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Date: Thu, 04 Mar 2010 14:31:44 -0500
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From: Sky2high@aol.com
Subject: Springs and Tabs - Another Variation
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I had an interesting conversation with Jim Auman - he has restored and  is 
flying a modified 235 airframe with a "stronger" engine (I don't remember 
how  strong, but he moves along right smartly).
 
His airplane is equipped with a MAC servo operated good-sized elevator trim 
 tab that did not yield enough nose-up trim authority at lower speeds  when 
the flaps were deployed.  Using a Paul Lipps inspired mod he has  overcome 
that problem.  
 
First, remember that the 235 flap actuation mechanism is a torque tube with 
 a console/tunnel located good-sized arm available that rotates the  tube.  
We didn't discuss the fwd/aft travel distance of the arm but it has  got to 
be several inches.  
 
So, one end of a screen door spring is attached to the arm and the other  
end to a turnbuckle which is attached to a clamp placed on the elevator  push 
rod.  The net result is that as the flaps are lowered, spring forces  
increase to add more nose up "trim" on the elevator proper.  Uh, can we  call 
this a hybrid system and get a tax credit for it?
 
Jim reports that, after some experimentation in setting spring tension,  
takeoff and climb does not require trim tab changes as the flaps are moved  
up. Very little trim tab adjustment is used in cruise and slowing down  for 
approach and landing with flap deployment require no adjustment to the trim  
tab since the spring "automatically" adjusts the overall elevator trim.  
 
Additional benefits of this system are realized when the flaps are  
retracted during a go-around and the aircraft does not go dramatically out of  trim 
(similar to the Skymaster I mentioned before).  If one is flying  a 300 
series with the spring driven elevator trim (whether or not the  Reichel wheel 
is used), the go-around from a full flap deployment requires  careful 
attention to the enormous change in pitch forces as the flaps are  raised.  In my 
airplane, after applying a moderate power increase, the  flaps are retracted 
and the trim adjusted in steps - unwanted additional  workload during this 
critical maneuver.
 
This discussion with Jim further illuminated that the 200 and 300 series  
Lancairs have a most diverse set of modifications not seen within model  
types in other Lancairs, and some of these modifications greatly affect the  
flying characteristics and piloting techniques of these  planes.  I am sure 
this must provide a challenge for HPAT and LOBO  training syllabi for these 
models. 
 
Scott Krueger
 
 
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<DIV>I had an interesting conversation with Jim Auman - he has&nbsp;restor=
ed and=20
is flying a modified 235 airframe with a "stronger" engine (I don't rememb=
er how=20
strong, but he moves along&nbsp;right smartly).</DIV>
<DIV>&nbsp;</DIV>
<DIV>His airplane is equipped with a MAC servo operated good-sized elevato=
r trim=20
tab that did not&nbsp;yield enough nose-up&nbsp;trim authority at lower sp=
eeds=20
when the flaps were deployed.&nbsp; Using a&nbsp;Paul Lipps inspired mod=
 he has=20
overcome that problem.&nbsp; </DIV>
<DIV>&nbsp;</DIV>
<DIV>First, remember that the 235 flap actuation mechanism is a torque tub=
e with=20
a console/tunnel located&nbsp;good-sized arm available that rotates the=20
tube.&nbsp; We didn't discuss the fwd/aft travel distance of the arm but=
 it has=20
got to be several inches.&nbsp; </DIV>
<DIV>&nbsp;</DIV>
<DIV>So, one end of a screen door spring is attached to the arm and the ot=
her=20
end to a turnbuckle which is attached to a clamp placed&nbsp;on the elevat=
or=20
push rod.&nbsp; The net result is that as the flaps are lowered, spring fo=
rces=20
increase to add more nose up "trim" on the elevator proper.&nbsp; Uh, can=
 we=20
call this a hybrid system and get a&nbsp;tax credit for it?</DIV>
<DIV>&nbsp;</DIV>
<DIV>Jim reports that, after some experimentation in setting spring tensio=
n,=20
takeoff and climb does not require trim tab&nbsp;changes as the flaps are=
 moved=20
up.&nbsp;Very little trim tab&nbsp;adjustment is used in cruise and slowin=
g down=20
for approach and landing with flap deployment require no adjustment to the=
 trim=20
tab since the spring "automatically" adjusts the overall elevator trim.&nb=
sp;=20
</DIV>
<DIV>&nbsp;</DIV>
<DIV>Additional benefits of this system&nbsp;are realized when the flaps=
 are=20
retracted during a go-around and the aircraft does not go dramatically out=
 of=20
trim (similar to the Skymaster&nbsp;I mentioned before).&nbsp; If one is=
 flying=20
a 300 series&nbsp;with the spring driven elevator trim (whether or not the=
=20
Reichel wheel is used), the go-around from a full flap deployment requires=
=20
careful attention to the enormous change in pitch forces as the flaps are=
=20
raised.&nbsp; In my airplane, after applying&nbsp;a moderate power increas=
e, the=20
flaps are retracted and the trim adjusted in steps -&nbsp;unwanted additio=
nal=20
workload during&nbsp;this critical maneuver.</DIV>
<DIV>&nbsp;</DIV>
<DIV>This discussion with Jim further illuminated that the 200 and 300 ser=
ies=20
Lancairs&nbsp;have a most diverse set of modifications not seen within mod=
el=20
types&nbsp;in other Lancairs, and some of these modifications greatly affe=
ct the=20
flying characteristics and&nbsp;piloting&nbsp;techniques&nbsp;of these=20
planes.&nbsp; I am sure this must provide a challenge for HPAT and LOBO=20
training&nbsp;syllabi for these models.&nbsp;</DIV>
<DIV>&nbsp;</DIV>
<DIV>Scott Krueger</DIV>
<DIV>&nbsp;</DIV>
<DIV>&nbsp;</DIV></FONT></BODY></HTML>

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