[moovova]

I wonder why the gradual descent rather than a nose-down plummet? Extend the terror for the passengers? Is there something built into the controls to disallow such an action?

[Squawk 8888]

More likely it was to prevent the pax from realizing something’s wrong until it was too late to do anything about it.

[DuncanWaring]

The flight controls appear to be designed to prevent a “plummet”:

http://theflyingengineer.com/tag/vmo/