Text in force at CS23-6: from CS23-5, effective 15 Aug 2017.
(a) The aeroplane must be free from flutter, control reversal, and divergence:
(1) at all speeds within and sufficiently beyond the structural design envelope;
(2) for any configuration and condition of operation;
(3) accounting for critical degrees of freedom; and
(4) accounting for any critical failures or malfunctions.
(b) The applicants’ design must account for tolerances for all quantities that affect flutter.
ED Decision 2017/013/R · Source