Frequency response of an aircraft as determined from transient flight tests using the fourier transformation method of analysis

Abstract

The longitudinal dynamic response characteristics of a twin-engined propeller-driven aircraft determined from flight measurements are presented and compared with predictions based on theoretical studies. Transient responses to pilot-applied Pulsed notions of the elevator control surfaces were recorded. The transient data was then converted into frequency response form by means of the Fourier transformation and compared with predicted responses calculated from the basic equations of motion of the aircraft. In particular, detailed experience of the determination of frequency responses with regard to data sampling frequency and control input shape, using the Fourier transformation method, was obtained. Experimentally-determined transfer functions were used for the evaluation of the stability derivatives that have the greatest effect on the dynamic response of the aircraft. Some experience was also obtained with automatic data recording and processing equipment using magnetic tape, but no satisfactory frequency responses were obtained using this method. However, with further development and use of this equipment, the analysis of large quantities of flight data would be facilitated.