Definition
The small air space between the face of an electromagnet and the movable iron armature it attracts in a relay, solenoid, or magneto breaker assembly. The size of this gap directly affects how strongly and how quickly the armature is pulled in when the coil is energized.
Plain English
The tiny space between a magnet and the metal piece it pulls toward itself when electricity flows through the coil. Too wide a gap and the pull is weak; too narrow and the part may stick or not release properly.
Context Anchor
Seen in aircraft maintenance instructions for electrical and ignition components, especially when checking starters, generators, or magneto-type ignition units.
Derivation
Armature comes from the Latin armatura, meaning 'armor' or 'equipment.' In electrical use it refers to the moving iron piece that responds to a magnetic field. The 'gap' is simply the air space the magnetic force has to bridge.
Why Pilots Care
An incorrect gap reduces magnetic flux, weakens the spark, and can cause rough running or magneto failure.
Analogy
It is like the small, even space between a brake pad and a spinning wheel part. The space is not there by accident; if it is wrong, the system may not work correctly.
Intuition Check
Do not confuse armature gap with an electrical setting or a timing value. It is a physical clearance: a small measured space between parts.
Example Sentence 1
During the 500-hour magneto inspection, the technician measured the armature gap with a feeler gauge and adjusted it to specification.
Example Sentence 2
Excessive armature gap caused a weak spark and intermittent engine miss at cruise power.