(7)
(8)
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737-300/400/500MAINTENANCE MANUAL
In the height indicator, the 10-kHz tracer signal to the servo-amplifier is processed to the integrity monitor when the servo is in a nulled state. The detected tracer signal maintains the flag amplifier in the conducting state allowing the flag solenoid to be energized (flag out of view). The tracer signal output from the integrity monitor is also supplied to the receiver-transmitter IND theshold sensor and flag gates. The absence of the tracer signal signifies improper height indicator operation.The inputs to the flag gates must be of sufficient magnitude to inhibit a flag alarm condition. If any one of the inputs drops below a specific value, an output is supplied to the flag alarm circuits which turns off the flag driver causing the height indicator warning flag to come into view and the receiver-transmitter FLAG indicator to illuminate.An output from the flag alarm circuit is also provided to the pointer stow circuit. An alarm condition activates this circuit causing the height indicator altitude pointer to freeze in position for approximately 1 second and then to be driven up behind the pointer mask.When the airplane is at an altitude of over 2500 feet, or for any condition when received signal strength is inadequate for normal system operation, an input is provided to the flag alarm circuit.The receiver-transmitter lights marked WARN (yellow) and FLAG (red) are controlled directly by the warn relay driver and flag alarm functions, respectively. The WARN lamp will light when there is a loss of signal and both the WARN and FLAG lamps will light if a malfunction occurs in the LRRA system. The four neon lights marked SENS, XMTR, COMP, and IND are controlled by the integrity gates. Power is applied to the neon lights only when the PRESS TO MONITOR button is pressed. Pressing this button will cause one or more of the neon lamps to light identifying the area in which a fault has occurred.
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34-48-00
ú ú 04 Page 11 ú Nov 15/90
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
737-300/400/500MAINTENANCE MANUAL
LOW RANGE RADIO ALTIMETER SYSTEM - TROUBLE SHOOTING
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1. General
_______
A. The low range radio altimeter (LRRA) system has two identical systems. The captain's system is LRRA-1 and the first officer's system is LRRA-2.
B. Each LRRA system has a receiver/transmitter(R/T), a transmit antenna and a receive antenna, a height indicator (HI), and interface connections to the user systems.
C. Replace defective components with known good components.
D. When you complete the troubleshooting, do the Low Range Radio Altimeter System Operational Tests (Ref 34-48-00/501).
2. Troubleshooting Procedure
__________________________
A. Prepare To Troubleshoot
(1)
Supply electrical power (Ref 24-22-00/201)
(2)
Make sure the circuit breaker for the LRRA system to be tested is closed and the circuit breaker for the system not under test is open.
(a)
RADIO ALTM-1 Left Load Control Center Panel P18
(b)
RADIO ALTM-2 Right Load Control Center Panel P6
B. LRRA Component Fault Isolation
(1)
Go to the HI Troubleshooting at the end of this section. If a HI trouble is identified, do the corrective action shown for the HI.
(2)
If the fail warn flag is in view on the HI, do the troubleshooting procedures as follows in sequence:
NOTE: Do not push the TEST pushbutton on the HI or the PRESS TO
____ MONITOR pushbutton on the R/T until directed to do so in these procedures.
(3)
Gain access to the applicable R/T on rack E2, shelf 4 in the lower equipment bay.
(4)
Push and hold the PRESS TO MONITOR pushbutton on the front face of the applicable R/T.
(a) If the IND light comes on, replace the applicable HI (Ref 34-48-31/401).
EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. AIRPLANES WITHOUT EFIS ú
34-48-00
ú ú 06 Page 101 ú Mar 15/92
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details. 中國航空網 www.k6050.com 航空翻譯 www.aviation.cn 本文鏈接地址：737-300 400 500 AMM 飛機維護手冊 導航 NAVIGATION 3(137)
