Definition
A type of mechanical fit between two mating parts in which the inside dimension of the outer part (the hole) is always larger than the outside dimension of the inner part (the shaft), so the two parts can slide together freely without force.
Plain English
A clearance fit is when a part fits inside another part with a little bit of room to spare, so it slides in and out easily without being forced.
Context Anchor
Seen in aircraft maintenance when checking how parts such as shafts, bushings, bearings, bolts, pins, and holes fit together.
Derivation
The word 'clearance' comes from 'clear,' meaning free of obstruction. In a clearance fit, there is always clear space between the two parts, which is exactly what allows the easy slide.
Why Pilots Care
Clearance fits matter in engine and airframe components where parts must move relative to each other -- like a piston pin in its bushing. Too little clearance and the part binds; too much and it wears or fails. Mechanics check these fits during overhaul.
Analogy
Think of sliding a pencil into a pencil holder that is slightly wider than the pencil. It drops in easily and pulls out easily -- that gap is the clearance.
Intuition Check
Do not read “clearance” here as permission from air traffic control. In this term, “clearance” means physical space between two fitted parts.
Example Sentence 1
The mechanic confirmed the piston pin had the proper clearance fit in the connecting rod bushing before reassembling the engine.
Example Sentence 2
The maintenance manual requires a clearance fit between the bolt and the spar hole to prevent stress concentrations.