TM 55-1905-223-24-14
(1) Coefficient A is constant on all headings and may be a combination of other parameters or may be mechanical, as
from an incorrectly placed lubber's line (binnacle misaligned).
(2) Coefficient B is maximum on compass headings east or west and zero on
compass headings north or south.
(3)
Coefficient C is maximum on compass headings north or south and zero on east or west.
(4) Coefficient D is quadrantal deviation. It is maximum on intercardinal headings (0450-1350-2250-3150), and zero
on cardinal headings (North-South-East-West).
(5) Coefficient E is quadrantal deviation, which is maximum on the cardinal compass headings and zero on the
intercardinal headings.
(6) Coefficients D and E are caused by induced magnetism in horizontal soft iron, and are compensated for by the
use of the soft iron quadrantal spheres mounted on brackets athwartships on the binnacle.
c. Heeling Error. Coefficient J is defined as the change of deviation for a heel of 1while the vessel is on compass 0
.
It is, in effect, the error caused because the compass, with its gimballing arrangement, remains in a horizontal plane
while the vessel, with its magnetic field, rolls and pitches. A slight change in the relative positions of the compass and
vessel is therefore introduced. This change in deviation caused by the motion of the vessel can cause the compass card
to oscillate. Coefficient J is compensated for by a heeling magnet placed in a vertical tube directly below the center of
the compass.
d. Flinders Bar. On the magnetic equator, there is no vertical component of the earth's magnetic field, and therefore
no induced magnetism in vertical soft iron. At other locations, such as at higher latitudes, the vertical component can
cause the compass to become more unreliable than if the force is neutralized. To compensate for or neutralize any
induced magnetism in vertical soft iron, a flinders bar is used. This consists of sections of soft iron having no permanent
magnetism; as many sections as required are installed vertically in a tube on the side of the compass opposite to the
effective pole of the vessel's field.
e. Periscopic Reflection. The periscopic reflection compass and binnacle can be used as a combined steering and
bearing compass. It permits installing the compass on the level above the pilothouse or wheelhouse. The image of the
compass card is reflected down periscopically and presented in the field of view of the soldier at the helm. The compass
itself is removed from the enclosed pilothouse, where it would be surrounded by metal and much electrical and electronic
equipment. On the open deck above, bearings and azimuths may be obtained directly on the compass itself, either for
navigation or for checking the compass.
1-10. Power Distribution . The binnacle (FIGURE 1-19) receives 24 Vdc from the pilothouse dc panel via ship's
cable. The cable is routed in the pilothouse top, up through the deck and pedestal to an internal terminal block. The
terminal block connections supply power to the hood lamp through a toggle switch and rheostat. The internal wiring is
terminated on the hood plug. The hood lamp cable runs out of the hood on the forward side and connects to the hood
plug.
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