To realize the improvement of engine output in a radio controlled helicopter in a simple, light-weighted and low-priced mechanism without adopting complicated mechanism and method.

An introduction pipe 11 for supercharging air is connected to an intake pipe of an engine 4 of a radio controlled helicopter 1. An introduction port 12 of the upper end of the introduction pipe 11 is positioned below a main rotor 7, so that some of an air flow blown off from the main rotor 7 is introduced as supercharging compressed air into an engine intake system from the introduction port 12. Simply the introduction pipe 11 is externally fitted without assembling parts such as a supercharging turbine or the like in an engine. Accordingly, it is possible to realize a small-sized, light-weighted and inexpensive engine supercharging mechanism.