Performance Qs
(Done the thread search - found no answers)
I fly the Q400. Vmo changes quite a bit during climb. The bird strike-Vmo-limit below 8.000 I understand (not an aerodynamic limit). What I don't understand, is why the Vmo increases slightly (4 kts) from 10.000ft to 18.000ft, and then starts to drop so steeply up to 25.000ft - from 286KIAS to 248KIAS in just 7.000ft?
At M.58, the compressibility effects cannot possibly be that pronounced? Or? Could it be due to the propellers? What am I missing?