[Helobubbas] Here Is Our First Clear Look At Chinas Z-20F Seahawk Helicopter Clone (Updated)
kblack1967 at gmail.com
kblack1967 at gmail.com
Tue Oct 15 17:59:17 PDT 2019
My theory talking to a lot of people over the years is 4 bladed systems seem to be more prone to vibration. Look at all the hoops Sikorsky had to jump through to deal with them in the 60. There are several absorbers embedded in the aircraft in addition to the nitrogen charged blade dampers. Not sure how the Puma gets away with 4 blades but as someone who has flown them for years the dampers are not nitrogen charged and are pretty “loose” in their damping. Starting one you wonder if you are going to flop over they wobble so bad before things get in sync. In flight though if things are tracked and balanced right they are just fine. The Super Puma 332 came out about the same time as the 60 and also has 4 blades but uses elastomeric straps instead of dampers, at least on L1s and newer. They don’t wobble around on start and also seem pretty smooth. I have never flown or been in a H-3 /S-61 in flight but hear when things are right they are pretty smooth. The AW 139 is 5 blades, very smooth. Bunch of other modern stuff uses odd blade counts and it seems to work well as it would seem the opposite quadrants can’t create some vibe of their own, 1 per 2 per. The EC225 I just finished training in is smooth until you get it up near VH then it starts getting sort of harsh or rough, but not like a 1 per, 2 per or such, more of a increased overall vibration. Maybe the Chinese were looking at other modern aircraft and decided their lift might be better with 5 and vibration challenges less. Frankly I would love to see how a 60 or a S-92 would do with a well designed 5 blade head.
From: HELOBUBBAS <helobubbas-bounces at nhahistoricalsociety.org> On Behalf Of Marc Liebman
Sent: Tuesday, October 15, 2019 5:26 PM
To: retiredreunionmgr at navalhelicopterassn.org; HELOBUBBAS <helobubbas at nhahistoricalsociety.org>
Cc: Killer <ray.doggett at virgin.net>
Subject: Re: [Helobubbas] Here Is Our First Clear Look At Chinas Z-20F Seahawk Helicopter Clone (Updated)
Maybe I missed something, but the 60Bs and 60Hs I flew had four bladed heads. The PLAN copy of the H-60 has five. So the question is why?
Is it blade area to give more carrying capacity, reduce blade loading to get more speed, or is airfoil construction capabilities limiting airfoil shape?
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From: HELOBUBBAS <helobubbas-bounces at nhahistoricalsociety.org <mailto:helobubbas-bounces at nhahistoricalsociety.org> > on behalf of "Michael G. Brattland" <retiredreunionmgr at navalhelicopterassn.org <mailto:retiredreunionmgr at navalhelicopterassn.org> >
Organization: www.nhahistoricalsociety.org <http://www.nhahistoricalsociety.org>
Reply-To: "retiredreunionmgr at navalhelicopterassn.org <mailto:retiredreunionmgr at navalhelicopterassn.org> " <retiredreunionmgr at navalhelicopterassn.org <mailto:retiredreunionmgr at navalhelicopterassn.org> >, HELOBUBBAS <helobubbas at nhahistoricalsociety.org <mailto:helobubbas at nhahistoricalsociety.org> >
Date: Tuesday, October 15, 2019 at 4:46 PM
To: HELOBUBBAS <helobubbas at nhahistoricalsociety.org <mailto:helobubbas at nhahistoricalsociety.org> >
Cc: Killer <ray.doggett at virgin.net <mailto:ray.doggett at virgin.net> >
Subject: [Helobubbas] Here Is Our First Clear Look At Chinas Z-20F Seahawk Helicopter Clone (Updated)
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