Other RC Engines
Besides the common nitro engines, and electric motors, there are a few other power systems available for your radio control model.
The two-stroke Gasoline rc engine is popular for larger airplanes. This is much like a lawnmower or other power tool engine. Indeed some people convert leaf-blower, chainsaw, etc., engines for RC use. There are also manufacturers that sell dedicated engines.
Typical gasoline-powered rc engine
These engines burn gasoline and have spark plugs. They need to carry a battery and ignition system onboard, making them generally heavier than comparable glow systems.
However, they are clean burning, and very economical to operate compared to large nitro engines. They are often the favorite rc engine choice for large scale planes.
Ducted Fans are commonly used to propel jet-style models. However, they are not jet engines. They consist of a nitro engine (or electric motor) turning a fan, which is housed in a cylinder (shroud).
The engine turns at high rpm and the fan arrangement generates enough airflow to push the craft forward at high speed.
No fuel is burned in the fan / shroud. Most "jet" models that you encounter have this type of system. See our page on the Electric Ducted Fan.
Some jet models now have actual miniature jet Turbines as rc engines. Instead of a power plant turning a fan, actual combustion of fuel takes place in a chamber much like a real jet engine. These model jet engines are powerful and quiet, and despite great expense are becoming more and more popular for scale models of real jets. See our page on Model Jet Engines.