Definition
A charted holding pattern used in place of a procedure turn to accomplish course reversal on an instrument approach. The pilot flies one circuit of the holding pattern at the depicted fix, which reverses course and aligns the aircraft with the inbound segment to the final approach fix. The HILO must be flown unless the aircraft is being radar vectored to final, is conducting a timed approach from a holding fix, or the procedure specifies 'NoPT' for the route being flown.
Plain English
Instead of the older teardrop or 45/180 procedure turn, the approach chart shows a small racetrack-shaped holding pattern at a fix. You fly one lap around it, which turns you around and lines you up to start the approach.
Context Anchor
Seen on instrument approach charts where a holding pattern is drawn at a fix and used as the course-reversal method.
Derivation
The name is literal: a hold flown 'in lieu of' (in place of) a procedure turn. 'In lieu of' comes from Old French 'lieu' meaning 'place,' so it simply means 'instead of.' The phrase tells the pilot that this hold is doing the job a procedure turn would otherwise do.
Why Pilots Care
It provides a standardized way to reverse direction while staying within protected airspace and avoiding terrain or traffic conflicts.
Intuition Check
Do not read “hold” here as simply waiting in the air. In a HILO, the holding pattern is part of the published approach path and is used to turn the aircraft around unless the chart or clearance allows it to be skipped.
Example Sentence 1
The approach chart showed a HILO at CENTR, so the pilot briefed one turn in the hold before tracking inbound to the final approach fix.
Example Sentence 2
The approach plate specified a HILO instead of a procedure turn due to nearby airspace restrictions.