TASK 34-42-21-404-018
3. Ground Proximity Warning Module Installation____________________________________________
A. References
(1)
24-22-00/201, Manual Control
(2)
IPC 34-46-00 Fig. 1
B. Access
(1) Location Zone
222 Control Cabin, RH
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A
737-300/400/500MAINTENANCE MANUAL
C. Procedure
S 864-006
(1) Open these circuit breakers and attach DO-NOT-CLOSE tags:
(a)
P42 5V Lighting Panel
1) 42, P3-P23-P10 LTG 28V AC SEC
(b)
P18-1 Electronic Load Circuit Breaker Panel
1) 18A7, GND PROX WARN
S 424-008
(2) Install the module:
(a)
Connect the electrical connector to the module.
(b)
Lightly push the module into the instrument panel.
(c)
Tighten the fasteners that attach the module to the instrument panel.
S 864-009
(3)
Remove the DO-NOT-CLOSE tags and close these circuit breakers:
(a)
P42 5V Lighting Panel
1) 42, P3-P23-P10 LTG 28V AC SEC
(b)
P18-1 Electronic Load Circuit Breaker Panel
1) 18A7, GND PROX WARN
(4)
Supply electrical power (Ref 24-22-00/201).
(5)
Make sure that the module panel lights are on.
(6)
Remove electrical power if it is not necessary (Ref 24-22-00/201).
S 864-011
S 714-016
S 864-013
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737-300/400/500MAINTENANCE MANUAL
LOW RANGE RADIO ALTIMETER SYSTEM - DESCRIPTION AND OPERATION
____________________________________________________________
1. General_______
A. The low range radio altimeter (LRRA) system provides vertical position information for use by the pilots during approach and landing phases of flight operation. The LRRA system provides measurement of absolute altitude (height above terrain) from 2500 feet to touchdown. LRRA valid flag alarm/failure warning, dc altitude, and vertical terrain clearance (altitude trip) outputs are available for use by other systems.
B. Two complete systems are installed. Each system consists of a receiver-transmitter (R/T), height indicator (HI), transmit antenna, receive antenna, and a DH light on each pilot's ADI. Location of components is shown on Fig. 1.
C. The No. 1 system (captain's - LRRA-1) receives 115-volt ac power through circuit breaker RADIO ALTM-1 located on panel P18-1 at the left load control center. System No. 2 (first officer's - LRRA-2) receives 115-volt ac power through circuit breaker RADIO ALTM-2 located on panel P6 at right load control center.
D. The LRRA systems supply LRRA flag alarm, dc altitude signals and fixed altitude trip signals to the FCS (flight control system), GPWS (ground proximity warning system), and the rising runway symbol or altitude bar circuit in the pilots ADI's. Also, the LRRA systems supply LRRA flag alarm and dc altitude signals for the TCAS (traffic collision avoidance system). The radio altimeters (height indicators) in the system receive LRRA flag alarm, dc altitude and test altitude signals from the LRRA R/T units. Signals supplied by the LRRA system to using equipments/systems are shown in Fig. 2 thru 4).
E. Each receiver/transmitter (R/T) in the dual LRRA system provides a continuous dc altitude signal to its associated HI. The dc signal varies in accordance with airplane height (absolute altitude) above terrain and is converted in the HI into a pointer indication (in feet) on the HI height scale. An adjustable DH (decision height) index (cursor) is provided on the HI. The DH control knob on the HI is turned by the pilot to position the index to a selected DH altitude. When the airplane descends to the selected altitude, the DH light on the associated ADI and HI come on. The DH lights remain on until reset by moving the index at least 75 feet below or above the previous setting that caused the DH lights to come on.
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