ABSTRACT
To shut down an airplane’s engine, one moves the mixture control to the “idle/cut off” position and lets the propeller rotate to a complete stop. Once the propeller has stopped, the ignition switch is turned OFF and the ignition key removed from the switch. The engine will shut down if you merely turn off the ignition switch as you do in your automobile, but while the propeller is rotating to a stop, it will be drawing fuel into the engine’s cylinders. This excess fuel sitting in the horizontally opposed cylinders may cause harm to the cylinders and difficulty in subsequent engine starts. But worse than that, if the ignition should fail to be truly grounded, and one should turn the propeller by hand, the engine might kick or begin to run and severely injure someone (see magneto grounding below).
