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Date: Sun, 29 Mar 2009 16:41:09 -0400
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From: "Dennis Johnson" <pinetownd@volcano.net>
Subject: Legacy Stiff Ailerons
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Last summer, after returning from flying my Legacy from California to =
Alaska and back, I posted a message here about stiff aileron controls.  =
Near Anchorage on my way home, at flight level 190 and minus 17=B0F, the =
ailerons became very stiff.  Stiff enough that the TruTrak autopilot's =
clutch was "ratcheting" when making a turn.  The airplane was fully =
controllable at all times, but the ailerons were stiffer to move than =
normal.  There was no feeling of binding or scraping. =20

I received helpful replies to my message, but I never felt comfortable =
that I understood the cause.  The airplane had been in Alaska a week, =
flying in the rain and sitting out in the rain every day of the trip.  =
Occasionally, both in flight and on the ground, the rain was ferocious.  =
What caused the stiff ailerons?  Was it the cold weather at FL 190?  Was =
it some aerodynamic effect of high altitude flight?  Was it trapped =
water that froze at high altitude?  I didn't know. =20

This winter, I went up with a friend to act as my flight test engineer.  =
I attached a "fish scale" to the stick and with practice, he developed a =
somewhat repeatable technique to measure how much stick force it took to =
move the ailerons.  The rate of aileron deflection was about the same as =
the roll rate while flying on instruments.

It was a cold day for Northern California, although not even close to =
Alaska cold.  The airplane had been in a dry hangar and was bone dry.  =
There was not a cloud in the sky.  As a result, I could reasonably =
conclude that there could be no "trapped water that froze" issue.  Any =
stiffness of the ailerons would have to be related to something other =
than ice.  The primary candidates were the cold temperature causing =
contraction somewhere in the aileron controls and binding, or dynamic =
pressure related to high altitude flight.

So off we went into the wild blue, cold, yonder up to flight level 210 =
on an instrument flight plan, checking the aileron breakout force all =
the way up.  There was no discernible change in aileron breakout force =
with altitude/temperature.  (If anything, the force might decrease with =
altitude, but the data are inconclusive.)  The ailerons never became =
stiff. =20

My tentative conclusion is that the stiff ailerons I experienced on the =
one flight in Alaska was not directly caused by either the high altitude =
or the cold weather and that stiff ailerons at altitude are not normal.

The reason my conclusion is tentative is that I experienced 1=B0F on my =
test flight but it was minus 17=B0F when I had stiff ailerons in Alaska. =
 It's possible that normal clearances are maintained until colder than =
1=B0F and that my test is invalid because it didn't duplicate the cold =
of Alaska.  But it does show that aileron forces don't increase linearly =
with altitude/temperature and that it's not normal to have stiff =
ailerons at high altitude/low temperature in California conditions.

Best,
Dennis
Legacy, 220 hours


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<DIV>Last summer, after returning from flying my Legacy from California =
to=20
Alaska and back, I posted a message here about stiff aileron=20
controls.&nbsp;&nbsp;Near Anchorage&nbsp;on my way home, at flight level =
190 and=20
minus 17=B0F, the ailerons became very stiff.&nbsp; Stiff enough that =
the TruTrak=20
autopilot's clutch&nbsp;was "ratcheting" when making a turn.&nbsp; The =
airplane=20
was fully controllable at all times, but the ailerons were stiffer to =
move than=20
normal.&nbsp; There was no feeling of binding or scraping.&nbsp; </DIV>
<DIV>&nbsp;</DIV>
<DIV>I received helpful replies to my message, but I never felt =
comfortable that=20
I understood the cause.&nbsp; The airplane had been in Alaska a week, =
flying in=20
the rain and sitting out in the rain every day of the=20
trip.&nbsp;&nbsp;Occasionally, both in flight and on the ground, the =
rain was=20
ferocious.&nbsp;&nbsp;What caused the stiff ailerons?&nbsp; Was it the =
cold=20
weather at FL 190?&nbsp; Was it some aerodynamic effect of high altitude =

flight?&nbsp; Was it&nbsp;trapped water that froze at high =
altitude?&nbsp; I=20
didn't know.&nbsp; </DIV>
<DIV>&nbsp;</DIV>
<DIV>This winter, I went up with a friend&nbsp;to act as my flight test=20
engineer.&nbsp; I attached a "fish scale"&nbsp;to the stick and with =
practice,=20
he developed a somewhat repeatable technique to measure how much stick =
force it=20
took to move the ailerons.&nbsp; The rate of aileron deflection was =
about the=20
same as the roll rate while flying on instruments.</DIV>
<DIV>&nbsp;</DIV>
<DIV>It was a cold day for Northern California,&nbsp;although not even =
close to=20
Alaska cold.&nbsp; The airplane had been in a dry hangar and was bone =
dry.&nbsp;=20
There was not a cloud in the sky.&nbsp; As a result, I could reasonably =
conclude=20
that there could be no "trapped water that froze" issue.&nbsp; Any =
stiffness of=20
the ailerons would have to be related to something other than ice.&nbsp; =
The=20
primary candidates were the cold temperature causing contraction =
somewhere=20
in&nbsp;the aileron controls and binding, or dynamic pressure related to =
high=20
altitude flight.</DIV>
<DIV>&nbsp;</DIV>
<DIV>So off we went into the wild blue, cold, yonder up to flight level =
210 on=20
an instrument flight plan, checking the aileron breakout force all the =
way=20
up.&nbsp;&nbsp;There was no&nbsp;discernible&nbsp;change in aileron =
breakout=20
force with altitude/temperature.&nbsp; (If anything, the force might =
decrease=20
with altitude, but the data are inconclusive.)&nbsp; The ailerons never =
became=20
stiff.&nbsp; </DIV>
<DIV>&nbsp;</DIV>
<DIV>My tentative&nbsp;conclusion is that the stiff ailerons I =
experienced on=20
the one flight in Alaska was not directly caused by either the high =
altitude or=20
the cold weather and that stiff ailerons at altitude are =
not&nbsp;normal.</DIV>
<DIV>&nbsp;</DIV>
<DIV>The reason my conclusion is tentative is that I experienced 1=B0F =
on my test=20
flight but it was minus 17=B0F when I had stiff ailerons in =
Alaska.&nbsp; It's=20
possible that normal clearances are maintained until colder than 1=B0F =
and that my=20
test is invalid because it didn't duplicate the cold of Alaska.&nbsp; =
But it=20
does show that aileron forces don't increase linearly with =
altitude/temperature=20
and that it's not normal to have stiff ailerons at high altitude/low =
temperature=20
in California conditions.</DIV>
<DIV>&nbsp;</DIV>
<DIV>Best,</DIV>
<DIV>Dennis</DIV>
<DIV>Legacy, 220 hours</DIV>
<DIV>&nbsp;</DIV>
<DIV>&nbsp;</DIV></BODY></HTML>

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