THE “FENESTRON” A SHROUDED TAIL ROTOR CONCEPT FOR HELICOPTERS

The paper presents a general review of the experience acquired and of the improvements achieved by Aérospatiale during eighteen years of operational utilization of the «fan-in-fin» tail rotor concept on light and medium weight helicopters. After a brief review of the quality criteria sought for tail rotors, the general characteristics of the first generation fan-in-fin are analyzed: problems encountered are identified along with the practical solutions which have been applied. The paper then covers broadly the research and development effort conducted at Aerospatiale in order to improve the fan-in-fin concept. These improvements mainly concern aerodynamics performance, handling qualities, noise, behaviour in special environments and application of advanced technology to reduce weight and production cost. Limitations of the fan-in-fin application as a function of helicopter size is discussed. The fan-in-fin next generation characteristics based upon the latest research and development results are then illustrated.