(a)
Gyro pitch signal removed and a synthetic nose-down pitch signal is supplied to the pitch amplifier.
(b)
Gyro roll signal removed and an artifical roll signal is injected, simulating a continuously alternating left and right roll.
NOTE: The azimuth drive signal, which is always generated,
____ together with the synthetic pitch and roll signals ensure a dynamic test on all three antenna axes. These test signals completely check the stabilization circuitry; however, if a flight complaint is logged for a deficiency in the stabilization accuracy, and the test mode indicates no abnormalities, the gyro inputs should be checked.
(c)
Status of fault monitor circuit (except VSWR monitor) is displayed on the indicator as presence or complete absence of video test bands.
(d)
If the test pattern does show loss of video test bands, the fault lamps on the front panel of the R/T unit should be observed to enable determination of the faulty unit. The ANT and R/T lamps (if included on the control panel) also provide a visual indication of ANT and/or R/T fault.
EFFECTIVITY
AT ALL; AZ ALL; LH ALL; CONFIG 1 AF 157, 161; 05 Page 17 IB406 THRU 499 Sep 25/94
34-43-00
(3)
The fault indicators, located on the R/T front panel, are designated T/R, VSWR and ANT. Should a malfunction occur in a unit, a fault indicator illuminates and the faulty unit can be determined.
(4)
A malfunction in any of the monitor circuits will activate the T/R fault lamp and, if in the TEST mode, cause disappearance of the video test band. The T/R fault lamp receives parallel inputs from the following monitor circuits.
(a)
The rf pulse detected by the afc crystal is used to indicate the condition of the transmitter output. If for any reason the power falls below the level of the monitor, the T/R fault lamp lights.
(b)
The local oscillator and afc monitor will give a fault indication when there is no output from the pulse amplifier in the afc loop. Some of the causes would be: no local oscillator output, malfunction in the afc circuit, or an excessive frequency shift of either the magnetron or local oscillator.
(c)
The rf limiter monitor is designed to monitor the rf energy that leaks through the rf limiter. Since an excessive amount of rf leakage can damage the mixer crystals, it is necessary to sense this level and disable the transmitter before any damage can be done.
(d)
The receiver monitor measures the agc voltage generated in the receiver. This monitor will detect failures that occur through the IF amplifiers to the video amplifier.
(e)
The power supply monitor detects out of tolerance changes of the output voltages from the power supply.
(f)
The pitch/tilt and roll servo-amplifiers are located in the R/T unit. The outputs of these amplifiers are monitored and any malfunction will be indicated by operation of the T/R fault lamp.
EFFECTIVITY
AT ALL; AZ ALL; LH ALL; CONFIG 1 AF 157, 161; 01 Page 18 IB406 THRU 499 Sep 25/94
34-43-00
RESET
Weather Radar System Fault Monitor Block Diagram
Figure 5
EFFECTIVITY AT ALL; AZ ALL; LH ALL;
CONFIG 1 AF 157,161; IB 406-499 703 Page 19
34-43-00
Sep 25/94
780330
(5) The VSWR monitor periodically cycles the transmitter to monitor an excessively high mismatch which can damage the duplexer and possibly the magnetron. This type of failure, which would normally occur at high altitudes, will activate the VSWR indicator. The VSWR circuits uses an electronic latching type device that continues to display a warning that sometime, since the last checkout, a high VSWR condition existed and may still be present. A reset button is included on the R/T front panel. The VSWR lamp is not directly interconnected with the test pattern. A VSWR fault will, however, appear as a periodic breakup in indicator display.
NOTE: In resetting the VSWR monitor circuit it is well to remember
____ that when the system is in the TEST mode the transmitter is operating into the dummy load. In order to duplicate the condition of a high VSWR caused by the waveguide or antenna, it may be necessary to operate the system in the NORM (normal) mode.
(6) Antenna sensors, or mechanical conditions which lead to either sluggish or oscillatory antenna motions can be rapidly detected. The ANT and the T/R fault lamps will light at the same time when a fault occurs within any of the following areas. If the system is in the TEST mode, video test bands will also disappear. Functions monitored are:
(a)
Azimuth axis rotation and position sensor
中国航空网 www.aero.cn
航空翻译 www.aviation.cn
本文链接地址：747飞机维护手册AMM CHAPTER 34 - NAVIGATION 第34章导航3(85)
