X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml Date: Wed, 02 Dec 2009 09:39:12 -0500 Message-ID: X-Original-Return-Path: Received: from mail.skywerx.com ([206.123.212.134] verified) by logan.com (CommuniGate Pro SMTP 5.3c3) with ESMTPS id 3998987 for lml@lancaironline.net; Wed, 02 Dec 2009 09:22:43 -0500 Received-SPF: none receiver=logan.com; client-ip=206.123.212.134; envelope-from=aflyer@lazy8.net Received: from mail.skywerx.com (mail.skywerx.com [206.123.212.134]) by mail.skywerx.com (8.12.8/8.12.8) with ESMTP id nB2EGh7n022182 for ; Wed, 2 Dec 2009 07:16:44 -0700 Received: from blueroom ([206.123.213.175] helo=blueroom) with IPv4:25 by mail.skywerx.com; 2 Dec 2009 07:16:43 -0700 From: "John Huft" X-Original-To: "'Lancair Mailing List'" References: In-Reply-To: Subject: flutter, tas, and vne X-Original-Date: Wed, 2 Dec 2009 07:21:39 -0700 X-Original-Message-ID: <000001ca735a$c3af58e0$4b0e0aa0$@net> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0001_01CA7320.175080E0" X-Mailer: Microsoft Office Outlook 12.0 Thread-Index: AcpyeN82li7bSDouSFerJCJlA5epzQAko5FQ Content-Language: en-us X-Assp-ID: mail.skywerx.com (63403-03951) X-Assp-Version: 1.5.1.8(1.0.00) X-Virus-Scanned: ClamAV 0.93/6963/Sun Apr 27 06:37:52 2008 on mail.skywerx.com X-Virus-Status: Clean This is a multi-part message in MIME format. ------=_NextPart_000_0001_01CA7320.175080E0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Here is the article, actually written by Ken Kruger, Van's chief engineer. http://www.vansaircraft.com/pdf/hp_limts.pdf It was written in response to a couple of turbo installations that were showing up, one on an RV8, and as soon as the RV10 came out talk started about flying high with turbo engines. Clearly, Van had not allowed for these power plants when he designed the airframe. While it is true that flutter is related to True Air Speed, since the airspeed indicator is the standard reference instrument, Vne is referenced as an indicated airspeed that leaves sufficient margin at high altitude be safe. When the threat of turbo engines suddenly raised the useful altitude, Van's decided the article was necessary to keep the RV guys out of trouble. It is interesting that the gliders have such a large altitude range that they need to placarded accordingly. There are other reasons for Vne besides flutter. I know from a test pilot that the Piper twin Comanche will suffer structural damage to the fuselage, just forward of the empennage, at Vne plus 5 at low altitude. Also, the early Cessna 180s would suffer a runaway trim situation only a little over Vne. In this case the stabilizer trim, which is mechanically operated by a jackscrew, would run away in the "nose up" direction. I actually talked to the flight test engineer who was aboard when this happened the first time.he and the pilot both blacked out from the g-forces, and luckily regained consciousness at the top of the climb and recovered the aircraft and landed safely. It was one of the few cases of structural damage to a strut-braced Cessna. The RV8 is specified to have a max speed only 8 mph shy of Vne. My own example will easily exceed Vne in level flight. So, I have spent some time worrying about this, especially racing in the AirVenture cup race year before last when we started in Mitchell, SD and raced eastbound. I went to 15,500 ft to catch a tailwind, but the problem comes in the decent.best racing would be done with a decent at Vne.but doing so at 15,500 would put me well over Vne TAS. That year, clouds forced me lower before the finish line, and my final decent started at 9500 ft, which still put me over Vne, but not more than I had previously tested. I think the responsible kit-plane manufacturer will build a lot of margin into this spec, considering build differences from one example to another. You still never know about your particular example until you have tested it. Or, just take Vne as a limit, one based on True Air Speed. John Huft RV spy ------=_NextPart_000_0001_01CA7320.175080E0 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

Here is the article, actually written by Ken Kruger, = Van’s chief engineer.

 

http://www.vansairc= raft.com/pdf/hp_limts.pdf

 

It was written in response to a couple of turbo = installations that were showing up, one on an RV8, and as soon as the RV10 came out = talk started about flying high with turbo engines. Clearly, Van had not = allowed for these power plants when he designed the airframe.

 

While it is true that flutter is related to True Air = Speed, since the airspeed indicator is the standard reference instrument, Vne = is referenced as an indicated airspeed that leaves sufficient margin at = high altitude be safe. When the threat of turbo engines suddenly raised the useful = altitude, Van’s decided the article was necessary to keep the RV guys out of trouble. It is interesting that the gliders have such a large altitude = range that they need to placarded accordingly.

 

There are other reasons for Vne besides flutter. I know = from a test pilot that the Piper twin Comanche will suffer structural damage to = the fuselage, just forward of the empennage, at Vne plus 5 at low altitude. = Also, the early Cessna 180s would suffer a runaway trim situation only a = little over Vne. In this case the stabilizer trim, which is mechanically operated by = a jackscrew, would run away in the “nose up” direction. I = actually talked to the flight test engineer who was aboard when this happened the = first time…he and the pilot both blacked out from the g-forces, and = luckily regained consciousness at the top of the climb and recovered the = aircraft and landed safely. It was one of the few cases of structural damage to a strut-braced Cessna.

 

The RV8 is specified to have a max speed only 8 mph shy = of Vne. My own example will easily exceed Vne in level flight. So, I have spent = some time worrying about this, especially racing in the AirVenture cup race = year before last when we started in Mitchell, SD and raced eastbound. I went = to 15,500 ft to catch a tailwind, but the problem comes in the = decent…best racing would be done with a decent at Vne…but doing so at 15,500 = would put me well over Vne TAS. That year, clouds forced me lower before the = finish line, and my final decent started at 9500 ft, which still put me over = Vne, but not more than I had previously tested.

 

I think the responsible kit-plane manufacturer will build = a lot of margin into this spec, considering build differences from one example = to another. You still never know about your particular example until you = have tested it. Or, just take Vne as a limit, one based on True Air = Speed.

 

John Huft

RV spy

 

 

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