RINGFIN AUGMENTATION EFFECTS

Recent comparative information on standard aircraft and ringfin tail rotor configurations from a Bell Helicopter Textron, Inc. (BHTI) flight test program are presented plus other data from the ongoing development. Five of the twelve full-scale flight-tested configurations are reviewed for measured thrust (ring and tail rotor) and other characteristics. Effects of ring parameters on thrust/power relationships of the antitorque device are presented. Ring augmentation forces are compared with static data from rotor cage tests, ground running on the aircraft, and flight operation. Appropriate factors for design performance estimation purposes are indicated. Hover, forward flight and maneuver data (to 50+ miles per hour sidewise) of the antitorque device, and the ring influence on aircraft flight characteristics are discussed in terms of pilot work load. Variations in sidewise/forward flight performance of the ring, including a positive thrust augmentation in a right side-direction, are examined for possible device modifications of the aircraft wake flow patterns. Different configurations of the ringfin provided benefits in various modes of flight and additional tests are planned for configurations to suit all modes. Future in depth examination of the concept, potential side flight velocity increases, improved vehicle handling qualities, and increased flight envelopes are discussed.