Deficiencies of long-term dynamics requirements and new perspectives

The long-term dynamics of aircraft in supersonic flight at a Mach number M ≥ 2 are considered and it is shown how their characteristics compare with existing flying qualities requirements and flight standards. One topic dealt with is concerned with the correlation between airspeed and pitch attitude for commanded pitch attitude changes. It is shown that the airspeed/pitch attitude correlation in supersonic flight is not unequivocal and substantially differs from the relationship for subsonic and transonic flight. The flight mechanics factors underlying are identified and it is shown that the height mode which is an additional mode existing in supersonic flight exerts a significant influence. Another topic considered is concerned with aperiodic airspeed divergence. It is shown that there are deficiencies in regard to the connection considered to be existent between the requirement concerning aperiodic airspeed divergence and related control gradients. There may be aperiodic instability despite the fact that the control gradients would indicate stability. The opposite can also be true. It is shown which are the reasons for these characteristics. Here again, the height mode exerts an influence.