(b)
With landing gear down, the minimum warning threshold decreases to 200 feet and a TOO LOW-FLAPS warning comes on if the flaps are not in landing configuration as shown in Fig. 10. The warning may be inhibited by setting the FLAP (FLAP/GEAR) INHIBIT switch on the ground proximity warning module to INHIBIT position. This will simulate a flaps down condition if the pilot prefers to land with less than normal landing flaps. A magnetic latch is used to select mode 4A or mode 4B, so that power interruption or missed approach below 500 feet prevent reactivation of mode 4A until at least 700 feet of terrain clearance is reached.
K88914
5C8 Mode 4-B Warning Envelope
Feb 20/89 Figure 10 34-42-01
Page 11
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
(5)
Glide Slope Deviation Warning (Mode 5)
(a)
The glide slope warning is armed when an ILS frequency is selected. The warning envelope consists of two regions as shown in the Fig. 11. The BELOW G/S indicators accompanied by a reduced volume of aural warning GLIDE SLOPE come on, if the deviation of the airplane below the glide slope exceeds 1.3 dots between 1000 and 150 feet of radio altitude. The aural warning increases to full volume if the deviations of the airplane below the glide slope exceeds 2 dots when the airplane in between 300 and 150 feet of radio altitude.
(b)
In order to allow the pilot to purposely descend below the glide slope without triggering a warning, the glide slope warning mode may be inhibited by pressing the BELOW G/S indicator when the radio altitude is below 1000 feet.
(6)
Decision Height Warning (Mode 6)
(a) With landing gear down, the computer will provide two cycles of MINIMUM aural warning when the airplane descends below the decision height (DH MDA) set on the captain's LRRA indicator.
F. System self-test may be initiated by pressing the TEST switch or on the control module on the computer. During self-test, the PULL UP, INUP, BELOW C/S indicators come on, and one cycle of aural warning consists of GLIDE SLOPE, and WHOOP-WHOOP PULL UP broadcast over the warning speaker.
H28996
Mode 5 Warning Envelope 533
34-42-01 Figure 11 Feb 15/78
Page 12
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
GROUND PROXIMITY WARNING SYSTEM - TROUBLE SHOOTING
1. General
A. The following trouble shooting procedures are based on performance of the system operational test and are presented in tree-type format. The test steps are connected to show the OK condition path. When all steps in the OK condition path check out, the system is operable.
B. When a test step does not check out, follow the NOT OK line to the box containing the trouble symptom. Turn to the procedure indicated and continue to follow a single line by analyzing the results of each test step until the required corrective action is determined. Perform the specified corrective action; then repeat the step at which the failure was encountered.
C. All trouble shooting procedures are based on the assumption that wiring is OK and that electrical power is available. If the corrective action in the procedure does not correct the problem, check wiring using the wiring diagram.
2. Prepare for Trouble Shooting
A. Verify that GROUND PROX WARN, RADIO ALTM-1, NO. 1 AIR DATA COMPUTER 115V AC and 26V AC circuit breakers on panel P18 are closed.
B. Verify that DIM & TEST, and INDICATOR LIGHTS circuit breaker panel P6 are closed.
C. Verify that flaps are up, and landing gear lever is in OFF or DN position.
D. Apply electrical power.
E. Verify that failure warning flag in captain's height indicator and altimeter are not in view.
F. Verify that RADIO NAV switch on overhead panel is set at NORMAL position, and that GS flag on captain's ADI is out of view.
575
Nov 15/78 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 34-42-01 Page 101
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