34-48-00
 ú ú 09 Page 9 ú Nov 12/01

BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.

D101115V AC
D101
B1ELEX

B4115V AC -15V DCB3 PWR 1
LRRA-1
+28V DCB8AC
B1PWR GND EXT RANGEB9P18-1 LOAD CONT CTR
RSVB10R/A VALID FLAG ALARMB12ARINC DC ALT SIG GND B46ARINC DC ALT DRIVE B47

B57 M140 TRANSMIT ANT NO. 2 B23(STA 390)
B22

B18
TRIPS 5&6

TO THRUST REV SYS B19 (10 FT)
(CHAPTER 78-34-00) B14B3 B15 UNUSEDNC B46
B20 R/A TRIPS
B47 NOTE:FOR SIGNAL PATH CLARITY,B12 ELECTRONIC SHELF WIRING
B8 NOT SHOWN B9B10

CRITICAL LENGTHS
(REF W/D 34-33-11 & -21)

M415 RADIO ALTIMETER RECEIVER/N10 F/O'S RADIO ALTIMETERTRANSMITTER NO. 2 (R/A-2) (E2-4) INDICATOR (P3)
Radio Altimeter Interface Schematic
Figure 4

A
737-300/400/500MAINTENANCE MANUAL
 (11) The receiver-transmitter dc altitude voltage is also supplied to the height indicator adjustable trip (decision height (DH), comparator. The comparator compares this voltage with the voltage from the adjustable trip DH potentiometer. As long as the airplane altitude exceeds the altitude of the adjustable trip (DH cursor) setting, the trip relay and DH light(s) will remain de-energized. When the airplane altitude is slightly less than the altitude of the DH setting, the trip relay will be energized causing the DH light to illuminate at the Captain's or F/O's ADI and height indicator, as applicable.
 B. Self-Test Operation
 (1)  
Self-test of LRRA system No. 1 and 2 is initiated at the captain's and first officer's height indicator, respectively. When the test switch is depressed, a ground signal is applied through a relay in the autopilot accessory box to the test circuits in the applicable receiver transmitter. The accessory box relay inhibits the self-test command when the autopilot is in the glide slope engage submode.

 (2)  
Depressing the test switch energizes the test relay. One set of relay contacts routes a test signal from the calibration loop mixer to the receiver circuits where it is processed in the same manner as a normal altitude signal. The other set of contacts applies a dc voltage to test circuits in the AID calibration unit to bring the dc altitude to the predetermined test altitude. During self-test, each height indicator should display the test altitude.

 C. Monitor, Fault Indicator, and Flag Operation
 (1)  
Two separately processed dc altitude output voltages are applied to a comparator in the R/T unit and if the two voltages do not agree within a specified tolerance, the comparator provides an output to the flag gates and COMP threshold sensor signifying improper operation.

 (2)  
At altitudes above the operational range of the receiver-transmitter, the low level signal coupled between antennas through the external interconnecting coaxial cable is processed through the receiver circuits and detected in the antenna coupling monitor to check the operation of the antenna system. At altitudes within the operational range of the receiver-transmitter, the normal received signal is processed through the receiver circuits and detected in the AGC circuit. The AGC circuit functions to maintain receiver gain and provides a signal to the singal presence monitor. The output from the antenna coupling monitor is applied to the SENS indicator threshold sensor and flag gate circuit. The output from the signal presence monitor is applied to the SENS indicator threshold sensor and flag alarm circuit.

 (3)  
An output fromm the calibration loop mixer is applied to the power modulation monitor and altitude calibration circuits. If the monitor detects a loss in signal that exceeds tolerances, an output is provided to the flag gates and XMTR threshold sensor signifying improper operation. The calibration circuits will do the same if the amount of altitude correction required is beyond the limits of the self-calibration circuits.

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 34-48-00

 ú ú 12 Page 10 ú Nov 12/01
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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