Definition
A single navigation fix that serves two roles at once: it is a Locator Outer Marker (a low-power non-directional beacon co-located with the outer marker of an ILS approach) and it is also published as the Initial Approach Fix for that approach. As an LOM, it provides bearing information to the pilot via an ADF and a positive position indication when the aircraft passes over the outer marker. As an IAF, it is the point at which the published instrument approach procedure formally begins, often serving as the holding fix from which timed approaches are conducted.
Plain English
It is one spot on the approach that does two jobs. It marks the start of the approach, and it is also the radio beacon and marker that confirms you are over the outer point of the final approach path.
Context Anchor
Seen on instrument approach charts and approach diagrams, especially when a pilot is holding at a point before starting the approach.
Derivation
Locator comes from the idea of helping the pilot locate themselves; Outer Marker because it sits at the outer end of the marker beacon sequence on an ILS. Initial Approach Fix is named for being the first fix where the published approach procedure begins. Combining the two labels on a chart simply tells the pilot the same point fills both functions.
Why Pilots Care
It provides a single, precisely located point for both holding and starting the timed final approach, ensuring proper separation and accurate timing.
Intuition Check
The slash does not mean choose LOM or IAF. It means the same published point is both the LOM and the IAF.
Example Sentence 1
ATC cleared the pilot to hold at the LOM/IAF and expect a timed approach with a one-minute departure interval.
Example Sentence 2
After departing the LOM/IAF the pilot began timing the outbound leg of the approach.