X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from cdptpa-omtalb.mail.rr.com ([75.180.132.120] verified) by logan.com (CommuniGate Pro SMTP 5.4.0) with ESMTP id 5041335 for flyrotary@lancaironline.net; Sun, 03 Jul 2011 17:16:16 -0400 Received-SPF: pass receiver=logan.com; client-ip=75.180.132.120; envelope-from=eanderson@carolina.rr.com Return-Path: X-Authority-Analysis: v=1.1 cv=8mDY8c80ZOa76EOwICuS+E2YRQjxDgO9xqUnRMONc7w= c=1 sm=0 a=5V8EPDt1A4oA:10 a=rPkcCx1H5rrOSfN0dPC7kw==:17 a=arxwEM4EAAAA:8 a=r1ClD_H3AAAA:8 a=ayC55rCoAAAA:8 a=0L1lWIZ5VOIgPIHdQu8A:9 a=njYNQMCSe7_djJAzlG8A:7 a=wPNLvfGTeEIA:10 a=pGLkceISAAAA:8 a=Ia-xEzejAAAA:8 a=vbDjzfcMagnrOscXfG8A:9 a=2RVebA4iQcGsovcVF5EA:7 a=MSl-tDqOz04A:10 a=EzXvWhQp4_cA:10 a=rPkcCx1H5rrOSfN0dPC7kw==:117 X-Cloudmark-Score: 0 X-Originating-IP: 174.110.167.5 Received: from [174.110.167.5] ([174.110.167.5:63046] helo=EdPC) by cdptpa-oedge03.mail.rr.com (envelope-from ) (ecelerity 2.2.3.46 r()) with ESMTP id 0D/98-00666-BFBD01E4; Sun, 03 Jul 2011 21:15:39 +0000 Message-ID: <0C519E42FEDC4818962ACD32D3D95B8E@EdPC> From: "Ed Anderson" To: "Rotary motors in aircraft" References: In-Reply-To: Subject: Re: [FlyRotary] Re: VNE / Flutter Testing Date: Sun, 3 Jul 2011 17:14:57 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_001A_01CC39A4.BB8AD740" X-Priority: 3 X-MSMail-Priority: Normal Importance: Normal X-Mailer: Microsoft Windows Live Mail 14.0.8117.416 X-MimeOLE: Produced By Microsoft MimeOLE V14.0.8117.416 This is a multi-part message in MIME format. ------=_NextPart_000_001A_01CC39A4.BB8AD740 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable One important step needs to be added for you brave souls anticipating = flutter testing. =20 When you "slap" the stick you need to ensure your aircraft is in a = gentle climb so that any excitation of surfaces face a decreasing = airspeed situation (putting your further way each millisecond from the = critical airspeed that might cause flutter). Also, I would not count a = whole lot on the usefulness of a parachute if you should encounter = flutter - the potentially extremely rapid disintegration of the airframe = may well preclude being able to get out and be conscious enough to = deploy it. But, hey, I would rather have one than not {:>) Also worthy of note, a lot of debate raged about the following viewpoint = - a case was made in one of Van's Rvatiors that flutter was a function = of True Airspeed rather than indicated Airspeed. The point was that = while all other airspeed restrictions could safely be related to = indicate airspeed, Vne could not. =20 The argument was that flutter was a function of the velocity of the = moving air molecules flowing across the control surface/wing. Further = while the dynamic pressure encountered varied with both the density and = velocity of the air molecules, the excitation force (causing the = flutter) was a function of velocity of the molecules and not their = density. Well, not being an aerodynamic engineer - it got beyond me. =20 The point was that the True velocity of the air molecules of an IAS = reached at 3000 feet was far different than when that same IAS was = reached at 20,000 ft. And that IF the argument was correct, then you = could be far in excess of the intended Vne airspeed. =20 This was all in the context of turbocharged engines as the power output = of NA engines falls off proportional to altitude and therefore did not = present the same problem relative to Vne as a engine capable of full = power at 18000. Me? I should be so lucky to have to worry about Vne {:>) Just thought I would pass it one. Ed Edward L. Anderson Anderson Electronic Enterprises LLC 305 Reefton Road Weddington, NC 28104 http://www.andersonee.com http://www.eicommander.com From: Dustin Lobner=20 Sent: Sunday, July 03, 2011 3:41 PM To: Rotary motors in aircraft=20 Subject: [FlyRotary] Re: VNE / Flutter Testing I read somewhere (I can't recall, sorry) that basically you speed up a = couple of knots, let go of the stick, and then bump it forward and see = what happens (being ready to grab it in a hurry). the the same with = elevator, rudder, and aileron. Speed up a couple of more knots, try it = again. The idea is that you can have a "metastable" situation where there is no = flutter until a gust of wind comes by, at which point you're 30 knots = over where it can happen, so it happens in a hurry. Creating the = disturbance yourself prevents it from being a metastable condition. Dustin On Sun, Jul 3, 2011 at 2:29 PM, Ernest Christley = wrote: On 07/03/2011 03:24 PM, Kelly Troyer wrote:=20 Ernest, The procedure is to test with many steps increasing speed in = small increments always ready to reduce throttle and increase AOA at the slightest indication of = flutter.............. Dang! I was hoping somebody had come up with something better than = that. Oh, well. At least that gives me a "reason" to take up parachuting = 8*) ------=_NextPart_000_001A_01CC39A4.BB8AD740 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
One important step needs to be added for you = brave souls=20 anticipating flutter testing. 
 
When you "slap" the stick you need to ensure = your aircraft=20 is in a gentle climb so that any excitation of surfaces face a = decreasing=20 airspeed situation (putting your further way each millisecond from the = critical=20 airspeed that might cause flutter). Also,  I would not count a = whole=20 lot on the usefulness of a parachute if you should encounter flutter - = the=20 potentially extremely rapid disintegration of the airframe may well = preclude=20 being able to get out and be conscious enough to deploy it.  But, = hey, I=20 would rather have one than not {:>)
 
Also worthy of note, a lot of debate = raged about=20 the following viewpoint - a case was made in one of Van's Rvatiors =  that=20 flutter was a function of True Airspeed rather than=20 indicated Airspeed.  The point was that while all = other=20 airspeed restrictions could safely be related to indicate airspeed, Vne = could=20 not. 
 
The argument was = that flutter  was a=20 function of  the velocity of the moving air = molecules=20 flowing across the control surface/wing.  Further while the dynamic = pressure encountered varied with both the density and velocity of the = air=20 molecules, the excitation force (causing the flutter) was a function of = velocity=20 of the molecules and not their density.  Well, not being an = aerodynamic=20 engineer - it got beyond me. 
 
The point was that the True velocity of the=20 air molecules of  an  IAS reached at 3000 feet was far = different=20 than when that same IAS was reached at 20,000 ft.  And = that=20 IF the argument was correct, then you could be far in excess of = the=20 intended Vne airspeed. 
 
This was all in the context of turbocharged = engines=20 as the power output of NA engines falls off proportional to altitude and = therefore did not present the same problem relative to Vne as a engine = capable=20 of full power at 18000.
 
Me?  I should be so  lucky to have to = worry=20 about Vne {:>)
 
Just thought I would pass it one.
 
Ed
 
Edward L. Anderson
Anderson Electronic = Enterprises=20 LLC
305 Reefton Road
Weddington, NC 28104
http://www.andersonee.com
http://www.eicommander.com

From: Dustin Lobner
Sent: Sunday, July 03, 2011 3:41 PM
To: Rotary motors in = aircraft
Subject: [FlyRotary] Re: VNE / Flutter = Testing

I read somewhere (I can't recall, sorry) that basically = you speed=20 up a couple of knots, let go of the stick, and then bump it forward and = see what=20 happens (being ready to grab it in a hurry).  the the same with = elevator,=20 rudder, and aileron.  Speed up a couple of more knots, try it=20 again.

The idea is that you can have a "metastable" situation = where there=20 is no flutter until a gust of wind comes by, at which point you're 30 = knots over=20 where it can happen, so it happens in a hurry.  Creating the = disturbance=20 yourself prevents it from being a metastable = condition.

Dustin

On Sun, Jul 3, 2011 at 2:29 PM, Ernest = Christley <echristley@nc.rr.com> = wrote:
On 07/03/2011 03:24 PM, Kelly Troyer wrote:=20
Ernest,
   The procedure is to test with many steps = increasing=20 speed in small increments always ready
to reduce throttle and = increase AOA at the=20 slightest indication of flutter..............

 

Dang!  I was = hoping=20 somebody had come up with something better than that.

Oh, = well. =20 At least that gives me a "reason" to take up parachuting=20 8*)

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