Definition
A charted holding pattern used on an instrument approach in place of a procedure turn, allowing the aircraft to lose altitude, reverse course, and align with the final approach course before continuing inbound. The holding pattern is depicted on the approach chart at a fix on the initial or intermediate approach segment, and pilots fly it as published unless cleared otherwise by ATC.
Plain English
A racetrack-shaped holding pattern shown on an approach chart that the pilot flies instead of doing a procedure turn, in order to get lined up and at the right altitude for the final approach.
Context Anchor
Seen on instrument approach charts during the initial approach segment, especially when the aircraft must turn around or line up before continuing inbound.
Derivation
The name describes its function: a holding pattern flown 'in lieu of' (in place of) a procedure turn. 'In lieu of' comes from French, meaning 'in the place of.'
Why Pilots Care
Proper execution prevents altitude busts and ensures obstacle clearance while aligning the aircraft for the approach.
Intuition Check
Do not read HILO as a normal hold used just for delay. In this context, it is part of the approach path and is used to turn the aircraft inbound unless the chart or ATC clearance allows otherwise.
Example Sentence 1
The approach chart showed a HILO at the initial approach fix, so the pilot entered the holding pattern to lose altitude and reverse course before flying inbound.
Example Sentence 2
HILO transitions are charted to keep the aircraft at a safe altitude until established on the final approach course.