[ArrogantBustard]

Wouldn’t you want some sort of internal lock

I'm pretty sure I wouldn't ... the consequences of such lock engaging during powered flight would be unpleasant.

When the aircraft is parked, even a slight "crosswind" can get the prop spinning.

I believe procedure in case of an engine failure is simply to feather the prop. The feathered prop presents very little area to the airstream whether it's spinning or not.

You know how far a Twin Otter will fly on one engine, right?

All the way to the scene of the crash!

BWAHAHAHAHahahahaha!

Actually, it's not that bad ...

[linear]

Good points - thanks.