Sender: <marv@lancaironline.net>
To: lml@lancaironline.net
Date: Tue, 09 Oct 2007 11:38:06 -0400
Message-ID: <redirect-2377524@logan.com>
Received-SPF: softfail
 receiver=logan.com; client-ip=209.55.3.85; envelope-from=2thman@cablespeed.com
From: "John Barrett" <2thman@cablespeed.com>
Subject: RE: [LML] Re: Backup DG equivalent
MIME-Version: 1.0
Content-Type: text/plain;
	charset="windows-1250"
Content-Transfer-Encoding: quoted-printable
Thread-Index: AcgKfQBRSRofcfGhRa243kAJUTdi7w==
Content-Language: en-us

For the enlightenment of all vis a vis the Tru Trak ADI, I spoke with =
Lucas
of Tru Trak this afternoon.  First of all he told me the =93pitch=94 =
indication,
as was mentioned before in this thread, is not pitch at all, but rather =
VSI.
Therefore if the aircraft is losing altitude, the indicator will be =
expected
to show accurate roll information, but will look as if the nose of the
aircraft is below horizontal when in fact you could be nose up.  I would
consider this to be  a very dangerous situation at any time I needed to =
use
the instrument.  Just consider the unpleasant event you could face when =
your
Cheltons or other MFD=92s all crap out while you=92re in IMC and there =
is lots
of turbulence.  First you have to reorient your scan to instruments that =
you
only use in practice, and then you have to overcome your well ingrained
training that says this thing that looks like an attitude indicator is =
NOT.
While your brain is assimilating this disparity between past learning =
and
reality, precious seconds are going by and the turbulence has caused =
your
aircraft attitude to change to any position other than wings level and =
nose
level =96 probably to be swinging past those desirable positions =
somewhat
erratically.  =20

I think it=92s a shame this very nice instrument has what I think is a =
fatal
flaw.  It=92s too bad Tru Trak put an electronic roll gyro in this =
thing, but
didn=92t think a pitch gyro was necessary.  I sincerely hope they=92ll =
rethink
the concept and will correct this discrepancy.  I will look forward to
buying one to complement my Tru Trak autopilot if they do. =20

By the way, the heading indication is totally GPS dependent and does not
derive information from the gyro or gyros that would allow it to keep
providing heading data if GPS is lost.  That would be another =
improvement if
it could use GPS to stabilize and correct a gyro track, which would =
continue
to function albeit with less accuracy when the GPS is lost.

My 2 cents.

Regards,
John Barrett

=20
As a backup direction indicator on my Legacy, which also has a=20
2-screen Chelton EFIS system, I'm using the 2-1/4" ADI from Tru-Trak. =20
It's a bit of an odd critter, but if you buy it with the GPS and backup=20
battery options, it does give a heading (track, actually) indication=20
that's completely independent of your plane's electrical system.  It=20
also provides pitch and bank info.  Hard to find equivalent info from=20
2-1/4" instruments without spending a fortune.

Jim Cameron
Legacy N132X


No virus found in this outgoing message.
Checked by AVG Free Edition.=20
Version: 7.5.488 / Virus Database: 269.14.5/1058 - Release Date: =
10/8/2007
4:54 PM
=20