Sender: <marv@lancaironline.net>
To:  lml@lancaironline.net
Date: Wed, 19 Jan 2011 13:07:28 -0500
Message-ID: <redirect-4791646@logan.com>
Received-SPF: none
 receiver=logan.com; client-ip=72.9.254.67; envelope-from=paul@tbm700.com
Content-Type: text/plain; charset=us-ascii
Mime-Version: 1.0 (Apple Message framework v1082)
Subject: Re: [LML] Re: elevator trim speed (TruTrak)
From: paul miller <paul@tbm700.com>
In-Reply-To: <list-4791568@logan.com>
Content-Transfer-Encoding: quoted-printable
References: <list-4791568@logan.com>

Colyn, I agree with you.  This is a case where the wiring should have =
been 12v to the trim system and it is 24v.  A secondary finding was that =
the trutrak autotrim box needs some mods which can handle that kind of =
error which tells me there are probably a few more 24v systems connected =
to 12v Ray Allen servos.   Once I correctly supply 12v to the trim =
system then I might sit down and consider some of the other trim safety =
things out there but getting the speed down and checking trim authority =
(as you said) is probably the best for now.  I've had this airplane for =
2 years and I've been reluctant to change anything until now.  I am =
impressed by Trutrak's commitment to fix a potential fault.   I know =
that a similar Honeywell KFC-325 issue would not be as forthcoming and =
certainly not as affordable to fix.

Paul
Spruce Creek
On 2011-01-19, at 10:22 AM, Colyn Case wrote:

> 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?
>=20
> 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.
>=20
> 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.
>=20
>=20
> On Jan 18, 2011, at 11:45 AM, paul miller wrote:
>=20
>> 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
>> --
>> For archives and unsub =
http://mail.lancaironline.net:81/lists/lml/List.html
>=20
>=20
> --
> For archives and unsub =
http://mail.lancaironline.net:81/lists/lml/List.html