Definition
A cam inside a magneto that has an extra lobe arrangement designed for use on radial engines, so that the breaker points open at the correct firing position for each cylinder despite the uneven angular spacing between cylinder firings on a radial.
Plain English
A specially shaped part inside the magneto that makes sure the spark fires at exactly the right moment for each cylinder on a radial engine, even though the cylinders aren't spaced evenly in firing order.
Context Anchor
Seen in aircraft ignition-system maintenance, especially when inspecting or timing a magneto.
Derivation
Compensated comes from Latin compensare, meaning 'to balance out' or 'make up for.' The cam is shaped to make up for the uneven firing intervals of a radial engine, so the timing comes out right at every cylinder.
Why Pilots Care
Maintains correct ignition timing across the RPM range for smooth power delivery and to avoid detonation or power loss.
Intuition Check
Compensated does not mean paid. Here it means purposely adjusted to make up for small timing differences.
Example Sentence 1
The radial engine's magneto uses a compensated cam so each of its nine cylinders fires at the correct point in its rotation.
Example Sentence 2
At higher RPM the compensated cam advances the spark automatically.