A Study of Dynamic Aeroelastic Effects on the Stability Control and Gust Response of a Slender Delta Aircraft

In this report four previously unpublished notes, concerned with aeroelastic effects on a particular slender delta aircraft configuration, are collected together. Some general flutter calculations show that decreasing stiffness leads to instability in the aircraft short period mode whilst the higher frequency modes remain stable. The reasons for the instability and the implications regarding aircraft controllability are examined by means of a much simpler mathematical model. It is shown that the instability is directly attributable to the aerodynamic moments arising from aeroelastic distortion defined by the fundamental chordwise bending mode. The same mathematical model is used in a study of the bending response of the aircraft to discrete step and ramp gusts. It is found that the dynamic overshoot factor due to chordwise bending can vary within much wider limits than the dynamic overshoot factor due to spanwise bending of a conventional aircraft.