12c/e/e4
Just read this thread. I had the "privilege"? of flying the 12C in Vermont, wooden blades and all; the 12E throughout the eastern USA, in PNG and Irian Jaya , and the 12E4 in the Philippines. Most operations were above 5000' which accentuated any play in the collective rod end train resulting in mucho vibration, all the time. Even with a well tracked aircraft at sea level, when it was operating at max gross and above 5000' it was a pig. Vibration was enough to make your right wrist numb from the cyclic feedback.
Collective drops were frightening. Hit a gust and the darn thing could rise an inch in response and then plummet to the lower stop. It is disconcerting to have the dust and pencil stub rise up before your eyes in the middle of an ear piercing shriek from the student being endorsed.One soon learned to never remove one's left leg from the collective if changing hands on the cyclic for radio switching or indicating some scenic point of interest.
I have a photo of the altimeter somewhere taken by the pax topping out at 13,400' over the Markham valley in a 12E with what was called "high altitude pistons" trying to beat the rising clouds. A Hiller cyclic at that altitude feels like a stick in a bucket of grease, with about the same effect.
Had one vibration damper depart in flight, and the machine got smoother!
Then we got the "Phoenix conversion", which had the "turbo normalised" VO540 . Landing at 11,000' was a blast. About 1/8" throttle rotation produced about 5" of manifold pressure at the hover. You can imagine the directional control.
Flew it on pontoons doing crocodile survey, landing and shutting down adjacent to the nests while intrepid researchers opened the nest, weighed and measured the eggs ...all the while hoping the mama salty wouldn't contest the turf while we were there.
One aircraft (not with me) had a stabiliser bar and paddle depart in flight at 500". He got it down but was cross eyed for some years afterward from the vibration on the way down.
All in all, a great work horse, and fine low level but above 5000' one of the roughest, most unpleasant helicopters I have ever had the misfortune to fly.
It was a happy day to put the Hiller behind me!