.  
pitch mode annunciates VNAV SPD, VNAV PTH, or VNAV ALT
YA613 - YC413, YK101 - YK104

.
pitch mode annunciates VNAV SPD, VNAV PTH

.
A/T mode annunciates FMC SPD, N1, RETARD, or ARM

.  
IAS/MACH display blanks and airspeed cursors positioned to FMC
commanded airspeed.

VNAV Mode
The FMC commands AFDS pitch and autothrottle to fly vertical profile selected on FMC CDUs. Profile includes climb, cruise, descent, speeds, and can also include waypoint altitude constraints.
YA613 - YC413, YK101 - YK104
Note:  If the airplane is between the FMC target altitude (depicted on the RTE LEGS page for the active waypoint) and the manually entered MCP target altitude, VNAV will not engage. To enable VNAV, adjust the FMC or MCP target altitude as appropriate.
Climb –
.
autothrottle holds FMC thrust limit

.
AFDS holds FMC target speed

.
automatic level-off occurs at MCP altitude or VNAV altitude, whichever

is reached first
YD651 - YD655

.
MCP constrained altitude annunciates VNAV ALT

.
VNAV constrained level-off annunciates VNAV PTH.

Cruise –
.
autothrottle holds FMC target speed

.
AFDS holds FMC altitude

.  
selecting a lower MCP altitude arms FMC to automatically begin descent
upon arrival at FMC top of descent point.

Descent –
.
VNAV SPD descent

.
autothrottle holds idle

.
AFDS holds FMC target speed.

.
VNAV PTH descent

.  
autothrottle holds idle but can command FMC SPD mode if ground speed becomes too low to maintain FMC vertical path

Copyright . The Boeing Company. See title page for details.
Automatic Flight -Controls and Indicators 737 Flight Crew Operations Manual

.
AFDS tracks FMC descent path.

.
automatic level-off occurs at MCP altitude or VNAV altitude, whichever

is reached first
YD651 - YD655

.
MCP constrained altitude annunciates VNAV ALT

.
VNAV constrained altitude annunciates VNAV PTH.

Inhibited below 400 ft RA or if performance initialization not complete.
VNAV mode is terminated by any one of the following:
.
selecting another pitch mode

.
glideslope capture

.  
reaching end of LNAV route
YA721, YA722

.  
transition of glideslope intercept waypoint
YA613 - YA687, YA801 - YK104

.  
transition of glideslope intercept waypoint if G/S is armed
YA721, YA722

.
crosstrack deviation exceeds the RNP value during PTH descent for an

active leg with a database vertical angle and LNAV not engaged
YA613 - YA687, YA801 - YK104

.  
crosstrack deviation exceeds twice the RNP value during PTH descent for
an active leg with a database vertical angle and LNAV not engaged

In the event of glideslope intercept waypoint transition, VNAV can be re-engaged.
YA613 - YC413, YK101 - YK104 When the pitch mode changes from VNAV SPD to ALT ACQ during an intermediate level off, the autothrottle will command a target IAS rather than Mach number. This is valid even at altitudes above the IAS/Mach changeover. If the climb is resumed in LVL CHG or V/S, the airspeed window opens at the target IAS which may result in an overspeed condition.

ALTITUDE Display
Displays selected altitude
.  
displayed altitude is reference for altitude alerting and automatic
level–offs

.  
with Mode S transponders installed, the displayed altitude is transmitted
to ATC

.
altitude range is 0 to 50,000 feet in 100 foot increments

.
displays previously selected altitude when power first applied.

Copyright . The Boeing Company. See title page for details.
4.10.8   September 29, 2005

Automatic Flight -Controls and Indicators 737 Flight Crew Operations Manual

Vertical Speed (VERT SPEED) Display
Displays:
.
blank when V/S mode not active

.
present V/S when V/S mode is engaged with V/S switch

.
selected V/S when V/S set with thumbwheel

.
range is –7900 to +6000 fpm.

Display increments are:
.
 50 fpm if V/S is less than 1000 fpm

.
100 fpm if V/S is 1000 fpm or greater.

Vertical Speed Thumbwheel
Rotate –
.
DN –

.
sets vertical speed in VERT SPEED display

.
increases rate of descent or reduces rate of ascent.
　
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