Autopilots and Flight Management Systems

Autopilots and flight management systems (FMS) have been grouped together in one chapter as modern aircraft require a high degree of integration between the two systems. It is explained that:

• The basic function of the autopilot is to control the flight of the aircraft and maintain it on a pre-determined path in space without any action being required by the pilot.
• The prime role of the FMS is to assist the pilot in managing the flight in an optimum manner by automating as many of the tasks as appropriate to reduce pilot workload.

The autopilot modes and their associated control and mathematics are explained with the aid of worked examples. These include height control, heading control, instrument landing system (ILS) and microwave landing system (MLS) coupled control and automatic landing systems. Also covered are satellite landing guidance systems, speed control and auto-throttle systems.

The FMS has become a key avionics system largely because it brings a significant reduction in pilot workload. Automatic navigation and flight path guidance allow the optimisation of the aircraft performance, civil air traffic density to be increased and flight costs reduced. Using an Airbus as an example, the main functions are described. These include navigation, flight planning, flight path optimisation, flight envelope monitoring, vertical flight path profile control and 4D flight management.

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