REFLECTOR: TR: Autopilot servos

Wed Mar 26 20:33:40 CDT 2008

Gilles...and others

I'm outta town at a Penn State faculty awards ceremony, but I can and will
contribute what I can to this is asked.  I do not have BM stuff, but I am in
phase one fly off and soon as I get my repairs done.  About that, I can say
a contributing factor to my gear up landing was monkeying around with
autopilot issues when I should have been more "fly the airplane" orientated
in Jan of this year particularly when below 2500 AGL.  

I have a TruTrak autopilot going into and out of a Grand Rapids EFIS.  I had
aileron cable issues with the factory, and had drilled so many holes in my
aileron bell cranks getting it all to fit and operate that I had to buy a
new set of bell cranks.  My roll servo is in the eng compartment.  Room to
do things and mount things was a challenge.  I sent my TT back to TT for
some software update that they needed to do when they found out I was a
Velocity.  Also the GRT EFIS has some manner of gain settings that can be
tweaked within their setup routines.  All I can say is that after several
attempts with the new a/p software/firmware it is still not holding a
heading or an altitude.    

Due to my inattention to flying I am dropping any emphasis on autopilot fine
tuning until I take somebody else up with me, and a voice recorder as well
so I can deduce for my own needs and to TruTrak a good squawk profile of
what it's doing (or not doing).

I have slop in my cable too that is not me.  It is in the system design.
There is also potentially too much friction for the default torque and throw
parameters of the TruTrak - GRT EFIS combo that is probably manufacturer
preset to address RV market needs which ain't us.  

If you are not there yet, take the time to decide how and where to mount
your roll servo and who to buy an autopilot from.

Terry Miles

-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Craig and Denise Woolston
Sent: Wednesday, March 26, 2008 7:47 AM
To: 'Velocity Aircraft Owners and Builders list'
Subject: Re: REFLECTOR: TR: Autopilot servos

We mounted our BM servos in a very similar location and are flying.  I would
strongly recommend moving the aileron servo to the engine compartment.  We
have not had very good luck get our roll control to be smooth and positive.
After complaining to BM they say we should have mounted the servo closer to
the actual surface, that the slop of the push-pull cables is affecting the
performance.  I've attached my pictures of install for reference.

Craig
XL5-FG Flying in Lancaster, CA

-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Alex Balic
Sent: Monday, March 24, 2008 5:26 PM
To: 'Velocity Aircraft Owners and Builders list'
Subject: Re: REFLECTOR: TR: Autopilot servos

Hi Gilles-

I will try to get out there and take a picture or you, but basically, I
removed the output arm from the servo- then fabricated an adapter that would
allow a small universal joint to attach to the output shaft of the servo,
then I adapted the end of the universal joint to fit into the  torque tube
directly- I probably could have made a plug to go directly from the servo
into the tube, but I felt that there might be the possibility of binding, so
I added the U-joint- the servo mounts on the floor behind of the keel on an
aluminum hat channel piece that I fabricated. The only disadvantage that I
see is that the servo has no mechanical advantage on the aileron system- if
you use an output arm, and a rod linkage to the end of the aileron arm that
pushes/pulls the flex cables, you can set it up with maybe 1.5 to one
advantage- I hear that the servo is plenty strong to move the ailerons
though, but the other advantage of using the mechanical  linkage is that the
servo would not have to be as precise- maybe 3 degrees servo travel to 2
degrees aileron arm travel- I have not flown with it yet, but the install is
clean.

Alex

-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Gilles Ross
Sent: Monday, March 24, 2008 10:58 AM
To: reflector at tvbf.org
Subject: REFLECTOR: TR: Autopilot servos

Thanks Alex
Do you know the arm lenght of your attachment in reference with the center
on the torque tube
and which hole (or arm lenght) did you used on the servo arm.
Gilles

-----Message d'origine-----
De : reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org]De la
part de Alex Balic
Envoye : 24 mars 2008 10:44
A : 'Velocity Aircraft Owners and Builders list'
Objet : Re: REFLECTOR: Autopilot servos

I put my elevator servo on top of the canard- I bought another trim spring
bracket from Velocity and attached it on the other elevator torque tube-
connected to that- I mounted my roll servo at the end of the keel co Axially
with the aileron torque tube- it is connected to the torque tube with a
small universal joint.

-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Gilles Ross
Sent: Sunday, March 23, 2008 8:54 PM
To: reflector at tvbf.org
Subject: REFLECTOR: Autopilot servos

I am looking where BMA autopilot servos have been installed for the elevator
and aileron.

Has anyone installed the elevator servo in the keel?

Gilles

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