S 862-069
(8)
Make sure that one navigation display (ND) shows a magnetic heading that is less than one degree from the other ND.
S 752-070
(9)
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:
____ S 582-042
(1)
Turn the airplane to a direction where the captain's ND shows a magnetic heading of 0 degrees.
S 032-043
(2)
Remove and keep the lower left and upper right mounting screws on the standby magnetic compass.
S 482-044
(3)
Use the two mounting screws to install the SCC on the face of the standby magnetic compass.
S 822-045
(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.
S 822-047
(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.
S 972-046
S 972-048
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747-400
MAINTENANCE MANUAL
S 822-049
(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.
S 822-050
(9)
Turn the top and bottom SCC dials to show an indication of N at the index line.
S 972-051
(10)
Make a record of the heading shown on the standby magnetic compass.
S 822-052
(11)
Turn the top and bottom SCC dials to show an indication of S at the index line.
S 972-053
(12)
Make a record of the heading shown on the standby magnetic compass.
S 822-054
(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.
S 822-055
(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:
S 582-074
(15) Adjust the SCC dials to indicate these magnetic headings: 0, 30, 60, 90, 120, 150, 180, 210, 240, 270, 300, and 330 degrees.
EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400 MAINTENANCE MANUAL
S 972-076
(16)
Make a record of the magnetic heading (MH) and standby compass heading (CH).
S 972-077
(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
S 972-079
(18) 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.
G. Put the airplane back to its usual condition.
S 862-032
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