TM 1-1500-204-23-4
Figure 4-20. Compass Correction Card
·
After each engine change
NOTE
Check
applicable
aircraft
special
inspection
to
determine
if
the
compass check and/or calibration is
required after engine change.
·
After any modification/change to the existing
electrical system of major structural change
·
At any time compass is suspected of
being in error
·
Whenever the flux valve has loosened
in its mounting, has been removed
during troubleshooting, or has been
replaced with a new unit
·
At
anytime
the
applicable
aircraft
technical manual specifies
(b)
Pre-compensation
instructions.
Accomplish
the
following
procedures
before
compensating:
1
Ensure that aircraft is at least 100
yards from any steel structure, underground cables,
metal pipes, reinforced concrete or other aircraft.
2
Ensure that all items in aircraft
containing ferrous materials are located in the positions
they will occupy during flight.
3
Remove all magnetic articles from
one's person. Use a nonmagnetic screwdriver.
4
Using a small permanent magnet,
cause compass card to deflect through a small angle.
Note whether the card rotates freely on its pivot, and
that its path of rotation is in a horizontal plane. To avoid
erroneous readings, read compass only directly in front
of the lubber line.
5
Prior to compensation of magnetic
compass, have aircraft headed successively toward
magnetic North, East, South, and West with engines
running and all systems operating. Compass readings
must read within 20 of deviation noted on DD Form
1613 (Pilot Compass Correction Card). When reading is
within specified tolerance, compass does not need
compensating. Transcribe readings from old DD Form
1613 to new DD Form 1613; date and sign form. If
magnetic compass is not within tolerance, proceed with
next paragraph.
6
Remove one of the retaining screws
and loosen the other from the compensator assembly
cover plate, and rotate the plate to allow access to the
compensator adjustment screws. Ensure that error
compensator adjustment screws are set to neutral prior
to realignment of compass transmitter.
7
Run the engines and turn on power
to all electrical equipment which may have magnetic
4-26
