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Date: Mon, 07 Jan 2013 16:08:19 -0500
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From: Terrence O'Neill <troneill@charter.net>
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Subject: Re: [LML] Re: Stalls & Spins
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References: <list-5999503@logan.com>


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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, <marv@lancair.net> <marv@lancair.net> =
wrote:

>=20
>=20
> Posted for "Peter Field" <pfield.avn@gmail.com>:
>=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


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<html><head></head><body style=3D"word-wrap: break-word; =
-webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">Amen =
to Pete's comments. &nbsp;<div>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..." &nbsp;etc.</div><div>That is, =
NASA Langley was still working on the problem.<br><div>All these =
relevant factors indicate the complexity of the problem of achieving =
reliable spin recovery once an airplane's configuration is =
set.&nbsp;</div><div>It's much easier to <b><i>prevent</i></b> the =
problem in configuration design, as with aerobatic designs. Too late for =
that for the experimental Lancairs.</div><div>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'.</div><div>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.</div><div><br><div>Since =
NASA's 1977 spin tunnel tests tested spins involved 2deg to 33deg =
&nbsp;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, =
&nbsp;stopping a spin is less than likely.</div><div>Since a plane can't =
spin unless it stalls first, stall resistance and prompt recovery is =
&nbsp;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.</div><div><br></div><div>Just offering a few =
comments to broaden an understanding of the problem.... hopefully they =
might be =
helpful.</div><div><br></div><div>Terrence</div><div><br></div><div><br><d=
iv><div>On Jan 7, 2013, at 12:25 PM, &lt;<a =
href=3D"mailto:marv@lancair.net">marv@lancair.net</a>&gt; &lt;<a =
href=3D"mailto:marv@lancair.net">marv@lancair.net</a>&gt; =
wrote:</div><br class=3D"Apple-interchange-newline"><blockquote =
type=3D"cite"><div id=3D"_htmlarea_default_style_" style=3D"font:10pt =
arial,helvetica,sans-serif"><br><br>Posted for "Peter Field" &lt;<a =
href=3D"mailto:pfield.avn@gmail.com">pfield.avn@gmail.com</a>&gt;:<br><br>=

Dear Lancair Drivers:<br> <br> <br> <br> I've been following the =
discussion on stalls and spins and I want to add<br> some additional =
factual
information purely for your personal consumption and<br> =
reflection.&nbsp;&nbsp;Attached are excerpts from 10 different 1980-90 =
NASA flight<br> test
final reports on a series of GA airplanes in which NASA evaluated =
the<br> use of cuffs on leading edges to improve the behavior of the =
test
airplane<br> approaching the stall.&nbsp;&nbsp;For various reasons the =
cuffs improved lateral<br> control entering the stall, but had the =
adverse
effect of destabilizing the<br> aircraft once a fully developed spin was =
achieved.&nbsp;&nbsp;Essentially, stall<br> behavior was improved at the
sacrifice of spin recovery.&nbsp;&nbsp;Cuffs on wing<br> leading edges =
are an add on design fix, the more elegant solution is<br> "washout," =
where the
wing is twisted so the outer portions of the wing<br> always operate at =
a lower angle of attack.<br> <br> <br> <br> To my knowledge, Lancair has =
never
subjected any of their aircraft to a<br> fully developed spin matrix =
complete with appropriate instrumentation and a<br> spin recovery
chute.&nbsp;&nbsp;There is no FAA requirement for them to do so - =
it's<br> an Experimental Category airplane.&nbsp;&nbsp;Early on they may =
have
lightly touched<br> on such testing; but I have never seen any =
documentation on a fully<br> completed spin matrix, which would involve =
at least 160
spins at various<br> cg's and lateral loadings.&nbsp;&nbsp;In my =
opinion, it would be highly risky to fool<br> around much beyond the =
stall in any
Lancair - there is no documentation that<br> indicates any of these =
airplanes can always be recovered from a one turn<br> incipient phase =
spin or any
fully developed spin.&nbsp;&nbsp;Being good at spin<br> recovery isn't =
so much a matter of how skillful a pilot you are, it's a<br> matter of =
how many
spins you've experienced in airplanes known to be<br> =
recoverable.&nbsp;&nbsp;Being familiar with the stall characteristics of =
your own<br> airplane
should be a matter of personal preference.&nbsp;&nbsp;<br> <br> <br> =
<br> Best regards, <br> <br> Pete Field (LNC2)<br> <br> USNTPS graduate =
&amp;
spin recovery instructor<br> <br> <br>--</div>For archives and unsub <a =
href=3D"http://mail.lancaironline.net:81/lists/lml/List.html">http://mail.=
lancaironline.net:81/lists/lml/List.html</a><br></blockquote></div><br></d=
iv></div></div></body></html>=

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