747飞机维护手册AMM CHAPTER 34 - NAVIGATION 第34章导航1(130)

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 B.  The process of ground swinging an airplane compass consists of accurately aligning the airplane at N, E, S and W cardinal headings in turn, using an average of the INS true heading output displays adjusted for local magnetic variation as a reference and observing the deviation between INS heading and compass heading in each case. The results are tabulated and necessary adjustments are made to reduce the deviations to within required limits. Another separate swing is made using 12 cardinal points spaced at 30-degree intervals for determining residual error and compiling a standby magnetic compass correction card. This card remains with the standby compass.
 C.  Deviation errors for which a compass swing is effective fall into two categories, index and single cycle error.
 (1)  
Index error exists when the direction error remains constant both in direction and value at each check point.

 (2)  
Single cycle error exists when the direction error is equal, but opposite in sign, at opposite check points on the compass. Such errors can be reduced by adjusting the E-W and N-S adjustments on the compensator.

 D.  The airplane compass swing is usually done in two parts; the first through four cardinal points (N, E, S, W) to take out the single cycle and index errors, and the second through 12 cardinal points spaced 30 degrees apart to compile the compass correction card.
 E.  It is not necessary to maintain a constant radius or tangency while towing the airplane around the compass rose or compass swinging area. The equations used to determine airplane heading are independent of these variables. They are also independent of airplane towing direction (clockwise or counterclockwise).
 F.  While airplane compasses are being swung, all electrical, radio, communications, and navigation equipment which would normally be operatin in flight and which could influence compass readings should be energized.
 G.  The standby magnetic compass should also be calibrated during the compass swinging procedure. Use nonmagnetic tools while adjusting the standby compass.
 H.  The MHRS should be checked out in accordance with 34-21-00 MHRS
 Adjustment/Test procedures prior to performing a compass swing.

 2.  Equipment and Materials
_______________________
 A.  Tow tractor
 B.  Nonmagnetic tools (for adjusting compensators on standby compass)
 C.  Precision synchro repeater (accuracy of | 0.1 degree), North Atlantic API 8025 (or equivalent)
 EFFECTIVITY
 

 ALL  01 Page 201  Oct 25/9634-21-00

APPROX 4 INCHES

(X)
TO
(Y)
API 8025
(Z)

AMPHENOL 48-10R2255P6 (OR EQUIV) AMPHENOL 48-10R2255S6 (OR EQUIV) CONNECTOR TO MATE WITH D2018P CONNECTOR TO MATE WITH D2018J
MHRS NO. 1
(X)
TO
(Y) API 8025
(Z)

AMPHENOL 48-10R2255P7 (OR EQUIV)  AMPHENOL 48-10R2255S7 (OR EQUIV) 
CONNECTOR TO MATE WITH D2024P  CONNECTOR TO MATE WITH D2024J 
MHRS NO. 2 

Synchro Repeater API 8025 Adapter Cable
Figure 201

EFFECTIVITY ALL

701 Page 202
34-21-00

 Oct 10/73
 D.  Adapter cables TE65B40880 or locally fabricated as shown in Fig. 201 to provide a capability of connecting synchro repeater to a synchro transmitter output of each coupler of the Magnetic Heading Reference System (MHRS)
 E.  Multimeter, Simpson 260 (or equivalent) for measuring the MHRS remote compensator adjustment settings
 3.  Reference Procedures
____________________
 A.  9-11-00, Towing
 B.  24-22-00, Maintenance Practices (Apply Power)
 C.  34-21-00, Adjustment/Test
 D.  34-41-00, Adjustment/Test
 4.  Prepare for Compass Swing
_________________________
 A.  Compass System Preparation
 (1)  
Disconnect connector D2018J (compass coupler No. 1) or D2024J (compass coupler No. 2) at flight instrument relay panel P73.

 (2)  
Connect the precision synchro repeaters into system using the adapter cables as shown in Fig. 201.

 (3)  
Connect 115 volts ac phase A power to the precision synchro repeater from radio bus No. 2.

 (4)  
Close all MHRS, RMI (RDDMI), HSI, and FLT INST SW RELAYS COMP circuit breakers on panel P7.

 (5)  
Allow compass systems (MHRS) to stabilize during INS alignment period.

 B.  Inertial Navigation Systems (INS) Run-up and Alignment
 (1)  Turn all INS mode selectors to ALIGN and wait for all NAV READY lights to illuminate (Ref 34-41-00).
 CAUTION: DO NOT MOVE THE AIRPLANE UNTIL ALL "NAV READY" LIGHTS
　
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