STATISCHE STABILITAET UND APERIODISCHE INSTABILITAET IM UNTER- UND UEBERSCHALL.

The relation between static stability and aperiodic divergence is shown. Due to the different conditions, the subsonic and supersonic regions are treated separately. With regard to the subsonic region, it is shown which conditions lead to aperiodic divergence in spite of the fact that the aircraft is statically stable. This gives the restrictions for the assumption commonly used according to which static stability is a sufficient criterion for avoiding aperiodic divergence. With regard to the supersonic region it is shown that the current concept of static stability is inadequate. A new cconcept is introduced which takes the conditions of supersonic flight properly into account. Furthermore, the conditions for aperiodic divergence are shown as well as the role of static stability in this context.