Mailing List flyrotary@lancaironline.net Message #20736
From: <kenpowell@comcast.net>
Subject: Re: [FlyRotary] Re: Upper Airspeed Data on Rotary-Powered Van's RV
Date: Mon, 25 Apr 2005 00:37:46 +0000
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
 
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

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