Auto Pilot Suggestions Needed BAD

[Bayou Bert]

I have the TruTrak Vision 385 in my 9A. I have the GRT HXr EFIS.
Today I was climbing out, had the destination loaded and activated
in the GTN 650 and turned on the AP at 2K with a 3K target at 500fpm.
I was at full power, had EFIS in GNAV and AP in GPSS VS and it went
right on through 3K and I finally reined it in at 3.5K. Reduced power
and trimmed down etc.
I have the recommended settings in the TruTrak AP for the 9A and all
the settings in the EFIS are at 100%. The lateral control is great but
vertical I can't depend on to be correct.
I don't have auto trim but not sure that would help.
The servos are 2008 blue motor style.
Any suggestions or help would be greatly appreciated.
I am working on my instrument and not being able to trust the AP
is really making things way more difficult than needed.
Any help/suggestions Greatly Appreciated.

[Mike S]

Originally Posted by Bayou Bert

I have the TruTrak Vision 385 in my 9A. I have the GRT HXr EFIS.
Today I was climbing out, had the destination loaded and activated
in the GTN 650 and turned on the AP at 2K with a 3K target at 500fpm.

You turned on the AP, or engaged it??

[Bayou Bert]

The last action I usually do when going to AP
is hit the mode button on AP and make sure it shows
GPSS VS in the window.

[BobTurner]

A typical wiring connection will have the autopilot?s ARINC lines going either directly to the 650, or to the HXr, with a dpdt switch choosing which.
1. Is the switch in the HXr position? If ?yes?, then
2. Have you set the final altitude (3000) in the HXr?
3. I have the Trio, which auto-defaults to arinc commands when present. But I *think* the TruTrak does not. Check the TruTrak manual, see what buttons you need to push to put it into the ?accept arinc commands? mode.

If your switch is in the ?650? position, you need to enter 3000 directly in the TruTrak.

[Bayou Bert]

Thanks Bob, but I keep the switch on the HXr. I like the bigger numbers and
dealing with EFIS instead of the little AP head and little green numbers.
I was wondering if I need to just try letting the 650 feed the AP directly.
I assume an approach could be flown in that configuration?

[BobTurner]

Originally Posted by Bayou Bert

Thanks Bob, but I keep the switch on the HXr. I like the bigger numbers and
dealing with EFIS instead of the little AP head and little green numbers.
I was wondering if I need to just try letting the 650 feed the AP directly.
I assume an approach could be flown in that configuration?

Yes, but only a gps approach. Going thru the efis gives you vor and ils approaches in addition to gps. Also you can do heading (not ground track) mode if you want, like if you?re getting vectors (controllers try to build in wind correction). And as you say, the efis presentation is much easier to read.
But try a direct connection 650 to autopilot gps approach. (You should know how to do this anyway, in case the efis dies. That?s the only reason for the switch.)
However, I still suspect you want something other than VS set in the autopilot, something like ?use arinc?. But I?ve only used a TT once, so my memory is fuzzy.

[BobTurner]

Reading page 33 of the 385 manual suggests that you need to set the autopilot vertical speed to zero prior to engaging it, in order for it to accept the ARINC commands. Try that?

[Bavafa]

Bob is right on with his suggestions. One other thing, set the EIFS to ENAV, it will flip to GNAV automatically when/if it needs.

[Tankerpilot75]

I assume you?re setting your desired altitude and rate of climb on your HXr EFIS and then engaging your autopilot for both heading/route and climbout. This doesn?t work.

If you?ll review your TruTrak operations manual section 6.4 I believe you?ll read that you have to sync the SVS mode (vertical speed) to less than 100 feet BEFORE the autopilot will enter GPSS mode. Once synced the EFIS and autopilot display GPSS indicating your EFIS and autopilot are truly communicating with each other.

When you initially engage your autopilot on climbout it will show an SVS rate equal to your actual rate of climb. You accomplish syncing by turning the autopilot knob until SVS indicates less than 100. The EFIS?s rate of climb you?ve entered will then continue your climb to your desired altitude. Failure to synchronize your autopilot rate of climb to your EFIS will result in the autopilot continuing to climb through your desired EFIS altitude.

Admittedly the TruTrak operating manual is poorly written. In fact it sucks! Like you, I struggled with this issue and couldn?t figure out why sometimes it would level off at the EFIS entered altitude and sometimes fly through it. I swore it was a intermittent system malfunction but eventually reread the operations manual and watched the GRT Jerry Morris videos enough times to figure out it was just operator error. The reason why it worked as advertised a few times but not always was simply because I accidentally had less than a hundred feet rate of climb at time of engagement.

I have the old WS EFIS system but the autopilot interface is the same. They are great systems but getting them to truly communicate is key. In fact I got so frustrated with my Garmin 430, GRT WS EFIS and autopilot not playing together as ?expected? I developed an ?Instrument Approach Procedures? checklist that I religiously use when flying a GPS or ILS approach. Starting an approach and engaging the autopilot only to have it take me a different direction than anticipated really frustrated me. I highly recommend you create one for yourself using the Jerry ?Widget? Morris videos available on the GRT support training website to assist you.

[BobTurner]

Yep. My one and so far only RV10 instrument student failed his check ride when his TT took him off in some unexpected direction (failed to capture the final approach course) and he was too slow to catch it. So, the alternative: This is just one reason why I went with a Trio Pro rather than the TT autopilot (although not my major reason). It auto-defaults to the ARINC inputs if there's data there, so all I do is set what I want in the HX, then push the horizontal and vertical servo engage buttons on the Trio. No other knob twirling or button pushing needed. Only real problem is staying current on the "no-efis" operation of the autopilot, should the need ever arise.