Magnetic flux detector correction system

Claim 1

An aircraft heading correction system of the type utilizing a magnetic flux detector to provide a signal as a function of magnetic heading of the aircraft, characterised in that the system comprises first means (14) responsive to a signal representative of north, east and down acceleration components of said aircraft, and to said signal as a function of magnetic heading of the aircraft, for providing a signal representative of horizontal field strength, second means (18) responsive to the signal representative of horizontal field strength, for providing a signal representative of the tangent of a dip angle, third means (13) responsive to said signal as a function of magnetic heading of the aircraft, for providing a magnetic heading signal, fourth means (16) responsive to the signal representative of horizontal field strength, the signal representative of the tangent of the dip angle, and the signal representative of north, east and down acceleration components of the aircraft, for providing a magnetic heading correction signal, and fifth means (22) responsive to the magnetic heading correction signal and the magnetic heading signal for providing a corrected magnetic heading signal.

Claim 6

A system according to any of the preceding claims, characterised in that the signal representative of the tangent of the Dip angle is of the form:- tangent of Dip = A₀ + A₁ x HFS + A₂ x HFS² + A₃ x HFS³ where A₀, A₁, A₂ and A₃ are predetermined constants HFS = the horizontal field strength.

Claim 7

A system according to any of the preceding claims, characterised in that the magnetic heading correction signal is of the form:- where east component = [tan(dip angle)x sin A EM /A DOWN ], north component = [tan(dip angle)x sin (A NM /A DOWN ) + cos (A NM /A DOWN )], A EM = aircraft east acceleration, A NM = aircraft north acceleration, A DOWN = aircraft down acceleration.