747飞机维护手册AMM CHAPTER 34 - NAVIGATION 第34章导航3(120)

 (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
 AF 101-120, 123-156, 158,

 159, 172-182, 185-199;  SN 301-350; IB 405; GN ALL; CONFIG MD ALL; VM ALL  01 C Page 109
   Sep 25/94

34-43-00
 WEATHER RADAR SYSTEM - TROUBLE SHOOTING
_______________________________________
 1.  General
_______
 A.  The trouble shooting procedure is based on the performance of the weather system R/T timing control and monitoring circuits. These circuits continuously monitor system operation in all modes.
 B.  The circuits identify most system malfunctions, and display alphanumeric messages (in legend fields on the indicator CRT) as an aid to trouble shoot system failures.
 C.  The legend field locations (Fig. 101) and the messages displayed are described as follows:
 (1)  
Legend field A - Located at the top left corner, presents, in blue, the selected range. A flashing display indicates the R/T has not received a range input.

 (2)  
Legend field B - Located at the top right corner, presents, in blue, the range mark interval for the selected range.

 (3)  
Legend field C - Located directly below field A (selected range). Displays, in blue, mode TEST, WX, TURB, or MAP as selected.

 (4)  
Legend field D - Located directly below field B (range mark interval). Displays selected degrees and direction of antenna tilt setting. Stabilization messages are also displayed in this location as follows:

 (a)  
STAB message displayed in blue if, attitude plus tilt setting exceeds excursion limits.

 (b)  
STAB message displayed in yellow if there is a weather radar stabilization fault.

 (5)  
Legend field E - Located directly below field C (selected Mode). Display COOL, in yellow, when R/T experiences cooling fault. Otherwise blank.

 (6)  
Legend field F - Located directly below field D (antenna tilt). Displays CAL in blue or yellow as follows:

 (a)  
CAL displayed in blue, when GAIN control not set to AUTO in MAP or TURB modes.

 (b)  
CAL displayed in yellow, when R/T receiver is out of calibration.

 (7)  
Legend field G - Located in the center of the CRT. Displays, in yellow, LRU fault warning. No other messages or data displayed on CRT. Messages displayed may be one or more of the following:

 (a)  
In a normal operating mode (WX, TURB, or MAP) R/T or ANT.

 (b)  
In TEST mode, R/T, ANT, CON, ATT, IND, or COOL.

 (8)  
Legend field H - Located below legend field F (CAL message). Displays in blue gain messsage of MIN, 1 thru 9, and MAX when the control panel GAIN control is rotated clockwise from just out of the detent AUTO position to the MAX position.

 2.  Prepare for Trouble Shooting
____________________________
 A.  Provide external electrical power (Ref 24-22-00, Manual Control -Maintenance Practices, Apply Power).
 EFFECTIVITY

 AF 121, 122; SN 351-399  CONFIG 3  02 B Page 101  Sep 25/9434-43-00
 B. Provide cooling air to electronic equipment (Ref 21-58-00).

 CAUTION: ENSURE EQUIPMENT COOLING IS OPERATING BEFORE TURN ON OF
_______ ELECTRONIC SYSTEMS OR DAMAGE TO EQUIPMENT MAY RESULT. EQUIPMENT COOLING SYSTEM MUST BE SET FOR NORMAL COOLING AS DESCRIBED IN 21-58-00.
 C.  Check WEA RDR R/T 1 and 2 and IND 1 and 2 circuit breakers on P7 panel are closed.
 D.  Prepare INS for operation and erect to at least coarse align (Ref 34-41-00). Attitude flags on captain's and first officer's ADI should be out of view.
 E.  Position ATTITUDE swith on captain's and first officer's instrument panels to NORMAL.
 F.  Position controls on indicator as follows:
 (1)  
Range switch - 40

 (2)  
BRT control - midcale

 (3)  
SN 351-399;
 SCAN/HOLD switch - SCAN

 G.  Position switches and controls on weather radar control panel as follows:
 (1)  
SYS switch - 1

 (2)  
TILT control - 0

 (3)  
GAIN control - AUTO

 (4)  
AF 121, 122;
 Mode Selector switch - OFF

 (5)  
SN 351-399;
 Mode Selector switch - TEST