(2)
Switch INS systems to NAV mode when NAV READY lights are illuminated prior to moving airplane. Check that NAV READY lights go out after switching to NAV mode.
(3)
Switch display selector switches on INS Control Display Units (CDU) to HDG/DA.
(4)
Check that compass systems are functioning properly in SLAVED mode of operation.
C. Determine Airplane Heading
(1)
Prepare airplane for towing (9-11-00) using electrical power from airplane APU (24-22-00).
(2)
Select a suitable compass swinging site.
NOTE: Site should be free from traffic and large magnetic objects
____ and in an area which has been found to be magnetically stable The horizontal component of the earths magnetic field measured at any point should not differ by more than 0.2 degree from that measured at any other point within the swinging site. The nominal magnetic variation should be known within 0.1 degree.
5. Swing Compass
_____________
EFFECTIVITY
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A. Calibrate Compass Systems
(1)
Position airplane within 2 degrees of north magnetic heading using true heading readings of inertial systems corrected for local magnetic variation.
(2)
Determine north magnetic heading (MHN) of airplane as follows:
(a) Record true heading readings (TH) of three INS (TH1, TH2, and TH3).
NOTE: Take readings using the numerical readouts on INS CDU's.
____
(b) Compute average true heading (THA) of airplane by averaging
readings of all INS: THA = TH1 + TH2 + TH3
_______________ 3
(c) Compute magnetic heading of airplane using local magnetic variation (VAR) and computed average true heading in one of following two equations: 1) MHN = THA + VAR (for westerly variations) 2) MHN = THA - VAR (for easterly variations)
(3) Record compass north magnetic heading indications (CHN) of compass systems 1 and 2 (CHN1 and CHN2) and standby compass (CHNS).
NOTE: Each compass system must be synchronized before readings are
____
taken.
(4)
Calculate and record north heading deviations (N) and sign for three compass systems (N1, N2 and NS): N1 = MHN - CHN1 N2 = MHN - CHN2 NS = MHN - CHNS
(5)
Position airplane within 2 degrees of east magnetic heading.
(6)
Determine east magnetic heading (MHE) of airplane using procedures in step (2).
(7)
Record compass east magnetic heading indications (CHE) of three compass systems (CHE1, CHE2 and CHES).
(8)
Calculate and record east heading deviations (E) and sign for three compass system (E1, E2 and ES): E1 = MHE - CHE1 E2 = MHE - CHE2 ES = MHE - CHES
(9)
Position airplane within 2 degrees of south magnetic heading.
(10)
Determine south magnetic heading (MHS) of airplane using procedures in step (2).
(11)
Record compass south magnetic heading indications (CHS) of compass systems (CHS1, CHS2, and CHSS).
(12)
Calculate and record south heading deviations (S) and sign for three compass systems (S1, S2 and SS): S1 = MHS - CHS1 S2 = MHS - CHS2 SS = MHS - CHSS
(13)
Calculate and record N-S single cycle error coefficient (C) for
______________________________________
compass systems 1 and 2 (C1 and C2) and standby compass (CS):
C1 = N1 - S1_______ C2 = N2 - S2_______ CS = NS - SS
2 2 2
(14) To obtain a standby compass indication compensated for N-S single cycle error (CHSS COMP), adjust N-S compensation screw on standby compass to produce a reading equal to : (CHSS COMP) = CHSS - CS
EFFECTIVITY
ALL 01 Page 204 Oct 25/9634-21-00
(15) Adjust N-S compensation screws on remote compensators of compass systems 1 and 2 to produce readings equal to: (CHS1 COMP) = CHS1 - C1 (CHS2 COMP) = CHS2 - C2
NOTE: Allow sufficient time for readings to stabilize.
____
(16)
Position airplane within 2 degrees of west magnetic heading.
(17)
Determine west magnetic heading (MHW) of airplane using procedures in step (2).
(18)
Record compass west magnetic heading indications (CHW) of compass systems (CHW1, CHW2 and CHWS).
(19)
Calculate and record west heading deviations (W) and sign for three compass systems (W1, W2 and WS): W1 = MHW - CHW1 W2 - MHW - CHW2 WS = MHW - CHWS
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本文链接地址：747飞机维护手册AMM CHAPTER 34 - NAVIGATION 第34章导航1(131)
