(c)
A dc altitude signal from receiver-transmitter 1 and 2 is applied to the captain's and first officer's ADI, respectively. The altitude signal controls the vertical movement of the rising runway symbol. The 200-foot altitude trip signal will initiate the vertical movement of the symbol provided the required valid signals are supplied to the ADI logic circuits to retract the runway flag from view. The LRRA system flag alarm signal is provided as one of the required valid signals. Additional signals are required from the VOR/ILS system (Ref 34-31-00).
(3)
Self-Test Operation (Fig. 3) (Bendix LRRA System)
(a)
Self-test of LRRA systems 1 and 2 is initiated at the captain's and first officer's height indicator, respectively. When the test button is depressed, a ground signal is applied through a relay in AFC-2 accessory box to the test circuits in the receiver-transmitter. The relays, one for each LRRA system, inhibit the self-test command after glide slope capture by autopilot system.
(b)
Actuating the test switch energizes the receiver-transmitter 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, the indicator should display the test altitude of 100 | 4 feet.
(4)
Warning Flag, and Integrity Monitor Operation (Fig. 3)
EFFECTIVITY
SN 301-350 CONFIG 3 03 Page 8 Apr 25/8834-33-00
(a)
A warning flag will come into view on a height indicator to indicate unsatisfactory system performance. The height indicator flag control circuit functions as a monitor of the servo loop, the ac voltage from the power supply, and the flag alarm voltage. When the signals applied to the null detector differ by more than the predetermined value, or if any of the other inputs to the flag control circuit are missing, the flag solenoid is de-energized and the warning flag comes into view. The integrity monitor circuit provides a flag monitor voltage to the receiver-transmitter IND fault circuit.
(b)
The two dc altitude voltages output from the receiver-transmitter are applied to the comparator 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.
(c)
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 signal 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.
(d)
An output from 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.
(e)
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 threshold sensor and flag gates. The absence of the tracer signal signifies improper height indicator operation.
EFFECTIVITY
SN 301-350 CONFIG 3 03 Page 9 Apr 25/8834-33-00
(f)
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. In addition, the warn relay is de-energized resulting in deactivation of the altitude trip circuits, and illumination of the receiver-transmitter WARN indicator.
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本文链接地址：747飞机维护手册AMM CHAPTER 34 - NAVIGATION 第34章导航2(67)
