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Date: Wed, 19 Jan 2011 12:22:53 -0500
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Subject: Re: [LML] Re: elevator trim speed (TruTrak)
From: Colyn Case <colyncase@earthlink.net>
In-Reply-To: <list-4790020@logan.com>
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References: <list-4790020@logan.com>

I don't know why you would want to rely on tru-trak to condition the =
trim voltage....because you would want it to work properly as manual =
trim too, right?

This reminds me: I wired my system so that I can turn the auto-trim off =
and still use the manual trim.  On a system with no auto-trim you would =
get the indication on the face of the auto-pilot telling you when to fix =
the trim.   When I got my system up, this indication was wrong.   =
Working with tru-trak we discovered that one of the signals was floating =
as a result of the design of the auto-trim box.   Tru-trak gave us =
instructions for a field mod to fix this.    If you are considering =
something similar you will want to ask about that field mod.

Other thoughts about trim speed though:
1) even though you can "blip" it, I think it beats the crap out of the =
relay deck when you use it that way.  Better to have the speed  mod.   I =
remember being at HPAT one day when they had to switch out the relay =
deck in 409L after not very long (less than 2 years? don't quote me) in =
service.
2) I don't know how to make safety-trim work with auto-trim.  What will =
the auto-pilot do if it's trying to trim for 4-5 seconds and safety-trim =
stops it?   My guess is it will keep its switch closed forever and =
safety-trim will fight back forever.  I have to confess I never talked =
to safety-trim about this.
3) Given all that, it seems like the most prudent policy is to make sure =
your trim travel is no more than it needs to be.


On Jan 18, 2011, at 11:45 AM, paul miller wrote:

> Doug and Colyn:  Yes, the trim servo is the Ray Allen unit which is =
only sold as 12v so it appears to be driven at 24v by my aircraft =
through the Trutrak box.   The normal Ray Allen travel time is about 15 =
seconds from their website and I'm around 5-8 seconds.   It would appear =
that Trutrak will mod the autotrim box to limit the output voltage to =
12v but I've got a note into them to confirm this before I send it back. =
 If that's correct Doug then the trim speed should be more manageable.  =
This is also a safety issue because a 5 second full trim move is not =
easy to live with in a runaway situation. Will advise shortly.
>=20
> Paul
> Spruce Creek
>=20
> On 2011-01-17, at 7:57 AM, Douglas Brunner wrote:
>=20
>> Paul,
>>=20
>> This is a problem experienced by other Legacy pilots.
>>=20
>> I am also a 28V plane, but don't think the problem is due to the =
voltage.
>> My trim speed is good for takeoff and landing, but way too fast for =
cruise.
>> I have adapted to it by learning to "blip" the trim in flight.
>=20
>=20
> --
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