Boslandrew,
I only just spotted your very informative post. Apologies - put it down to quick lunch time posting...
Interesting that Chinook had no peculiarities in handling. Still the idea of VRS in the rear rotor is not pleasant - i guess you had to roll the machine sideways to recover. Prouty commented that they climbed best flying slightly sideways, since this increased the rotor area to flow. I must admit to having tried to work out if there was any reason other than blade clearance for the 5 or 6 degree difference in rotor g/box mounting angles.
I'm not suprised about the vibration being the main constraint though. There are lots of opportunities for the tip vortices to impinge other rotors and structure. The other vibration source would be drivetrain eigenmodes, which i imagine are not insignificant (massive rotors and flexible drivelines). I'm also slightly suprised that they haven't followed the trend and moved to 4 blade hingeless rotors.
Still, good bit of versatile design - it clearly delivers.
Brett,
Thanks for the driveline details. I'll have to do some googling to come up with weights and materials. I imagine the guy that did the original layout (based on Piasecki's concept drawings no doubt) lost a lot of sleep about getting the stress calcs right - i know i do!
From Boslandrew's comments i would imagine that the cost of maintaining such a complicated powertrain is a disadvantage.
Do the electric trimmers bias the forward thrust in any way, or are they just there to compensate for flapback?
Mart