Return-Path: Received: from relay02.roc.ny.frontiernet.net ([66.133.131.35] verified) by logan.com (CommuniGate Pro SMTP 4.2.5) with ESMTP id 592982 for flyrotary@lancaironline.net; Wed, 05 Jan 2005 23:43:44 -0500 Received-SPF: pass receiver=logan.com; client-ip=66.133.131.35; envelope-from=canarder@frontiernet.net Received: from filter02.roc.ny.frontiernet.net (filter02.roc.ny.frontiernet.net [66.133.131.177]) by relay02.roc.ny.frontiernet.net (Postfix) with ESMTP id 1761E1025C for ; Thu, 6 Jan 2005 04:43:14 +0000 (UTC) Received: from relay02.roc.ny.frontiernet.net ([66.133.131.35]) by filter02.roc.ny.frontiernet.net (filter02.roc.ny.frontiernet.net [66.133.131.177]) (amavisd-new, port 10024) with LMTP id 00621-08 for ; Thu, 6 Jan 2005 04:43:13 +0000 (UTC) Received: from [127.0.0.1] (70-97-234-61.dsl2.cok.tn.frontiernet.net [70.97.234.61]) by relay02.roc.ny.frontiernet.net (Postfix) with ESMTP id 5872E1020B for ; Thu, 6 Jan 2005 04:43:12 +0000 (UTC) Message-ID: <41DCC256.6050204@frontiernet.net> Date: Wed, 05 Jan 2005 22:45:10 -0600 From: Jim Sower User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7) Gecko/20040514 X-Accept-Language: en-us, en MIME-Version: 1.0 To: Rotary motors in aircraft Subject: Re: [FlyRotary] Re: IAS and Vne! Whoa! References: In-Reply-To: Content-Type: multipart/alternative; boundary="------------040103030202070106070809" X-Antivirus: avast! (VPS 0501-0, 01/04/2005), Outbound message X-Antivirus-Status: Clean X-Virus-Scanned: by amavisd-new-20040701 (2.0) at filter02.roc.ny.frontiernet.net This is a multi-part message in MIME format. --------------040103030202070106070809 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Stall speed approaches *Critical Mach* at altitude. One component of the "coffin corner" in the performance curves of airliners. Idle fuel flow (which is a constant) approaches cruise power fuel flow (which decreases with altitude). Minimum IAS approaches Critical Mach.. These conditions can intersect, depending on aircraft and weight, at some point in the early 40s. You're at idle power, but also cruise power - you can't reduce power. You're at critical Mach so you can't accelerate. If you want to go down, you can't reduce power because you can't go past idle; you can't push the nose over because you'll go transonic. You're stuck. You can shut down an engine or two for a while - that will let you come down without busting Mach. You might deploy a little spoiler or lower the landing gear, but the former assures some transonic regions on the top of the wing and the latter could cause some supersonic flow around the gear with unpredictable results. Sort of painting yourself into a corner ... Jim S. cardmarc@charter.net wrote: >Stall speed approaches TAS at altitude. I think that is one reason why the big boys use Mach numbers and stick shakers. Now I said more than I know. Maybe the military and heavy iron guys can chime in. >Marc > > >>From: Jim Sower >>Date: 2005/01/05 Wed AM 07:10:04 GMT >>To: "Rotary motors in aircraft" >>Subject: [FlyRotary] Re: IAS and Vne! Whoa! >> >>Actually, I'm talking about flutter. VNE (for our homebuilt purposes) >>seems to be that IAS at which the designer who almost certainly hasn't >>gone into it too very deeply, begins to perceive that he is on the cusp >>of being uncomfortably close to it. Flutter that is. It's on that page >>in the POH that even SMELLS like it's been pulled out of someone's ass :o) >>I think I'll get some sleep ... Jim S. >> >>Jim Sower wrote: >> >> >> >>>Actually, I've been given to understand that *both* IAS and TAS are a >>>factor. I don't know exactly what the relationship is, just that they >>>both come into play. >>>But now I've told you more than I know ... Jim S. >>> >>>John Slade wrote: >>> >>> >>> >>>> > Apparently Vne is NOT, it is a factor of True Airspeed!! That's >>>>contrary to what I've read with respect to canard pushers, Ed. >>>>As I understand it VNE for the Cozy, for example, is 220 mph IAS. >>>>It's all to do with how many air molecules are hitting the airplane. >>>>Someone tell me I'm wrong. ??? >>>> >>>>John >>>> >>>> >>>> >>>> >>>> >>> >>> >>>>> Homepage: http://www.flyrotary.com/ >>>>> Archive: http://lancaironline.net/lists/flyrotary/List.html >>>>> >>>>> >>> >>> >> >> > > > > >>> Homepage: http://www.flyrotary.com/ >>> Archive: http://lancaironline.net/lists/flyrotary/List.html >>> >>> > > > > --------------040103030202070106070809 Content-Type: text/html; charset=us-ascii Content-Transfer-Encoding: 7bit Stall speed approaches Critical Mach at altitude.  One component of the "coffin corner" in the performance curves of airliners.  Idle fuel flow (which is a constant) approaches cruise power fuel flow (which decreases with altitude).  Minimum IAS approaches Critical Mach..  These conditions can intersect, depending on aircraft and weight, at some point in the early 40s.  You're at idle power, but also cruise power - you can't reduce power.  You're at critical Mach so you can't accelerate.  If you want to go down, you can't reduce power because you can't go past idle; you can't push the nose over because you'll go transonic.  You're stuck.  You can shut down an engine or two for a while - that will let you come down without busting Mach.  You might deploy a little spoiler or lower the landing gear, but the former assures some transonic regions on the top of the wing and the latter could cause some supersonic flow around the gear with unpredictable results.

Sort of painting yourself into a corner ... Jim S.

cardmarc@charter.net wrote: 
Stall speed approaches TAS at altitude. I think that is one reason why the big boys use Mach numbers and stick shakers. Now I said more than I know. Maybe the military and heavy iron guys can chime in.
Marc
  
From: Jim Sower <canarder@frontiernet.net>
Date: 2005/01/05 Wed AM 07:10:04 GMT
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Subject: [FlyRotary] Re: IAS and Vne! Whoa!

Actually, I'm talking about flutter.  VNE (for our homebuilt purposes) 
seems to be that IAS at which the designer who almost certainly hasn't 
gone into it too very deeply, begins to perceive that he is on the cusp 
of being uncomfortably close to it.  Flutter that is.  It's on that page 
in the POH that even SMELLS like it's been pulled out of someone's ass :o)
I think I'll get some sleep ... Jim S.

Jim Sower wrote:

    
Actually, I've been given to understand that *both* IAS and TAS are a 
factor.  I don't know exactly what the relationship is, just that they 
both come into play.
But now I've  told you more than I know ... Jim S.

John Slade wrote:

      
 > Apparently Vne is NOT, it is a factor of True Airspeed!!  That's 
contrary to what I've read with respect to canard pushers, Ed.
As I understand it VNE for the Cozy, for example, is 220 mph IAS.
It's all to do with how many air molecules are hitting the airplane.
Someone tell me I'm wrong. ???
 
John
 
 
 
        
      
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