737 Flight Crew Operations Manual
Landing Gear Chapter 14
System Description Section 20
Boeing Proprietary. Copyright © Boeing. May be subject to export restrictions under EAR. See title page for details.
D6-27370-866-EGP 14.20.1
20 System DescriptionSystem DescriptionFile High light
Introduction
The airplane has two main landing gear and a single nose gear. Each main gear is
a conventional two–wheel landing gear unit. The nose gear is a conventional
steerable two–wheel unit.
Hydraulic power for retraction, extension, and nose wheel steering is normally
supplied by hydraulic system A. A manual landing gear extension system and an
alternate source of hydraulic power for nose wheel steering are also provided.
The normal brake system is powered by hydraulic system B. The alternate brake
system is powered by hydraulic system A. Antiskid protection is provided on both
brake systems, but the autobrake system is available only with the normal brake
system.
Landing Gear Operation
The landing gear are normally controlled by the LANDING GEAR lever. On the
ground, a landing gear lever lock, prevents the LANDING GEAR lever from
moving to the up position. An override trigger in the lever may be used to bypass
the landing gear lever lock. In flight, the air/ground system energizes a solenoid
which opens the lever lock.
Landing Gear Retraction
When the LANDING GEAR lever is moved to UP, the landing gear begins to
retract. During retraction, the brakes automatically stop rotation of the main gear
wheels. After retraction, the main gear are held in place by mechanical uplocks.
Rubber seals and oversized hubcaps complete the fairing of the outboard wheels.
The nose wheels retract forward into the wheel well and nose wheel rotation is
stopped by snubbers. The nose gear is held in place by an overcenter lock and
enclosed by doors which are mechanically linked to the gear.
Hydraulic pressure is removed from the landing gear system with the LANDING
GEAR lever in the OFF position.
If a main landing gear tire is damaged during takeoff, it is possible that braking of
the main gear wheels during retraction may be affected. A spinning tire with a
loose tread must be stopped prior to entering the wheel well or it can cause damage
to wheel well components. When a spinning tire with loose tread impacts a fitting
in the wheel well ring opening, that gear stops retracting and free falls back to the
down position. The affected gear cannot be retracted until the fitting is replaced.
September 28, 2006
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