X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml Date: Thu, 03 Dec 2009 06:21:20 -0500 Message-ID: X-Original-Return-Path: Received: from blu0-omc3-s13.blu0.hotmail.com ([65.55.116.88] verified) by logan.com (CommuniGate Pro SMTP 5.3c3) with ESMTP id 3999307 for lml@lancaironline.net; Wed, 02 Dec 2009 13:32:00 -0500 Received-SPF: pass receiver=logan.com; client-ip=65.55.116.88; envelope-from=randystuart@hotmail.com Received: from BLU0-SMTP9 ([65.55.116.72]) by blu0-omc3-s13.blu0.hotmail.com with Microsoft SMTPSVC(6.0.3790.3959); Wed, 2 Dec 2009 10:31:26 -0800 X-Originating-IP: [76.194.231.72] X-Originating-Email: [randystuart@hotmail.com] X-Original-Message-ID: X-Original-Return-Path: randystuart@hotmail.com Received: from laptop ([76.194.231.72]) by BLU0-SMTP9.blu0.hotmail.com over TLS secured channel with Microsoft SMTPSVC(6.0.3790.3959); Wed, 2 Dec 2009 10:31:25 -0800 From: "Randy" X-Original-To: "Lancair Mailing List" References: Subject: Re: [LML] Re: Vne is NOT a meaningless number X-Original-Date: Wed, 2 Dec 2009 10:31:24 -0800 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0056_01CA733A.99015820" 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 X-OriginalArrivalTime: 02 Dec 2009 18:31:25.0494 (UTC) FILETIME=[A7B05D60:01CA737D] This is a multi-part message in MIME format. ------=_NextPart_000_0056_01CA733A.99015820 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable To the best of my knowledge these were the only Lancair's that ever came = apart in the air. I also heard sometime back that the outback ( large = tail ) was susceptible to tail flutter at high speeds. Some builders = added a bid or two of carbon across the tail sections in anticipation of = that known issue. But not one of those came off. Does anyone remember the wing tests Lance did, the picture of sand or = cement bags stacked from one end to the other over the wing? He said the = plane would take 9+ & 6- G's. But during the stress tests he never was = able to break the structure. He under quoted the what the structure = could actually stand.=20 I believe Lance, like other designers, always sets the safe limits to = the lowest common denominator. They take into consideration the worst = builders that cut corners, use to much resin, build heavy or not = straight, etc. Under these conditions Vne would be an unsafe speed, but = a light quality built, straight aircraft would be safe beyond the = published limits. Again, these are published numbers in a POH that = covers multiple models of aircraft. Not from the "Builder" but the kit = maker. I wonder what the Vne was on the actual test plane Lance built? = It would be my guess the Vne was much higher then the POH.=20 The ironic part of this whole discussion is that I stated that I fly my = 360 past Vne but the lion share of crashes in this model ARE from slow = airspeeds. There's the IAS side I don't push the limit. This design = loves to go fast.... Slow.. not so much..=20 Randy Stuart LNC-2 ----- Original Message -----=20 From: Sky2high@aol.com=20 To: lml=20 Sent: Wednesday, December 02, 2009 6:37 AM Subject: [LML] Re: Vne is NOT a meaningless number Dom old chap (et al), Y'know, I also have problems with the TAS argument and I read the = report (Flying High and Fast) written for a Van's publication by Ken = Krueger (no relation). No other publication I have ever read discussed = Vne related to TAS. In any event, the emphasis of this report is the = overpowering RVs with big turbo-charged engines and thereby exceeding a = variety of design limited specifications. Vne being one of them. One = way to look at Vne is that it pertains to theoretical design limits = beyond which the concept "unknown consequences" enters the picture. = Flutter is not the only issue as structural limits may also be exceeded. = Remember that aluminum can become distorted (a hint) before it breaks = whilst glass fails explosively when stressed beyond its limits. =20 That idea should bring the following into focus. The 320/360 Vne was = set by the designer. From a structural view, the wings were tested to 9 = Gs for a Max Wt of 1685 pounds with the stated load limit of 4.5 Gs - a = 100% safety factor. Some have set the MTOW somewhat higher thus = reducing the safety factor. Then we have those that added outer fuel = bays or extended wing tips along with the big/small tail difference. = Flutter can be induced by airframe and flying surface interactions that = create a destructive resonance, a resonance peculiar to the construction = characteristics of the whole system. Thus, the same differences that = may alter original structural limitations may also affect resonance = relationships - i.e. The stiffening of the tail cone may affect the = stabilizer response to prop pulses and maybe even the natural harmonics = in the airframe. Vne in our Lancairs (200/300 series) may be a conservative value and = exceeding it (IAS) makes one a serious test pilot. For myself, exceeding 225 KIAS (235 KIAS Vne) requires conscious work = as rudder trim is exceeded requiring the left foot to exert some = pressure to keep the ball centered and the nose down trim is also = exceeded requiring a good push on the stick. Thus, power is often = reduced in a dive (Hmmmm, power used as a trim device). I looked at NTSB reports for fatal Lancair accidents from 2001 to now = (97 total) and could only find 3 where, uh, things came apart, 2 IVs = were broken up in thunderstorms (N29ME 5-16-03 and N241DM 6-6-08) and a = IVP where one aileron couldn't be found among the debris (N299SD = 5-15-04). I forgot which one of these raised questions about = re-balancing control surfaces after a paint job............. Scott Krueger PS During my review of the 97, it seemed that the most common cause = of a fatal crash was loss of control because of going too slow while too = low. In a message dated 12/1/2009 7:52:20 P.M. Central Standard Time, = domcrain@tpg.com.au writes: G=E2=80=99day Bill, So Van, of Van=E2=80=99s is saying that when I was flogging along in = my B727 and Airbus at 470 KTAS each of which had a VMO of 350 KIAS I was = exceeding Vne? Don=E2=80=99t think so. Cheers Dom VH-CZJ =20 From: Lancair Mailing List [mailto:lml@lancaironline.net] On Behalf = Of Bill Kennedy Sent: Tuesday, 1 December 2009 10:29 PM To: lml Subject: [LML] Re: Vne is NOT a meaningless number =20 Van of Van's Aircraft wrote about VNE a couple of years ago. Much to = my surprise, VNE is true airspeed, not indicated. It's pretty easy to = exceed in my Lancair. Results can be explosive, meaning onset of flutter = to component failure can be nearly instantaneous. I can't wear a = parachute in my plane (Lancair 320), so I wouldn't screw around with it. ------=_NextPart_000_0056_01CA733A.99015820 Content-Type: text/html; charset="utf-8" Content-Transfer-Encoding: quoted-printable =EF=BB=BF
To the best of my = knowledge=20 these were the only Lancair's that ever came apart in the air. I also = heard=20 sometime back that the outback ( large tail ) was susceptible to tail = flutter at=20 high speeds. Some builders added a bid or two of carbon across the = tail=20 sections in anticipation of that known issue. But not one of those came=20 off.
Does anyone = remember the wing=20 tests Lance did, the picture of sand or cement bags stacked from one end = to the=20 other over the wing? He said the plane would take 9+ & 6- G's. But = during=20 the stress tests he never was able to break the structure. He under = quoted the=20 what the structure could actually stand.
I believe Lance, = like other=20 designers, always sets the safe limits to the lowest common denominator. = They=20 take into consideration the worst builders that cut corners, use to much = resin,=20 build heavy or not straight, etc. Under these conditions Vne would be an = unsafe=20 speed, but a light quality built, straight aircraft would be safe = beyond=20 the published limits. Again, these are published numbers in a POH that = covers=20 multiple models of aircraft. Not from the "Builder" but the kit maker. I = wonder=20 what the Vne was on the actual test plane Lance built? It would be my = guess the=20 Vne was much higher then the POH.
The ironic part of = this whole=20 discussion is that I stated that I fly my 360 past Vne but the lion = share of=20 crashes in this model ARE from slow airspeeds. There's the IAS side I = don't push=20 the limit. This design loves to go fast.... Slow.. not so much..=20
 
Randy=20 Stuart
LNC-2
 
----- Original Message -----
From:=20 Sky2high@aol.com=20
To: lml
Sent: Wednesday, December 02, = 2009 6:37=20 AM
Subject: [LML] Re: Vne is NOT a = meaningless number

Dom old chap (et al),
 
Y'know, I also have problems with the TAS argument and I = read the=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 = discussed=20 Vne 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=20 hint) before it breaks whilst glass fails explosively when = stressed=20 beyond its limits. 
 
That idea should bring the following into focus.  The = 320/360 Vne=20 was set by the designer.  From a structural view, the wings were = tested=20 to 9 Gs for a Max Wt of 1685 pounds with the stated load limit of 4.5 = Gs - a=20 100% safety factor.  Some have set the MTOW somewhat higher = thus=20 reducing the safety factor.  Then we have those that added outer = fuel=20 bays or extended wing tips along with the big/small tail = difference. =20 Flutter can be induced by airframe and flying surface interactions = that create=20 a destructive resonance, a resonance peculiar to the construction=20 characteristics of the whole system.  Thus, the same differences = that may=20 alter original structural limitations may also affect resonance=20 relationships - i.e. The stiffening of the tail cone may affect the = stabilizer=20 response to prop pulses and maybe even the natural harmonics in the=20 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=20 conscious work as rudder trim is exceeded requiring the = left=20 foot to exert some pressure to keep the ball centered and the = nose down=20 trim is also exceeded requiring a good push on the stick.  Thus, = power is=20 often reduced in a dive (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 = broken=20 up in thunderstorms (N29ME 5-16-03 and N241DM 6-6-08) and a=20 IVP where one aileron couldn't be found among the debris (N299SD=20 5-15-04).  I forgot which one of these raised questions = about=20 re-balancing control 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 too=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=99day=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 KTAS=20 each of which had a VMO of 350 KIAS I was exceeding=20 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 Van'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=20 be nearly instantaneous. I can't wear a parachute in my plane = (Lancair 320),=20 so I wouldn't screw around with=20 it.

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