Return-Path: Sender: "Marvin Kaye" To: lml@lancaironline.net Date: Fri, 24 Sep 2004 13:49:30 -0400 Message-ID: X-Original-Return-Path: Received: from mail-relay-2.tiscali.it ([213.205.33.42] verified) by logan.com (CommuniGate Pro SMTP 4.2.3) with ESMTP id 430783 for lml@lancaironline.net; Fri, 24 Sep 2004 13:45:51 -0400 Received-SPF: none receiver=logan.com; client-ip=213.205.33.42; envelope-from=robert.overmars@tiscali.it Received: from trottolino (62.11.16.127) by mail-relay-2.tiscali.it (7.1.021.3) id 415293410007003A; Fri, 24 Sep 2004 19:45:19 +0200 X-Original-Message-ID: <008101c4a25f$0a18b240$7f100b3e@interbusiness.it> From: "Robert Overmars" X-Original-To: "Lancair Mailing List" X-Original-Cc: Subject: incidence difference X-Original-Date: Fri, 24 Sep 2004 19:50:52 +0200 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_007E_01C4A26F.CC0EAD40" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1158 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1165 This is a multi-part message in MIME format. ------=_NextPart_000_007E_01C4A26F.CC0EAD40 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Salutti tutti, Referring to Mike Easley's posting of a measured difference of 2.7 = degrees between the wingtip incidence of his Lancair leaves me = completely astounded! If Lancair has such poor workmanship and quality = control and not just on ESs but across the range of Lancairs as I = suspect, I strongly believe that Lancair Company is significantly = responsible for the extraordinary rate of fatalities in Lancairs. ANY = aeroplane that has such an enormous difference in wing(tip) incidence is = nothing short of a deathtrap in my opinion. Mount such a wing any way = you like to average the lift in cruise flight so the aeroplane flies = more or less wings level and at or close to max AoA the wing(tip) with = the higher AoA will stall first and drop....with yaw...into spin. In NO = WAY is 2.7 degrees difference in wintip incidence acceptable, ground the = aeroplane, return the wing to Lancair, DEMAND a new wing built properly, = your life and the life of whoever flies with you is at risk.... Over time I have come to believe that the quality and accuracy of = Lancair's workmanship is unacceptable. My own experience of Lancair fast = build is that the accuracy is poor and for instance on the last = unfortunately "fast build" Lancair IV I built it took longer to do the = remedial work than to do the work correctly in the first place. Just a = few days ago we all saw the pictures of the fast built Legacy that lost = it's stub wing upper surface panel, now Mike Easley writes of an = extraordinary 2.7 degrees difference in wingtip incidence...what will it = be next? Suspecting that differences in wing(tip) incidence may be a factor in = the all too common Lancair stall/spin fatality rate I have been = calculating some numbers to give some perspective. I'm so astounded at = Mike Easley's measued difference of 2.7 degrees in wing tip incidence = that even though I don't have all the material ready which I want to = include in my post I will write this tonight from memory as my notes are = back in my workshop; for a Lancair IV wing flying at 200 knots, using = sea level density, a difference of 0.1 degrees between the port and stbd = wing results in a difference of 56.6 lbs of lift. As the lift curve = slope of the wing is linear it follows that for a wing with 0.5 degrees = difference between port and stbd wings the lift of the wing with the = lessor A0A is 56.6lbs x 5 =3D 282.5 lbs. To get a perspective on this = imagine a spring balance hanging from a hypothetical sky hook and = attached to your "heavy" Lancair IV wing at about mid span, for the = aeroplane to fly straight and level the spring balance will have to hold = 282.5 lbs of force! And that's for a wing with "only" 0.5 degrees of = difference in incidence. If you use aileron to hold up your "heavy" = wing--- beware! Getting down to stall speeds is interesting....the = outboard wing section with down aileron will stall at a lessor angle of = attack, probably less than the inboard. It doesn't take great = imagination to understand the consequences. Looking at what happens at slower speeds is interesting. A clean and = straight LIV wing has a maximum coefficient of lift of 1.4, the = calculated stall speed is a just a little less than 80 knots in this = configuration. Calculating, a difference of 0.5 degrees of wing = incidence means the wing with the higher AoA will stall first by 1.25 = knots, but that's not taking into account on the other wing using the = aileron to hold up the "heavy" wing. It may well be that the "heavy" = wing outboard section will stall first with interesting consequences to = say the least....but my calculations haven't gotten that far yet so I = have no solid information. And I haven't even started to look at differences in washout (twist) but = I have no doubt that the numbers will be very interesting and revealing. = And the numbers don't lie!! Then combine port and stbd differences in = incidence and washout, asymmetric flap rigging... and it all gets very = interesting...=20 It's EASY to set up a jig to build a straight and clean and SYMMETRICAL = wing. Measuring wing incidence to 0.1 degrees or better is not = difficult. Those persons, (or Lancair Company) who can't measure to such = accuracy shouldn't be doing such work, get help from persons who can. = Your life depends on it. ciao, Roberto d'Italia. ------=_NextPart_000_007E_01C4A26F.CC0EAD40 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Salutti tutti,
 
Referring to Mike Easley's posting of a = measured=20 difference of 2.7 degrees between the wingtip incidence of = his Lancair=20 leaves me completely astounded! If Lancair has such = poor workmanship and=20 quality control and not just on ESs but across the range of Lancairs as = I=20 suspect, I strongly believe that Lancair Company = is significantly=20 responsible for the extraordinary rate of fatalities in Lancairs. ANY = aeroplane=20 that has such an enormous difference in wing(tip) incidence is nothing = short of=20 a deathtrap in my opinion. Mount such a  wing any way you = like to=20 average the lift in cruise flight so the aeroplane flies more or less = wings=20 level and at or close to max AoA the wing(tip) with the higher = AoA=20 will stall first and drop....with yaw...into spin. In NO WAY is 2.7 = degrees=20 difference in wintip incidence acceptable, ground the aeroplane, return = the wing=20 to Lancair, DEMAND a new wing built properly, your life and the life of = whoever=20 flies with you is at risk....
 
Over time I have come to believe that = the quality=20 and accuracy of Lancair's workmanship is unacceptable. My own experience = of=20 Lancair fast build is that the accuracy is poor and for instance on = the=20 last unfortunately "fast build" Lancair IV I built it = took longer to=20 do the remedial work than to do the work correctly in the first = place. Just=20 a few days ago we all saw the pictures of the fast built Legacy that =  lost=20 it's stub wing upper surface panel, now Mike Easley writes of an=20 extraordinary 2.7 degrees difference in wingtip incidence...what = will it be=20 next?
 
Suspecting that differences in = wing(tip) incidence=20 may be a factor in the all too common Lancair stall/spin fatality = rate I=20 have been calculating some numbers to give some perspective. I'm so = astounded at=20 Mike Easley's measued difference of 2.7 degrees in wing tip incidence = that even=20 though I don't have all the material ready which I want to include = in my=20 post I will write this tonight from memory as my notes are = back in my=20 workshop; for a Lancair IV wing flying at 200 knots, using sea level=20 density, a difference of 0.1 degrees between the port and stbd wing = results=20 in a difference of 56.6 lbs of lift. As the lift curve slope of the wing = is=20 linear it follows that for a wing with 0.5 degrees difference between = port and=20 stbd wings the lift of the wing with the lessor A0A is = 56.6lbs x=20 5 =3D 282.5 lbs. To get a perspective on this imagine a spring balance = hanging=20 from a hypothetical sky hook and attached to your "heavy" = Lancair=20 IV wing at about mid span, for the aeroplane to fly straight = and=20 level the spring balance will have to hold 282.5 lbs of = force! =20 And that's for a wing with "only" 0.5 degrees of difference in = incidence. If you=20 use aileron to hold up your "heavy" wing--- beware! Getting down to = stall speeds=20 is interesting....the outboard wing section with down aileron will stall = at a=20 lessor angle of attack, probably less than the inboard. It doesn't = take=20 great imagination to understand the consequences.
 
Looking at what happens at slower = speeds is=20 interesting. A clean and straight LIV wing has a maximum = coefficient of=20 lift of 1.4, the calculated stall speed is a just a little less than 80 = knots in=20 this configuration. Calculating, a difference of 0.5 degrees of = wing=20 incidence means the wing with the higher AoA will stall first by 1.25 = knots,=20 but that's not taking into account on the other wing using the = aileron=20 to hold up the "heavy" wing. It may well be that the "heavy" = wing outboard=20 section will stall first with interesting consequences to say the=20 least....but my calculations haven't gotten that far yet so I have = no solid=20 information.
 
And I haven't even started to look at = differences=20 in washout (twist) but I have no doubt that the numbers will be very = interesting=20 and revealing.  And the numbers don't lie!! Then combine port and = stbd=20 differences in incidence and washout, asymmetric flap = rigging... and=20 it all gets very interesting...
 
It's EASY to set up a jig to build = a straight=20 and clean and SYMMETRICAL wing. Measuring wing incidence to 0.1 degrees = or=20 better is not difficult. Those persons, (or Lancair Company) who = can't=20 measure to such accuracy shouldn't be doing such work, get help from = persons who=20 can. Your life depends on it.
 
ciao,
 
Roberto = d'Italia.
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