Definition
A second set of breaker points inside certain aircraft magnetos that open later than the main (advance) points. During engine start, the ignition system fires from the retard points instead of the advance points, producing a spark after the piston passes top dead center. This prevents the engine from kicking back against the starter at low cranking speeds.
Plain English
An extra set of contact points in the magneto that delays the spark during engine start, so the engine doesn't fire too early and kick backward while the starter is still turning it.
Context Anchor
Seen in aircraft ignition system maintenance, magneto timing checks, and troubleshooting hard starting or engine kickback during start.
Derivation
Retard' comes from the Latin retardare, meaning 'to delay or hold back.' In ignition systems, it means delaying the spark relative to its normal firing position. 'Breaker points' are the small mechanical contacts that open ('break') the primary circuit to trigger the spark. So 'retard breaker points' literally means 'the contacts that produce a delayed spark.'
Why Pilots Care
Retard breaker points protect the engine and anyone hand-propping it by eliminating violent kickback at low RPM.
Intuition Check
Do not read “retard” here as an insult or as reducing engine power. In ignition timing, “retard” means the spark is made to happen later than normal.
Example Sentence 1
During engine start, the ignition system fires through the retard breaker points so the spark occurs after top dead center, preventing kickback.
Example Sentence 2
The engine started smoothly once the retard breaker points delayed the spark until the crankshaft had turned far enough.