.
MED (2 or 3, as installed): Should be used for wet or slippery runways or
when landing rollout distance is limited
.
MIN (1, as installed): These settings provide a moderate deceleration
suitable for all routine operations.
Experience with various runway conditions and the related airplane handling characteristics provide initial guidance for the level of deceleration to be selected.
Immediate initiation of reverse thrust at main gear touchdown and full reverse thrust allow the autobrake system to reduce brake pressure to the minimum level. Since the autobrake system senses deceleration and modulates brake pressure accordingly, the proper application of reverse thrust results in reduced braking for a large portion of the landing roll.
The importance of establishing the desired reverse thrust level as soon as possible after touchdown cannot be overemphasized. This minimizes brake temperatures and tire and brake wear and reduces stopping distance on very slippery runways.
The use of minimum reverse thrust as compared to maximum reverse thrust can double the brake energy requirements and result in brake temperatures much higher than normal.
After touchdown, crewmembers should be alert for autobrake disengagement annunciations. The PM should notify the PF anytime the autobrakes disengage.
If stopping distance is not assured with autobrakes engaged, the PF should immediately apply manual braking sufficient to assure deceleration to a safe taxi speed within the remaining runway.
737 Flight Crew Training Manual
A table in the PI section of the QRH shows the relative stopping capabilities of the available autobrake selections.
Transition to Manual Braking
The speed at which the transition from autobrakes to manual braking is made depends on airplane deceleration rate, runway conditions and stopping requirements. When transitioning to manual braking, keep the speedbrakes deployed and use reverse thrust as required until taxi speed. This is especially important when nearing the end of the runway where rubber deposits affect stopping ability.
When transitioning from the autobrake system to manual braking, the PF should notify the PM. Techniques for release of autobrakes can affect passenger comfort and stopping distance. These techniques are:
.
stow the speed brake handle. When stopping distance within the
remaining runway is assured, this method provides a smooth transition to
manual braking, is effective before or after thrust reversers are stowed,
and is less dependent on manual braking technique
.
smoothly apply brake pedal force as in a normal stop, until the autobrake
system disarms. Following disarming of the autobrakes, smoothly release
brake pedal pressure. Disarming the autobrakes before coming out of
reverse thrust provides a smooth transition to manual braking
.
manually position the autobrake selector off (normally done by the PM at
the direction of the PF).
Manual Braking
The following technique for manual braking provides optimum braking for all runway conditions:
The pilot’s seat and rudder pedals should be adjusted so that it is possible to apply maximum braking with full rudder deflection.
Immediately after main gear touchdown, smoothly apply a constant brake pedal pressure for the desired braking. For short or slippery runways, use full brake pedal pressure.
.
do not attempt to modulate, pump or improve the braking by any other
special techniques
.
do not release the brake pedal pressure until the airplane speed has been
reduced to a safe taxi speed
.
the antiskid system stops the airplane for all runway conditions in a
shorter distance than is possible with either antiskid off or brake pedal
modulation.
Copyright . The Boeing Company. See title page for details.
6.40 FCT 737 (TM) October 31, 2006
737 Flight Crew Training Manual
The antiskid system adapts pilot applied brake pressure to runway conditions by sensing an impending skid condition and adjusting the brake pressure to each individual wheel for maximum braking. When brakes are applied on a slippery runway, several skid cycles occur before the antiskid system establishes 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.
737-300 - 737-500 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.
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