X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Mon, 05 Jun 2006 12:11:55 -0400 Message-ID: X-Original-Return-Path: Received: from mxsf23.cluster1.charter.net ([209.225.28.223] verified) by logan.com (CommuniGate Pro SMTP 5.0.9) with ESMTP id 1141371 for lml@lancaironline.net; Mon, 05 Jun 2006 10:41:05 -0400 Received-SPF: pass receiver=logan.com; client-ip=209.225.28.223; envelope-from=troneill@charter.net Received: from mxip32a.cluster1.charter.net (mxip32a.cluster1.charter.net [209.225.28.247]) by mxsf23.cluster1.charter.net (8.12.11/8.12.11) with ESMTP id k55EeI4J017323 for ; Mon, 5 Jun 2006 10:40:19 -0400 Received: from 68-184-229-22.dhcp.stls.mo.charter.com (HELO axs) ([68.184.229.22]) by mxip32a.cluster1.charter.net with SMTP; 05 Jun 2006 10:40:19 -0400 X-Original-Message-ID: <001f01c688ad$f754b000$6401a8c0@axs> From: "terrence o'neill" X-Original-To: "Lancair Mailing List" References: Subject: Re: [LML] Re: David Hickman Crash X-Original-Date: Mon, 5 Jun 2006 09:40:18 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_001C_01C68884.0E1B5250" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.2869 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2869 This is a multi-part message in MIME format. ------=_NextPart_000_001C_01C68884.0E1B5250 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Colyn, Yes. We all like to think that if we just decide we will avoid = dangerous situations, that situation can never happen to us. We should = read the bumper sticker: Shit Happens. We can all be distracted for a = few seconds, and suddenly, There you are. Now what? =20 The FAA made a fatal change in aircraft Type Certification requirements = right after WW II. They caved into pressure from the suddenly-powerful = and huge new wartime aviation industry, by rescinding the requirement = that all general aviation aircraft should demonstrate recovery from a = six turn spin. Because, they pleaded, it was very risky and very = expensive to demonstrate. non sequitur argument. Instead they = pressured the bureaucracy to require what's called 'Placard Safety"... = but it is really a cop-out, whereby we avoid deliberate stalls and the = resulting spins. Now it's just to demonstrate recovery from an = incipient spin... the first top turns, during which a plane usually = unstalls itself once or twice. But, what about unintentional stalls and spins? That could never happen = to me? Now, we die, because the marketing department and the unwise do = not design planes to be able to recover ... like the aerobatic pilots = demand.=20 I remember like yesterday when my instructor had me make a steep = climbing turn in the SNJ, and cross the controls. We were instantly = over the top and upside down and entering a spin. The SNJ, however, was DESIGNED to recover from unusual attitudes and = spins ... He even had me demonstrate I could recover from an inverted = spin. The SNJ could do it. Any plane can have its surfaces and CG = range designed to do it. You may recall that GenAv designs from before WW II, like the Howard = DGA, had to demonstrated that they could recover from a six turn spin, = at aft CG, to get their Aircraft Type Certificate, and so they can ... = because the airplanes were designed to be able to. Now we put top priority on speed, ignoring the possible surprise, and = use the (several, not all) laminar airfoils that stall like you said ... = see the dashed-line in the Lift/AOA curves in Abbott & Doenhoff ... that = stall at say 16 degrees, but won't unstall till they AOA is reduced to = half that. We are not told, and do not know, at what angle of attack = these critical airfoils will unstall ... and it's not at the same AOA at = which they stall. We do not know whether our planes will 'trim', or = deep-stall, at some CG and AOA combination. A wind tunnel test could = reveal that. Further, as noted in my last comment a few days ago on tails, we don't = know when the horizontal tails stall and lose at least half their = unstall power. =20 The designers of GenAv, like Piper, Cessna, etc., for 50 years now, use = thin airfoils there, and high aspect ratios, both characteristics result = in stalls at low tail-AOAs... only a few degrees past the wing's stall = AOA. They ignore the lessons of the old days, with stubby tails of low = ARs and lots of leading edge sweepback, which kept the tails unstalled = and powerful to high AOAs. =20 It would be nice, wouldn't it, to have some University use it's wind = tunnel to do a Cl and Cmac survey of the Lancairs, from zero to 90 = degrees, plus and minus, and then modify the tails, horizontal and = vertical, until they could enable the pilot to recover from any -- any = -- unusual attitude. The drag penalty, I believe, would be less than perhaps 5 knots, if any = at all. =20 The builders and pilots like yourself on this list are remarkably = experienced and rational, and the excellent airplane designs we = appreciate outperforms nearly everything, except at high AOAs. Good = guys and their loved ones are suffering. How could this be remedied? Comments and other viewpoints could add more perspective. Terrence O'Neill N211AL L235/320 (modifying the horizontal tail) ----- Original Message -----=20 From: colyncase on earthlink=20 To: Lancair Mailing List=20 Sent: Monday, June 05, 2006 08:43 AM Subject: [LML] Re: David Hickman Crash Far as I can tell Martin did an awesome job on the structure of the = LIVP. Notably, Martin said to me "No one should ever stall a LIVP" I'm afraid I can't credit the statement "The wing tip is not designed = to stall and as such the question of how it stalls is not relevant" The = lift vs. AOA curve on that airfoil I can only describe as discontinuous. = It goes from 100% CL to 50% in a small fraction of a degree. (like less = than .2). Washout doesn't make that go away. If the root has stalled = and the tips are all that is flying and they are just a little bit = different in incidence, guess what happens next? Washout only gives = you a little more time to notice what is going on and get flying again = before that happens. =20 There is no question in my mind that you don't want to go there. I = think most of the community agrees. There is a huge question in my mind why experienced Lancair pilots get = there. I don't suppose I am better than any of them. but I wonder = what happens in your mind that you let it happen, and how you can = prepare for whatever THAT is. =20 Colyn ------=_NextPart_000_001C_01C68884.0E1B5250 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Colyn,
Yes.  We all = like to think=20 that if we just decide we will avoid dangerous situations, that = situation can=20 never happen to us.  We should read the bumper sticker: Shit=20 Happens.  We can all be distracted for a few seconds, and suddenly, = There=20 you are.  Now what? 
The FAA made a = fatal change in=20 aircraft Type Certification requirements right after WW II.  They = caved=20 into pressure from the suddenly-powerful and huge new wartime aviation = industry,=20 by rescinding the requirement that all general aviation aircraft = should=20 demonstrate recovery from a six turn spin.  Because, they pleaded, = it was=20 very risky and very expensive to demonstrate.   non sequitur=20 argument.  Instead they pressured the bureaucracy to require = what's =20 called 'Placard Safety"... but it is really a cop-out, whereby we avoid=20 deliberate stalls and the resulting spins.  Now it's just to = demonstrate recovery from an incipient spin... the first top turns, = during which=20 a plane usually unstalls itself once or twice.
But, what about=20 unintentional stalls and spins?  That could never happen to=20 me?  Now, we die, because the marketing department and the unwise = do not=20 design planes to be able to recover ... like the aerobatic pilots=20 demand. 
I remember like = yesterday when=20 my instructor had me make a steep climbing turn in the SNJ, and cross = the=20 controls.  We were instantly over the top and upside down and = entering a=20 spin.
The SNJ, however, = was DESIGNED=20 to recover from unusual attitudes and spins ... He even had me = demonstrate I=20 could recover from an inverted spin.  The SNJ could do it.  = Any plane=20 can have its surfaces and CG range designed to do it.
You may recall that = GenAv=20 designs from before WW II, like the Howard DGA, had to=20 demonstrated that they could recover from a six turn spin, at aft = CG, to=20 get their Aircraft Type Certificate, and so they can ... because the = airplanes=20 were designed to be able to.
Now we put top = priority on=20 speed, ignoring the possible surprise, and use the (several, not all) = laminar=20 airfoils that stall like you said ... see the dashed-line in the = Lift/AOA curves=20 in Abbott & Doenhoff ... that stall at say 16 degrees, but = won't=20 unstall till they AOA is reduced to half that.  We are not told, = and do not=20 know, at what angle of attack these critical airfoils will = unstall ...=20 and it's not at the same AOA at which they stall.  We do not know = whether=20 our planes will 'trim', or deep-stall, at some CG and AOA = combination.  A=20 wind tunnel test could reveal that.
 
Further, as noted = in my last=20 comment a few days ago on tails, we don't know when the horizontal tails = stall=20 and lose at least half their unstall power. 
The designers of = GenAv, like=20 Piper, Cessna, etc., for 50 years now, use thin airfoils there, and high = aspect=20 ratios, both characteristics result in stalls at low tail-AOAs... only a = few=20 degrees past the wing's stall AOA.  They ignore the lessons of the = old=20 days, with stubby tails of low ARs and lots of leading edge sweepback,=20 which kept the tails unstalled and powerful to high = AOAs. =20
It would be nice, = wouldn't it,=20 to have some University use it's wind tunnel to do a Cl and Cmac survey = of the=20 Lancairs, from zero to 90 degrees, plus and minus, and then modify the=20 tails, horizontal and vertical, until they could enable the pilot = to=20 recover from any -- any -- unusual attitude.
The drag penalty, I = believe,=20 would be less than perhaps 5 knots, if any at all. 
The builders and = pilots like=20 yourself on this list are remarkably experienced and rational, = and the=20 excellent airplane designs we appreciate outperforms nearly everything, = except=20 at high AOAs.  Good guys and their loved ones are suffering.  = How=20 could this be remedied?
Comments and other = viewpoints=20 could add more perspective.
 
Terrence = O'Neill
N211AL
L235/320 (modifying = the=20 horizontal tail)
----- Original Message -----
From:=20 colyncase on earthlink =
Sent: Monday, June 05, 2006 = 08:43=20 AM
Subject: [LML] Re: David = Hickman=20 Crash

Far as I can tell Martin did an = awesome job on=20 the structure of the LIVP.
Notably, Martin said to me "No one = should ever=20 stall a LIVP"
I'm afraid I can't credit the = statement "The wing=20 tip is not designed to stall and as such the question of how it stalls = is not=20 relevant"  The lift vs. AOA curve on that airfoil I can only = describe as=20 discontinuous.  It goes from 100% CL to 50% in a small fraction = of a=20 degree. (like less than .2).  Washout doesn't make that = go=20 away.  If the root has stalled and the tips are all that is = flying and=20 they are just a little bit different in incidence, guess what happens=20 next?   Washout only gives you a little more time to = notice=20 what is going on and get flying again before that happens.   =
 
There is no question in my mind that = you don't=20 want to go there.  I think most of the community = agrees.
There is a huge question in my mind = why=20 experienced Lancair pilots get there.    I don't = suppose I am=20 better than any of them.   but I wonder what happens in your = mind=20 that you let it happen, and how you can prepare for whatever THAT=20 is.  
 
Colyn
 
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