X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Mon, 07 Jan 2013 16:08:19 -0500 Message-ID: X-Original-Return-Path: Received: from mta31.charter.net ([216.33.127.82] verified) by logan.com (CommuniGate Pro SMTP 6.0.1) with ESMTP id 5999736 for lml@lancaironline.net; Mon, 07 Jan 2013 16:01:57 -0500 Received-SPF: pass receiver=logan.com; client-ip=216.33.127.82; envelope-from=troneill@charter.net Received: from imp10 ([10.20.200.15]) by mta31.charter.net (InterMail vM.8.01.05.02 201-2260-151-103-20110920) with ESMTP id <20130107210124.XWPV24708.mta31.charter.net@imp10> for ; Mon, 7 Jan 2013 16:01:24 -0500 Received: from [192.168.1.100] ([75.132.241.174]) by imp10 with smtp.charter.net id l91P1k0043mUFT70591PWB; Mon, 07 Jan 2013 16:01:24 -0500 X-Authority-Analysis: v=2.0 cv=foeE/yEf c=1 sm=1 a=VxlS/kh5Y2KhHY/Xui1ATg==:17 a=yUnIBFQkZM0A:10 a=hOpmn2quAAAA:8 a=-4Zy7PhmlH0A:10 a=fLuM78UsAAAA:8 a=pGLkceISAAAA:8 a=Ia-xEzejAAAA:8 a=BeDugri8y_W158vhXHQA:9 a=CjuIK1q_8ugA:10 a=CVU0O5Kb7MsA:10 a=3jk_M6PjnjYA:10 a=MSl-tDqOz04A:10 a=sNTWS0HoY_uJwcAl:21 a=6pcLSLFgCMPj1lZn:21 a=S0rmaVKOTBnFAxjjO3oA:9 a=_W_S_7VecoQA:10 a=nSL0L8_M8ajxXqPz:21 a=VxlS/kh5Y2KhHY/Xui1ATg==:117 From: Terrence O'Neill Mime-Version: 1.0 (Apple Message framework v1085) Content-Type: multipart/alternative; boundary=Apple-Mail-362--819322578 Subject: Re: [LML] Re: Stalls & Spins X-Original-Date: Mon, 7 Jan 2013 15:01:22 -0600 In-Reply-To: X-Original-To: "Lancair Mailing List" References: X-Original-Message-Id: <38902DAB-8E47-42C0-81E1-7FA029BDC947@charter.net> X-Mailer: Apple Mail (2.1085) --Apple-Mail-362--819322578 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=us-ascii Amen to Pete's comments. =20 A review of Part 23, several texts, NASA 1977 Tech Paper 1009, TN2016, = TN1779 and others, and a letter from James Bowman, ass't director at = Langley in 1972 when I was trying to type certify my Model W, in which = he noted "a need or additional research for light planes... the = influence of tail design, tail length, center of gravity, mass (wing = loading), and mass distribution, on spin recoveries of both high and low = wing airplanes... to be correlated with existing Tail Dampening Power = Factor criterion..." etc. That is, NASA Langley was still working on the problem. All these relevant factors indicate the complexity of the problem of = achieving reliable spin recovery once an airplane's configuration is = set.=20 It's much easier to prevent the problem in configuration design, as with = aerobatic designs. Too late for that for the experimental Lancairs. I think FAA certified Part 23 standard category aircraft only have to = demonstrate recovery from an incipient spin (first two turns) at an aft = CG, during which most aircraft will unstall themselves once.... and = after that, you're in the 'twilight zone'. I read somewhere that before WW II planes had to demonstrate recovery = from a 6-turn spin... and I suspect that after the war the big powerful = aviation companies (North American, Republic, Ryan etc.)persuaded the = CAA/FAA to reduce this 'business risk and cost' to the present = requirements which only placard against deliberate spins, but ignore the = accidental, developed spins. Since NASA's 1977 spin tunnel tests tested spins involved 2deg to 33deg = sideslipping, and AOAs from 15 to over 68 degrees, the yawing = demonstrates why rudder power is needed to stop it, and the high AOAs = indicate why the horizontal tail (and CG position) has to be able to = reduce the AOA to unstall the wing. If the planes' configuration = blankets the rudder or horizontal (blanketed or stalled) tail, stopping = a spin is less than likely. Since a plane can't spin unless it stalls first, stall resistance and = prompt recovery is a priority... like, keeping the CG forward helps. I = added slots to my horizontal stabilizer, and it seems to keep = de-pitching control strong at the stall. Just offering a few comments to broaden an understanding of the = problem.... hopefully they might be helpful. Terrence On Jan 7, 2013, at 12:25 PM, = wrote: >=20 >=20 > Posted for "Peter Field" : >=20 > Dear Lancair Drivers: >=20 >=20 >=20 > I've been following the discussion on stalls and spins and I want to = add > some additional factual information purely for your personal = consumption and > reflection. Attached are excerpts from 10 different 1980-90 NASA = flight > test final reports on a series of GA airplanes in which NASA evaluated = the > use of cuffs on leading edges to improve the behavior of the test = airplane > approaching the stall. For various reasons the cuffs improved lateral > control entering the stall, but had the adverse effect of = destabilizing the > aircraft once a fully developed spin was achieved. Essentially, stall > behavior was improved at the sacrifice of spin recovery. Cuffs on = wing > leading edges are an add on design fix, the more elegant solution is > "washout," where the wing is twisted so the outer portions of the wing > always operate at a lower angle of attack. >=20 >=20 >=20 > To my knowledge, Lancair has never subjected any of their aircraft to = a > fully developed spin matrix complete with appropriate instrumentation = and a > spin recovery chute. There is no FAA requirement for them to do so - = it's > an Experimental Category airplane. Early on they may have lightly = touched > on such testing; but I have never seen any documentation on a fully > completed spin matrix, which would involve at least 160 spins at = various > cg's and lateral loadings. In my opinion, it would be highly risky to = fool > around much beyond the stall in any Lancair - there is no = documentation that > indicates any of these airplanes can always be recovered from a one = turn > incipient phase spin or any fully developed spin. Being good at spin > recovery isn't so much a matter of how skillful a pilot you are, it's = a > matter of how many spins you've experienced in airplanes known to be > recoverable. Being familiar with the stall characteristics of your = own > airplane should be a matter of personal preference. =20 >=20 >=20 >=20 > Best regards,=20 >=20 > Pete Field (LNC2) >=20 > USNTPS graduate & spin recovery instructor >=20 >=20 > -- > For archives and unsub = http://mail.lancaironline.net:81/lists/lml/List.html --Apple-Mail-362--819322578 Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=us-ascii Amen = to Pete's comments.  
A review of Part 23, several texts, NASA = 1977 Tech Paper 1009, TN2016, TN1779 and others, and a letter from James = Bowman, ass't director at Langley in 1972 when I was trying to type = certify my Model W, in which he noted "a need or additional research for = light planes... the influence of tail design, tail length, center of = gravity, mass (wing loading), and mass distribution, on spin recoveries = of both high and low wing airplanes... to be correlated with existing = Tail Dampening Power Factor criterion..."  etc.
That is, = NASA Langley was still working on the problem.
All these = relevant factors indicate the complexity of the problem of achieving = reliable spin recovery once an airplane's configuration is = set. 
It's much easier to prevent the = problem in configuration design, as with aerobatic designs. Too late for = that for the experimental Lancairs.
I think FAA certified Part = 23 standard category aircraft only have to demonstrate recovery from an = incipient spin (first two turns) at an aft CG, during which most = aircraft will unstall themselves once.... and after that, you're in the = 'twilight zone'.
I read somewhere that before WW II planes had = to demonstrate recovery from a 6-turn spin... and I suspect that after = the war the big powerful aviation companies (North American, Republic, = Ryan etc.)persuaded the CAA/FAA to reduce this 'business risk and cost' = to the present requirements which only placard against deliberate spins, = but ignore the accidental, developed spins.

Since = NASA's 1977 spin tunnel tests tested spins involved 2deg to 33deg =  sideslipping, and AOAs from 15 to over 68 degrees, the yawing = demonstrates why rudder power is needed to stop it, and the high AOAs = indicate why the horizontal tail (and CG position) has to be able to = reduce the AOA to unstall the wing. If the planes' configuration = blankets the rudder or horizontal (blanketed or stalled) tail, =  stopping a spin is less than likely.
Since a plane can't = spin unless it stalls first, stall resistance and prompt recovery is =  a priority... like, keeping the CG forward helps. I added slots to = my horizontal stabilizer, and it seems to keep de-pitching control = strong at the stall.

Just offering a few = comments to broaden an understanding of the problem.... hopefully they = might be = helpful.

Terrence


On Jan 7, 2013, at 12:25 PM, <marv@lancair.net> <marv@lancair.net> = wrote:



Posted for "Peter Field" <pfield.avn@gmail.com>:

= Dear Lancair Drivers:



I've been following the = discussion on stalls and spins and I want to add
some additional = factual information purely for your personal consumption and
= reflection.  Attached are excerpts from 10 different 1980-90 = NASA flight
test final reports on a series of GA airplanes in which NASA evaluated = the
use of cuffs on leading edges to improve the behavior of the = test airplane
approaching the stall.  For various reasons the = cuffs improved lateral
control entering the stall, but had the = adverse effect of destabilizing the
aircraft once a fully developed spin was = achieved.  Essentially, stall
behavior was improved at the sacrifice of spin recovery.  Cuffs on wing
leading edges = are an add on design fix, the more elegant solution is
"washout," = where the wing is twisted so the outer portions of the wing
always operate at = a lower angle of attack.



To my knowledge, Lancair has = never subjected any of their aircraft to a
fully developed spin matrix = complete with appropriate instrumentation and a
spin recovery chute.  There is no FAA requirement for them to do so - = it's
an Experimental Category airplane.  Early on they may = have lightly touched
on such testing; but I have never seen any = documentation on a fully
completed spin matrix, which would involve = at least 160 spins at various
cg's and lateral loadings.  In my = opinion, it would be highly risky to fool
around much beyond the = stall in any Lancair - there is no documentation that
indicates any of these = airplanes can always be recovered from a one turn
incipient phase = spin or any fully developed spin.  Being good at spin
recovery isn't = so much a matter of how skillful a pilot you are, it's a
matter of = how many spins you've experienced in airplanes known to be
= recoverable.  Being familiar with the stall characteristics of = your own
airplane should be a matter of personal preference.  


=
Best regards,

Pete Field (LNC2)

USNTPS graduate = & spin recovery instructor


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