.
pitch mode annunciates MCP SPD for climb or descent

.  
autothrottle mode annunciates N1 for climb and RETARD followed by
ARM for descent

.
IAS/MACH display and airspeed cursors display target speed.

LVL CHG Mode
The LVL CHG mode coordinates pitch and thrust commands to make automatic climbs and descents to preselected altitudes at selected airspeeds.
Copyright . The Boeing Company. See title page for details.
4.10.6   June 6, 2003

Automatic Flight -Controls and Indicators 737 Operations Manual
 A LVL CHG climb or descent is initiated by:
.
 selecting a new altitude

.
 pushing LVL CHG switch

.
 setting desired airspeed.

Climb –
.
autothrottle holds limit thrust

.
AFDS holds selected airspeed.

Descent –
.
autothrottle holds idle thrust

.
AFDS holds selected airspeed.

Airspeed –
.  
if a speed mode is active when LVL CHG is engaged, this speed is
retained as target speed

.  
if a speed mode is not active when LVL CHG is engaged, existing speed becomes target speed

.
speed can be changed with MCP IAS/MACH Selector.

The LVL CHG mode is inhibited after glideslope capture.

Approach (APP) Switch
(See Lateral Navigation)

Altitude Hold (ALT HLD) Switch
Push –
.
engages ALT HOLD command mode

.  
commands pitch to hold uncorrected barometric altitude at which switch was pressed

.  
annunciates ALT HOLD pitch mode and illuminates ALT HLD switch
light.

Altitude Hold Command Mode
ALT HOLD mode commands pitch to hold either:
.
MCP selected altitude

.
pitch mode annunciates ALT HOLD

.
ALT HLD switch light extinguishes

.  
uncorrected barometric altitude at which ALT HLD switch was pressed if not at MCP selected altitude

.
pitch mode annunciates ALT HOLD

.
ALT HLD switch light illuminates.

Automatic Flight -Controls and Indicators 737 Operations Manual

When in ALT HOLD at selected MCP altitude:
.  
selecting a new MCP altitude illuminates the ALT HLD switch light and
arms V/S mode

.  
LVL CHG, V/S, and VNAV climb and descent functions are inhibited
until a new MCP altitude is selected.

ALT HOLD mode is inhibited after G/S capture.
The selected MCP altitude is referenced to:
.
Captain’s barometric altimeter setting for A A/P and F/D.

.
First Officer’s barometric altimeter setting for B A/P and F/D.

Note:  After ALT HOLD engages, changes in altimeter barometric settings do not change the selected altitude reference.

Vertical Speed (V/S) Switch
Push –
.
arms or engages V/S command mode

.
commands pitch to hold vertical speed

.
engages A/T in speed mode to hold selected airspeed

.
annunciates V/S pitch mode and illuminates V/S switch light.

Vertical Speed Command Mode
The V/S mode commands pitch to hold selected vertical speed and engages A/T in SPEED mode to hold selected airspeed. V/S mode has both an armed and an engaged state.
Engaged –
.
annunciates V/S pitch mode

.
vertical speed display changes from blank to present vertical speed

.
desired vertical speeds can be selected with vertical speed thumbwheel.

V/S becomes armed if:
.
pitch mode is ALT HLD at selected MCP altitude and

.
new MCP altitude is selected (more than 100 feet from current altitude).

With V/S armed, V/S mode is engaged by moving vertical speed thumbwheel.
V/S mode automatically engages if ALT ACQ mode is engaged and a new MCP altitude is selected which is more than 100 feet different from previously selected altitude
.  Vertical speeds can be selected which command flight toward or away
from selected altitude.

Inhibited if:
.
ALT HOLD mode is active at selected MCP altitude

.
glide slope captured in APP mode.

Copyright . The Boeing Company. See title page for details.
4.10.8   June 6, 2003

Automatic Flight -Controls and Indicators 737 Operations Manual
Lateral Navigation

COURSE Display
Displays course set by course selector.
Note:  Different courses and frequencies on two VHF NAV receivers can cause disagreement between Captain and FO F/D displays and affect A/P operation.