Load Variability Of A Two-Bladed Helicopter

A flight loads variability analysis program was conducted using the Bell Model OH-58C helicopter. A representative flight consisting of 33 maneuvers was repeated 30 times using six pilots (three from Bell Helicopter Textron and three from the Army) who fiew the aircraft five times each. The resulting data was analyzed statistically to determine the parameters of distribution and variability using three different sets of data: peak loads, maneuver loads and total flight loads. In addition, the damage rates were also analyzed statistically. The results indicate that the maximum oscillatory loads exhibit a larger variability than that obtained by analyzing either maneuver loads or the flight loads and that the Weibull distribution can be used to represent the distribution shapes of both the maneuver and flight loads. Assessment of load variability on a total flight basis reduces the complexity of reliability computations.