Definition
An IF leg defines the starting point of an RNAV procedure or a procedure segment. It establishes a fixed waypoint where the aircraft begins the leg, but it does not define a path to that point — the aircraft is assumed to already be at the IF when the leg becomes active. The next leg in the sequence defines the path away from the IF.
Plain English
An IF leg marks where a procedure starts. It tells the aircraft's navigation system, 'this is the beginning point' — but it doesn't tell the aircraft how to get there. Once the aircraft is at that point, the next leg takes over and defines where to fly.
Context Anchor
Seen in RNAV and instrument procedure coding, especially when a GPS or flight management system loads an approach, arrival, or departure procedure.
Derivation
‘Initial’ comes from the Latin initialis, meaning ‘at the beginning.’ ‘Fix’ in aviation means a defined geographic point. So an Initial Fix is literally the ‘beginning point’ of a procedure leg.
Why Pilots Care
It sets the exact starting location for the next leg so the aircraft is properly positioned before flying the remainder of the procedure.
Intuition Check
Do not read “fix” as a repair, and do not assume an IF leg is a full route segment leading to the fix. Here, the fix is a named position, and the IF leg marks the starting point.
Example Sentence 1
The approach begins with an IF leg at WAYPT, followed by a TF leg to the final approach fix.
Example Sentence 2
After completing the IF leg the aircraft continues on the next specified path terminator.