Recent Development of Rotorcraft Configuration

In view of the flight theory of rotorcraft, breakthroughs in the field of rotorcraft configuration during recent twenty years are described in this paper. From the traditional configuration (including the single main rotor with tail rotor, tandem rotors, side by side twin rotors, coaxial rotors and crossing rotors) to the recent ones (including ducted tail rotor, non-tail rotor helicopter, hingeless rotor, bearingless rotor, tilt-rotor, tip-jet rotor, reverse velocity rotor system, the compound helicopter and rotor/wing transition helicopter), the great progress on rotorcraft configuration have been revolutionarily made. These new technologies have an effect on the rotorcraft performance in high speed and supermaneuverability and high-agility flights. In light of advancing blade transonic shock and stall of retreating blade at high angle of attack in forward flight for helicopter conventional layout, the new progress in rotorcraft configuration in recent years show the potential to exceed maximum flight speed limit for current helicopters, and even to be greater than the cruise speed of propeller aircraft. At the same time, maneuverability and stability in forward flight have been improved. With the increased rotor efficiency, overload capability and good flight performance, these new types of rotorcraft have good maneuverability and lower vibration/noise level, and avoid ground or air resonance. Owing to the introduction of the new types of rotor configuration, the reliability and maintainability as well as survivability of the rotorcraft can be improved significantly. Therefore, their service life has been prolonged. In short, the rotorcraft with new types of configuration will become the more economical, effective and rapid vehicles for air traffic transportation in the future.