FAA Ground School Practice Test

If the ground wire between the magneto and the ignition switch becomes disconnected, what is the most noticeable result?

1. The engine will start unexpectedly

2. It cannot be shut down by turning the switch to the OFF position

3. The engine will run smoothly

4. The ignition switch will function normally

The correct answer is: It cannot be shut down by turning the switch to the OFF position

When the ground wire between the magneto and the ignition switch becomes disconnected, the most notable effect is that the engine cannot be shut down by turning the switch to the OFF position. This is because the ignition switch is responsible for grounding the magneto to shut off the engine. If the ground wire is disconnected, the magneto continues to receive power, and thus, the spark plugs will still ignite the fuel-air mixture. This situation can lead to an inability to stop the engine using the ignition switch, which can be particularly dangerous in flight or during ground operations. The other outcomes are less likely or not directly related to this specific failure in the grounding system.