FAA Aviation Mechanic Powerplant (AMP)Reciprocating EnginesHard
During magneto internal timing, a technician sets the breaker points to open exactly when the rotating magnet is at the position producing the maximum rate of flux change. What is this position called?
- AFull register position
- BNeutral position
- CE-gap (efficiency gap) position
- DTop dead center position
Show answer & explanationAnswer & explanation
Correct answer: C. E-gap (efficiency gap) position
The E-gap, or efficiency gap, is the number of degrees of magnet rotation past the neutral position at which the breaker points open, corresponding to the point of maximum rate of change of flux and producing the hottest spark.
Why the other options are wrong
- A. Full register describes distributor gear alignment for magneto-to-engine timing, not the E-gap.
- B. Neutral position is where flux is zero, not where points should open.
- D. Top dead center refers to piston position in the cylinder, not magneto magnet position.
E-Gap (Efficiency Gap)
The number of degrees the magnet rotates past neutral position before the breaker points open, timed to coincide with maximum rate of change of magnetic flux for the hottest spark.
- Neutral position is where flux is zero, not where points open
- E-gap angle is specified by the magneto manufacturer
- Internal timing sets breaker point opening at E-gap for max spark energy
Memory trick: E-gap gives the Extra-hot spark Exactly past neutral