737 Flight Crew Operations Manual
Automatic Flight -
System Description
Boeing Proprietary. Copyright © Boeing. May be subject to export restrictions under EAR. See title page for details.
D6-27370-866-EGP 4.20.15
YK981 - YQ456
Glideslope (G/S) capture is inhibited prior to localizer capture.
Localizer Capture
The LOC capture point is variable and depends on intercept angle and rate of
closure. Capture occurs no later than 1/2 dot. Upon LOC capture, VOR/LOC
annunciates captured, SINGLE CH is annunciated for A/P status, the previous roll
mode disengages and the airplane turns to track the LOC.
Glideslope Capture
YK981 - YQ456
Glideslope capture is inhibited prior to localizer capture.
The G/S can be captured from above or below. Capture occurs at 2/5 dot and
results in the following:
• G/S annunciates captured
• previous pitch mode disengages
• APP light extinguishes if localizer has also been captured
• airplane pitch tracks the G/S
• GA displayed on thrust mode display (N1 thrust limit).
After VOR/LOC and G/S are both captured, the APP mode can be exited by:
• pushing a TO/GA switch
• disengaging A/P and turning off both F/D switches
• retuning a VHF NAV receiver.
After LOC and G/S Capture
Shortly after capturing LOC or G/S and below 1500 feet RA:
• the second A/P couples with the flight controls
• test of the ILS deviation monitor system is performed and the G/S or
LOC display turns amber and flashes
• FLARE armed is annunciated
• the SINGLE CH annunciation extinguishes
• A/P go–around mode arms but is not annunciated.
Note: During a dual autopilot approach and after FLARE ARM annunciation,
any attempted manual override of the autopilots may result in an autopilot
disconnect.
The A/Ps disengage and the F/D command bars retract to indicate an invalid ILS
signal.
September 15, 2016
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