X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml Date: Fri, 04 Dec 2009 16:28:30 -0500 Message-ID: X-Original-Return-Path: Received: from cdptpa-omtalb.mail.rr.com ([75.180.132.121] verified) by logan.com (CommuniGate Pro SMTP 5.3c3) with ESMTP id 4002954 for lml@lancaironline.net; Fri, 04 Dec 2009 15:56:56 -0500 Received-SPF: pass receiver=logan.com; client-ip=75.180.132.121; envelope-from=dfs155@roadrunner.com Received: from dan ([76.178.186.181]) by cdptpa-omta01.mail.rr.com with SMTP id <20091204205620359.CCM5818@cdptpa-omta01.mail.rr.com> for ; Fri, 4 Dec 2009 20:56:20 +0000 X-Original-Message-ID: <907E9B182697479ABC6F25429E7C6397@dan> From: "Dan Schaefer" X-Original-To: "Lancair list" Subject: Control balance and flutter X-Original-Date: Fri, 4 Dec 2009 12:56:18 -0800 MIME-Version: 1.0 Content-Type: text/plain; format="flowed"; charset="iso-8859-1"; reply-type="original" Content-Transfer-Encoding: 7bit X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.5843 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.5579 Good post, Justin. In 1964 when I started working at Rockwell's aircraft division (where we later designed the B-1) every new hire was given an extensive review of the company's current projects and it's history. Back then, Rockwell was (or had been) building several small GA aircraft and one of the things shown that day was a film of wind tunnel flutter tests on a tail section of one of those airplanes during the design phase. It still stands out vividly in my memory how suddenly the vertical tail assembly literally blew up and disappeared as the wind velocity was slowly raised past the equivalent VNE. Just a few knots over the limit and the vertical was simply gone. Slow-motion showed that there was no more than three - four lateral excursions before the structure turned to confetti (as a matter of fact, I believe the airplane's empennage was subsequently redesigned to increase the demonstrated margins before comitting to production). If such a violent flutter onset occurred to some part of your airplane, you ain't gonna save it, no matter how quickly you tried to slow down. Certainly we must test our aircraft extensively to establish the safe flight envelope we intend to use but sneaking up on, or exceeding published limits like VNE, weight or CG could result in you being the proud owner of some quite interesting, but wholly useless data - for the time it takes you to hit the ground. So be careful out there! Dan Schaefer -- I am using the free version of SPAMfighter. We are a community of 6 million users fighting spam. SPAMfighter has removed 639 of my spam emails to date. Get the free SPAMfighter here: http://www.spamfighter.com/len The Professional version does not have this message