Definition
An ARINC 424 path-and-terminator leg type that defines a holding pattern flown until the pilot or controller manually ends it. The aircraft flies the published holding pattern continuously, exiting only when cleared to do so or when the pilot decides to leave the hold. HM is one of three holding leg codes (HA, HF, HM) used by avionics to construct holding patterns from procedure data.
Plain English
A holding pattern in the database that keeps the aircraft circling until a person decides to leave it. Unlike other holds that end automatically after one lap or at a set altitude, this one only ends when you say so.
Context Anchor
Seen in RNAV instrument procedures and navigation database discussions, especially when describing how a hold is coded and when it ends.
Derivation
In ARINC 424 leg coding, the letter H designates a holding leg, and the second letter shows how the hold ends: A for altitude, F for one fix-to-fix circuit, and M for manual. So HM literally reads as Hold, Manual termination.
Why Pilots Care
Understanding this leg prevents the flight management system from remaining in the hold indefinitely and supports correct timing of the next course change.
Grounding Statement
Picture the navigation display showing the aircraft flying the hold repeatedly until the pilot selects the command to continue.
Intuition Check
Manual termination does not mean the procedure is cancelled or that the flight is over. It means this specific hold ends only when the pilot manually commands the system to continue.
Example Sentence 1
The missed approach procedure ends with an HM leg at the holding fix, so the autopilot will keep flying the pattern until the crew requests further clearance.
Example Sentence 2
The crew received an ATC instruction to manually terminate the HM leg and proceed direct to the initial approach fix.