An autopilot system consists of three main elements: a computerized guidance program that plots the aircraft’s course and compares its real position to its virtual one, a series of motion and position sensors such as airspeed indicators and gyroscopes to deliver real-time feedback, and a selection of servomotors to actuate the craft’s engines and alter its flight-altering components when changes are necessary.
By syncing these three elements autopilots can not only stabilize an aircraft’s pitch, yaw and roll movements – greatly relieving pilots on long-haul flights – but also handle, in poor visibility conditions, automatic runway approaches and landings.
In modern, commercial jets, autopilots are the central hub of the craft’s flight management system, a grouping of sensors such as GPS and INS (inertial guidance system) that help calculate the current positioning and course of the aircraft without need for external reference. The feedback from these systems are equalized and, in the case of accuracy discrepancies, resolved through a multidimensional Kalman filter, a mathematical model for mitigating random variations in feedback values.
Cutting-edge advanced autopilot systems may also include an autoland sub-system, however these are usually only available at major international airports, which have various ground-based systems to communicate with the autopilot flight management system on board to help alignment and ratify its current and potential approach and landing course.
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