Aircraft manufacturer has to demonstrate aircraft is free of flutter up to VD/MD which is normally reached only in dive. The difference between VMO and VD is around 50KTS. for non FBW aircraft. This margin in case of FBW aircraft is reduced because of protection. In case of A380 it is 35KTS and MMO .89 and MD.96 That is why it is reduced with loss of high speed protection.
Last edited by vilas; 16th Jan 2015 at 17:20.