Thanks, WillDAQ!
Just FYI, the application is a major motion picture. One of the big action sequences involves an Mi26. Asking this question is due diligence for all the obvious safety reasons, but also for SFX and the Art Department as the legendary downwash from the Mi26 could have some serious construction implications.
So if you think that 1,090mph is high - and I do too, then maybe you could help steer me in the right direction.
Cheers,
Luca