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 593016 for flyrotary@lancaironline.net; Thu, 06 Jan 2005 00:18:24 -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 75DDD101E7 for ; Thu, 6 Jan 2005 05:17:54 +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 00774-11-37 for ; Thu, 6 Jan 2005 05:17:54 +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 D30B01010B for ; Thu, 6 Jan 2005 05:17:53 +0000 (UTC) Message-ID: <41DCCA77.7000307@frontiernet.net> Date: Wed, 05 Jan 2005 23:19:51 -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: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit 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 Your prop tips are going to go supersonic and slow you down a waaaay before anything transonic happens on a flying surface. Jack Ford wrote: >Thanks, David, > >You mention 10,000 ft. Some of us are looking at FL 250 or so, and THAT'S >why there are so many tears and gnashing. > >Any help? > >Thanks again, > >Jack Ford > >Cozy MKIV #882 > >----- Original Message ----- >From: "David Carter" >To: "Rotary motors in aircraft" >Sent: Wednesday, January 05, 2005 2:32 PM >Subject: [FlyRotary] Re: IAS and Vne! Whoa! > > > > >>Vne is principally a function of CAS (IAS corrected for instrument and >>pitot-static system errors) as far as we are concerned flying below Mach >>0.5. Someone just observed TAS is also a factor - but not a significant >> >> >one > > >>below jet aircraft speeds and altitudes. >> >>As far as "Mach tuck", we are talking about pitch trim changes that are >>related to/caused by shock waves on curved aircraft surfaces where the >>local, repeat, local, air speed is reaching Mach 1.0 due to speeding up to >>get around the curve. It is not something you'll get at 250 CAS at 10,000 >>or below. It is NOT the "normal"/predictable pitch trim change that >> >> >occurs > > >>as the center of pressure moves aft (further behind CG) as angle attack >>decreases at high speed/very low angles of attack (high speed meaning >> >> >"above > > >>cruise speed", "during descent with power on", NOT up near Mach 0.8 or >>higher). >> - Mach tuck is related to "Mach number" - shock wave formation. >> >> >There > > >>is a TAS for each "Mach number" you may consider, but the effect is due to >>Mach number, not TAS. I.e., if you fly at that same TAS but at a lower >>altitude (lower Mach number) you won't have the Mach tuck. >> >>David >>----- Original Message ----- >>From: "John Slade" >>To: "Rotary motors in aircraft" >>Sent: Tuesday, January 04, 2005 10:38 PM >>Subject: [FlyRotary] Re: IAS and Vne! Whoa! >> >> >> >> >>>>IAS is a pretty good indicator of the amount of force acting on the >>>> >>>> >>>airframe. >>>That's the way I understood it. The main issue for most of us with VNE >>> >>> >is > > >>>the potential for flutter, and catastrophic failure of control surfaces. >>>However, I've read that at high TAS there's another nasty little demon >>>lurking called "Mach Tuck". The problem is well named, since it can >>> >>> >cause > > >>an >> >> >>>unrecoverable dive where the "tucked" part can be the wings :(. >>>I believe Mach tuck is more related to TAS. >>> >>>Here's a quote from someone who "seems to know what he's talking about" >>>borrowed from another list..... >>> >>>"Mach tuck is an interesting phenomenon, basically it is the result of >>> >>> >the > > >>>CL moving back as speed increases, increasing the twisting moment of the >>>main wing to the point where it overrides the horizontal stabilizers' >>> >>> >(or > > >>>canards') capability to counteract it causing the nose to suddenly pitch >>>forward, and in extreme cases twisting the wings off the aircraft >>>altogether." >>> >>>I'd love to where these nasty little buggars live, so I can avoid the >>>neighborhood. Unfortunately without destructive wind tunnel testing we >>> >>> >>don't >> >> >>>know where they are till we find them, then we don't get much of a >>> >>> >chance > > >>to >> >> >>>document it. :( >>> >>>Anyone know more? >>> >>>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 >>>> >>>> > > > > >>> Homepage: http://www.flyrotary.com/ >>> Archive: http://lancaironline.net/lists/flyrotary/List.html >>> >>> > > > >