Definition
An ARINC 424 path and terminator leg type used in RNAV procedure coding that begins at a defined fix and continues outbound on a specified course or track until the pilot manually terminates the leg, typically by selecting the next leg or activating a heading or vector mode. The leg has a defined starting point and direction but no predetermined endpoint; termination depends on pilot or controller action rather than distance, altitude, or another fix.
Plain English
A flight-path segment in the navigation database that starts at a known point and runs along a set course, with no fixed end. It keeps going until the pilot manually ends it, usually after ATC instructions.
Context Anchor
Seen in RNAV and flight management system procedure coding, especially when reviewing how an instrument procedure is built from path-and-terminator legs.
Derivation
The label comes from ARINC 424, the industry standard for navigation database coding. Each leg type is named by its start and end conditions. 'F' marks a fix as the starting point; 'M' marks a manual termination as the ending condition. So 'FM' literally describes the leg: Fix-to-Manual.
Why Pilots Care
Pilots must recognize that the procedure does not end at a fixed waypoint, so they remain responsible for deciding when to terminate the leg and what to do next.
Grounding Statement
An FM leg keeps going from its starting fix until the pilot deliberately ends it.
Intuition Check
“Manual termination” does not mean the whole procedure is over. It means this one leg does not end by itself at a named next fix; the pilot must manually move beyond it.
Example Sentence 1
After crossing the departure fix, the FMS sequenced onto an FM leg, and the crew flew the published track until ATC issued a radar vector.
Example Sentence 2
During the missed approach we flew the FM leg outbound until reaching visual conditions and then turned toward the holding fix.