737 Flight Crew Operations Manual
Flight Controls -
System Description
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9.20.18 D6-27370-866-EGP
Flaps and Slats
The flaps and slats are high lift devices that increase wing lift and decrease stall
speed during takeoff, low speed maneuvering and landing.
LE devices consist of four flaps and eight slats: two flaps inboard and four slats
outboard of each engine. Slats extend to form a sealed or slotted leading edge
depending on the TE flap setting. The TE devices consist of double slotted flaps
inboard and outboard of each engine.
YK981 - YQ456
TE flap positions 1–15 provide increased lift; positions 15–40 provide increased
lift and drag. Flaps 15, 30 and 40 are normal landing flap positions. Flaps 15 is
normally limited to airports where approach climb performance is a factor.
Runway length and conditions must be taken into account when selecting a
landing flap position.
To prevent excessive structural loads from increased Mach at higher altitude, flap
extension above 20,000 feet should not be attempted.
Flap and Slat Sequencing
LE devices and TE flaps are normally extended and retracted by hydraulic power
from system B. When the FLAP lever is in the UP detent, all flaps and LE devices
are commanded to the retracted or up position. Moving the FLAP lever aft allows
selection of flap detent positions 1, 2, 5, 10, 15, 25, 30, or 40. The LE devices
deployment is sequenced as a function of TE flaps deployment.
When the FLAP lever is moved from the UP position to the 1, 2, 5, 10, 15, or 25
position, the TE flaps extend to the commanded position and the LE:
• flaps extend to the full extended position and
• slats extend to the extend position.
When the FLAP lever is moved beyond the 25 position the TE flaps extend to the
commanded position and the LE:
• flaps remain at the full extended position and
• slats extend to the full extended position.
The LE devices sequence is reversed upon retraction.
Mechanical gates hinder inadvertent FLAP lever movement beyond flaps 1 for
one engine inoperative go–around and flaps 15 for normal go–around.
Indicator lights on the center instrument panel provide overall LE devices position
status. The LE DEVICES annunciator panel on the aft overhead panel indicates
the positions of the individual flaps and slats.
September 15, 2016
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