747飞机维护手册AMM CHAPTER 34 - NAVIGATION 第34章导航3(116)

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 B.  Observe the following precautions when operating the weather radar system.
 WARNING: DO NOT OPERATE WEATHER RADAR WHILE THE AIRPLANE IS BEING
_______ REFUELED OR DEFUELED AND DO NOT OPERATE IN ANY RADIATING MODE WHILE A FUELING OPERATION IS BEING CONDUCTED WITHIN 300 FEET OF THE ANTENNA OR AN EXPLOSION MAY OCCUR.
 PERSONNEL MUST NOT ENTER AN AREA CLOSER THAN 50 FEET OF A RADIATING ANTENNA OR INJURY TO PERSONNEL MAY OCCUR.
 CAUTION: WHEN THE WEATHER RADAR IS OPERATED IN ANY MODE OTHER THAN
_______ STANDBY OR TEST, DIRECT THE NOSE OF THE AIRPLANE SO THE FORWARD 180-DEGREE SECTOR IS FREE OF LARGE METALLIC OBJECTS (HANGARS, TRUCKS, OTHER AIRPLANES, ETC.) FOR A DISTANCE OF 300 FEET AND TILT THE ANTENNA UPWARD 15 DEGREES OR DAMAGE TO RECEIVER MAY OCCUR.
 DO NOT OPERATE WEATHER RADAR IN TEST MODE UNLESS AIRPLANE ATTITUDE REFERENCE SYSTEM (INU-1 AND 2) HAS ATTAINED AT LEAST COARSE ALIGN STATUS AND IS PROVIDING VALID STABILIZATION SIGNALS. THIS IS TO PREVENT ANTENNA FROM BUMPING REPEATEDLY AGAINST STOPS.
 C. Place weather radar control panel controls in the following positions:
 (1)  
Mode function selector switch - OFF

 (2)  
Systems (R/T) transfer selector - 1

 (3)  
Antenna TILT - 14 degrees up

 (4)  
STAB (stabilization) control (if provided) - STAB (or on) position

 (5)  
GAIN control - AUTO or NORM

 EFFECTIVITY
 AT ALL; AZ ALL; LH ALL;  CONFIG 1 AF 157, 161; IB 406-499  03 Page 103  Sep 25/94

34-43-00
 D.  Place controls on both weather radar indicators in following positions:
 (1)  
RANGE - Set to maximum range shown on test pattern (Fig. 101).

 (2)  
BRIGHTNESS (BRT) - Midposition

 (3)  
Offset controls (if provided) - AHEAD

 (4)  
SCAN/HOLD control (if provided) - SCAN

 E.  Provide electrical power. (Ref 24-22-00, Manual Control - Maintenance Practices (Apply Power).
 F.  Close WEA RAD R/T 1, R/T 2, IND 1, and IND 2 circuit breakers.
 G.  Provide equipment cooling. (Ref 21-58-00, Equipment Cooling -Adjustment/Test (Operational Test).
 H.  Turn on INS and erect to at least coarse align status. (Ref 34-41-00, INS Adjustment/Test (Operational Test).
 I.  The test pattern actuated by setting the mode select switch to TEST on the pilots' weather radar control panel is shown in Fig. 101. After the TEST mode is selected, the test pattern will be available after approximately 8-20 seconds.
 J.  Set BRIGHTNESS (BRT) control on each indicator to mid position, then follow procedures in the trouble shooting chart to attain proper indications on the test pattern and to isolate malfunctions.
 K.  Use the following information in association with the procedures in the trouble shooting chart.
 (1)  
Absence of the far targets may indicate a poor VSWR in the antenna and waveguide components. Make a visual check of these components for physical damage and/or perform VSWR test to confirm high VSWR when trouble shooting procedures in chart do not reveal malfunctioning LRU.

 (2)  
Inadequate or missing midtargets is usually an indication of a defective R/T unit.

 (3)  
If the near targets are missing, it may be an indication of a fault in the antenna stabilization circuits in the R/T units.

 EFFECTIVITY

 AT ALL; AZ ALL; LH ALL;  CONFIG 1 AF 157, 161; IB 406-499  06 Page 104  Sep 25/94

34-43-00
TDA-ON (TUNNEL DIODE AMPLIFIER)
RANGE MARK
150
TDA-OFF (TUNNEL DIODE AMPLIFIER)
100 STC (SENSITIVITY TIME CONTROL)
SELF TEST NOISE SIGNAL 50 VIDEO BANDS
CONTOUR BAND
NORMAL TEST PATTERN (PPI-1L)
TDA OFF
150
100
STC
50 VIDEO BAND
CONTOUR BAND
TDA ON
VIDEO BAND
RANGE MARK

OFFSET TEST PATTERN (PPI-1L)
Self-Test Display
Figure 101 (Sheet 1)

E40038
EFFECTIVITY

CONFIG 1AZ 201-224799 Page 105
34-43-00
 Sep 25/94
200  TDA-OFF (TUNNEL DIODERANGE AMPLIFIER)MARK TDA-ON
150 STC100
(SENSITIVITY TIME CONTROL) CONTOUR BAND
VIDEO BANDS
NORMAL TEST PATTERN (PPI-1L)
TDA
OFF 200
150
100
STC
RANGE MARK 50 VIDEO BAND
TDA ONCONTOUR BAND
VIDEO BAND
OFFSET TEST PATTERN (PPI-1L)
Self-Test Display Figure 101 (Sheet 2)
EFFECTIVITY
E40043
CONFIG 1AF 157,161799 Page 106
34-43-00
Sep 25/94
RANGE TDA-OFF MARK
150 
CONTOUR BAND  TDA-ON (TUNNEL DIODE AMPLIFIER) STC (SENSITIVITY TIME CONTROL) 
　
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