.
landing gear is in disagreement with LANDING GEAR lever position (in
transit or unsafe).
.
landing gear is not down and locked--with either or both forward thrust
levers retarded to idle. All lights extinguished – landing gear is up and locked with the LANDING GEAR lever UP or OFF.
Aural Indications
A steady warning horn is provided to alert the flight crew whenever the airplane is in a landing configuration and any gear is not down and locked. The landing gear warning horn is activated by forward thrust lever and flap position as follows:
Flaps 1 through 10 –
. either or both forward thrust levers set between idle and approximately 10
degrees thrust lever angle--(for some airplanes) below 1500 feet radio
altitude; the landing gear warning horn can be silenced (reset) with the
landing gear warning HORN CUTOUT switch.
Flaps 15 –
.
either forward thrust lever between idle and approximately 10 degrees and
the opposite thrust lever greater than approximately 30 degrees--(for some
airplanes) below 1500 feet radio altitude; the landing gear warning horn
can be silenced with the landing gear warning HORN CUTOUT switch.
.
both forward thrust levers set below approximately 30 degrees--at any
radio altitude; the landing gear warning horn cannot be silenced with the
landing gear warning HORN CUTOUT switch.
Warning Systems -System Description 737 Operations Manual
Flaps greater than 15 –
. regardless of forward thrust lever position, the landing gear warning horn
cannot be silenced with the landing gear warning HORN CUTOUT
switch.
The warning indication is cancelled when the configuration error is corrected.
Mach/Airspeed Warning System
Two independent Mach/airspeed warning systems provide a distinct aural warning, a clacker, any time the maximum operating airspeed of Vmo/Mmo is exceeded. The warning clackers can be silenced only by reducing airspeed below Vmo/Mmo.
The systems operate from a mechanism internal to each pilot’s Mach/airspeed indicator. Test switches allow a system operation check at any time.
The airspeed indicator displays red warning bands indicating maximum and minimum airspeeds. Amber bands indicate maximum and minimum maneuvering airspeeds.
Stall Warning System
Natural stall warning (buffet) usually occurs at a speed prior to stall. In some configurations the margin between stall and natural stall warning is less than desired. Therefore, an artificial stall warning device, a stick shaker, is used to provide the required warning.
The stall warning “stick shaker” consists of two eccentric weight motors, one on each control column. They are designed to alert the pilots before a stall develops. The warning is given by vibrating both control columns. The system is armed in flight at all times. The system is deactivated on the ground.
Two independent, identical computers determine when stall warning is required based upon:
.
wing configurations
.
air/ground sensing
.
thrust
.
angle of attack
.
Air Data Computer outputs.
The stall warning computers provide outputs for all stall warnings to include stick shaker, signals to the pitch limit indicator and airspeed displays, as well as the GPWS windshear detection and alert.
Two test switches are installed in the aft overhead panel. Pushing either of these initiates a self-test of the respective stall warning channel. The No.1 activates the Captain stick shaker, and the No. 2 activates the F/O stick shaker. Either stick shaker vibrates both columns through column interconnects.
Copyright . The Boeing Company. See title page for details.
15.20.6 December 6, 2002
Warning Systems -System Description 737 Operations Manual
Altitude Alerting System
Altitude alerting references the altitude selected on the MCP. Alerting occurs when approaching or departing the selected altitude. Altitude alerting is inhibited when wing flaps are extended to 25 or greater, or while G/S is captured.
Alerting consists of a momentary tone and illumination of an ALTITUDE ALERT light located on the captain’s and first officer’s instrument panels.
Acquisition Alerting
When approaching within 900 feet (some airplanes 750 feet) of selected altitude both ALTITUDE ALERT lights illuminate steady and--for the 900 alert only--a momentary tone sounds. When at 300 feet (some airplanes 250 feet) from selected altitude, both ALTITUDE ALERT lights extinguish.
Deviation Alerting
Upon deviating from the selected altitude by more than 300 feet (some airplanes 250 feet), a momentary tone sounds and the ALTITUDE ALERT lights flash. Flashing continues until:
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