Attitude compensated electronic compass for aircraft navigation

Abstract

A magnetic compass has been developed by the Research Laboratory for Avionics System of the University of Florida intended to replace the common mechanical directional gyroscope for aircraft heading indication. The compass is based on an assembly of three mutually orthogonal single-core magnetic sensors, affixed to the fuselage, thus remaining in the aircraft frame of reference. The sensor electronics incorporate a feedback circuit that applies direct current to the sensor, sufficient to cancel the magnetic flux bias of the Earth field. This scheme results in a very accurate three dimensional measurement of the Earth's magnetic field vector, which is related to the attitude (roll, pitch and heading) of the aircraft through a set of algebraic equations. If the pitch angle is known, from an artificial horizon for instance, these equations can be served using a microprocessor in order to obtain the heading and the roll of the aircraft.