Good one Dan but I'd rather have a banana to eat thanks.
The apparently curved prop is an artefact of the frame rate/propellor speed. I watched the video again this morning and you can see it at 1:10, 2:43(briefly), and 6:12.
The shot at 6:16 to 6:17 gives the impression that the prop is changing shape as it revolves
Brilliant.
Alan
Thanks to the other forum for the specifics - it's a rolling shutter on the CMOS sensor that causes the bendy prop effect, either that or the Apache is using a Bananna prop too..
http://en.wikipedia.org/wiki/Rolling_shutter