TruTrak Nav question.

Capt · #1 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 · #2 02-22-2018, 05:15 AM

Quote:

Originally Posted by Capt

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 · #3 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 · #4 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 · #5 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 · #6 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 · #7 02-23-2018, 12:35 AM

Quote:

Originally Posted by Capt

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 · #8 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 · #9 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 · #10 02-23-2018, 03:38 PM

Quote:

Originally Posted by Capt

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.