gf, I believe the hub cover's primary purpose is to reduce hub energy transmission which shows up on radar like a billboard which is how/why Comanche's head was designed the way it was . I'm unfamiliar with the theory of cavitation, but we have terminology that is endemic to my service. I think you may talking about tip vortex reduction? The 5th blade could/should allow a slower headspeed with a more slippery airfoil which would certainly reduce the accoustic signature. The UH-60's and even the AH-64's have decent accoustic signatures and can't be heard from 2k at altitude which is only takes 30 seconds to transit. From lower levels this range is even less.
the original detail I got was from ex USArmy LTG who used to manage helo programs. I met him in the US when I was working there a few years back. We were dealing with cavitation/turbulence and acoustic transmission issues
I'll trawl through my emails and ask him whether I can pass on detail (but it will be by PM)
He's got impressive credentials,,,,
Dual-rated, an experimental test pilot, and program manager (PM) for both the Kiowa and Apache programs
Pioneered the integration of high capability electro-optic and radar systems on Army aircraft.
First officer selected by the Army for astronaut training
First Aviation Program Executive Officer.
First US military officer elected to the Russian Academy of Natural Science.
two Distinguished Service Medals,
two Legions of Merit,
two Bronze Stars,
Distinguished Flying Cross,
17 Air Medals,
two Meritorious Service Medals,
the Army Commendation Medal,
the Senior Army Aviator Badge,
the Senior Space Operations Badge,
the Army Aviation Association of America Order of St. Michael (Gold Award)
NASA Award for Outstanding Service.
American Helicopter Society (AHS) Special Award for Lifetime Achievement in advancing vertical flight technology.
Chaired the Board on Army Science and Technology
Serves on the Army Science Board.
I'm only citing his credentials as its why I have some faith in his input - based on what we were also doing with cavitation/turbulence management. (Not that I don't have faith in you as you're an operator so don't talk from just theory)
the original designer of the Blackhawk (Leoni) also has made mention of the cavitation/turbulence issues in his book on Blackhawk development development. It was primarily a set of features to manage (reduce) turbulence and hence acoustic transmission.
funny how all these meetings from years ago all of a sudden turn into revelations and you suddenly go from a "WTF was he on about?" to "so thats what he was on about"
