(4)
Supply equipment cooling to the INS (AMM 21-58-00/501).
(5)
Align the INS to the NAV mode (AMM 34-41-00/501).
CAUTION:_______USE TOOLS THAT ARE NOT MAGNETIC. MAGNETIC TOOLS CAN CAUSE COMPASS DIFFERENCES.
(6)
Make sure that the N-S and E-W adjustment screws on the standby compass are at neutral.
(7)
Make sure all vehicles but the tow truck are not less than 250 feet from the airplane.
F. Standby Compass Adjustment
NOTE: The steps that follow are for the four-point calibration swing:
____
(1) Turn the airplane to a magnetic heading of 0 degrees.
NOTE: Use the true heading display on the captain's INS CDU
____ corrected for the local magnetic variation.
(2)
Remove and keep the lower left and upper right mounting screws on the standby magnetic compass.
(3)
Use the two mounting screws to install the SCC on the face of the standby magnetic compass.
(4)
Turn the top and bottom SCC dials to show an indication of E at the index line.
(5)
Make a record of the heading shown on the standby magnetic compass.
(6)
Turn the top and bottom SCC dials to show an indication of W at the index line.
(7)
Make a record of the heading shown on the standby magnetic compass.
EFFECTIVITY
ALL 01 Page 204 Apr 25/9834-22-00
(8) Turn the E-W adjustment screw on the standby magnetic compass until the error in the last two recorded values is at a minimum.
NOTE: Divide the error in each of the two directions as equally as
____
possible.
(9)
Turn the top and bottom SCC dials to show an indication of N at the index line.
(10)
Make a record of the heading shown on the standby magnetic compass.
(11)
Turn the top and bottom SCC dials to show an indication of S at the index line.
(12)
Make a record of the heading shown on the standby magnetic compass.
(13)
Turn the N-S adjustment screw on the standby magnetic compass until the error in the last two recorded values is at a minimum.
NOTE: Divide the error in each of the two directions as equally as
____
possible.
(14) Continue to adjust the SCC dials for each pair of directions (E-W, N-S). Then turn the E-W and N-S adjustment screws until the errors are at a minimum.
NOTE: Continue to do this procedure until the error in each pair of
____ directions is at a minimum. Start with E-W and turn the E-W adjustment screw. Then do N-S and turn the N-S adjustment screw.
When the errors are at a minimum, do the steps that follow for the 12-point accuracy swing:
(15)
Adjust the SCC dials to indicate these magnetic headings: 0, 30, 60, 90, 120, 150, 180, 210, 240, 270, 300, and 330 degrees.
(16)
Make a record of the magnetic heading (MH) and standby compass heading (CH).
(17)
Calculate and make a record of the difference for each 30 degree heading in the steer column on the compass correction card as follows:
D = MH - CH
(18)
During these steps, make sure each difference is less than | 8 degrees. Make sure the difference between the maximum positive and maximum negative value is 10 degrees or less.
(19)
CAA CERTIFICATION; During these steps, make sure each difference is less than | 5 degrees. Make sure the difference between the maximum positive and maximum negative value is 10 degrees or less.
(20)
Put the SCC dials back to the N-N position.
NOTE: Do this step to keep the magnetic strength high.
____
EFFECTIVITY
ALL 01 Page 205 Apr 25/9834-22-00
G. Put the airplane back to its usual condition.
(1)
Set the mode selector switch for each INS to OFF.
(2)
Remove the electrical power if it is not necessary (AMM 24-22-00/201).
(3)
Remove the equipment cooling if it is not necessary (AMM 21-58-00/501).
EFFECTIVITY
ALL 01 Page 206 Apr 25/9834-22-00
STANDBY COMPASS - REMOVAL/INSTALLATION
______________________________________
1. Referenced Procedures
_____________________
A. 34-21-00, Adjustment/Test
2. Remove Compass (Fig. 401)
______________
A. Disconnect electrical cable from socket assembly at rear of compass.
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