Part 7 of 9: Cessna Annual 172P - magnetos (cont), propeller, and engine services

I was taking some notes as Brent showed me around the engine of this 172P. The Lycoming engine of this 172P is a horizontally opposed engine. One magneto is wired to the bottom left side and the top right side of the engine. The other magneto is wired to the top left and the bottom right side of the engine. In the photo below, you see a close up of this wiring on one side of the Lycoming engine.

For those of you who are interested, a magneto works by means of a rotating magnet. A charge is created a that eventually travels through the distributer cap to a wiring harness to the spark plug on the engine.

The bottom spark plugs are disconnected during the inspection so the propeller can be safely turned. While you can start a Cessna 172P by turning a key inside the cockpit, you can also start the plane by turning the propeller by hand (known as hand propping). So, disconnecting the bottom spark plugs is a safety measure. There is no risk that the 172P will start accidentally. See the two pictures below.

The engine service includes but is not limited to servicing the alternator belt, inspecting the engine controls, and inspecting the engine.

After the propeller is inspected it is polished. In the photo below you see John polishing the propeller.

Next up on Monday, May 16: Finishing up the annual.