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Effects of Flaps and Ailerons on Pitch Trim
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Troy Maynor



Joined: 10 Jan 2006
Posts: 162

PostPosted: Sat Apr 10, 2010 6:21 pm    Post subject: Effects of Flaps and Ailerons on Pitch Trim Reply with quote

Hi All,

Ok, you know what they say about dumb questions. Are my flaps reflexed too far (up) if I have to dial in 2 marks of nose down trim for straight and level flight or am I thinking backwards? I rechecked the weight and balance as well as the stabilator and anti servo limits and they are all good. I was thinking maybe just the indicator needed adjusting but the tabs are aligned with the stabs. and the stabs. are aligned with the fuselage molding, and the indicator is on zero. Not sure whats going on for sure. It flies ok but if the tabs aren't aligned it can't be clean and efficient. Any thoughts? I figure it's got to be ailerons or flaps.
Had to get back home today before I had time to investigate further. Just need some reenforcing thoughts from you experts.
Troy Maynor
Europa Monowheel Classic
Flying

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PostPosted: Sat Apr 10, 2010 7:11 pm    Post subject: Effects of Flaps and Ailerons on Pitch Trim Reply with quote

Troy,

In every in-flight photo I have seen of a Europa in level flight, the trim tabs have been noticably deflected upwards (nose down trim).

A few years ago I posted the question "Why is it so?" on this list but apart from somebody remarking that I was observant, there were no reasons given so I am still left wondering???

I think you will find yours is perfectly normal and like you, I hope somebody can explain.

Cheers
Kingsley in Oz

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PostPosted: Sun Apr 11, 2010 12:08 am    Post subject: Effects of Flaps and Ailerons on Pitch Trim Reply with quote

Troy
you will have less drag at cruise with flaps reflexed up. I would leave them alone.
There are several issues affecting trim, CG for starters, also the wide range of speed. Flaps down there is a lot of up trim needed because the flaps are very powerful.
Graham, (not an expert)
From: Troy Maynor <wingnut54(at)charter.net>
To: europa-list(at)matronics.com
Sent: Sunday, 11 April, 2010 3:18:20
Subject: Effects of Flaps and Ailerons on Pitch Trim

Hi All,

Ok, you know what they say about dumb questions. Are my flaps reflexed too far (up) if I have to dial in 2 marks of nose down trim for straight and level flight or am I thinking backwards? I rechecked the weight and balance as well as the stabilator and anti servo limits and they are all good. I was thinking maybe just the indicator needed adjusting but the tabs are aligned with the stabs. and the stabs. are aligned with the fuselage molding, and the indicator is on zero. Not sure whats going on for sure. It flies ok but if the tabs aren't aligned it can't be clean and efficient. Any thoughts? I figure it's got to be ailerons or flaps.
Had to get back home today before I had time to investigate further. Just need some reenforcing thoughts from you experts.
Troy Maynor
Europa Monowheel Classic
Flying

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PostPosted: Sun Apr 11, 2010 12:22 am    Post subject: Effects of Flaps and Ailerons on Pitch Trim Reply with quote

On 04/11/2010 05:10 AM, Kingsley Hurst wrote:

Quote:
In every in-flight photo I have seen of a Europa in level flight, the
trim tabs have been noticably deflected upwards (nose down trim).

The position of the trim tab is is not an indication of nose up or nose
down trim. The idea of the trim is to offset the trim tab, so that
*consequently* the tailplane will find a new balance, negating the
offset of the trim tab. So, ideally, the trim tab will always align with
the tailplane, regardless of the trim setting.

The whole design idea must have been that the tailplane will find its
balance when it is aligned with the trim tab. Apparently however, this
balance will always be found with the trim tabs deflected upwards.

Again, this is no indication of trim. The trim determines (after
balancing out the aerodynamic forces) the position of the tailplane, and
the trim tabs will always remain in the same relative position to the
tail plane.

Playing on the ground with the tailplane and the trim tab will make this
obvious.

Frans


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PostPosted: Sun Apr 11, 2010 1:57 am    Post subject: Effects of Flaps and Ailerons on Pitch Trim Reply with quote

Quote:
Again, this is no indication of trim. The trim determines (after
balancing out the aerodynamic forces) the position of the tailplane, and
the trim tabs will always remain in the same relative position to the
tail plane.

Hello Frans,

I'm not sure that I fully understand what you are saying.

Are you saying that for a given aircraft, if you fly at AUW with CG at its
forward limit, the trim tab will be in the same position relative to the
tailplane as when at AUW with the CG at its rearmost limit?

Cheers
Kingsley


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PostPosted: Sun Apr 11, 2010 4:44 am    Post subject: Effects of Flaps and Ailerons on Pitch Trim Reply with quote

On 04/11/2010 11:54 AM, Kingsley Hurst wrote:

Quote:
> Again, this is no indication of trim. The trim determines (after
> balancing out the aerodynamic forces) the position of the tailplane, and
> the trim tabs will always remain in the same relative position to the
> tail plane.

Are you saying that for a given aircraft, if you fly at AUW with CG at
its forward limit, the trim tab will be in the same position relative to
the tailplane as when at AUW with the CG at its rearmost limit?

Yep. You say it correctly. The trim tab will remain in the same position
relative to the tailplane at all times.
If you change the trim, you introduce imbalance, and the tailplane moves
to another position to restore the balance again, i.e. get into the same
position relative to the trim tab. It is this "balance seeking movement"
which eases the forces on the stick.

You can easily see this on the ground, as for every trim tab position
you can find a tailplane position where the trim tab lines up with the
tailplane.

In flight, the trim tab position is always in the same relative position
to the tailplane.

I always assumed that this position would be straight in line with the
tailplane, but apperently this balance is found when the trim tab is
somewhat deflected upwards...
I thought that the tail plane was supposed to be aerodynamically
neutral, but this is not so. With the trim tab deflected up, there is
more force acting upon the underside of the tailplane than on the upperside.

Anyone with an explanation for this?

Frans


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PostPosted: Sun Apr 11, 2010 5:48 am    Post subject: Effects of Flaps and Ailerons on Pitch Trim Reply with quote

Hi Troy,
Belated congratulations on your first flight.
I'm no expert and only have been in 2 Europas, mine and Chris Staines mono.
Both of us need nose down trim in cruise, during my first flights, it seemed to me that perhaps slightly less incidence on the wing
could have been used for more efficient flying, now I just accept the fact that nose down trim is required on my aircraft.

Regards,

Dave, C-FBZI
 
On 10-Apr-10, at 10:18 PM, Troy Maynor wrote:
[quote] Hi All,
 
Ok, you know what they say about dumb questions. Are my flaps reflexed too far (up) if I have to dial in 2 marks of nose down trim for straight and level flight or am I thinking backwards?  I rechecked the weight and balance as well as the stabilator and anti servo limits and they are all good. I was thinking maybe just the indicator needed adjusting but the tabs are aligned with the stabs. and the stabs. are aligned with the fuselage molding, and the indicator is on zero. Not sure whats going on for sure. It flies ok but if the tabs aren't aligned it can't be clean and efficient. Any thoughts?  I figure it's got to be ailerons or flaps.
Had to get back home today before I had time to investigate further. Just need some reenforcing thoughts from you experts.
Troy Maynor
Europa Monowheel Classic
Flying  
 
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PostPosted: Sun Apr 11, 2010 6:50 am    Post subject: Effects of Flaps and Ailerons on Pitch Trim Reply with quote

From: Frans Veldman <frans(at)privatepilots.nl>
To: europa-list(at)matronics.com
Can't promise an explanation but what the tailplane does is balance the pitching moment of the wing but also the difference between the CG and the centre of lift. The CoL moves significantly with AoA, especially with flap deflection. This is one reason we have an all flying tail, fixed tail and elevator can't produce enough range for all flight conditions. Big jets are the same (well almost)
Graham
not an expert!
I thought that the tail plane was supposed to be aerodynamically
neutral, but this is not so. With the trim tab deflected up, there is
more force acting upon the underside of the tailplane than on the upperside.
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PostPosted: Sun Apr 11, 2010 7:12 am    Post subject: Effects of Flaps and Ailerons on Pitch Trim Reply with quote

On 04/11/2010 04:00 PM, david miller wrote:

Quote:
Both of us need nose down trim in cruise, during my first flights, it
seemed to me that perhaps slightly less incidence on the wing
could have been used for more efficient flying, now I just accept the
fact that nose down trim is required on my aircraft.

If you change the incidence of the wing, you actually change the
incidence of the fuselage. The wing remains in the same position during
flight.

Frans


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PostPosted: Sun Apr 11, 2010 7:43 am    Post subject: Effects of Flaps and Ailerons on Pitch Trim Reply with quote

Frans,

and the incidence of the fuselage will affect the incidence of the
tailplane.
just going back to my model aircraft days of 50 years ago so no
science on my part,
with the advent of digital levels it would have been possible to
specify 2.4 or 2.3 degrees, my feeling was that this would have
lessened the amount of down trim required.
Troy, Chris and I all have classic wings, perhaps this affects the trim.

Dave
On 11-Apr-10, at 11:12 AM, Frans Veldman wrote:

Quote:

<frans(at)privatepilots.nl>

On 04/11/2010 04:00 PM, david miller wrote:

> Both of us need nose down trim in cruise, during my first flights, it
> seemed to me that perhaps slightly less incidence on the wing
> could have been used for more efficient flying, now I just accept the
> fact that nose down trim is required on my aircraft.

If you change the incidence of the wing, you actually change the
incidence of the fuselage. The wing remains in the same position
during
flight.

Frans



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PostPosted: Sun Apr 11, 2010 8:00 am    Post subject: Effects of Flaps and Ailerons on Pitch Trim Reply with quote

On 04/11/2010 05:55 PM, david miller wrote:
Quote:


Frans,

and the incidence of the fuselage will affect the incidence of the
tailplane.

You are right.

Frans


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Joined: 24 Nov 2009
Posts: 792

PostPosted: Sun Apr 11, 2010 9:14 am    Post subject: Effects of Flaps and Ailerons on Pitch Trim Reply with quote

"If you change the incidence of the wing, you actually change the incidence of the fuselage. The wing remains in the same position during flight."This is true, just to give a visual idea, I have a friend who raced formula V racers. Since for a significant part of flight he was pulling a lot of gs going around pylons, he noted that since his wings were coaxed into a much higher angle of attack to pull those Gs, the fuse was dragging through air at less than streamlined head on angle. He then increased angle of attack of wings to some crazy amount that allowed fuse to be streamlined during racing. Said it worked as planned and he went faster. During 1 G flight he said visability over nose was outstanding! Ron Parigoris [quote][b]

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PostPosted: Sun Apr 11, 2010 11:46 am    Post subject: Effects of Flaps and Ailerons on Pitch Trim Reply with quote

From: Frans Veldman <frans(at)privatepilots.nl>
To: europa-list(at)matronics.com
Sent: Sunday, 11 April, 2010 16:59:05
Subject: Re: Effects of Flaps and Ailerons on Pitch Trim

--> Europa-List message posted by: Frans Veldman <frans(at)privatepilots.nl (frans(at)privatepilots.nl)>
But the tail won't move, or the wing, just the fuselage.
Does an all flying tail have an incidence at all?
Graham


On 04/11/2010 05:55 PM, david miller wrote:
Quote:
--> Europa-List message posted by: david miller <loboloda(at)execulink.com (loboloda(at)execulink.com)>

Frans,

and the incidence of the fuselage will affect the incidence of the
tailplane.

You are right.

Frans

_

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PostPosted: Mon Apr 12, 2010 7:06 am    Post subject: Effects of Flaps and Ailerons on Pitch Trim Reply with quote

Graham,
I think that for most efficient flight the incidence of the wing and tail should be such that at cruise there is no up or down trim on the elevator
or all flying tail.
seems to me that on my aircraft I am holding some down tail to maintain level flight in cruise, if that is the case slightly less incidence on the wing would have helped.
Again just going back to model days, to get a model to glide right was a matter of altering the incidence on the wing or tail or adding weight to the nose.
But that's about the extent of my aeronautical knowledge, I'm sure brighter minds can correct this.

Dave    
On 11-Apr-10, at 3:43 PM, GRAHAM SINGLETON wrote:
[quote]
From: Frans Veldman <frans(at)privatepilots.nl (frans(at)privatepilots.nl)>
To: europa-list(at)matronics.com (europa-list(at)matronics.com)
Sent: Sunday, 11 April, 2010 16:59:05
Subject: Re: Effects of Flaps and Ailerons on Pitch Trim

--> Europa-List message posted by: Frans Veldman <frans(at)privatepilots.nl (frans(at)privatepilots.nl)>
But the tail won't move, or the wing, just the fuselage.
Does an all flying tail have an incidence at all?
Graham


On 04/11/2010 05:55 PM, david miller wrote:
Quote:
--> Europa-List message posted by: david miller <loboloda(at)execulink.com (loboloda(at)execulink.com)>

Frans,

and the incidence of the fuselage will affect the incidence of the
tailplane.

You are right.

Frans

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PostPosted: Mon Apr 12, 2010 8:25 am    Post subject: Effects of Flaps and Ailerons on Pitch Trim Reply with quote

On Apr 12, 2010, at 6:24 AM, david miller wrote:

Quote:
I think that for most efficient flight the incidence of the wing and
tail should be such that at cruise there is no up or down trim on
the elevator or all flying tail.

Fascinating discussion...as a non-aerodynamicist, I can't resist the
temptation to add a comment...

I've always understood that the elevator or an all-flying tail
(horizontal tail plane) has a "job"...namely, to exert a force, either
up or down, in order to balance the lift of the wing and stabilize the
flight path of a normally configured aircraft (i.e., not a canard
type). To do this "job" requires "work"; the tail plane is never
neutral. And w/ our Europae...with it's trim tabs acting in
opposition to the all-flying tail plane thru a direct mechanical
connection...whenever the tail plane is doing its job (at whatever
angle of incidence), the trim tabs will be doing their job as well
(that of counterbalancing forces on the tailplane), and will
necessarily be raised or lowered w/ reference to the tailplane.

Of course if this explanation is correct, one might ponder the
aerodynamics of my tail-less biplane...pix below.

Fred


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PostPosted: Mon Apr 12, 2010 9:32 am    Post subject: Effects of Flaps and Ailerons on Pitch Trim Reply with quote

On 04/12/2010 06:14 PM, Fred Klein wrote:

Quote:
I've always understood that the elevator or an all-flying tail
(horizontal tail plane) has a "job"...namely, to exert a force, either
up or down, in order to balance the lift of the wing and stabilize the
flight path of a normally configured aircraft (i.e., not a canard type).
To do this "job" requires "work"; the tail plane is never neutral.

I understood the tail plane of the Europa is aerodynamically neutral
indeed, and the sole function of the trim tabs is to give the pilot
tactile feedback and to push the tailplane in such a position that the
trim tab neutralizes itself again.
Without the trim tabs, the tail plane would be happy to remain in any
position where you set it, including in positions that pull excessive
G's. It is the trim tab that spoiles this neutrality and always tries to
work out a tail plane position where it can line up again with the tail
plane. So, the trim tab will always remain in the same relative position
of the tail plane regardless trim setting, but it is the whole
combination of tail plane and trim tab that change incidence as a whole
relatively to the main wings.

You might want to execute the following experiment:
Put a spring clamb on the trim tab and overlap it with the tail plane.
It should try to keep the tail plane and trim tab lined up.
Now carefully exercise the trim button and see what happens: It is not
the trim tab that moves, but the whole tailplane/trim tab combination!
This is what happens in flight as well. The clamb is no longer there,
but instead a flow of air over and under the trim tab, and as soon as
the trim tab tries to move outside the airflow, it will be pused back to
the tail plane, just as if there is a spring clamb on them.

This is true as long as you don't push or pull on the stick. As soon as
you do that, you will push or pull the trim tab out of its center, and
it becomes subject to a disbalance in air flow. It is the air pushing
against the trim tab what gives you the feeling of resistance when you
push or pull on the stick... As soon as you release the force, it will
rotate again to the same relative position.

Frans


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PostPosted: Mon Apr 12, 2010 10:12 am    Post subject: Effects of Flaps and Ailerons on Pitch Trim Reply with quote

This is an interesting subject indeed.

I was taught that on an inherently stable aircraft (operating within its CG envelope) with a tail, the tailplane is always exerting a downward force in cruise to counteract the tendency of the wing to twist forward in the airflow due to the lift vector.    As opposed to a canard where the forward wing provides lift, making it a more efficient design.

I'm perplexed - all the photos I've ever looked at of Europas in cruise, the trim tab is *up* (as others have noted), thus the flying elevator is by definition providing *lift* to the tail.... a contradiction to my teachings. 

Confused,
Pete
A239

On Mon, Apr 12, 2010 at 12:14 PM, Fred Klein <fklein(at)orcasonline.com (fklein(at)orcasonline.com)> wrote:
Quote:

On Apr 12, 2010, at 6:24 AM, david miller wrote:

Quote:
I think that for most efficient flight the incidence of the wing and tail should be such that at cruise there is no up or down trim on the elevator or all flying tail.


Fascinating discussion...as a non-aerodynamicist, I can't resist the temptation to add a comment...

I've always understood that the elevator or an all-flying tail (horizontal tail plane) has a "job"...namely, to exert a force, either up or down, in order to balance the lift of the wing and stabilize the flight path of a normally configured aircraft (i.e., not a canard type). To do this "job" requires "work"; the tail plane is never neutral.  And w/ our Europae...with it's trim tabs acting in opposition to the all-flying tail plane thru a direct mechanical connection...whenever the tail plane is doing its job (at whatever angle of incidence), the trim tabs will be doing their job as well (that of counterbalancing forces on the tailplane), and will necessarily be raised or lowered w/ reference to the tailplane.

Of course if this explanation is correct, one might ponder the aerodynamics of my tail-less biplane...pix below.

Fred






--
"A man is not old until his regrets take the place of his dreams. "
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Joined: 09 Jan 2006
Posts: 136
Location: Golden, Colorado USA

PostPosted: Mon Apr 12, 2010 10:43 am    Post subject: Effects of Flaps and Ailerons on Pitch Trim Reply with quote

The airfoil of the wing of any aircraft with a non symmetrical section will produce a negative pitching moment (-cm) around the aerodynamic center of the wing. This means that without the tailplane producing an equal but opposite moment the acft will pitch over into a vertical dive. The all flying tailplane on the Europa has no fixed angle of incidence so to produce an opposing positive torque moment to the wings negative one the trim tab must be held out of plane. At higher speeds then the tailplane must provide greater downforce then requiring even more trim tab offset. We have to pay a small drag penalty to achieve a level trim condition in cruise flight. This penalty can be reduced somewhat by loading the acft towards the aft cg limits requiring less trim tab offset reducing the downforce the tailplane must produce to maintain level flight.

The tailless flying wing derives it's pitch stability due to the outer portions of the wing being reflexed up to produce that necessary positive pitching moment but also introduces that small drag penalty again. There is no free lunch in aerodynamics! Every desireable aerodynamic quality (like pitch stability) has a price that must be paid.

Glenn

Fred Klein <fklein(at)orcasonline.com> wrote:

Quote:

On Apr 12, 2010, at 6:24 AM, david miller wrote:

> I think that for most efficient flight the incidence of the wing and
> tail should be such that at cruise there is no up or down trim on
> the elevator or all flying tail.

Fascinating discussion...as a non-aerodynamicist, I can't resist the
temptation to add a comment...

I've always understood that the elevator or an all-flying tail
(horizontal tail plane) has a "job"...namely, to exert a force, either
up or down, in order to balance the lift of the wing and stabilize the
flight path of a normally configured aircraft (i.e., not a canard
type). To do this "job" requires "work"; the tail plane is never
neutral. And w/ our Europae...with it's trim tabs acting in
opposition to the all-flying tail plane thru a direct mechanical
connection...whenever the tail plane is doing its job (at whatever
angle of incidence), the trim tabs will be doing their job as well
(that of counterbalancing forces on the tailplane), and will
necessarily be raised or lowered w/ reference to the tailplane.

Of course if this explanation is correct, one might ponder the
aerodynamics of my tail-less biplane...pix below.

Fred




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PostPosted: Mon Apr 12, 2010 10:51 am    Post subject: Effects of Flaps and Ailerons on Pitch Trim Reply with quote

On 04/12/2010 08:06 PM, Peter Zutrauen wrote:

Quote:
I was taught that on an inherently stable aircraft (operating within its
CG envelope) with a tail, the tailplane is always exerting a downward
force in cruise to counteract the tendency of the wing to twist forward
in the airflow due to the lift vector. As opposed to a canard where
the forward wing provides lift, making it a more efficient design.

I agree with this.

Quote:
I'm perplexed - all the photos I've ever looked at of Europas in cruise,
the trim tab is *up* (as others have noted), thus the flying elevator is
by definition providing *lift* to the tail.... a contradiction to my
teachings.

I'm stating again: The position of the trim tab is NOT an indication of
the trim setting. The position of the trim tab is determined by the tail
plane... as you can easily see when you move the tailplane up or down.
The trim setting merely affects the tailplane position where the trim
tab is lined up with the tailplane. For the same relative position of
the trim tab to the tailplane, the whole tail plane has to move to a
different position if you change the trim setting.

The confusing part is that this position, where everything is in
balance, is not when the trim tab is lined out perfectly with the
tailplane. It is always somewhat UP, again regardless of trim setting.

The tailplane itself is designed as aerodynamically neutral: which means
that the tailplane won't favor a certain position by itself. Place it in
the airflow in any position you like... it won't rotate to a different
position.

This is where the trim tab comes into the equation. It artificially
makes the tailplane favor a certain position in the air stream.

The only thing I'm troubled with is that the stable rest position of the
tailplane plus trim tab is not when they are perfectly lined out in
relation to each other.

Maybe, just maybe, this may have something to do with the fact that the
hinges are on the upper side of the tailplane, rather than in the
center. The forces acting on the lower side have more leverage than the
forces acting on the upper side, hence the stable position of the trim
tab where all forces are cancelled out, is slightly up.

The more I think about this, the more I think that this is the reason
why we always see a trim tab up position.

Any comments about this hypothesis?

Frans


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PostPosted: Mon Apr 12, 2010 11:06 am    Post subject: Effects of Flaps and Ailerons on Pitch Trim Reply with quote

On 04/12/2010 08:51 PM, Frans Veldman wrote:

Quote:
The more I think about this, the more I think that this is the reason
why we always see a trim tab up position.

Any comments about this hypothesis?

Anyone who reached the flying status interested in a harmless experiment?

My idea is that if you get the trim tab to line up with the tailplane
you will experience less drag.

There is a very easy way to achieve this: apply some nose UP trim, and
use your muscles to keep the stick in the desired (forward) position so
the nose doesn't move up.
This will have the effect that the trim tab moves down, and you prevent
the tailplane to get into a position where the trim tab sticks up again
by pushing the stick forward.
Of course you should try to remain at the same altitude.

If everything is right, you would see a small increase in speed.
I just wonder how much that is.

If it is worth the trouble, we could load the stick somewhat forward
with a spring or bungee. This would have the effect that the trimmed
position is always with the trim tab in line with the tailplane... as it
was supposed to be in the first place.

Frans


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