Abstract: A system to control the effect of northerly turning error which may occur in any direction indicating navigation instrument which includes a component responsive to the earth's magnetic field. In one form, an aircraft magnetic compass is compensated by electric current in an electromagnet which is made responsive to the rate of turn as sensed by a turn and bank indicator. In another form, an aircraft type slaved gyro directional system is protected from the effect of northerly turning error which occurs in its remotely located magnetic azimuth sensor by disconnecting its control circuit from the gyro when the turn rate reaches a predetermined level, thus allowing the gyro to act solely as a directional gyro during the turn.

Abstract: This is an apparatus to provide automatic self-steering for seacraft, particularly high speed sailing craft of the multi-hull type such as catamarans and trimarans which tend to respond instantly to small shifts in rudder angle. It includes a wind vane, many types of which are well known, which can be pre-set to respond to the direction of the apparent wind encountered by the craft while sailing on a pre-selected compass course to control a rudder and a damping mechanism or course stabilizer which is responsive to any temporary attempt of the craft to turn in either direction away from the desired and pre-selected compass course by either opposing the action of the wind vane as the wind vane responds to a temporary shift in apparent wind direction and tries to turn the craft away from the pre-selected course or, if the craft is turned off course as by wave action, acting to help the wind vane turn the rudder so as to bring the craft back onto the pre-selected compass course.