HUP vs S-58
Main reason for using S-58 vs HUP would be power: 1525 vs 550. I believe the HUP head was articulated, so the 2/3P inherent in the rotor was there. I don't know anyone to ask! Took a look at the video clip and one can see that the rotors are wobbling at a fairly low frequency but at " scary " ( sorry, couldn't resist ) amplitudes. Nobody around to report on whether they did a shake test on the frame to look for natural frequencies, and the other thing that comes to mind is that the 2/3P is a wobble, i.e., a combined pitch/roll excursion, which would transmit accompanying high oscillatory loads into the frame structure that it may/may not have been designed to take. The rotor is at high thrust in the clip, so the thrust is high, thus the oscillatory loads were high.
Last edited by JohnDixson; 10th Dec 2012 at 15:38.
Reason: typos