FAA Powerplant Written Practice Test

When does the internal timing of a magneto begin to show signs of operation during internal timing?

1. When the piston reaches top dead center

2. When the magnet poles are positioned at neutral

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

4. When the ignition is turned on

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

The timing of a magneto is crucial for proper engine operation, as it determines when the spark will be generated to ignite the fuel-air mixture in the cylinder. The internal timing of a magneto begins to show signs of operation when the magnet poles are a few degrees beyond the neutral position. This occurs because, as the magnet rotates past the neutral position, it begins to create a magnetic field that induces voltage in the coil of the magneto. This induced voltage is what ultimately generates the spark needed for ignition. The specific timing—just beyond the neutral position—is necessary to ensure that the spark occurs at the optimal moment in relation to the position of the piston, specifically just before the piston reaches top dead center. If the timing were to occur at neutral or later, it could result in a delayed ignition, which can lead to engine performance issues or even misfires. Thus, understanding the precise timing of the magneto operation is essential for effective ignition and overall engine performance, confirming that the best choice of timing occurs just beyond neutral.