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Van is hedging on the conservative side, and there is nothing wrong
with that. Many RV's have been flown at faster True Air Speeds
without problem.
If flutter is causing the limitatin that imposes Vne, then TAS is
probably best to use, but flutter varies so widely even between
individual aircraft and other influences that making a truly
conservative Vne that will avoid flutter in all cases would leave a
lot of room for increased speed for all but the lowest common
demoniator. This is the safest way to approach the issue, but not
necessarily the only way to approach the issue of Vne.
Dave Leonard
On 4/24/05, kenpowell@comcast.net <kenpowell@comcast.net> wrote:
Hi Dave (and welcome John),
I agree that this (TAS) is really strange and not intuitive. But consider
the source - Van himself!!! When I read this in RVator I had doubts but I
gotta go with John on this unless we hear from another impeccable source to
the contray. TAS it is!!!! Call Van if you need more info; I doubt any of
us (do we have any aeronautical engineers on the list? I know we have every
other flavor of engineer here!) have the knowledge to debate this with Van.
--
Ken Powell Bryant, Arkansas 501-847-4721
-------------- Original message -------------- rv-7a wrote:
However, my bubble was busted by the Van's RVAtor article on flutter (6th
issue 2004). Van's engineers instructed their readership on flutter – that
Vne is really a TAS limit, not an IAS limit. A US Air Force pilot and RV
commuter corroborated the Van's article by telling his disturbing TAS
flutter story (first 2005 RVAtor issue). If you haven't read this, I
recommend it for all pilots, no matter what they fly.
I've decided to follow Van's advice and restrict my upper airspeed to limit
to 200 KTS TAS in smooth air. I don't want to be a test pilot. Therefore,
I'm reconsidering my plan to supercharge the Renesis/RD-1C installation. The
weight penalty may not be worth climb performance increase if 200 KTS TAS
cruise can be easily achieved with a normally aspirated installation. If I
can collect empirical data from RV Rotary flyers, it would sure help my
decision.
Thanks,
John Burns
rv-7a@comcast.net
http://mywebpages.comcast.net/jgburns/Engine/Engine.html
for my engine webpage.
Intuitively it does not make sense that flutter is a TAS issue. I would be
interested in reviewing the engineering/hypothesis on which this is based.
The plane "feels" IAS.. not TAS... you can have a TAS of 400 and still have
only an IAS of 200 (if you are high enough).. IAS is the dynamic pressure
and state that the aircraft experiences. So.. I would be greatly interested
in knowing why the engineers are making this claim and what its basis is.
Dave
>> Homepage: http://www.flyrotary.com/
Archive:
http://lancaironline.net/lists/flyrotary/List.html
--
Wm. David Leonard
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