Fan-In-Fin Antitorque Concept Study
Final rept. Jun 1971-Mar 1972
VOUGHT HELICOPTER INC DALLAS TX
Pagination or Media Count:
A study of the development of the Fenestron fan-in-fin helicopter antitorque device and a survey of applicable data from the literature provided the means to analyze the fan-in-fin concept. The objective was to design and evaluate a ducted fan-in-fin system for a helicopter in the 14,000-lb to 15,000-lb gross weight and 150-kt to 160-kt speed class. A review and study of fan-in-wing literature and shrouded propeller and fan technology provided the foundation to analyze the Fenestron and to determine the basic fan and fin characteristics. A direct performance comparison of an SA 341 helicopter with Fenestron and conventional antitorque systems was conducted to assess the advantages and penalties of the Fenestron. From the knowledge gained, a ducted fan-in-fin antitorque device was designed for the utility transport helicopter in the specified weight and speed class of the SA 330. A parametric analysis of the fan design parameters showed the performance gains achievable with larger diameter fans. The MIL-H-8501A requirements were considered. A fin design was accomplished taking into account area, lift coefficient, lift curve slope, and effective aspect ratio. A trim flap was found to be desirable to optimize performance at off-design conditions.