Definition
Thin strands of stainless steel wire threaded through small holes in fasteners, fittings, or hardware and twisted together to physically prevent them from loosening, backing off, or separating during flight due to vibration.
Plain English
Small wires looped through bolts or fittings and twisted tight so vibration cannot shake them loose. They are a mechanical lock, not an electrical wire.
Context Anchor
Seen during preflight inspection around landing gear, brakes, and other places where fasteners must stay secure.
Derivation
Called 'safety' because their job is to keep critical hardware safe from working loose. The wire itself does no other job — it exists purely as a backup lock.
Why Pilots Care
Loose fasteners on landing gear or brakes can cause component failure or loss of control; safety wires provide a positive mechanical lock that survives vibration.
Intuition Check
Safety wires are not electrical wires, and they are not general tie-down wire. In this context, they are locking wires used to help keep fasteners from loosening.
Example Sentence 1
During preflight, the pilot noticed a broken safety wire on the oil filter and called a mechanic before flying.
Example Sentence 2
During the preflight walk-around the pilot verified that the safety wires on the brake caliper bolts were still tight and unbroken.