I read recently of the "Whisper S-55s" over the Grand Canyon in the USA.
Why not over the lovely countryside of Britain?
From a post 5 years ago:
About the quiet technology S-55T, it was tried out at the South Rim base while I was there (as well as at Las Vegas around the same time). I wasn’t personally involved in the project but it seemed to me to be a combination of good ideas that were worth trying but didn’t work out in practice.
On the good side, the aircraft really was remarkably quiet for its size and moreover, the sound it produced was rather inoffensive. Whether it was coming, going, hovering, passing overhead or to the side, all one would hear was the same low hum. No clattering, pounding or whistling at all.
The passenger capacity of 9 was the highest allowed without a 2-man flight crew being required. This is important because of the restrictions imposed on aerial tours over the Grand Canyon: the number of flights per year is limited to a fixed number so using larger aircraft will allow operators to continue growing their business.
Passenger visibility was very good with large windows and a transparent panel in the floor, kind of like a glass-bottomed boat in the air.
On the downside, the concept of limited upgrades to a very old design caused serious problems. The aircraft required a large amount of daily maintenance, to the point where it was hurting our B206L operation as all mechanics who might have helped with minor problems (e.g. a blown light or freeing a stuck linear actuator) were busy preparing one S-55 for service; even so it never was ready for the first flight of the day.
The main rotor had been made quiet by slowing it down and adding two blades (from 3 to 5) to maintain adequate lift, but combined with the old airfoil this gave the aircraft very nasty retreating blade stall characteristics, a real concern with the high DAs in the Grand Canyon in summertime. Whereas the LongRanger would give plenty of warning from increased vibration followed by cyclic shake, remaining fully controllable, one S-55 pilot told me of being rolled “nearly inverted” without any warning – bad for business if there are any paying passengers on board! The aircraft was slow anyway but this required seriously limiting load (I don’t remember it ever carrying pax in all 9 seats) and airspeed (cutting down on tour route for the same flight time, bad for customers, or increasing flight time for the same tour route, bad for operator).
Finally, the main transmission wasn’t up to the task. I don’t know if this was caused by keeping the original transmission and running it at lower speed or what, but every aircraft I know of (at least three) required replacing the MGB at about 200 hours TIS, an unacceptably short service life.
On proper reflection the (IMHO correct) decision was taken to stop throwing good money after bad, and buy the EC130 when it would become available.