What is the best energy source for the RC helicopter gyro store

What is the best energy source for the rc helicopter gyro store? Two variants of the turbine or reciprocating engine. Turbomachines the same basic structure of the jet engine, but the energy of the expanding gases may be used to drive a turbine to produce thrust position. The engine is equipped with gear that causes the main rotor of a helicopter transfer. Also controls the piston engine, the output shaft of the main rotor transmission, but these machines are traditionally considered less reliable.
To understand where we can see the drawings by helicopter when they first appear. Product helicopter aircraft piston engine and installed on their helicopters. However, these engines are not powerful enough to levitate. For more power, the motor operates at a higher speed and thus the reliability immediately. Once the Lycoming O-360 lower TBT was built from 2000 hours to 1600 hours for RC helicopter brushless motor engines. This piston engine powered reputation for reliability.
In 1979, Frank Robinson R22 took tandem. His idea was a lot of helicopter descends to reduce the energy required. For example, the ring system T-bar and weighs less easily than traditional dual control. Then he took the Lycoming O-320 engine reliability and reduces the speed and capacity of 160-124 maximum exploration 2700-2652. So Lycoming TBO 2000 hours was approved for fixed wing. He did the same thing with the R44, Lycoming O-540 engine. The engine was reliable Lycoming MSW increased to 2,200 hours for the two helicopters fuselages of this plant is installed in the engine itself MSW in planes. Accident data NTSB ensures the reliability of energy reduction achieved several engines.
Even with significantly improved reliability, piston engines suffer from low power to weight. Thus, for helicopters over 2500 pounds gross weight, the direction of the turbine. It is compact, lightweight and has a simple design, offering exceptional reliability. Perhaps the most important feature is the high power to weight ratio. This makes Turbomeca is the only option for large electronic speed controller design and two engines. However, the disadvantage of these engines is to provide the high costs of operation and maintenance.