.
previous pitch mode disengages
Automatic Flight -System Description 737 Operations Manual
.
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:
.
pressing 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 both LOC and 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 and
LOC displays turn amber and flash
.
FLARE armed is annunciated
.
the 1 CH annunciation extinguishes
.
A/P go–around mode arms but is not annunciated.
Note: After localizer and glideslope capture during a dual autopilot approach,
CWS cannot be engaged by manually overriding pitch and roll. Manual
override of autopilots causes autopilot disengagement.
The A/Ps disengage and the F/D command bars retract to indicate an invalid ILS signal.
800 Feet Radio Altitude
The second A/P must be engaged in CMD by 800 feet RA to execute a dual channel A/P approach. Otherwise, CMD engagement of the second A/P is inhibited.
400 Feet Radio Altitude
The stabilizer is automatically trimmed an additional amount nose up. If the A/Ps subsequently disengage, forward control column force may be required to hold the desired pitch attitude.
If FLARE is not armed by approximately 350 feet RA, both A/Ps automatically disengage.
Flare
The A/P flare maneuver starts at approximately 50 feet RA and is completed at touchdown:
.
FLARE engaged is annunciated and F/D command bars retract
.
On airplanes with a –4 FCC installed, the stabilizer is automatically
trimmed an additional amount nose up at 50 feet RA
Copyright . The Boeing Company. See title page for details.
4.20.16 December 1, 2000
Automatic Flight -System Description 737 Operations Manual
.
The A/T begins retarding thrust at approximately 27 feet RA so as to
reach idle at touchdown. A/T FMA annunciates RETARD
.
The A/T automatically disengages approximately 2 seconds after
touchdown
.
The A/P must be manually disengaged after touchdown. Landing rollout
is executed manually after disengaging the A/P.
Automatic Flight Approach
The AFDS provides guidance for single A/P non–precision approaches. The VOR/LOC switch arms the AFDS for VOR or localizer tracking. Descent prior to the final approach fix may be accomplished using VNAV, LVL CHG, or V/S. V/S is the appropriate mode for descent on final approach. VOR/LOC, LNAV, or HDG SEL may be used for the roll mode.
The AFDS provides guidance for single A/P precision approaches. The approach mode arms the AFDS to capture and track the localizer and glide slope.
Approach (APP) Mode Single A/P
A single A/P ILS approach can be executed by engaging only one A/P in CMD. Single A/P approach operation is the same as dual, with the following exceptions:
.
Full automatic flare and touchdown capability are not available. FLARE
is not annunciated, and stabilizer trim bias is not applied
.
An A/P go–around is not available.
One VHF NAV receiver must be tuned to an ILS frequency before the approach mode can be selected.
Localizer and Glide Slope Armed
After setting the localizer frequency and course, pressing the APP switch selects the APP mode. The APP switch illuminates, and VOR/LOC and G/S annunciate armed. The APP mode permits selecting the second A/P to engage in CMD. This arms the second A/P for automatic engagement after LOC and G/S capture and when descent below 1500 RA occurs.
The localizer can be intercepted in the HDG SEL, CWS R or LNAV mode. On some airplanes, glide slope capture cannot occur prior to localizer capture.
Localizer Capture
The LOC capture point is variable and depends on intercept angle and rate of closure, but does not occur at less than 1/2 dot. Upon LOC capture, VOR/LOC annunciates captured, on some airplanes 1 CH is annunciated for A/P status, the previous roll mode disengages and the airplane turns to track the LOC.
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