FAA Aviation Mechanic Powerplant (AMP)Reciprocating EnginesMedium
A technician is performing a magneto internal timing check. The breaker points begin to open at the exact moment the rotating magnet is at its greatest magnetic field strength (E-gap). What is the primary purpose of timing the points to open at this specific position?
- ATo ensure maximum spark duration.
- BTo prevent magneto overheating.
- CTo minimize wear on the breaker points.
- DTo produce the strongest possible spark.
Show answer & explanationAnswer & explanation
Correct answer: D. To produce the strongest possible spark.
The E-gap (efficiency gap) is the position where the rotating magnet produces its maximum magnetic field strength. Opening the breaker points at this precise moment causes the primary coil current to collapse when the magnetic field is strongest, inducing the highest possible voltage in the secondary coil and thus producing the strongest spark.
Why the other options are wrong
- A. While a strong spark is important, the E-gap primarily focuses on the spark's initial intensity (voltage), not its duration.
- B. Magneto overheating is generally related to internal resistance or component failure, not specifically E-gap timing.
- C. Minimizing wear on breaker points is achieved through proper materials and spring tension, not directly by E-gap timing.
E-Gap Timing (Magneto)
The precise adjustment of magneto breaker points to open when the rotating magnet is at its maximum magnetic field strength.
- Points open at maximum magnetic flux.
- Induces highest voltage in secondary coil.
- Produces strongest spark for ignition.
Memory trick: E-gap is for 'Excellent Spark' – maximum field, maximum power.