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A scaled unmanned helicopter can be highly useful in various applications such as high-volume pesticide spraying in agriculture, aero-dynamics and stability study of helicopters etc. Though the development of such small model helicopters has long been successfully carried out, dated back to early 1970, the calculation, design and development of a multipurpose unmanned helicopter is now still of important significance in terms of providing a low-cost, custom built facilities etc. for both research and local needs. This report presents initial results of the research, development and testing of a mini radio controlled – RC helicopter powered by a two-stroke 32cc lawn-mower piston engine. The engine rated power is 2.2 hp which is 1.64 kW. The helicopter’s lifting-rotor diameter is 1.5 m, that of the tail rotor is 0.25 m. Each rotor has two blades of rectangular type. No fly bar – stabilizer bar is used with the lifting rotor. A swashplate driven by three electric servos is used to control the collective and cyclic pitch angle of the blades of the main rotor. A collective pitch-angle control mechanism driven by one electric servo is used for the tail rotor. The weight of the helicopter is about 6.5 kg. The helicopter has a payload of about 2 kg. It is radio-controlled by using a 2.4 GHz, 6-channel transmitter – receiver. Initial tests have been carried out in two flying conditions: first, hovering with a ground-fixed anchor rod attached to its nose (without gyroscopes, payload), and second, hovering freely out in the field without any anchor, gyroscopes, but with 1 kg payload. In the first case, the helicopter has successfully lifted off, descended and stabilized. In the second case, it is able to lift off and move. Further tests and fine adjustments are required in the second case so that the helicopter can hover properly.
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