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Capt
02-22-2018, 03:40 AM
Hi guys/gals.
Bit of a long shot here but am seeking some advice on an installation I have that I can't seem to get working.
I have recently bought an 8 with steam driven stuff (which I prefer) that has an older Garmin Apollo GX65 and a TruTrak DigiFlight ll. The problem I'm having is that I can't get the auto pilot to track in Nav mode from the GPS Flt Pln. I've got all the manuals and read them but it simply won't connect as per the books. Autopilot works fine in Hdg & Alt hold. The previous owner said it used to track via Nav but he hadn't flown it for some years and couldn't remember much.
Anyone any ideas??
Thanks

rleffler
02-22-2018, 05:15 AM
Hi guys/gals.
Bit of a long shot here but am seeking some advice on an installation I have that I can't seem to get working.
I have recently bought an 8 with steam driven stuff (which I prefer) that has an older Garmin Apollo GX65 and a TruTrak DigiFlight ll. The problem I'm having is that I can't get the auto pilot to track in Nav mode from the GPS Flt Pln. I've got all the manuals and read them but it simply won't connect as per the books. Autopilot works fine in Hdg & Alt hold. The previous owner said it used to track via Nav but he hadn't flown it for some years and couldn't remember much.
Anyone any ideas??
Thanks

It could be as simple as an open circuit on one of the pins to a hardware issue with either the AP or GPS.

1. Document your schematic, what pins go to,what pins.
2. Document your port settings, speeds and protocols at both ends
3. If you received schematics and settings from the seller, validate that?s exactly how things are wired and compare to the vendor manuals
4. Test circuit continuity based upon #1 with an ohm meter
5. Test for shorts between pins or to ground
6. Then give Trutrak a call if you haven?t found the problem

Capt
02-22-2018, 05:19 AM
Yeah that was the next thing to look at, a hardware problem along with checking the settings on both, haven't delved into the manuals that deep at this stage, just putting it out there from an operators point of view. I'm located down under so calling TruTrak won't be an easy option.
thanks for your reply.
Cheers.

Bob Martin
02-22-2018, 06:04 AM
What you are describing, sounds like it is just not getting info from the GPS. The TT unit will follow heading and hold altitude all by itself. It takes the RS232 line output to feed the AP NAV info.
First thing I would check is input/output settings per the manuals.
Then check that the RS232 wire is connected and making contact.
Good Luck.

Jesse
02-22-2018, 06:32 AM
Pin 17 on the TruTrak should be getting serial (RS232) data from the gps. From the manual:

Primary Serial Input. Baud rate selectable 1200, 2400, 4800 or 9600 baud. Automatically decodes NMEA-0183, Garmin Aviation Format, or Apollo/UPSAT Moving-Map or GPSS format. Provides directional reference to the autopilot.

Make sure you have a good connection (check continuity) from that pin to the gps, and verify it doesn?t have continuity to ground. It very well could be a broken wire or a chafed wire that is touching ground.

Capt
02-22-2018, 11:41 PM
Thanks guys. Today I checked all the settings of the Digiflight with the manual on my lap, a couple of the settings weren't available as per the manual so set up the unit best I could. The Baud is at 9600 which I believe should be ok for the Garmin GX65. This W/E I intend to do some hardware checking as suggested by you guys.

More to come watch this space:-)

P.s...When I asked the previous owner about a week after I flew it home on Hdg how to get it to track via the GPS (as it used to) he couldn't remember (3 years since he had flown it due medical) but mentioned too well but I had to push the small GPSS button to trk Nav is all he could recall. This he also mentions in the flight manual he designed & made up years ago but be buggered if I can find any 'small button' anywhere on the panel to do same! Got me stumped!

Mike S
02-23-2018, 12:35 AM
I had to push the small GPSS button to trk Nav is all he could recall. This he also mentions in the flight manual he designed & made up years ago but be buggered if I can find any 'small button' anywhere on the panel to do same! Got me stumped!

Any buttons on the control stick grip you cant figure out??

Capt
02-23-2018, 04:43 AM
The stick is like a porcupine but no none that are unidentifiable:)
Short of there being a hardware problem it might be one of those fugazis👍

tim2542
02-23-2018, 09:04 AM
The serial connection is easily checked, you should see a period flashing (no gps position), an asterisk (meaning gps position obtained), or a plus sign, (gps position and a flight plan) if you don’t see any of these you have a serial issue, electrical or baud rate or protocol.

Tim Andres

BobTurner
02-23-2018, 03:38 PM
l but I had to push the small GPSS button to trk Nav is all he could recall. This he also mentions in the flight manual he designed & made up years ago but be buggered if I can find any 'small button' anywhere on the panel to do same! Got me stumped!

My dim memory (I've only flown behind this autopilot once) is that the button is at the bottom of the autopilot itself? Or do you push in on the knob? I may well be all wrong here, but I seem to recall that you need to take some action on the autopilot to put it into GPSS mode.

Capt
02-23-2018, 03:55 PM
Yes there is a deliberate action required as per the TruTrak operating manual and that's pushing the Mode button once an active Flt Pln is available and then the + sign should be in view but I can't get the autopilot out of Hdg. Now to pull the units out of the panel to check for hardware issues as a few have suggested here.
More to come am sure:)

Mike S
02-23-2018, 03:57 PM
http://www.manualsdir.com/manuals/714887/trutrak-digiflight-ii-operating-manual.html?page=5

Looks like the Mode button is the winner:D

Capt
02-24-2018, 05:37 AM
Hi Mike.
Yeah got the manual in hard copy as well as in PDF already thanks, gone right thru it, am aware of the Mode button activation for Nav tracking but it does nothing, stays in Hdg all the time.
Might have to sell it. buy a Cessna.....oh what am I saying?:D

Mike S
02-24-2018, 08:44 AM
Might have to sell it. buy a Cessna..... D

Ouch, that hurts;)

rleffler
02-24-2018, 02:47 PM
Dumb question.....

You do have the Arinc interfaces wired between the two devices, correct?

To get gpss to work the AP needs the data from the arinc out of the gps to function correctly. Otherwise the mode button won?t engage in gpss mode.

BobTurner
02-24-2018, 07:18 PM
Dumb question.....

You do have the Arinc interfaces wired between the two devices, correct?

To get gpss to work the AP needs the data from the arinc out of the gps to function correctly. Otherwise the mode button won?t engage in gpss mode.

Does the -65 gps output gpss data?

Capt
02-25-2018, 03:58 AM
Dumb question.....

You do have the Arinc interfaces wired between the two devices, correct?

To get gpss to work the AP needs the data from the arinc out of the gps to function correctly. Otherwise the mode button won?t engage in gpss mode.

Not dumb at all Bob, I haven't checked any hardware as yet, that's my next task, to pull it all out of the panel. What intrigues me though is that it used to couple to Nav but hasn't flown in 3 years (other than engine runs)

Capt
02-25-2018, 03:59 AM
Does the -65 gps output gpss data?

Must do as it used to track in GPS Nav.

BobTurner
02-25-2018, 11:50 AM
Must do as it used to track in GPS Nav.

These are different things. ?GPS nav? most autopilots/gps boxes will do. This is point A to point B to point C. Autopilot will not fly to C prior to reaching B. GPSS involves turn anticipation. On the above route the autopilot will commence the turn to C just prior to B, so there?s no overshoot. Not all gps boxes provide gpss commands.

Capt
02-25-2018, 02:40 PM
With this set up the TruTrak a/p must overfly each waypoint in a multi leg Flt plan, well so the operating manual says. Simply put the TruTrak won't recognise a valid GPS Flt Pln so it's time to pull it all to pieces.

rleffler
02-26-2018, 04:52 AM
Must do as it used to track in GPS Nav.

Like I mentioned before, must likely an open circuit or a hardware issue if it worked previously.

Since you aren?t the builder, the only option is to trace each and very wire to ensure continuity. While painful, this will add the benefit that you will know your aircraft better.

I had a similar issue in which all the vendors were pointing fingers at the wiring harness. That?s when Rob Hickman reminded me that the GtN650 has a Arinc diagnostic page in which you can view all the data labels being transmitted.

Trutrak was very insistent that they never had an issue with the Vizion and that the problem was that data wasn?t getting to the device. With the data from the GTN650 and some translation help from Ken @ AFS, I was able to prove the proper data was getting to the AP. It turned out that the Arinc receiver in the Vizion had failed. I was told it was the first failed Vizion for Trutrak.

The point I?m trying to make is it was tedious to troubleshoot this issue. I can?t tell you how many times I tested continuity and for shorts on the harness. I also learned that what I thought were long service loops, weren?t nearly long enough. I probably spent several months chasing this gremlin. I was extremely grateful for the guys @ AFS who took calls and offered assistance in the evening and on weekends.

You?ve got the additional burden of not being the builder. My recommendation is to document all of the wiring harness while you got things taken apart. Identify that pin 1 on device x goes to pin 5 on device y. Then you?ll gain the education and know exactly how things are suppose to work.

Capt
02-26-2018, 03:14 PM
Thanks again Bob.
I am planning to do a hardware continuity check soon with a guy I know who is a bit of an electronics guru but he's not handy so will plan to fly up there one day and get help -:)
There's nothing else I can do externally but it is frustrating.
Thanks for all the advice guys, shall keep everyone updated when and if I get to the bottom of this👍

Bugsy
02-26-2018, 07:03 PM
I was frustrated cause my trutrack wouldn't capture the glideslope. Called EFIS manufacture (Advanced Flight) and they had me check software version.

Software version shows on bootup of Trutrack. Recent version is about 2.8 for digiflight II. Mine was at V2.32, so I just mailed AP back to Trutrack yesterday for software update.

Call Trutrack with Software version and they will tell you if it needs and update.

Paul