current Boeing Flight Crew
Training Manuals should be followed. From the standpoint of brake
wear however, it is more critical that these techniques be
observed on carbon brake equipped airplanes.
The Boeing recommended taxi braking technique is as follows
(quoting from page 1-13 of the 767 Flight Crew Training Manual):
“Avoid “riding” the brakes to control taxi speed as brake
heat build-up could become excessive. If taxi speed is too
high, reduce speed with a steady brake application and then
release the brakes to allow them to cool. Continuous braking
should be avoided. Allow for decreased braking effectiveness
on slick surfaces.”
Recommendations
While all brake wear is dependent on frequency of brake
applications, carbon brake wear is more sensitive to frequency of
brake applications than steel brakes. The following
recommendations should help improve brake life and are applicable
to both steel brakes and carbon brakes:
1. Anticipate traffic conditions to minimize taxi braking
requirements.
2. Avoid the use of excessive thrust during taxi accelerations
and/or during sustained taxi runs.
3. Anticipate engine spool-up and spool-down characteristics
to avoid overshooting the desired taxi speed.
4. Minimize brake applications by planning ahead, not by
"riding" the brakes during taxi.
These above recommendations are intended as general taxi
guidelines only: SAFETY AND PASSENGER COMFORT SHOULD REMAIN THE
PRIMARY CONSIDERATION.
BOEING PUSLISHES THE "FLIGHT OPERATIONS REVIEW' FOR OPERATORS AND THE R FLIGHT CREWS IN
ORDER TO PROVIDE ADVISORY INFORTAATIOIY RELATED TO FLIGHT OPERATIONS. ALL INFORMATION IN
THE "FLIGHT OPERATIONS REVIEW' IS CONSIDERED ACCURATE. HOWEVER. IT IS NOT INTENDED TO
REPLACE OR SUPERCEDE INFORTAATION CONTAINED IN APPROVED OPERATING OOCUTAENTATION.

979199501

CFM56-7 Starter Reliability

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tonyblairer

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332356357

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