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CORRECTION CARD
ADJUSTING YOUR COMPASS
Before your compass can be adjusted the aircraft must be capable of being aligned to both the East /West axis and North/South axis.
The use an another compass outside the aircraft, to determine the cardinal points is advised.
These following notes should be used for initial installation guidance only, the corrections should be checked by a qualified Compass Adjuster before flying.
CORRECTION EAST/WEST (‘B’ Coefficient)
1) Align your aircraft facing East, insert the Corrector Key provided, into the Left hand hole at the front of the compass, rotate the key in either direction so that the East point is
directly under the Index line.
2) Align your vehicle/aircraft facing west and check that the West Point is under the Index line, Any error may be corrected by readjusting to remove HALF the error shown.
CORRECTION NORTH/SOUTH (‘C’ Coefficient)
1) Align your vehicle/aircraft facing North, insert the Corrector Key into the Right hand hole at the front of the compass, rotate the key in either direction so that the North point is
directly under the Index line.
2) Align your vehicle/aircraft facing South and check that the South point is under the Index Line. Any error may be corrected by readjusting to remove HALF the error shown
.
The above procedures can be repeated until the errors are minimised.
If these adjustments result in consistent errors on each of the Cardinal points the compass may not be aligned correctly on the Fore and Aft directions of the aircraft, to correct this mis-
alignment proceed as follows: -
Fig 2 Fig 3
CORRECTION FOR MIS-ALIGNMENT (‘a’ Coefficient)
Only follow this procedure if the results obtained so far do not meet your
required levels of accuracy.
1) Align the aircraft facing North; record the compass error in Box A.
2) Align the aircraft facing South; record the compass error in Box B.
3) Align the aircraft facing East, record the compass error in Box C.
4) Align the aircraft facing West; record the compass error in Box D.
CORRECTION TABLE
Technical Help can be provided by SIRS Navigation Ltd.
Tel: +44 (0) 1474-816320 Fax: +44 (0) 1474-816321 or email: sales@sirs.co.uk
Website: www.sirs.co.uk
BOX Sample Error BOX ACTUAL ERROR
A (NORTH)
+15
A
B (SOUTH)
+5
B
C (EAST)
-10
C
D (WEST)
+10
D
E (TOTAL)
+20
E
F (“E” / 4)
+5
F
SIRS Navigation Ltd
Compass House, Bowes Estate,
Wrotham Road, Meopham,
Kent DA13 0QB
England
Spares:
Please contact us for an up to date leaflet of spares and prices.
Note:
Errors to the Left of the true heading should be prefixed with a plus sign (+). [Fig 2]
Errors to the right of the true reading should be prefixed with a minus sign (-). [Fig 3}
5) Add the readings in Boxes A to D, enter the result in Box E. Divide the figure in Box E by 4,
record the result in Box F, this figure is the error due to mis-alignment and may be corrected.
Correction can be achieved by rotating the front mounting face (in the horizontal plane) of the
compass in the opposite direction to the error, and by the same magnitude. Altering the angle of
the mounting bracket or fitting shims to the rear of the compass mounting face will result in the
rotation of the compass.
In this example the compass body would need to be rotated by -5 degrees
If having carried out these procedures the results are not satisfactory a new
location must be found. Before this can be done, the PEGASUS must be
returned to its ZERO correction status by rotating the correctors using the
special key.
The correction card, supplied with the compass, is designed to be stuck or screwed
to a convenient panel, local to the compass.
Spare compass cards are available as a spare item.
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