Sikorsky Aircraft Corporation

David M Walsh

Bryan S Cotton

Christopher A Thornberg

Sherman Corning, Iii

An aircraft autopilot system provides a wind correction angle which is added to the desired course to provide commanded heading, the wind correction angle being generated as a proportional and integral function of ground track error. When the aircraft is off its desired course, it can be returned to the desired course by means of a course intercept angle, added to the desired course, to provide a corrected commanded course, the course intercept angle being a proportional function of the perpendicular error (the lateral distance of the aircraft from the original course) suitably limited to some angle within 90.degree. of the desired course. The course correction angle may be generated as a proportion of the perpendicular course error determined by the degree of importance of accuracy, and may be switched over to a course directly toward a waypoint in dependence upon the importance of efficiency. The course intercept angle may be a variable proportion of the perpendicular error as a function of the importance of accuracy, and the limits on the intercept angle determined by the relative importance of efficiency.

Aircraft course correction for wind and fuzzy logic course intercept

The airspeed limiting performance envelope of a helicopter is converted to a groundspeed envelope by factoring-in the wind speed and direction. A groundspeed command for an unmanned helicopter is provided as a function of the range to the helicopter's destination. The function may be calculated so as to provide a nominal groundspeed command equal to a nominal groundspeed command limit, or the function may be a fixed function to cause the aircraft to creep toward final approach. The cosine and sine of the desired relative flight direction of the aircraft, which is equal to the true bearing to the destination minus the true heading of the aircraft, are utilized to scale the groundspeed command into a longitudinal groundspeed command and a lateral groundspeed command. If one of the groundspeed commands is over a corresponding limit, the other groundspeed command is scaled back so that the vector addition of the two commands will cause flight in the desired direction. Exceedance of either a right or left groundspeed command, as well as saturation of the right or left cyclic pitch channel will cause the aircraft heading to be yawed into the direction of the limit exceedance or channel saturation.

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Palm City, FL, United States of America

David M Walsh