Definition
A holding pattern in which the aircraft makes left turns rather than the standard right turns. Nonstandard holding is used only when specified by ATC or depicted on a chart, and all other elements of the pattern (one-minute inbound leg below 14,000 feet, standard rate turns) remain the same as a standard hold.
Plain English
A racetrack-shaped holding pattern flown with left turns instead of right turns. Everything else about the pattern is the same; only the turn direction is reversed.
Context Anchor
Seen on instrument charts and in air traffic control holding instructions when a hold must be flown with left turns.
Derivation
Nonstandard' simply means 'not the default.' The default (standard) holding pattern uses right turns, so any pattern that turns the other way is labeled nonstandard.
Why Pilots Care
Executing the wrong turn direction can cause traffic conflicts, airspace deviations, or failure to remain in protected airspace.
Intuition Check
Nonstandard does not mean improvised, unofficial, or optional. In this context, it usually means the holding pattern is still a proper assigned or published hold, but with left turns instead of the normal right turns.
Example Sentence 1
ATC issued a holding clearance with left turns, so the pilot briefed and flew a nonstandard holding pattern at the fix.
Example Sentence 2
The approach plate showed a nonstandard holding pattern with left turns for this procedure.