Definition
A deformation in a material that remains after the load causing it has been removed. It occurs when a material has been stressed beyond its elastic limit, so it cannot fully return to its original shape.
Plain English
When metal or another material is bent or stretched so far that it does not spring back, the leftover bend or stretch is called a permanent set.
Context Anchor
Seen in aircraft maintenance, structural inspection, control-cable checks, landing gear parts, springs, and other components that may be bent or stretched by load.
Derivation
From 'permanent' (lasting) and 'set' (a fixed position or shape). Together they describe a shape that has been fixed in place and will not undo itself.
Why Pilots Care
Signals that a structural component has been overstressed and may need replacement to restore airworthiness.
Analogy
Think of bending a paperclip a little — it springs back. Bend it too far and it stays bent. That stay-bent shape is a permanent set.
Intuition Check
Permanent set does not mean a part was intentionally installed in a fixed position. It means the part was deformed and stayed that way after the load was removed.
Example Sentence 1
After the hard landing, the mechanic found a permanent set in one of the main gear support fittings and grounded the aircraft for repair.
Example Sentence 2
The mechanic measured for permanent set in the landing gear strut following the turbulence encounter.