Nitro
From RC Helicopter Wiki
Also known as "glow fuel", nitro is a model fuel that is made chiefly of methanol (alcohol), nitromethane and natural or synthetic oil. The percentage of nitromethane content will determine how quickly the mixture burns and will give more power. Helicopter engines usually give the best performance if run on 15% to 30% nitro.
Nitro engines achieve combustion from compression and a glow plug (similar to a diesel engine). The glow plug is heated electrically when the engine is first started, and afterwards is kept hot by the reaction of the methanol with platinum catalyst in the glow plug wire.
Nitro engines are sized by their displacement, measured in cubic inches (or, really, hundredths of a cubic inch). The engine in a typical model helicopter may have a displacement of 0.3 to 0.5 cubic inches, and so are called 30 or 50 sized helicopters.