Design and Development Tests of a Four‐Bladed Light Helicopter Rotor System

A FOUR‐BLADED, soft‐inplane rotor of composite construction has been designed and flight tested on a 206L prototype helciopter as part of the continuing research and development effort of Bell Helicopter Textron. In the first 10 months of operation, 300 hours of flight were accumulated. These encompassed both development tests and service suitability evaluations in high altitude, cold weather, and desert environments. Measurements during flights to 147 knots and maneuvers to 2.6g indicate the hub and blades have unlimited fatigue lives. Vibrations are low throughout the helicopter flight envelope. High altitude tests show the rotor to provide exceptionally good autorotative characteristics. Cold weather evaluation has demonstrated trouble‐free operation to −26°F, while desert environmental tests show little or no erosion of the blades after 500 landings and takeoffs. This program has confirmed Bell's technical predictions and provides an additional option in offering a rotor system for every specific mission.