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Date: Wed, 23 Apr 2014 12:01:04 -0400
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From: Chris Zavatson <chris_zavatson@yahoo.com>
Reply-To: Chris Zavatson <chris_zavatson@yahoo.com>
Subject: Large/small tail stability comparison
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=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=0AChris,=0A=0AExcell=
ent Analysis.=0A=0ASince the 320 has got to be the most individually modifi=
ed kit plane, could  you be more specific about details of=A0the elevator s=
ystem in the 320 used  for comparison:=0A=0A1. Was the elevator bell crank =
arm 4" (original design) or 3" (popular mod)  as this affects stick forces =
and movement distances?=0A=0A2.=A0Since the spring trim system was used, wa=
s=A0the trim  the=A0original crucifix and spring=A0system or was=A0the=A0Re=
ichel  trim wheel with stronger springs used?.=A0 This has some effect on t=
rim  rigidity and stick forces for elevator movement away from the trimmed =
 position.=A0 You did mention that trim tabs could alter certain results (e=
ven  the tab sizes used by builders may be quite different).=0A=0A3. Was th=
e bob weight installed?=A0 Recently some builders  claimed=A0that they did=
=A0not install the bob weight that was designed to  increase stick forces u=
nder increased aircraft=A0loading.=0A=0AConsidering these variables, what i=
mplications might they have with respect  to observations/conclusions made =
in=A0your report?=0A=0AThanks,=0A=0AScott Krueger=0A=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=0A=0AScott,=0AGood observations.=
=0A1. Shortened. I will add that detail along with stick travel per elevato=
r travel.=0A2.=A0 Reichel trim wheel.=A0 I am trying to line=A0up=A0an abbr=
eviated=A0test on a small tail 360 that uses an electric trim tab to evalua=
te the influence of the spring.=0A3. Yes, bob weight installed, will add th=
at as well.=0A=0AStick fixed stability is not affected by any of the above.=
=A0 It looks at rigid elevator position regardless of how it is achieved.=
=A0 Stick free response may be influenced by the spring, in particular, whe=
n getting farther off the trim point.=A0 For example the phugoid that=A0bec=
ame somewhat violent.=A0 Initial thoughts are that=A0the spring=A0could be =
negatively influencing the low speed end where hinge moments start dropping=
 off rapidly.=A0=A0I hope to have some data on that soon.=0AChris=0A
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<html><body><div style=3D"color:#000; background-color:#fff; font-family:ti=
mes new roman, new york, times, serif;font-size:14pt"><div>=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D</div><div>Chris,</div><div>&nbsp;</=
div><div>Excellent Analysis.</div><div>&nbsp;</div><div>Since the 320 has g=
ot to be the most individually modified kit plane, could  you be more speci=
fic about details of&nbsp;the elevator system in the 320 used  for comparis=
on:</div><div>&nbsp;</div><div>1. Was the elevator bell crank arm 4" (origi=
nal design) or 3" (popular mod)  as this affects stick forces and movement =
distances?</div><div>&nbsp;</div><div>2.&nbsp;Since the spring trim system =
was used, was&nbsp;the trim  the&nbsp;original crucifix and spring&nbsp;sys=
tem or was&nbsp;the&nbsp;Reichel  trim wheel with stronger springs used?.&n=
bsp; This has some effect on trim  rigidity and stick forces for elevator m=
ovement away from the trimmed  position.&nbsp; You did mention that trim ta=
bs could alter certain results
 (even  the tab sizes used by builders may be quite different).</div><div>&=
nbsp;</div><div>3. Was the bob weight installed?&nbsp; Recently some builde=
rs  claimed&nbsp;that they did&nbsp;not install the bob weight that was des=
igned to  increase stick forces under increased aircraft&nbsp;loading.</div=
><div>&nbsp;</div><div>Considering these variables, what implications might=
 they have with respect  to observations/conclusions made in&nbsp;your repo=
rt?</div><div>&nbsp;</div><div>Thanks,</div><div>&nbsp;</div><div>Scott Kru=
eger</div><div>=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D</div><div><br></div><div>Scott,</div><div>Good observations.</div><div>=
1. Shortened. I will add that detail along with stick travel per elevator t=
ravel.</div><div>2.&nbsp; Reichel trim wheel.&nbsp; I am trying to line&nbs=
p;up&nbsp;an abbreviated&nbsp;test on a small tail 360 that uses an electri=
c trim tab to evaluate the influence of the spring.</div><div>3. Yes, bob w=
eight installed, will add that as
 well.</div><div><br></div><div>Stick fixed stability is not affected by an=
y of the above.&nbsp; It looks at rigid elevator position regardless of how=
 it is achieved.&nbsp; Stick free response may be influenced by the spring,=
 in particular, when getting farther off the trim point.&nbsp; For example =
the phugoid that&nbsp;became somewhat violent.&nbsp; Initial thoughts are t=
hat&nbsp;the spring&nbsp;could be negatively influencing the low speed end =
where hinge moments start dropping off rapidly.&nbsp;&nbsp;I hope to have s=
ome data on that soon.</div><div>Chris</div><div><br></div></div></body></h=
tml>
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