Parameter Identification Technology Used in Determining In-Flight Airload Parameters

An investigation was conducted to determine the feasibility of utilizing a modified Newton-Raphson computer program, developed by Taylor and Iliff of NASA, to determine the airload and the aircraft parameters concurrently from in-flight empennage and aircraft response data. Only the lateral directional mode was considered in this study. The airload responses consisted of the horizontal stabilizer rolling moment and the vertical tail sideforce. Pilot rudder pedal force time history responses were also included in the investigation. Comparisons of the in-flight coefficient parameters are made with wind-tunnel results. The a priori feature of the program was not utilized. Although there are many other techniques available, this technique is becoming recognized throughout the industry as the preferred or standard approach. The results of this investigation substantiate the practicality of the technique for the purpose of evaluating airload derivatives.