An Integrated Procedure for Estimating Modal Parameters During Flight Testing

Abstract

This paper presents the methodology used for the flight test conducted as part of the gross weight increase program for NASA’s WB-57F aircraft. The primary focus is on the synergy of data processing procedures to track the trends of the frequency and damping of the modes of interest in near-real time during the flight test. These procedures include spatial filtering with FEM mode shapes, time domain parameter estimation, and a pole density diagram. This method can be used to estimate modal parameters from free-decay response-only measurements using only a few acceleration response measurements on the aircraft. The authors will show that with this method, a robust estimate for frequency and damping can be extracted and statistics of the estimated values can be evaluated at each flight test point. The paper will also discuss the preliminary testing and analyses as well as the overall logistics of the flight test program, including instrumentation selection and installation, data acquisition and transfer, and operational considerations.