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 TM 55-1905-217-34
(1) Remove heading indicator by removing eight screws and washers from indicator protective cover, removing
indicator protective cover, removing four screws and washers from indicator bezel, lifting indicator from panel, and
disconnecting cable connector.
NOTE
Do not tamper with four calibrating screws on rear of indicator except during calibration
(2) Remove induction compass transmitter by removing eight nonmagnetic screws and washers from case cover
and three nonmagnetic screws and washers from transmitter, lifting transmitter from mounting surface, and disconnecting
cable connector.
NOTE
Do not tamper with two screws securing transmitter indexing key to mounting surface, three
external mounting nuts securing transmitter case to mast support, or three nuts and bolts
securing mast stop bracket to mast retainer bracket.
(3) Remove interconnect cables by disconnecting wires from terminal box terminals and removing all tiedown
straps securing cables.
NOTE
Record position of cable wires on terminals to ensure correct installation.
b. Installation. Install in reverse order of removal.
c. Calibration.
(1) Aline landing craft to 0heading. Algebraically add heading of landing craft and reading of heading indicator.
Record sum.
(2) Repeat step (1) for 90 180 and 270headings.
,
,
(3) Algebraically add sums from steps (1) and (2) and divide total by four. Record the quotient (index error).
(4) Aline landing craft to 0 heading and record heading of heading indicator.
(5) Remove all magnetic material from person who is to be adjusting transmitter case. Loosen three nuts securing
transmitter case to mast support (fig. 2-6) and rotate transmitter case so that new heading on heading indicator is equal to
heading recorded in step (4) minus the index error (magnitude and sign) calculated in step (3).
(6) Secure transmitter case with three mounting nuts, ensuring that position of transmitter does not change.
(7) Adjust N-S adjustment screw to obtain 0 reading on heading indicator.
(8) Aline landing craft to 90heading and adjust E-W adjustment screw to obtain 90reading on heading indicator.
(9) Aline landing craft to 180 heading and adjust N-S adjustment screw to remove one-half error of heading
indicator reading.
(10) Aline landing craft to 270 heading and adjust E-W adjustment screw to remove one-half error of heading
indicator reading.
(11) Repeat steps (7) thru (10) as required to optimize adjustment.
(12) Aline landing craft to 0 heading and adjust 0 adjustment screw at rear of heading indicator to obtain 0
reading on heading indicator.
(13) Aline landing craft to. 180 heading and adjust 0 adjustment screw to remove one-half error of heading
indicator reading.
(14) Aline landing craft to 45heading and adjust 45 adjustment at rear of heading indicator to obtain 45reading
on heading indicator.
(15) Aline landing craft to 225 heading and adjust 45 adjustment screw to remove one-half error of heading
indicator reading.
(16) Repeat steps (12) thru (15) as required to optimize adjustment.
6-11
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