Boeing 737 - 600/700/800/900. Operations Manual (1997 year)

Automatic Flight -

Controls and Indicators

Boeing 737 Operations Manual

Rotate Captain’s course selector - provides selected course information to:

• A FCC

• No. 1 VHF NAV receiver

• Captain’s course pointer and course deviation bar.

Note: In VOR LOC or APP mode, the A A/P and Captain’s F/D use selected

course and navigation data from the No. 1 VHF NAV receiver.

Rotate First Officer’s course selector - provides selected course information to:

• B FCC

• No. 2 VHF NAV receiver

• First Officer’s course pointer and course deviation bar.

Note: In VOR LOC or APP mode, B A/P and First Officer’s F/D use selected

course and navigation data from No. 2 VHF NAV receiver.

Bank Angle Selector

Rotate -

• sets maximum bank angle for AFDS operation in HDG SEL or VOR

modes

• commanded bank angle can be selected at 10, 15, 20, 25, or 30 degrees.

Heading Select (HDG SEL) Switch

Push -

• engages HDG SEL command mode

• commands roll to follow selected heading

• annunciates HDG SEL as FMA roll mode and illuminates HDG SEL

switch light.

Heading Select Command Mode

The HDG SEL mode commands roll to turn to and maintain heading shown in

MCP HEADING display:

• initial selection commands turn in shortest direction toward selected

heading bug

• after mode engagement, roll commands are given to turn in same

direction as rotation of heading selector

• bank angle limit is established by bank angle selector

• HDG SEL mode automatically disengages upon capture of selected radio

course in VOR LOC and APP modes (VOR/LOC armed).

4.10.14

Automatic Flight -

Controls and Indicators

Boeing 737 Operations Manual

Approach (APP) Switch

Push -

• illuminates APP switch light

• arms the AFDS for localizer and glideslope capture

• roll mode annunciates VOR/LOC armed

• pitch mode annunciates G/S armed

• enables engagement of both autopilots.

APP Mode

The approach mode arms AFDS to capture and track localizer and glideslope and

can be engaged for dual or single autopilot operation.

One VHF NAV receiver must be tuned to an ILS frequency before approach mode

can be engaged. With one VHF NAV receiver tuned, onside AFDS is enabled for

guidance and operation.

For dual autopilot operation, both VHF NAV receivers must be tuned to the ILS

frequency and both autopilots must be selected in CMD prior to 800 feet RA.

APP mode operation:

[Option - G/S capture inhibited before LOC capture]

• localizer must be captured prior to glideslope

• localizer can be intercepted in HDG SEL, LNAV, or CWS R

[Option - EFIS/MAP]

•

1 CH annunciates in A/P Status Display after localizer capture

• for single autopilot approach, 1 CH remains annunciated for entire

approach

• for dual autopilot approach, 1 CH annunciation extinguishes when

second autopilot engages and FLARE armed is annunciated

[Option - PFD/ND]

• SINGLE CH annunciates in A/P Status Display after localizer capture

• for single autopilot approach, SINGLE CH remains annunciated for

entire approach

• for dual autopilot approach, SINGLE CH annunciation extinguishes

when second autopilot engages and FLARE armed is annunciated

• glideslope capture occurs at 2/5 dot below glideslope

• APP switch light extinguishes after localizer and glideslope capture.

After localizer and glideslope capture, APP mode can be disengaged by:

• pushing a TO/GA switch

• disengaging autopilot(s) and turning off both F/D switches

• retuning the VHF NAV receiver.

4.10.15

Automatic Flight -

Controls and Indicators

Boeing 737 Operations Manual

While engaged in the APP mode:

• the A autopilot and Captain’s F/D use information from Captain’s Course

Selector and No. 1 VHF NAV receiver

• the B autopilot and First Officer’s F/D use information from First

Officer’s Course Selector and No. 2 VHF NAV receiver

• different courses and/or frequencies for the two VHF NAV receivers can

cause disagreement between Captain’s and First Officer’s F/D displays

and affect A/P operation.

[Option - CWS deactivated on approach]

Note: After localizer and glideslope capture, CWS cannot be engaged by

manually overriding pitch and roll. Manual override of autopilots causes

autopilot disengagement.

Autopilot / Flight Director

Pushing a CMD or CWS switch engages related A/P in CMD or CWS and

illuminates switch lights. A/P can operate in CMD, CWS, or a combination of

CMD and CWS.

A/P ENGAGE

COURSE

CMD A

CMD B

CWS A

CWS B

DISENGAGE

F/D

OFF

GLARESHIELD

Command Engage (CMD ENGAGE) Switch (A or B):

Push -

• engages A/P

• enables all command modes

• displays CMD in A/P status display

• pushing an engage switch for second A/P, while not in approach mode,

engages second A/P and disengages first A/P

• enables CWS operation

• CWS engages if:

• pitch or roll mode not selected

• pitch or roll mode deselected

• pitch or roll mode manually overridden with control column force.

4.10.16

Automatic Flight -

Controls and Indicators

Boeing 737 Operations Manual

[Option - CWS deactivated on approach]

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.

• CWS engaged displays:

• CWS P and/or CWS R in A/P status display

• blank in pitch and/or roll mode FMA

• when approaching a selected altitude in CWS P, the pitch mode engages

in ALT ACQ and ALT HOLD when reaching selected altitude

• when approaching a selected radio course in CWS R with VOR/LOC or

approach mode armed, VOR/LOC engages when course is intercepted

• if pitch is manually overridden while in ALT HOLD and control force is

released within 250 feet of selected altitude, A/P pitch mode engages in

ALT ACQ and returns to selected altitude in ALT HOLD mode.

Note: During F/D only operation while pitch or roll commands are more than 1/2

scale from center, pushing a CMD A or B switch engages the A/P in CWS

for pitch and/or roll and the related F/D bar(s) retract.

Control Wheel Steering Engage (CWS ENGAGE) Switch (A or B):

Push -

• engages A/P

• engages pitch and roll modes in CWS. Other pitch and roll modes not

enabled

• displays CWS P and CWS R in A/P status display

• CMD not displayed in A/P status display

• F/Ds, if ON, display guidance commands and FD annunciates in A/P

status display. A/P does not follow commands while in CWS

• A/P pitch and roll controlled by pilot with control wheel pressure

• when control pressure released, A/P holds existing attitude. If aileron

pressure released with 6 degrees or less bank, the A/P rolls wings level

and holds existing heading. Heading hold feature inhibited:

• below 1500 feet RA with gear down

• after LOC capture in APP mode

• after VOR capture with TAS 250 knots or less.

Autopilot Disengage (DISENGAGE) Bar

Pull down -

• exposes yellow background

• disengages both A/Ps

• prevents A/P engagement.

4.10.17

Automatic Flight -

Controls and Indicators

Boeing 737 Operations Manual

Lift up -

• conceals yellow background

• enables A/P engagement.

Master (MA) Flight Director Indicators (white letters)

If a F/D switch is ON, the light indicates which FCC is controlling the F/D modes.

• illuminated - related FCC is controlling F/D modes.

• extinguished - F/D modes are controlled from opposite FCC

• both lights illuminated - each FCC is controlling modes for related F/D.

Flight Director (F/D) Switch

Left F/D switch activates command bars on the Captain’s attitude indicator. Right

F/D switch activates command bars on the First Officer’s attitude indicator.

Left F/D switch activates the command bar on the Captain’s attitude indicator.

Right F/D switch activates the command bar on the First Officer’s attitude

indicator.

ON -

• in flight with A/P ON and F/Ds OFF, turning a F/D switch ON engages

F/D in currently selected A/P modes

• displays FD in A/P status display if A/P is OFF or engaged in CWS

• enables command bar display on related pilot’s attitude indicator

• command bars are displayed if command pitch and/or roll modes are

engaged

• command bars are displayed if command pitch and roll modes are

engaged

• on ground, arms pitch and roll modes for engagement in TO/GA and

wings level when TOGA switch is pushed.

• on ground, arms pitch and roll modes for engagement in TO/GA and

HDG SEL when TOGA switch is pushed.

OFF - command bars retract from related pilot’s attitude indicator.

OFF - command bar retracts from related pilot’s attitude indicator.

4.10.18

Automatic Flight -

Controls and Indicators

Boeing 737 Operations Manual

Autopilot / Autothrottle Controls

CONTROL STAND

CONTROL WHEELS

Autopilot Disengage Switch

Push -

• disengages both autopilots

• A/P disengage lights flash

• A/P disengage warning tone sounds for a minimum of two seconds

• second push extinguishes disengage lights and silences disengage

warning tone

• if autopilot automatically disengages, extinguishes A/P Disengage lights

and silences A/P warning tone.

Autothrottle Disengage Switches

Push -

• disengages autothrottle

• A/T disengage lights flash

• A/T ARM switch trips OFF

• second press extinguishes A/T disengage lights

• extinguishes A/T disengage lights after automatic A/T disengagement.

Takeoff/Go-Around (TO/GA) Switches

Push - engages AFDS and A/T in takeoff or go-around mode if previously armed.

4.10.19

Automatic Flight -

Controls and Indicators

Boeing 737 Operations Manual

Autopilot / Autothrottle Indicators

A/P

A/T

FMC

P/RST

TEST

LEFT FORWARD PANEL

RIGHT FORWARD PANEL

STAB

OUT OF

TRIM

LEFT FORWARD PANEL

Autopilot (A/P) Disengage Light

Illuminated (red) -

• flashes and tone sounds when autopilot has disengaged

• reset by pushing either disengage light or either A/P disengage switch

• steady for any of following conditions:

• stabilizer out of trim below 800 feet RA on dual channel approach

• ALT ACQ mode inhibited during A/P go-around if stabilizer not

trimmed for single A/P operation

• disengage light test switch held in position 2

• automatic ground system tests fail.

Illuminated (amber) -

• steady - disengage light test switch held in position 1.

[Option - CWS warning activated]

• flashing - A/P automatically reverts to CWS pitch or roll while in CMD.

Resets by pushing either light or selecting another mode.

Autothrottle (A/T) Disengage Light

Illuminated (red) -

• flashing - autothrottle has disengaged

• steady - disengage light test switch held in position 2.

4.10.20

Automatic Flight -

Controls and Indicators

Boeing 737 Operations Manual

Illuminated (amber) -

• steady - disengage light test switch held in position 1

[Option - Airspeed deviation warning activated]

• flashing - indicates A/T airspeed error under following conditions:

• inflight

• flaps not up

• airspeed differs from commanded value by +10 or -5 knots and is not

approaching commanded value.

Disengage Light Test (TEST) Switch

TEST 1 - illuminates autopilot/autothrottle disengage and FMC alert lights steady

amber.

TEST 2 - illuminates autopilot/autothrottle disengage lights steady red and FMC

alert light steady amber.

Spring-loaded to center position.

Stabilizer Out Of Trim (STAB OUT OF TRIM) Light

Operates only with autopilot engaged. Remains extinguished with autopilot not

engaged.

Illuminated (amber) - autopilot not trimming stabilizer properly.

Autoland Warning

[Option]

AUTOLAND

LEFT FORWARD PANEL

RIGHT FORWARD PANEL

AUTOLAND Warning Light

Armed during dual ILS A/P approach below 500 feet

Flashes (red) if:

• A/P disengages

• stabilizer trim warning occurs

• ILS deviation occurs below 200 feet.

4.10.21

Automatic Flight -

Controls and Indicators

Boeing 737 Operations Manual

Thrust Mode Display

[Option - Side by side display]

A/T LIM

CRZ

TAT-

96.0

TAI

87.7

UPPER DISPLAY UNIT

[Option - Over/Under display]

TAT-

CRZ

96.0

TAI

87.7

UPPER DISPLAY UNIT

[Option - Over/Under display]

TAT-

A/T LIM

96.0

TAI

87.7

UPPER DISPLAY UNIT

Thrust Mode Display

N1 limit reference is the active N1 limit for autothrottle and manual thrust control.

N1 limit reference is also displayed by N1 reference bugs with N1 SET control in

AUTO position.

N1 limit reference is normally calculated by the FMC.

Thrust mode display annunciations are:

• TO - takeoff

• R-TO - reduced takeoff

4.10.22

Automatic Flight -

Controls and Indicators

Boeing 737 Operations Manual

• R-CLB - reduced climb

[Option]

• TO B - takeoff bump thrust

• CLB - climb

• CRZ - cruise

• G/A - go-around

• CON - continuous

•

--- - FMC not computing thrust limit.

Note: R-TO does not indicate the type of reduced takeoff. The N1 limit may be

reduced due to the entry of an assumed temperature, a takeoff thrust derate

or a combination of both assumed temperature and takeoff thrust derate.

Autothrottle Limit (A/T LIM) Indication

Illuminated (white) - the FMC is not providing the A/T system with N1 limit

values. The A/T is using a degraded N1 thrust limit from the related EEC.

4.10.23

Automatic Flight -

Controls and Indicators

Boeing 737 Operations Manual

Flight Mode Annunciations (FMAs)

[Option - EFIS/MAP]

A/T ENGAGED MODE

PITCH ENGAGED MODE ROLL ENGAGED MODE

(G)

TO/GA

(G)

HDG SEL (G)

(G)

V/S

(G)

VOR/LOC (G)

RETARD

(G)

ALT ACQ

(G)

LNAV

(G)

FMC SPD (G)

ALT HOLD (G)

MCP SPD (G)

VNAV SPD (G)

THR HLD (G)

VNAV PTH (G)

ARM

(W)

MCP SPD

(G)

A/P STATUS

G/S

(G)

CMD

(G)

FLARE

(G)

VNAV PTH

HDG SE L

CMD

G/S

VOR/LOC

PITCH ARMED MODE

CWS ROLL ENGAGED

CWS R (Y)

G/S

(W)

V/S

(W)

ROLL ARMED MODE SINGLE CHANNEL

G/S V/S (W)

VOR/LOC (W)

1 CH (Y)

FLARE

(W)

CWS PITCH ENGAGED

CWS P (Y)

MODE CHANGE HIGHLIGHT SYMBOL

A mode change highlight symbol

(rectangle) is drawn around each

(G) - Green

pitch, roll, CWS, and thrust engaged

mode annunciation for a period of 10

(W) - White

seconds after each engagement.

(Y) - Yellow

CAPTAIN’S AND FIRST OFFICER’S

DISPLAY UNITS

4.10.24

Automatic Flight -

Controls and Indicators

Boeing 737 Operations Manual

[Option - PFD/ND]

A/T ENGAGED MODE

ROLL ENGAGED MODE

PITCH ENGAGED MODE

(G)

HDG SEL (G)

TO/GA

(G)

VOR/LOC (G)

V/S

(G)

RETARD

(G)

LNAV

(G)

ALT ACQ

(G)

FMC SPD (G)

ALT HOLD (G)

MCP SPD (G)

VNAV SPD (G)

THR HLD (G)

VNAV PTH (G)

ARM

(W)

MCP SPD

(G)

ROLL ARMED MODE

G/S

(G)

VOR/LOC (W)

FLARE

(G)

HDG SEL

VNAV PTH

VOR/LOC

G/S

.82

31000

360

31400

CWS R CMD CWS P

340

CWS ROLL ENGAGED

PITCH ARMED MODE

CWS R (Y)

G/S

(W)

V/S

(W)

A/P STATUS

G/S V/S (W)

CMD

(G)

FLARE

(W)

(G)

SINGLE CHANNEL

CWS PITCH ENGAGED

SINGLE

CWS P (Y)

(Y)

MODE CHANGE HIGHLIGHT SYMBOL

A mode change highlight symbol

(rectangle) is drawn around each

(G) - Green

pitch, roll, CWS, A/P status, and thrust

(W) - White

engaged mode annunciation for a period

of 10 seconds after each engagement.

(Y) - Yellow

OUTER DISPLAY UNITS

4.10.25

Boeing 737 Operations Manual

Automatic Flight

Chapter 4

System Description

Section 20

General

The automatic flight system (AFS) consists of the autopilot flight director system

(AFDS) and the autothrottle (A/T). The flight management computer (FMC)

provides N1 limits and target N1 for the A/T and command airspeeds for the A/T

and AFDS.

The AFDS and A/T are controlled using the AFDS mode control panel (MCP) and

the FMC. Normally, the AFDS and A/T are controlled automatically by the FMC

to fly an optimized lateral and vertical flight path through climb, cruise and

descent.

AFS mode status is displayed on the flight mode annunciation on each pilot’s

primary display.

Autopilot Flight Director System (AFDS)

The AFDS is a dual system consisting of two individual flight control computers

(FCCs) and a single mode control panel.

The two FCCs are identified as A and B. For A/P operation, they send control

commands to their respective pitch and roll hydraulic servos, which operate the

flight controls through two separate hydraulic systems.

For F/D operation, each FCC positions the F/D command bars on the respective

attitude indicator.

MCP Mode Selector Switches

The mode selector switches are pushed to select desired command modes for the

AFDS and A/T. The switch illuminates to indicate mode selection and that the

mode can be deselected by pushing the switch again. While a mode is active,

deselection can be automatically inhibited and is indicated by the switch being

extinguished.

When engagement of a mode would conflict with current AFS operation, pushing

the mode selector switch has no effect. All AFDS modes can be disengaged either

by selecting another command mode or by disengaging the A/P and turning the

F/Ds off.

4.20.1

Automatic Flight -

System Description

Boeing 737 Operations Manual

Autopilot Engagement Criteria

Each A/P can be engaged by pushing a separate CMD or CWS engage switch. A/P

engagement in CMD or CWS is inhibited unless both of the following

pilot-controlled conditions are met:

• no force is being applied to the control wheel

• the STAB TRIM AUTOPILOT cutout switch is at NORMAL.

Only one A/P can be engaged at a given time unless the approach (APP) mode is

engaged. Approach mode allows both A/Ps to be engaged at the same time. Dual

A/P operation provides control through landing flare and touchdown or an

automatic go-around.

In single A/P operation, full automatic flare and touchdown capability and A/P

go-around capability are not available.

Autopilot Disengagement

The A/P automatically disengages when any of the following occurs:

• pushing either A/P disengage switch

• pushing either Takeoff/Go-around (TO/GA) switch with a single A/P

engaged in CWS or CMD below 2000 feet RA

[Option - A/P auto-disengages for TO/GA above 2000 feet RA]

[Option - Honeywell -708 FCC]

• pushing either Takeoff/Go-around (TO/GA) switch with a single A/P

engaged in CWS or CMD above 2000 feet RA with flaps down or G/S

engaged.

• pushing either TO/GA switch after touchdown with both A/Ps engaged in

CMD

• pushing an illuminated A/P ENGAGE switch

• pushing the A/P DISENGAGE bar down

• activating either pilot’s control wheel trim switch

• moving the STAB TRIM AUTOPILOT cutout switch to CUTOUT

• either left or right IRS system failure or FAULT light illuminated

• loss of electrical power or a sensor input which prevents proper operation

of the engaged A/P and mode

• loss of respective hydraulic system pressure.

Note: Loss of the system A engine-driven hydraulic pump, and a heavy demand

on system A, may cause A/P A to disengage.

AFS Failures

Power interruption or loss may cause disengagement of the AFDS and/or A/T.

Re-engagement is possible after power is restored.

4.20.2

Automatic Flight -

System Description

Boeing 737 Operations Manual

Dual channel A/P operation is possible only when two generators are powering the

busses.

Two independent radio altimeters provide radio altitude to the respective FCCs.

With a radio altimeter inoperative, do not use the associated FCC for approach or

landing, and do not use the associated autopilot for approach.

Flight Director Display

Turning a F/D switch ON displays command bars on the respective pilot’s attitude

indicator if command pitch and roll modes are engaged. If command pitch and roll

modes are not engaged, the F/D command bars do not appear. The F/Ds can be

operated with or without the A/P and A/T. F/D command modes can be used with

an A/P engaged in CWS.

F/D commands operate in the same command modes as the A/P except:

• the takeoff mode is a F/D only mode

• dual F/D guidance is available for single engine operation

• the F/D has no landing flare capability. F/D command bars retract from

view at approximately 50 feet RA on an ILS approach.

Normally, FCC A drives the captain’s command bars and FCC B drives the first

officer’s command bars. With both F/D switches ON, the logic for both pilots’ F/D

modes is controlled by the master FCC, and both FMA displays show the same

mode status.

The master FCC is indicated by illumination of the respective master (MA) F/D

indicator light. The master FCC is determined as follows:

• with neither A/P engaged in CMD, the FCC for the first F/D turned on is

the master

• with one or both A/Ps engaged in CMD, the FCC for the first A/P in CMD

is the master FCC, regardless of which F/D is turned on first.

F/D modes are controlled directly from the respective FCC under certain

conditions. This independent F/D operation occurs when neither A/P is engaged

in CMD, both F/D switches are ON and one of the following mode conditions

exists:

• APP mode engaged with LOC and G/S captured

• GA mode engaged and below 400 feet RA

• TO mode engaged and below 400 feet RA.

Independent F/D operation is indicated by illumination of both MA lights. When

independent operation terminates, the MA light extinguishes on the slaved side.

If a generator is lost during a F/D TO or GA, or while in dual F/D APP mode

below 800 feet, the FCC on the unaffected side positions the F/D command bars

on both attitude indicators. If the F/D MA light on the affected side had been

illuminated, it extinguishes upon electrical bus transfer.

4.20.3

Automatic Flight -

System Description

Boeing 737 Operations Manual

AFDS Status Annunciation

The following AFDS status annunciations are displayed in the A/P status display

located above the attitude indicator on the outboard display unit:

• CMD (one or both autopilots are engaged)

• FD (the flight director is ON and the autopilot is either OFF or engaged in

CWS)

• CWS P (pitch mode engaged in CWS)

• CWS R (roll mode engaged in CWS)

[Option - EFIS/MAP]

•

1 CH (for single A/P ILS approach, annunciates after localizer capture

and remains on for entire approach. For dual A/P ILS approach,

annunciates after localizer capture and extinguishes after pitch monitor

confidence test is successfully completed).

[Option - PFD/ND]

• SINGLE CH (for single A/P ILS approach, annunciates after localizer

capture and remains on for entire approach. For dual A/P ILS approach,

annunciates after localizer capture and extinguishes after pitch monitor

confidence test is successfully completed).

AFDS Flight Mode Annunciations

The flight mode annunciations are displayed just above the attitude indicator on

the outboard display unit. The mode annunciations, from left to right, are:

[Option - EFIS/MAP]

• autothrottle

• pitch

• roll.

[Option - PFD/ND]

• autothrottle

• roll

• pitch.

Engaged or captured modes are shown at the top of the flight mode annunciation

boxes in large green letters. Armed modes are shown in smaller white letters at the

bottom of the flight mode annunciation boxes.

Autothrottle Modes

• N1 - the autothrottle maintains thrust at the selected N1 limit displayed

on the thrust mode display

• GA - the autothrottle maintains thrust at reduced go-around setting or full

go-around N1 limit

• RETARD - displayed while autothrottle moves thrust levers to the aft

stop. RETARD mode is followed by ARM mode

4.20.4

Automatic Flight -

System Description

Boeing 737 Operations Manual

• FMC SPD - the autothrottle maintains speed commanded by the FMC.

The autothrottle is limited to the N1 value shown on the thrust mode

display

• MCP SPD - the autothrottle maintains speed set in the MCP IAS/MACH

display. The autothrottle is limited to the N1 value shown on the thrust

mode display

• THR HLD - the thrust lever autothrottle servos are inhibited; the pilot can

set the thrust levers manually

• ARM - no autothrottle mode engaged. The thrust lever autothrottle servos

are inhibited; the pilot can set thrust levers manually.

Pitch Modes

• TO/GA - Takeoff

Engaged for takeoff by turning both F/D switches ON and pushing either

TO/GA switch. Both F/Ds must be ON to engage TO/GA prior to starting

takeoff.

The AFDS commands pitch attitude in the following order:

•

10 degrees nose down until 60 knots IAS

•

15 degrees nose up after 60 knots IAS

•

15 degrees nose up after lift-off until a sufficient climb rate is

acquired. Then, pitch is commanded to maintain MCP speed plus 20

knots.

TO/GA can also be engaged for takeoff with F/D switches OFF if a

TO/GA switch is pushed after 80 knots IAS below 2000 feet AGL and

prior to 150 seconds after lift-off.

• TO/GA - Go-around

Engaged for go-around by pushing the TO/GA switch under the

following conditions:

• inflight below 2000 feet radio altitude

[Option - A/P auto-disengages for TO/GA above 2000 feet RA]

[Option - Honeywell -708 FCC]

• inflight above 2000 feet radio altitude with flaps down or G/S

captured

• not in takeoff mode

• either F/D ON or OFF.

4.20.5

Automatic Flight -

System Description

Boeing 737 Operations Manual

The F/Ds command 15 degrees nose up pitch and roll to hold the

approach ground track at time of go-around engagement. After

reaching a programmed rate of climb, pitch commands the target

airspeed for each flap setting based on maximum takeoff weight

calculations.

•

VNAV -

VNAV is engaged by pushing the VNAV switch. With a VNAV mode

engaged, the FMC commands AFDS pitch and A/T modes to fly the

vertical profile.

• VNAV SPD - the AFDS maintains the FMC speed displayed on the

airspeed indicator and/or the CDU CLIMB or DESCENT pages

• VNAV PTH - the AFDS maintains FMC altitude or descent path with

pitch commands.

•

V/S (engaged) - commands pitch to hold selected vertical speed

•

V/S (armed) - V/S mode can be engaged by moving Vertical Speed

thumbwheel

•

ALT ACQ - transition maneuver entered automatically from a V/S, LVL

CHG, or VNAV climb or descent to selected MCP altitude. Engages but

does not annunciate during VNAV transition

•

ALT HOLD - commands pitch to hold MCP selected altitude or

uncorrected barometric altitude at which ALT HOLD switch was pushed

•

MCP SPD - pitch commands maintain IAS/MACH window airspeed or

Mach

•

G/S (armed) - the AFDS is armed for G/S capture

•

G/S (engaged) - the AFDS follows the ILS glideslope

•

FLARE (armed) - during a dual A/P ILS approach, FLARE is displayed

after LOC and G/S capture and below 1500 feet RA. The second A/P

couples with the flight controls and A/P go-around mode arms

•

FLARE (engaged) - during a dual A/P ILS approach, flare engages at 50

feet radio altitude. FLARE accomplishes the autoland flare maneuver.

Roll Modes

• LNAV - the AFDS intercepts and tracks the active FMC route. Either of

the following capture criteria must be met:

• on any heading and within 3 NM of the active route segment

• if outside of 3 NM of active route segment, airplane must be on an

intercept course of 90 degrees or less and intercept the route segment

before the active waypoint.

• HDG SEL - the airplane is turning to, or is on the heading selected in the

MCP Heading Display

• VOR/LOC (armed) - AFDS is armed to capture selected VOR or LOC

COURSE

• VOR/LOC (engaged) - AFDS tracks selected VOR course or tracks

selected localizer course along the inbound front course bearing.

4.20.6

Automatic Flight -

System Description

Boeing 737 Operations Manual

Autopilot Control Wheel Steering

CWS Engage Switch Selected

Pushing a CWS engage switch engages the A/P pitch and roll axes in the CWS

mode and displays CWS P and CWS R on the FMAs.

With CWS engaged, the A/P maneuvers the airplane in response to control

pressures applied by either pilot. The control pressure is similar to that required

for manual flight. When control pressure is released, the A/P holds existing

attitude.

If aileron pressure is released with 6 degrees or less bank, the A/P rolls the wings

level and holds existing heading. This heading hold feature with bank less than 6

degrees is inhibited when any of the following conditions exists:

• below 1,500 feet RA with the landing gear down

• after F/D VOR capture with TAS 250 knots or less

• after F/D LOC capture in the APP mode.

Pitch CWS with a CMD Engage Switch Selected

The pitch axis engages in CWS while the roll axis is in CMD when:

• a command pitch mode has not been selected or was deselected

• A/P pitch has been manually overridden with control column force. The

force required for override is greater than normal CWS control column

force. This manual pitch override is inhibited in the APP mode with both

A/Ps engaged.

CWS P is annunciated on the FMAs while this mode is engaged. Command pitch

modes can then be selected.

When approaching a selected altitude in CWS P with a CMD engage switch

selected, CWS P changes to ALT ACQ. When at the selected altitude, ALT HOLD

engages.

If pitch is manually overridden while in ALT HOLD at the selected altitude, ALT

HOLD changes to CWS P. If control force is released within 250 feet of the

selected altitude, CWS P changes to ALT ACQ, the airplane returns to the selected

altitude, and ALT HOLD engages. If the elevator force is held until more than 250

feet from the selected altitude, pitch remains in CWS P.

Roll CWS with a CMD Engage Switch Selected

The roll axis engages in CWS while the pitch axis is in CMD when:

• a command roll mode has not been selected or was deselected

• A/P roll has been manually overridden with control wheel force. The

force required for override is greater than the normal CWS control wheel

force.

CWS R is annunciated on the FMAs while this mode is engaged.

4.20.7

Boeing 737 - 600/700/800/900. Operations Manual (1997 year) - page 30