coefficient C[¦kō·ə′fish·ənt ′sē]
A component of magnetic compass deviation, varying with the cosine function of the compass heading, resulting from the athwartship component of the craft's permanent magnetic field and induced magnetism in unsymmetrical vertical iron port or starboard of the compass.
The coefficient of semicircular compass deviation caused by magnetism in the body of the carrying aircraft along its lateral axis. Its value is maximum on northerly and southerly headings. Coefficient C = ¼(Deviation on magnetic North − Deviation on magnetic South).