Power
Power models are those with an onboard power source which is not a rubber motor. Frequently this is an internal combustion engine, and the engine run is limited, typically to just five seconds. Designing an aircraft which climbs as high as possible, with minimum drag at a low lift coefficient, but then must convert to a slow flying glider, is a challenge unique in aviation. However, the category also includes compressed gas motors and electric power. The FAI power class is F1C. F1C models are equipped with an internal combustion engine of up to 2.5cc and need to weight at least 300 g per 1cc (i.e. minimum weight of a 2.5cc equipped model is 750 g). These engines are usually custom made for optimal power output and often yield 1 hp (0.75 kW) at more than 30,000 RPM. Many F1C models feature folding wings, to minimize the aerodynamic drag during the climb phase.
Another type of powered free flight models is CO2 (its FAI category is F1K ). These models fly using a small engine powered by carbon dioxide. This models are very light. The amount of CO2 is limited to 2 cm³, which is enough for cca. 2 minutes of flight.
Another popular free flight Class is FAI category F1J which is similar to F1C however the engines are 1/2A Class is less than .050 cubic inches. These models use engines like the Cox Tee Dee .049 model engine.
Sport free flight fliers also use Cox model engines and others to power free flight scale models.
Read more about this topic: Free Flight (model Aircraft)
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