Time controlled navigation and guidance for 737 aircraft

Specified time-of-arrival navigation and guidance control laws have been developed for the 737 flight management computer system. A required time of arrival can be specified at any geographical point in addition to altitude and airspeed. The earliest and latest arrival times within aircraft limits are computed along with the most cost-economic arrival time. Upon designation of a specified time, as may be requested by ATC for traffic spacing, the most fuel efficient speed is computed and automatically controlled as flight progresses to ensure that the aircraft meets the specified time. A variable time control window is provided to reduce unnecessary control activity when some time tolerance is permissible. The time control law uses the accurate time prediction capability of the flight management software. The control law can be retrofitted in existing 737 aircraft through software updating. The pilot interface requirements for time-controlled navigation and guidance are discussed, and the control laws used in this implementation are described