The Autopilot Flight Director System and Its Operations

Autopilot systems are very useful tools for flight, allowing for a pilot to be relieved of various duties so that they may focus on what is most important. For large aircraft, Autopilot Flight Director Systems (AFDS) are quite common, combining multiple systems together. The capabilities of the AFDS may vary based on the type of system that is implemented, ranging from simple autopilot systems to ones that are quite complex. In this blog, we will discuss Autopilot Flight Director Systems, allowing you to better understand their use and features.

Autopilot Flight Director Systems Work & Types

In general, the AFDS is set apart from other system types due to the integration of an autothrottle system and the ability to undertake glideslope and auto landing modes. Such systems also have two basic operating modes for conducting flight, those of which are strategic and tactical operating modes. Strategic operation is when FMS programming with lateral navigation (LNAV) and vertical navigation (VNAV) is selected. Tactical operation, meanwhile, allows for mode control panel or flight control unit manipulation.

With strategic operation, an increased level of automation can be carried out, allowing for long-term goals to be attained. With the FMS, each navigation system, the autopilot, and autothrottle system are all interlinked. The FMS may also manage all flight phases, capable of carrying out takeoff, approach, and landing procedures with full engine thrust.

Strategic operations are beneficial for accurate operations across vertical and lateral navigation, the FMS being capable of determining the most efficient speed, level, and other conditions for the set route while accounting for aircraft weight, temperature, atmospheric pressure, etc. As a result, the route that is calculated by the FMS can be considered to be the most precise and efficient solution. If VNAV and LNAV navigation modes ever need to be adjusted, such profiles may be modified by the flight crew.

Tactical operations provide a more simplistic form of automation, allowing for manual input to be provided by the flight crew through the use of the MCP/FCU. Generally, tactical operations are for carrying out more short-term goals. With mode selector controls, the pilot may select roll and pitch modes for the autopilot system, and basic inputs include heading, speed, vertical speed, altitude, and flight level. Once a mode is selected and inputs are made, the aircraft will then adjust and maintain pitch angle, heading, and thrust to meet a set goal. When conducting such operations, vertical and lateral profiles do not need to be provided to the FMS.

FMA modes are important to be aware of, those of which are the modes that the autothrottle and autopilot systems may work in. Due to the fact that different modes have varying principles, pilots should regularly check the FMA mode to ensure that the correct one is engaged. As the FMA displays the mode, pilots may make their confirmations as they conduct their typical instrument scans. As a result of the importance of FMA checks, it is standard procedure that FMA mode changes are called out either by the PF or PM.


While the FMA indicates the engaged mode, changes in modes may be made with controls located on the MCP. With As the Autopilot Flight Director System can provide much use to countless aircraft, it is important that they are well maintained over time for their reliability. If you find yourself in need of various aircraft parts, instrument components, or other such items, look no further than RFQ Experts. RFQ Experts is an online distributor of aircraft parts, and we are your sourcing solution for new, used, obsolete, and hard-to-find products that have come from leading global manufacturers that we trust. Due to our unwavering commitment to strict quality control initiatives and practices, we proudly conduct operations with AS9120B, ISO 9001:2015, and FAA AC 00-56B certification and accreditation. Get started on the purchasing process today with a competitive quote on items when you fill out and submit an RFQ form as provided on our website.


January 23, 2023

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