K88869
Ground Proximity Warning System Component Location 501
34-42-01 Figure 1 Feb 20/89
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BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
3. GPWS Warning Lights (Fig. 1)
A. A rectangular shaped red warning light labeled PULL UP is installed on the captain's and first officer's instrument panels. Access to the bulbs within the light assembly is provided by removing the lens cover.
B. The lights come on to provide a visual indication of mode 1, 2, 3, and 4 warnings.
4. G/S Warning Light (Fig. 1)
A. A rectangular shaped amber G/S (advisory) light labeled BELOW G/S is installed on the captain's and first officer's instrument panels. Access to the bulbs and a fuse within the light assembly is provided by removing the lens cover. The light comes on to provide a visual indication that the airplane is below the glide slope beam when an ILS frequency is selected.
B. The G/S warning light will inhibit the glide slope deviation warning when pressed, provided the hard glide slope warning is not already on.
5. Ground Proximity Warning System Control Module (Fig. 1)
A. The ground proximity warning control module is located on the first officer's instrument panel. It consists of an INOP indicator light; a SYS TEST switch; On GUN B-2501 thru B-2503 and B-2511 thru B-2516, a FLAP INHIBIT switch; and On GUN B-2504, B-2505, B-2509, B-2510 and XIA B-2524, a FLAP/GEAR INHIBIT switch. The INOP indicator light comes on when the monitor circuit in the computer senses a fault condition. The TEST switch provides a confidence check of the system, either in flight or on ground. The FLAP (FLAP/GEAR) INHIBIT switch enables the pilots to simulate a flap down (flap and gear down) condition when the switch is set to INHIBIT position.
6. Warning Speaker (On GUN ALL)
A. A warning speaker is installed in overhead panel P5. The speaker provides an aural indication that the GPWC has generated a warning of an unsafe flight path.
7. Aural Warnings (On XIA ALL)
A. Aural warning signals from the GPWC are sent to the remote electronics unit of the flight interphone system (Ref 23-52-0). The aural warnings are then broadcast over the flight interphone speakers.
8. Operation (Fig. 2)
A. The GPWS is operational when load control center P18 is energized and the GPWS, CADC, VHF-NAV, and LRRA circuit breakers are closed.
5C8
Feb 20/89 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 34-42-01 Page 3
Ground Proximity Warning System Block Diagram 501
34-42-01 Figure 2 (Sheet 1) Feb 20/89
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BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
5C8 Ground Proximity Warning System Block Diagram
Feb 20/89 Figure 2 (Sheet 2) 34-42-01
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BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
B. Signal inputs to the GPWC consist of radio altitude information from LRRA No. 1, mach and altitude rate information from central air data computer No. 1. The radio altitude signal is a dc voltage which is a function of airplane height above ground level and is useful to approximately 2500 feet. The barometric rate signal is ac with a scale of 250 mv/1000 fpm altitude change. This rate signal is in phase with the 26-volt ac reference from the CADC during ascent and out-of-phase during descent. The glide slope deviation signal provides a low level input with a sensitivity of 75 mv/deviation dot. The airspeed signal is a three wire synchro output calibrated from zero degrees for a 0.2 mach indication and increasing to one synchro revolution for a 1.2 mach indication.
C. Binary inputs to the GPWC consist of a landing gear and landing flap position signal and 28-volt dc radio altimeter valid, glide slope valid, and baro rate computer valid signals. The landing gear position signal is open when the landing gear is in any position other than down and locked and ground potential when the landing gear is down and locked. The landing flap position signal is ground potential when the flaps are less than 15 degrees, and open when the flaps are extended more than 15 degrees.
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