man-made. The magnetic fields of aircraft
components cause deviation. These components
are engines, electric equipment, landing gear
struts, and flight control surfaces and their
control cables. You can keep the effects of
deviation to the very minimum by a process called
compass swinging.
As an AE, you must be completely familiar
with the two methods of compass swinging. These
two methods are the MC-2 compass calibration
set and the use of a compass rose. For a gyro-
Figure 7-58.-Compass rose, with aircraft on south heading.
stabilized compass or inertial navigation system,
the MC-2 is considered the primary means of
swinging. Deviation in a wet or standby compass
dog tags, bracelets, eyeglasses, jewelry, officer
is corrected for on a compass rose. The following
caps, badges, etc. Remember, too, that you use
paragraphs describe the compass rose and the
a nonmagnetic screwdriver in adjusting universal
MC-2 calibration set.
compensator screws.
You actually swing a compass in one of several
Compass Rose
ways. However, as an AE, your chief interest is
in ground swings. You usually accomplish a
Aircraft magnetic compasses (wet or standby)
have devices called compensators, which provide
ground swing with the aircraft at rest on a
a means for correcting deviation errors. You
compass rose. Look at figure 7-58.
Most air stations have a compass rose. The
cannot eliminate all errors, but you can reduce
them to a minimum.
compass rose looks much like an oversized card
from a navigation compass. The directions shown
Swinging the compass, you first compensate
the N-S and E-W headings. Then set the aircraft
by it are magnetic directions, and the north
on every 15- or 30-degree heading on the
arrow points toward the earth's north magnetic
pole. A compass rose may also have a line
compass rose. Here, you note the difference
showing true north.
between the aircraft heading and the indicated
heading. You then adjust the compensators to
Jacks, lifts, hoists, or any dolly needed to
reduce this difference or deviation to a minimum.
p e r f o r m the ground swinging job should
There are two types of compensators. One
preferably be of nonmagnetic material. However,
type is the universal screw type. It consists of an
this is not always possible. Devices used in the
assembly having a group of small compensating
swinging process must be tested for their effects
magnets permanently installed in it. To change
on the compasses. You do this by moving them
the compensating effect of the assembly, you use
about the aircraft in a circle with normal
two adjusting screws. One screw is for north-south
separation distance between the device and the
compensation, the other for east-west. The other
instruments. Do not use devices that cause more
type of compensator has small, loose magnets that
than one-quarter degree change in the compass
reading.
you place in special chambers on the compass as
needed. The chamber positions allow one to make
Trucks, automobiles, railroad cars, and other
east-west corrections. The other (at right angles
aircraft containing magnetic metals should not be
within the swinging area. These items could have
to the east-west chamber) corrects north-south
deviation. Compensation is done only on the
a magnetic effect on the compasses of the aircraft
being adjusted. You should be sure that the
cardinal headings on standby compasses. How-
ever, on all other compass systems in naval
compass is in good condition. Examine the
aircraft, compensation is at 15-degree increments.
compass for clear liquid and proper level. Check
Before starting the swinging operation, you
to see that the card assembly is level. Also check
should make sure all magnetic equipment is in the
that it turns freely when the aircraft's tail is in
posit ion it occupies in normal flight. Also, be sure
a level flying position.
that no one near the aircraft compasses during
Set the compensator so it has no effect on the
swinging operations has any magnetic materials
main compass magnets. Using a loose-magnet
compensator, remove all loose magnets from their
on their person. Magnetic materials include tools,
chambers. Set universal screw-type compensators
pocketknives, mechanical pencils, wristwatches,
7-48
