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the right amount of brake pressure for the most effective braking.
If the pilot modulates the brake pedals, the antiskid system is forced to readjust the
brake pressure to establish optimum braking. During this readjustment time,
braking efficiency is lost.
Low available braking coefficient of friction on extremely slippery runways at
high speeds may be interpreted as a total antiskid failure. Pumping the brakes or
turning off the antiskid degrades braking effectiveness. Maintain steadily
increasing brake pressure, allowing the antiskid system to function at its optimum.
Although immediate braking is desired, manual braking techniques normally
involve a four to five second delay between main gear touchdown and brake pedal
application even when actual conditions reflect the need for a more rapid initiation
of braking. This delayed braking can result in the loss of 800 to 1,000 feet of
runway. Directional control requirements for crosswind conditions and low
visibility may further increase the delays. Distractions arising from a
malfunctioning reverser system can also result in delayed manual braking
application.
Braking with Antiskid Inoperative
When the antiskid system is inoperative, the following techniques apply:
• ensure that the nose wheel is on the ground and the speedbrakes extended
before applying the brakes
• initiate wheel braking using very light pedal pressure and increase
pressure as ground speed decreases
• apply steady pressure and DO NOT PUMP the pedals.
Antiskid-off braking requires even greater care during lightweight landings.
Carbon Brake Life
Brake wear is primarily dependent upon the number of brake applications. For
example, one firm brake application causes less wear than several light
applications. Continuous light applications of the brakes to keep the airplane from
accelerating over a long period of time (riding the brakes) to maintain a constant
taxi speed produces more wear than proper brake application.
During taxi, proper braking should involve applying brakes to decelerate the
airplane, releasing the brakes when the lower speed is attained and allowing the
airplane to accelerate, then repeating.
October 31, 2004
767 Flight Crew Training Manual
Landing
Copyright © The Boeing Company. See title page for details.
6.30 FCT 767 (TM)
During landing, one hard, high energy, long-duration brake application produces
the same amount of wear as a light, low-energy, short application. This is different
from steel brakes that wear as a function of the energy input during the stop.
Brake Cooling
A series of taxi-back or stop and go landings without additional in-flight brake
cooling can cause excessive brake temperatures. The energy absorbed by the
brakes from each landing is cumulative.
Extending the gear a few minutes early in the approach normally provides
sufficient cooling for a landing. Total in-flight cooling time can be determined
from the Performance Inflight section of the QRH.
The optional brake temperature monitoring system may be used for additional
flight crew guidance in assessing brake energy absorption. This system indicates
a stabilized value approximately fifteen minutes after brake energy absorption.
Therefore, an immediate or reliable indication of tire or hydraulic fluid fire, wheel
bearing problems, or wheel fracture is not available. The brake temperature
monitor readings may vary between brakes during normal braking operations.
Note: Brake energy data provided in the QRH should be used to identify potential
overheat situations.
To minimize brake temperature build-up:
• for airplanes without operative brake temperature monitoring systems:
If the last ground time plus present flight time is less than 90 minutes,
extend the landing gear 5 minutes early or 7 minutes prior to landing
• for airplanes with operating brake temperature monitoring systems:
Extend the landing gear approximately one minute early for each unit of
brake temperature above normal.
Close adherence to recommended landing roll procedures ensures minimum brake
temperature build up.
Reverse Thrust Operation
Awareness of the position of the forward and reverse thrust levers must be
maintained during the landing phase. Improper seat position as well as long
sleeved apparel may cause inadvertent advancement of the forward thrust levers,
preventing movement of the reverse thrust levers.
The position of the hand should be comfortable, permit easy access to the
autothrottle disconnect switch, and allow control of all thrust levers, forward and
reverse, through full range of motion.
Note: Reverse thrust always reduces the “brake only” stopping distance, brake
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767机组训练手册Flight Crew Training Manual (FCTM)767(97)
