Figure 7-61.-Electrical swing and manual swing at a 90-degree heading.
Controlled dc currents to the secondary coils
The compass calibrator set is used to conduct
o f the transmitter generate an electromagnetic
an area magnetic survey. The survey determines
field (electrical swing). By applying a current to
the size and direction of the earth's magnetic field
coil leg A of the transmitter (fig. 7-61), you
at a proposed aircraft swing site. You will also
generate a field that aligns to leg A. In the
use the compass calibrator to conduct the actual
electrical swing, this field provides the north-south
compass swing. The control console provides
component of the simulated earth's field. A dc
controlled dc currents for the transmitter. The
current also goes through coil legs B and C to
monitor detects the size and direction of the
generate two fields, each aligned to its respective
earth's magnetic field and supplies this informa-
coil. These fields are so oriented that north-south
tion to the control console. You use the alignment
components of these two fields cancel, leaving one
equipment with the turntable to optically align the
east-west component. By reversing the direction
compass system transmitter (flux valve).
of the current flow, you can rotate the east-west
A review of the flux valve will be helpful in
component 180.
the following discussion.
The procedures for an electrical compass
swing using the magnetic compass calibrator set
In an electrical compass swing, a dc magnetic
are as listed below.
field is generated in the transmitter and varied in
size and direction. This allows the MC-2, in
1. Set up the turntable over the spot where
combination with the horizontal component of
the remote compass transmitter will be when the
the earth's field, to simulate an equivalent earth's
aircraft is on the north line.
field in the transmitter at a desired heading.
2. Remove the remote compass transmitter
Errors in the compass system are measured as the
(flux valve) from the aircraft and mount it on the
difference between the aircraft magnetic heading
turntable.
and the simulated earth's field magnetic heading.
3. Determine the alignment of the transmitter
The aircraft heading shows on the aircraft
to magnetic north and its electrical calibration to
compass indicator. The simulated earth's field
the ambient magnetic field. Calibrate the N-S and
heading shows by selecting the HEADING
E-W adjustments on the transmitter.
SELECTOR switch on the control console.
7-52
