Spark plugs are installed in aero engines in which location?

• A. In the crankcase.
• B. In the cylinder head.
• C. In the exhaust manifold.
• D. In the piston crown.

Answer: (B)

Spark plugs must ignite the air-fuel mix inside the combustion chamber. In aero piston engines, that chamber is formed in the cylinder head, so the spark plug is threaded into the head and extends into the chamber. This position places the spark right where ignition needs to occur and allows proper cooling of the plug. Placing a plug in the crankcase would miss the combustion event and interfere with lubrication and crank mechanisms; the exhaust manifold handles only exhaust gases after combustion; and the piston crown is a moving part that would be impractical and unreliable for ignition. Hence, the correct location is in the cylinder head.