Definition
An IF leg is an RNAV path-and-terminator leg type that defines a single fix used to begin a procedure or a new segment of one. It has no defined path of its own — it simply identifies the starting point that the next leg will fly from. An IF leg is always followed by another leg type (such as a TF or RF leg) that establishes the actual track to fly.
Plain English
It's a starting point fix in an RNAV procedure. The IF leg itself doesn't tell you which way to fly — it just marks 'begin here,' and the next leg in the procedure tells you where to go.
Context Anchor
Seen in instrument procedure coding and RNAV procedure descriptions, especially when reading how a published procedure is built in the navigation database.
Derivation
IF stands for Initial Fix. 'Fix' in aviation means a defined geographic point. So an IF leg is literally the 'first point' of a procedure or segment — the anchor the rest of the route is built from.
Why Pilots Care
It defines the exact starting fix for legs in GPS and RNAV procedures, ensuring the aircraft begins the segment at the correct position.
Intuition Check
IF does not mean “if” as a condition here. It means Initial Fix: the named point where this part of the procedure starts.
Example Sentence 1
The approach begins with an IF leg at WAVRY, followed by a TF leg to the final approach fix.
Example Sentence 2
After crossing the IF leg the aircraft proceeds on the next coded segment to the following fix.