Definition
Measurements of the physical size of an aircraft component or feature, typically expressed as length, width, height, diameter, thickness, depth, or clearance. Dimensional measurements are taken with precision instruments such as rules, calipers, micrometers, dial indicators, and gauges, and are compared against the manufacturer's specified tolerances to determine whether a part is serviceable, requires repair, or must be replaced.
Plain English
The actual physical sizes of a part — how long, wide, thick, or round it is — checked with measuring tools to see if the part is still within the limits set by the manufacturer.
Context Anchor
Seen in aircraft maintenance inspections, repair work, part replacement, and when comparing a part to a maintenance manual, drawing, or specification.
Derivation
From Latin 'dimensio' meaning 'a measuring,' built from 'dis-' (out, apart) and 'metiri' (to measure). A dimensional measurement is literally a measurement taken across the physical extent of the object — its size in space.
Why Pilots Care
Worn or out-of-tolerance parts can fail in service. Dimensional measurements are how mechanics decide whether a cylinder, bearing, shaft, or structural part is still safe to use, needs reworking, or must be scrapped.
Intuition Check
Do not read dimensional measurements as rough size estimates. In maintenance, they mean careful measured values that are compared with an approved requirement or limit.
Example Sentence 1
Before reinstalling the cylinder, the technician took dimensional measurements of the bore to confirm it was within service limits.
Example Sentence 2
After the overhaul, dimensional measurements were recorded on the propeller hub before reinstallation.