Abstract: The accuracy of estimated stability and control
derivatives of a light aircraft from flight test data were evaluated. The light aircraft, named ChangGong-91, is the first certified aircraft from
the Korean government. The output error method, which is a maximum likelihood estimation technique and considers measurement
noise only, was used to analyze the aircraft responses measures. The
multi-step control inputs were applied in order to excite the short period mode for the longitudinal and Dutch-roll mode for the lateral-directional motion. The estimated stability/control derivatives of Chan Gong-91 were analyzed for the assessment of handling
qualities comparing them with those of similar aircraft. The accuracy of the flight derivative estimates derived from flight test measurement
was examined in engineering judgment, scatter and Cramer-Rao bound, which turned out to be satisfactory with minor defects..