Definition
Small adjustable magnets built into the magnetic compass housing that produce their own magnetic fields to cancel out unwanted magnetic influences from the aircraft's own electrical systems and ferrous metal components. They are adjusted during a procedure called 'swinging the compass' to reduce deviation errors on the cardinal headings.
Plain English
Tiny adjustable magnets inside the compass that can be turned to cancel out the magnetic interference caused by the aircraft itself, so the compass reads more accurately.
Context Anchor
Seen in magnetic compass theory, compass inspection, and compass accuracy checks, especially when discussing why a compass may not point exactly where the aircraft is heading.
Derivation
From Latin 'compensare', meaning 'to weigh against' or 'balance out'. The assemblies do exactly that — they balance out unwanted magnetic pull from the aircraft with an equal and opposite magnetic pull of their own.
Why Pilots Care
Accurate compensation prevents heading errors that can lead to navigation mistakes, especially when relying on the compass alone in instrument conditions.
Intuition Check
Do not think of compensator assemblies as parts that make the compass perfect. They reduce aircraft-caused compass error as much as practical, but some remaining error may still exist.
Example Sentence 1
After installing the new radio stack, the mechanic adjusted the compensator assemblies and updated the compass correction card.
Example Sentence 2
The pilot verified that the compensator assemblies had not been disturbed before accepting the aircraft for an IFR flight.