Model Airplane Engines
Model airplane engines provide the power for most rc airplanes. These engines are usually piston and cylinder internal combustion engines, although other types are available. These engines are often referred to as "glow" or "nitro" engines.
Typical Nitro Engine
RC engines work by burning a fuel. The burnt gases expand and move a piston, which moves a rotating crankshaft, which in turn drives the airplane's propeller.
The fuel for most model airplane engines is something called "glow" fuel. It is actually mostly a type of alcohol (methanol, please do not drink), plus nitromethane to help burning, plus some oil to help keep the metal parts lubricated.
It's called "glow" because the engine uses a glow plug instead of the spark plug found in regular gasoline engines. In the glow plug, a heated element causes the fuel to burn. The plug has a steady glow instead of an intermittent spark.
To start the engine, a battery is used to create the initial glow; after that, the heat of burning keeps the plug glowing, and the battery is removed (saving weight). The typical glow model airplane engine is a "two-stroke".
The engine burns fuel (produces power) on every second stroke of the piston. See our detailed illustrated tutorial on how a two-stroke glow engine works.
"Four-stroke" engines are also available, that produce power on every fourth stroke of the piston. The four strokes are more complex and expensive, but quieter as well as more fuel efficient. We also have a detailed illustrated tutorial on how four-stroke model airplane engines work.
There is an ongoing debate about the merits of nitro engines versus electric power. The electric systems are quiet, clean, low-vibration.
The drawbacks are generally lower power to weight ratio than a comparable glow-power engine. Newer technology lithium polymer batteries are beginning to remove this disadvantage, although currently at a price premium. Many modelers now fly both types of power systems.
It is something of an art to operate a glow-powered model airplane engine. The next sections are designed to help you with that.
Note that these are general recommendations, if possible you should follow your engine manufacturer's advice. If such advice is not available or falls short, these pages should prove helpful: