X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml Date: Sun, 04 Jun 2006 13:40:44 -0400 Message-ID: X-Virus-Scanned: clean according to Sophos on Logan.com X-SpamCatcher-Score: 30 [X] X-PolluStop-Diagnostic: ########## X-Orig-Return-Path: johnlittle@ansonic.com.au X-PolluStop-Score: 1.00 X-PolluStop: Scanned with Niversoft PolluStop v2.3.1d X-Original-Return-Path: Received: from sv6.per.eftel.com ([203.24.100.151] verified) by logan.com (CommuniGate Pro SMTP 5.0.9) with ESMTP id 1139608 for marv@lancaironline.net; Sat, 03 Jun 2006 23:54:31 -0400 Received-SPF: none receiver=logan.com; client-ip=203.24.100.151; envelope-from=johnlittle@ansonic.com.au Received: from little (unknown [203.129.148.89]) by sv6.per.eftel.com (Postfix) with SMTP id 20DB6E3A0B for ; Sun, 4 Jun 2006 11:53:39 +0800 (WST) X-Original-Message-ID: <000c01c6878a$7bddae00$599481cb@little> From: "John Little" X-Original-To: "Marvin Kaye" Subject: David Hickman Crash X-Original-Date: Sun, 4 Jun 2006 13:52:59 +1000 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0007_01C687DE.30E8A400" 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_0007_01C687DE.30E8A400 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Could another explanation exist for the loss of a highly skilled pilot? = I knew David from the High Performance training sessions he and Pete = Zaccagnino ran at Lakeland and I extend to Kathy my deep condolences. If one discounts the theory that he tried to turn back, perhaps there is = an explanation to be found in the deep stall characteristics of that = particular aircraft. Observers in the crash report said "the airplane pitched nose-up about = 20 to 30 degrees". "Black smoke trailed from the engine exhaust = system, the engine sputtered and then stopped producing power". "The = climb and the turn after the loss of engine power were performed at a = very high deck angle". "The aircraft entered a smooth roll to the left, = yawed left then plunged to the ground, near vertically". =20 Diverging for a moment to a report by Dave Allen (LML 05.15.04) who was = flight testing an ES for an owner. "I was doing a stall series, and = near the end was taking the deep stall to the point of wing drop. When = I brought the stick forward and applied full opposite rudder, the = Lancair not only did not recover, but fell into a fully developed 3 turn = spin". When one peruses the Summary of Lancair Accidents in the NTSB database, = there is an over-representation of stall/spin incidents involving = IV/IVP's. Some of these accidents involved the loss of highly = experienced pilots. Kissimee FL 7/11/01 Bozeman MT 11/05/02 Geelong (Aust) 12/20/02 Mesa AZ 2/17/04 Novalato (Mexico) 4/7/04 Grand Canyon AZ 5/18/04 Vermontville MI 5/31/04 A discussion on the stall characteristics of the Lancair wing led to a = posting from Martin Hollmann (LML 01/26/05) referring to the airfoil = used at the ROOT of the Lancair wing. "The wing is designed with the = RXM5-217 airfoil - a very gentle stalling airfoil" This benign = characteristic is further discussed in his book 'Modern Aircraft Design' = (page 40) and further represented by a lift curve (p 225) showing a = smooth stall with a gradual loss of lift.=20 The same posting from Martin Hollmann (LML 01/26/05) states of the = airfoil at the TIP of the Lancair wing "Yes, the NACA64212 airfoil has a = sharp stall. However the wing is designed with the RXM5-217airfoil, a = very gentle stalling airfoil, at the root and the NACA64212 at the tip. = The wing is washed out so that the root stalls first. The wing tip is = not designed to stall and as such the question of how it stalls is not = relevant. The NACA64212 airfoil was chosen for the tip because it has a = high lift coefficient and it is very effective with an aileron". These = comments are outlined also in 'Modern Aircraft Design' (p 40) and = represented by a lift curve (p223) showing a sharp stall and complicated = lift tendencies. In a normal stall, the airflow detaches from the lift surface starting = at the rear of the wing surface and progressively moving forward as the = angle of attack increases. Then by lessening the angle of attack the = air progressively reattaches to the surface. However the graph (p223) = suggests this wing foil does not show this progression. The air does = not progressively reattach, but pauses, then suddenly reattaches over a = very short variation in angle of attack, producing a sudden maximum = lift. Returning to the Dave Allen posting (LML 05.15.04) he stated "when I = brought the stick forward, the Lancair not only did not recover, but = fell into a fully developed 3 turn spin" He was a test pilot and = experienced a totally unexpected response - an uncommanded response. This anomoly may have little consequence in an aircraft with perfectly = symmetrical wings, but these are home-built wings and any lack of = symmetry at the tip provides the basis for assymetric lift. Even if = the assymetric lift is only momentary, the aircraft is at or past stall = and at its most vulnerable. Could this phenomenon explain the over-representation of stall/spin = accidents in the statistics? Could this explain the demise of some highly experienced pilots, facing, = like Dave Allen, a totally unexpected occurrence? Could this explain the David Hickman experience? He was in a nose high = attitude, losing or having lost power, the wings were stalling and he = was experiencing an uncommanded roll to the left. It appears to me as a non-aerodynamist, a non-engineer, but a keenly = interested follower of the tragedies that are befalling our community, = that this aircraft cannot be flown slow, cannot be inadvertently flown = close to its stall and must be built with great care and an even higher = level of precision. Ref: Dave Allen 23831 Robert Overmars 27776 Martin Hollmann 27896 Modern Aircraft Design 6th Edition 2002 ------=_NextPart_000_0007_01C687DE.30E8A400 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Could another explanation exist for the = loss of a=20 highly skilled pilot?     I knew David from the High = Performance training sessions he and Pete Zaccagnino ran at Lakeland and = I=20 extend to Kathy my deep condolences.
 
If one discounts the theory that he = tried to turn=20 back, perhaps there is an explanation to be found in the deep stall=20 characteristics of that particular aircraft.
Observers in the crash report said "the = airplane=20 pitched nose-up about 20 to 30 degrees".   "Black smoke = trailed from=20 the engine exhaust system, the engine sputtered and then stopped = producing=20 power".   "The climb and the turn after the loss of engine = power were=20 performed at a very high deck angle".  "The aircraft entered a = smooth=20 roll to the left, yawed left then plunged to the ground, near=20 vertically".
 
Diverging for a moment to a report by = Dave Allen=20 (LML 05.15.04) who was flight testing an ES for an owner.  "I = was=20 doing a stall series, and near the end was taking the deep stall to the = point of=20 wing drop.  When I brought the stick forward and applied full = opposite=20 rudder, the Lancair not only did not recover, but fell into a fully = developed 3=20 turn spin".
 
When one peruses the Summary of Lancair = Accidents=20 in the NTSB database, there is an over-representation of stall/spin = incidents=20 involving IV/IVP's.  Some of these accidents involved the loss of = highly=20 experienced pilots.
 
    Kissimee FL = 7/11/01
    Bozeman MT = 11/05/02
    Geelong (Aust)=20 12/20/02
    Mesa AZ =   2/17/04
    Novalato (Mexico) 4/7/04
    Grand Canyon AZ=20 5/18/04
    Vermontville = MI =20 5/31/04
 
A discussion on the stall = characteristics of the=20 Lancair wing led to a posting from Martin Hollmann (LML 01/26/05) = referring to=20 the airfoil used at the ROOT of the Lancair wing.  "The wing is = designed=20 with the RXM5-217 airfoil - a very gentle stalling airfoil"  This = benign=20 characteristic is further discussed in his book 'Modern Aircraft=20 Design'  (page 40) and further represented by a lift curve (p = 225)=20 showing a smooth stall with a gradual loss of lift.
The same posting from Martin Hollmann = (LML=20 01/26/05) states of the airfoil at the TIP of the Lancair wing "Yes, the = NACA64212 airfoil has a sharp stall.  However the wing is designed = with the=20 RXM5-217airfoil, a very gentle stalling airfoil, at the root and the = NACA64212=20 at the tip.  The wing is washed out so that the root stalls = first. =20 The wing tip is not designed to stall and as such the question of how it = stalls=20 is not relevant.  The NACA64212 airfoil was chosen for the tip = because it=20 has a high lift coefficient and it is very effective with an=20 aileron".   These comments are outlined also in 'Modern = Aircraft=20 Design' (p 40) and represented by a lift curve (p223) showing a sharp = stall and=20 complicated lift tendencies.
 
In a normal stall, the airflow detaches = from the=20 lift surface starting at the rear of the wing surface and progressively = moving=20 forward as the angle of attack increases.  Then by lessening the = angle of=20 attack the air progressively reattaches to the surface.  However = the graph=20 (p223) suggests this wing foil does not show this progression.  The = air=20 does not progressively reattach, but pauses, then suddenly reattaches = over a=20 very short variation in angle of attack, producing a sudden maximum=20 lift.
 
Returning to the Dave Allen posting = (LML 05.15.04)=20 he stated "when I brought the stick forward, the Lancair not only did = not=20 recover, but fell into a fully developed 3 turn spin"  He was a = test pilot=20 and experienced a totally unexpected response - an uncommanded=20 response.
 
This anomoly may have little = consequence in an=20 aircraft with perfectly symmetrical wings, but these are home-built = wings and=20 any lack of symmetry at the tip provides the basis for assymetric=20 lift.   Even if the assymetric lift is only = momentary, the=20 aircraft is at or past stall and at its most vulnerable.
 
Could this phenomenon explain the=20 over-representation of stall/spin accidents in the = statistics?
 
Could this explain the demise of some = highly=20 experienced pilots, facing, like Dave Allen, a totally unexpected=20 occurrence?
 
Could this explain the David Hickman=20 experience?  He was in a nose high attitude, losing or having lost = power,=20 the wings were stalling and he was experiencing an uncommanded roll to = the=20 left.
 
It appears to me as a non-aerodynamist, = a=20 non-engineer, but a keenly interested follower of the tragedies that are = befalling our community, that this aircraft cannot be flown slow, cannot = be=20 inadvertently flown close to its stall and must be built with great care = and an=20 even higher level of precision.
 
Ref:  Dave Allen = 23831
        Robert=20 Overmars 27776
        Martin Hollmann = 27896
        Modern=20 Aircraft Design 6th Edition 2002
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