Brittain Accutrack Troubleshooting

[Hector]

I have a 67 M20C with a working PC system but my Accutrack hunts left and right constantly. Servos and computer were sent to Brittain and checked good, so I think I'm getting a stray voltage from one of my other boxes. The other 'boxes' are an Apollo GX60 IFR certified GPS, and a KX-170B both slaved to a KI-209A. The KI-209A is actually driving the Accutrak. Before i start troubleshooting to see which of these 3 boxes is causing the problem i wanted to try something rather simple to rule out any problems with Accutrack. I want to disconnect the Accutrack from existing boxes and connect it directly to my dock mounted Garmin 496 and verify that it works correctly. My question is does anyone have a Garmin 496 driving their Accutrak AP? I'm thinking I should be able to purchase a power/data cable for the 496 and connect the data out pin to the Accutrak. Just need to know if any of you have done this before I try it.

Sent from my iPad using Tapatalk HD

[andrew]

Is there a way to have a 496 drive a CDI? The Accutrak uses an AC CDI error signal for the nav input. Brittain has always been extremely helpful with me, they may have some suggestions drawn from their experience on ways to diagnose an installation.

[N601RX]

The 496 outputs serial data, the brittain inputs a small DC voltage that is used to drive the CDI. There is a company out west somewhere that makes a small inexpensive adaptor box for the eperimental market. I believe I remember a gain adjustment that can cause this. Do you have the install manual? I think it covers the adjustment. There could also be a ground potential difference between the 3 boxes. They should all be grounded at the same point.

http://www.porcine.com/gps/sc/sc_frameset.html

[scottfromiowa]

Do you have a panel mount GPS? I have a GNC300XL connected to AccuTrac via Left and right analog outputs. Works well. Good luck troubleshooting...maybe a good excuse to upgrade.

[scottfromiowa]

Sorry, needed to read your original post better. Can you hook up directly to the analog out for the Apollo?

[scottfromiowa]

That wouldn't be legal in a certified Mooney, would it? Might want to PM on that one.

[kerry]

The 496 outputs serial data, the brittain inputs a small DC voltage that is used to drive the CDI. There is a company out west somewhere that makes a small inexpensive adaptor box for the eperimental market. I believe I remember a gain adjustment that can cause this. Do you have the install manual? I think it covers the adjustment. There could also be a ground potential difference between the 3 boxes. They should all be grounded at the same point.

http://www.porcine.c...c_frameset.html

Smart coupler works well. It's for experimentals. It can be made into your power cable for your 496 so that its not mounted into your panel making it portable. Is it legal. ?

[Hector]

The 496 outputs serial data, the brittain inputs a small DC voltage that is used to drive the CDI. There is a company out west somewhere that makes a small inexpensive adaptor box for the eperimental market. I believe I remember a gain adjustment that can cause this. Do you have the install manual? I think it covers the adjustment. There could also be a ground potential difference between the 3 boxes. They should all be grounded at the same point.

http://www.porcine.com/gps/sc/sc_frameset.html

Thanks N601RX, I don't remember reading anything about a gain adjustment. I'll have to look that up.

Sent from my iPad using Tapatalk HD

[Hector]

Do you have a panel mount GPS? I have a GNC300XL connected to AccuTrac via Left and right analog outputs. Works well. Good luck troubleshooting...maybe a good excuse to upgrade.

Yes I have a panel mounted GPS (GX60) driving a KI-209 and the output from the KI-209A feeds the Accutrak AP. One of my potential troubleshooting paths is to de-pin the AP from the KI-209A and route the GX60 AP outputs directly to the Accutrack AP. I was going to do the same for the KX-170B and bypass the KI-209A altogether. By doing this I would eventually figure out which box is the source of the problem. The only reason I wanted to try the Garmin 496 first was as a quick verification that the AP (isolated from the other 3 boxes) is working fine. I do not intend to make the Garmin my final solution, but before I start to do a lot of other troubleshooting it would be nice to hook up the Garmin and show that it all works. It doesn't look like it will be that simple if I need another box between the Garmin and the AP.

Sent from my iPad using Tapatalk HD

[scottfromiowa]

Understand. My AccuTrak does "hunt" a little bit while on Trak, but the swings are 2-3 degrees (max). How big are your movements as it "hunts"? My biggest frustration is that Brittain is so slow in getting the Elevator servo rubber boots (altitude hold) done so that I might purchase and have altitude hold feature with the AccuTrak. Good luck sorting it out.

[takair]

Have you tried tuning the AccuTrack? There are gain adjustments that must be optimized. Jerry, at Brittain, can talk you through it. They are one of the most helpful manufacturers out there. It is not too hard to set it up, but does need to be done. Have you tried Hi gain vs low gain? I typically fly my GPS on Hi. Low gain was made for sloppy VORs.

[Hector]

The 496 outputs serial data, the brittain inputs a small DC voltage that is used to drive the CDI. There is a company out west somewhere that makes a small inexpensive adaptor box for the eperimental market. I believe I remember a gain adjustment that can cause this. Do you have the install manual? I think it covers the adjustment. There could also be a ground potential difference between the 3 boxes. They should all be grounded at the same point.

http://www.porcine.com/gps/sc/sc_frameset.html

Another good point to check. I don't know if the ground for the 3 boxes is common and perhaps one of them may not be grounded properly. I'll add that to the troubleshooting list. Thanks!!!

Sent from my iPad using Tapatalk HD

[meddesign]

another thing to bring up, How much does it hunt? Mine is not perfect, sometimes allows the needle to get to the edge of the little ring.

[Hector]

another thing to bring up, How much does it hunt? Mine is not perfect, sometimes allows the needle to get to the edge of the little ring.

Unfortunately it hunts quite a bit. It will roll left for around 10 degree heading change and immediately role right an so on. Definitely not usable. Went up today and turned off the GPS and tried to track on the KX-170B and it would hunt. Did the opposite and turned off the KX-170 and tried to track on the GPS with same results. Both boxes are feeding the KI-209 indicator which in turn feeds the AP. If I don't find an issue with the grounding, I'm going to bypass the KI-209 and hook up the GPS directly to the AP.

Sent from my iPad using Tapatalk HD

[scottfromiowa]

When I first installed the AccuTrak the GAIN was adjusted on the ground. During flight when you turned the AccuTrak on (regardless of hi/lo sensitivity) it would enter a steep bank to the left. Once you held yoke it would stop and the turn function worked, but would not trak properly. The avionics tech did the gain adjustment and the system has worked perfectly since. My guess is that you need the gain adjusted. Good luck,

Scott