X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml Date: Wed, 02 Dec 2009 09:37:25 -0500 Message-ID: X-Original-Return-Path: Received: from imr-da02.mx.aol.com ([205.188.105.144] verified) by logan.com (CommuniGate Pro SMTP 5.3c3) with ESMTP id 3998590 for lml@lancaironline.net; Tue, 01 Dec 2009 22:11:14 -0500 Received-SPF: pass receiver=logan.com; client-ip=205.188.105.144; envelope-from=Sky2high@aol.com Received: from imo-da03.mx.aol.com (imo-da03.mx.aol.com [205.188.169.201]) by imr-da02.mx.aol.com (8.14.1/8.14.1) with ESMTP id nB23APBj011571 for ; Tue, 1 Dec 2009 22:10:25 -0500 Received: from Sky2high@aol.com by imo-da03.mx.aol.com (mail_out_v42.5.) id q.d66.4d79ff8b (29679) for ; Tue, 1 Dec 2009 22:10:22 -0500 (EST) From: Sky2high@aol.com X-Original-Message-ID: X-Original-Date: Tue, 1 Dec 2009 22:10:22 EST Subject: Re: [LML] Re: Vne is NOT a meaningless number X-Original-To: lml@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="-----------------------------1259723422" X-Mailer: AOL 9.5 sub 155 X-Spam-Flag:NO X-AOL-SENDER: Sky2high@aol.com -------------------------------1259723422 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Content-Language: en Dom old chap (et al), =20 Y'know, I also have problems with the TAS argument and I read the report= =20 (Flying High and Fast) written for a Van's publication by Ken Krueger (no= =20 relation). No other publication I have ever read discussed Vne related= to=20 TAS. In any event, the emphasis of this report is the overpowering RVs= with=20 big turbo-charged engines and thereby exceeding a variety of design limit= ed=20 specifications. Vne being one of them. One way to look at Vne is that= it=20 pertains to theoretical design limits beyond which the concept "unknown= =20 consequences" enters the picture. Flutter is not the only issue as=20 structural limits may also be exceeded. Remember that aluminum can becom= e distorted=20 (a hint) before it breaks whilst glass fails explosively when stressed=20 beyond its limits. =20 =20 That idea should bring the following into focus. The 320/360 Vne was set= =20 by the designer. From a structural view, the wings were tested to 9 Gs = for=20 a Max Wt of 1685 pounds with the stated load limit of 4.5 Gs - a 100%=20 safety factor. Some have set the MTOW somewhat higher thus reducing the= safety=20 factor. Then we have those that added outer fuel bays or extended wing= =20 tips along with the big/small tail difference. Flutter can be induced by= =20 airframe and flying surface interactions that create a destructive resonan= ce, =20 a resonance peculiar to the construction characteristics of the whole =20 system. Thus, the same differences that may alter original structural =20 limitations may also affect resonance relationships - i.e. The stiffening= of the=20 tail cone may affect the stabilizer response to prop pulses and maybe eve= n the=20 natural harmonics in the airframe. =20 Vne in our Lancairs (200/300 series) may be a conservative value and =20 exceeding it (IAS) makes one a serious test pilot. =20 For myself, exceeding 225 KIAS (235 KIAS Vne) requires conscious work as= =20 rudder trim is exceeded requiring the left foot to exert some pressure to= =20 keep the ball centered and the nose down trim is also exceeded requiring= a=20 good push on the stick. Thus, power is often reduced in a dive (Hmmmm,= power=20 used as a trim device). =20 I looked at NTSB reports for fatal Lancair accidents from 2001 to now (97= =20 total) and could only find 3 where, uh, things came apart, 2 IVs were brok= en=20 up in thunderstorms (N29ME 5-16-03 and N241DM 6-6-08) and a IVP where one= =20 aileron couldn't be found among the debris (N299SD 5-15-04). I forgot=20 which one of these raised questions about re-balancing control surfaces= after=20 a paint job............. =20 Scott Krueger =20 PS During my review of the 97, it seemed that the most common cause of= a=20 fatal crash was loss of control because of going too slow while too low. =20 =20 In a message dated 12/1/2009 7:52:20 P.M. Central Standard Time, =20 domcrain@tpg.com.au writes: =20 G=E2=80=99day Bill,=20 So Van, of Van=E2=80=99s is saying that when I was flogging along in my= B727 and=20 Airbus at 470 KTAS each of which had a VMO of 350 KIAS I was exceeding Vn= e?=20 Don=E2=80=99t think so.=20 Cheers=20 Dom=20 VH-CZJ=20 =20 =20 From: Lancair Mailing List [mailto:lml@lancaironline.net] On Behalf Of=20 Bill Kennedy Sent: Tuesday, 1 December 2009 10:29 PM To: lml Subject: [LML] Re: Vne is NOT a meaningless number Van of Van's Aircraft wrote about VNE a couple of years ago. Much to my= =20 surprise, VNE is true airspeed, not indicated. It's pretty easy to exceed= in=20 my Lancair. Results can be explosive, meaning onset of flutter to compone= nt=20 failure can be nearly instantaneous. I can't wear a parachute in my plane= =20 (Lancair 320), so I wouldn't screw around with it. -------------------------------1259723422 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Content-Language: en
Dom old chap (et al),
 
Y'know, I also have problems with the TAS argument and I read th= e=20 report (Flying High and Fast) written for a Van's publication by= Ken=20 Krueger (no relation).  No other publication I have ever read discuss= ed Vne=20 related to TAS.  In any event, the emphasis of this report is the=20 overpowering RVs with big turbo-charged engines and thereby exceeding= a=20 variety of design limited specifications.  Vne being one of=20 them.  One way to look at Vne is that it pertains to theoretical= =20 design limits beyond which the concept "unknown consequences" enters= the=20 picture.  Flutter is not the only issue as structural limits may also= be=20 exceeded.  Remember that aluminum can become distorted (a hint) = before=20 it breaks whilst glass fails explosively when stressed beyond its limits.&= nbsp;=20
 
That idea should bring the following into focus.  The 320/360 Vn= e was=20 set by the designer.  From a structural view, the wings were tested= to 9 Gs=20 for a Max Wt of 1685 pounds with the stated load limit of 4.5 Gs - a 100%= safety=20 factor.  Some have set the MTOW somewhat higher thus reducing th= e=20 safety factor.  Then we have those that added outer fuel bays or exte= nded=20 wing tips along with the big/small tail difference.  Flutter can be= induced=20 by airframe and flying surface interactions that create a destructive reso= nance,=20 a resonance peculiar to the construction characteristics of the whole=20 system.  Thus, the same differences that may alter original structura= l=20 limitations may also affect resonance relationships - i.e. The stiffe= ning=20 of the tail cone may affect the stabilizer response to prop pulses and may= be=20 even the natural harmonics in the airframe.
 
Vne in our Lancairs (200/300 series) may be a conservative value= and=20 exceeding it (IAS) makes one a serious test pilot.
 
For myself, exceeding 225 KIAS (235 KIAS Vne) requires conscious = ;work=20 as rudder trim is exceeded requiring the left foot to exert= some=20 pressure to keep the ball centered and the nose down trim is also exceeded= =20 requiring a good push on the stick.  Thus, power is often reduced in= a dive=20 (Hmmmm, power used as a trim device).
 
I looked at NTSB reports for fatal Lancair accidents from 2001 to now= (97=20 total) and could only find 3 where, uh, things came apart, 2 IVs were brok= en up=20 in thunderstorms (N29ME 5-16-03 and N241DM 6-6-08) and a IVP whe= re one=20 aileron couldn't be found among the debris (N299SD 5-15-04).  I=20 forgot which one of these raised questions about re-balancing co= ntrol=20 surfaces after a paint job.............
 
Scott Krueger
 
PS  During my review of the 97, it seemed that the most common= cause=20 of a fatal crash was loss of control because of going too slow while to= o=20 low.
 
In a message dated 12/1/2009 7:52:20 P.M. Central Standard Time,=20 domcrain@tpg.com.au writes:

G=E2=80=99= day=20 Bill,

So Van, of= Van=E2=80=99s=20 is saying that when I was flogging along in my B727 and Airbus at 470 KT= AS=20 each of which had a VMO of 350 KIAS I was exceeding Vne?

Don=E2=80= =99t think=20 so.

Cheers

Dom

VH-CZJ

 = ;

From:=20 Lancair Mailing List [mailto:lml@lancaironline.net] On Behalf Of = Bill=20 Kennedy
Sent: Tuesday, 1 December 2009 10:29 PM
To:= =20 lml
Subject: [LML] Re: Vne is NOT a meaningless=20 number

 

Van of Va= n's=20 Aircraft wrote about VNE a couple of years ago. Much to my surprise, VNE= is=20 true airspeed, not indicated. It's pretty easy to exceed in my Lancair.= =20 Results can be explosive, meaning onset of flutter to component failure= can be=20 nearly instantaneous. I can't wear a parachute in my plane (Lancair 320)= , so I=20 wouldn't screw around with=20 it.

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