When most people think of spark plugs, they envision automotive engines. Most automotive engines have a single spark plug per cylinder. As shown in the adjacent illustration, they are small conductive devices that are designed to generate a spark. But spark plugs aren’t limited to cars, trucks and other automobiles. Many airplanes have spark plugs as well. Airplanes with piston engines will typically have several spark plugs.

What Are Spark Plugs?

Spark plugs are conductive devices that are used for ignition purposes. They are made of an electrically conductive material, such as copper. The inner core is conductive so that electricity can flow through it. And as electricity flows through the conductive core, the spark plug will generate a spark at the end.

Why Airplanes Have Spark Plugs

Airplanes have spark plugs for the same reason automobiles have them. Spark plugs ignite the mixture of fuel and air within the engines’ combustion chambers.

Piston engines run on a mixture of jet fuel and air. They suck in air, which they mix with jet fuel. This mixture of jet fuel and air is then burned within a combustion chamber, which propels the airplane forward via the exhaust. But jet fuel and air don’t burn on their own. It requires some type of ignition system to get started.

Spark plugs are used in airplanes’ ignition systems. Most airplanes feature a magnetos. The magnetos supplies electricity to the airplane’s spark plugs. As electricity flows through the spark plugs, they’ll generate a spark. This spark will ignite the mixture of jet fuel and air for the engine with which it’s used.

How Many Spark Plugs Do Airplanes Have?

While automobiles typically have one spark plug per engine cylinder, airplanes are equipped with more spark plugs. Most airplanes have two spark plugs per cylinder.

With two spark plugs per cylinder, there’s a lower risk of failure. Spark plugs, of course, can fail. The gap at the end may become larger over time. If it’s too big, the spark plug may not generate a spark. Fortunately, piston engines in airplanes typically have two spark plugs per cylinder. Even if one of the spark plugs is unable to generate a spark, the other spark plug should function as intended.

A dual spark plug setup also increases combustion. It encourages the piston engines to burn more of the jet fuel and air, resulting in increased combustion.