FAA Powerplant Written Practice Test

When internally timing a magneto, when do the breaker points begin to open?

1. When the piston reaches top dead center

2. When the magnet poles are a few degrees beyond the neutral position

3. When the ignition switch is turned on

4. When the engine reaches a specific RPM

The correct answer is: When the magnet poles are a few degrees beyond the neutral position

The timing of a magneto involves precise coordination between the movement of the piston and the position of the magnet poles. The breaker points in a magneto are designed to open at a specific moment to ensure that the spark occurs at the correct timing within the engine's cycle. The correct answer indicates that the breaker points begin to open when the magnet poles are a few degrees beyond the neutral position. This is critical because it allows the magneto to generate a spark at the optimal point in the piston's cycle for effective ignition. The neutral position of the magnet poles refers to the point where they are neither attracting nor repelling; moving beyond this point allows the magnetic flux to change in such a way that it effectively induces a high voltage necessary to create a spark. Timing is also essential for ensuring that the ignition occurs just before the piston reaches the top dead center (TDC), which is typically a few degrees after the neutral position of the magnet poles. This timing contributes to better engine efficiency and performance. Therefore, understanding the mechanics of magneto timing is crucial for proper ignition timing in engine operation.