.
altitude deviation becomes more than 900 feet (some airplanes 750 feet)

.
a new altitude is selected.

Warning Systems -System Description

Altitude Alert Profile

- *No aural warning tone sounds; only both
ALTITUDE lights illuminate
ALERTsteady.
Deviation - Aural warning tone momentarily sounds and both
ALTITUDE lights flash.
ALERT
* As installed
 Ground Proximity Warning System (GPWS)
WARNING: Do not deactivate the GPWS (by pulling the circuit breaker or using the inhibit switch) except for approved procedures where landing flaps are required at a less-than-normal position, or where leaving landing gear up is specified.
The GPWS provides alerts for potentially hazardous flight conditions. To the extent GPWS warnings are installed, they warn of imminent impact with the ground, detected windshear condition, excessive angle of bank, and glide slope deviation.
Copyright . The Boeing Company. See title page for details.
15.20.8  June 8, 2001

Warning Systems -System Description 737 Operations Manual
GPWS may also provide radio altitude and decision height callouts.
Note:  GPWS does not provide alerts for flight toward vertically sheer terrain, or of shallow descents when the airplane is in landing configuration.
Alert Conditions
The GPWS provides alerts based on radio altitude and combinations of barometric altitude, airspeed, glide slope deviation, and airplane configuration. The alerts are for:
.
excessive barometric descent rate

.
excessive terrain closure rate

.
altitude loss after takeoff or go–around

.
unsafe terrain clearance (when not in the landing configuration)

.
excessive deviation below glide slope
. on some airplanes, descent below specific radio altitudes
. on some airplanes, descent below selected minimum radio altitude
. on some airplanes, excessive bank angle

.
windshear.

The GPWS alerts and the condition which causes each alert are presented on the following GPWS annunciation chart.
GPWS Annunciations
AURAL ALERT  VISUAL ALERT  DESCRIPTION 
Siren followed by WINDSHEAR  WINDSHEAR on EADIs  Excessive downdrafts or tailwind detected when below 1500 feet. Windshear detection begins at rotation. 
WHOOP WHOOP PULL UP  PULL UP lights  Follows “SINK RATE” if sink rate becomes severe. Also follows “TERRAIN” alert if excessive terrain closure rate continues and landing gear and/or flaps not in landing configuration. 
DON’T SINK  PULL UP lights  Excessive altitude loss after takeoff or go–around. 
GLIDESLOPE  BELOW G/S P–INHIBIT lights on  Deviation below glideslope. The volume and repetition rate increase as deviation continues. 
SINK RATE  PULL UP lights  Excessive descent rate. 

Copyright . The Boeing Company. See title page for details.
December 7, 2001   15.20.9
Warning Systems -System Description 737 Operations Manual

TERRAIN  PULL UP lights  Excessive terrain closure rate. 
TOO LOW FLAPS  PULL UP lights  Unsafe clearance during approach with flaps not in landing configuration. 
TOO LOW GEAR  PULL UP lights  Unsafe clearance during approach with landing gear up. 
TOO LOW TERRAIN  PULL UP lights  Unsafe terrain clearance with landing gear up or flaps not in landing position. 

Bank Angle Alert
On airplanes with bank angle alert, the aural alert “BANK ANGLE, BANK ANGLE” sounds when roll angle exceeds 35 degrees, 40 degrees, and 45 degrees. Once sounded the alert is silent if bank angle is decreased to 30 degrees.
Radio Altitude Callouts
On airplanes with radio altitude callouts, the following callouts occur during approach:
“ONE HUNDRED”
“FIFTY”
“THIRTY”
“TWENTY”
“TEN”
or
“ONE HUNDRED”
“FIFTY”
“THIRTY”
“TEN”
or
“FIFTY”
Decision Height Callouts
On airplanes with decision height callout, the following callout is subject to the altitude set on the Captain’s DH selector:
Copyright . The Boeing Company. See title page for details.
15.20.10  June 7, 2002

Warning Systems -System Description 737 Operations Manual
“MINIMUMS – MINIMUMS”
or
“PLUS HUNDRED”, “MINIMUMS”

or
“FIFTY”, “APPROACHING
　
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