Interesting TruTrak Info

Update 28 April. On page two of this thread, TruTrak explains that I misunderstood a post on their forum.

Having two GPSes connected, one via ARINC and one via serial with both having identical active flight plans, - will not revert to the serial source for Flight Plan if the ARINC source fails.

It will instead revert to GPS ground track using the serial source UNLESS you hit the mode button again on the TruTrak.

Not as good as I thought, but still possibly a useful feature.

______________________________________________________

Hey gang,

For those of you with TruTrak II (I believe all variations) I have some interesting news which comes of asking "stupid questions." From the TruTrak forum:

TruTrakTech said:

<paraphrased> said:

So, what would happen if I wired only the ARINC lines from my GNS480 and wired the serial line from my 496?

Are you saying that steering commands from the 496 would be ignored as long as the unit is receiving ARINC steering from the 480?

Would that not provide true backup in the event my GNS 480 failed?

Click to expand...

Nothing adverse would happen. It would work perfectly. When an ARINC steering command is present, it gets priority as we assume you'd like to use GPSS if it's available over GPS Nav.

That would be a great way to have a back up rigged. It would also eliminate the need for switched input. Thanks!

Click to expand...

So, for those of you who have a "typical" setup with a GNS 480/430/530 as primary and an x96 as backup, there is no need to have a "switch" to have the best of both worlds. Just hook up the ARINC lines from the primary, and the serial line from the x96, and in the event the primary fails you will still have GPS guidance to your TruTrak.

When the TruTrak loses GPSS, does it drop back to TRK SEL or TRK GPS mode?

If have a different flight plan in your 496 vs. your 430, and the A/P just starts following the 496's plan... could be a stressful few moments there.

--Paul

Garage Guy said:

When the TruTrak loses GPSS, does it drop back to TRK SEL or TRK GPS mode?

Click to expand...

If it loses ARINC it will drop back to Serial.

It can only "lose GPSS" if a) the connection is broken or b) you discontinue / delete the flight plan. In the latter case it will revert to TRUE course; if the connection is lost completely it will revert to Magnetic course tracking.

If have a different flight plan in your 496 vs. your 430, and the A/P just starts following the 496's plan... could be a stressful few moments there.

--Paul

Click to expand...

hehe - I'd say it would be more stressful flying with someone who has two simultaneously active flight plans!



I'm still struggling to get cross-fill working, but in the mean time I don't put a flight plan in the 496.

breister said:

It can only "lose GPSS" if a) the connection is broken or b) you discontinue / delete the flight plan. In the latter case it will revert to TRUE course; if the connection is lost completely it will revert to Magnetic course tracking.

Click to expand...

So if you lose GPSS from the 430, and there is a flight plan on the serial pin because you have that connected to your 496 and the 496 has a flight plan, the TruTrak won't follow that flight plan, but instead will just track the current course?

hehe - I'd say it would be more stressful flying with someone who has two simultaneously active flight plans!

Click to expand...

I have different flight plans in my 496 vs. my GX60 all the time. These won't cross-feed anyway, but I find the 496 useful for checking bearing and distance to some waypoint that isn't the next waypoint on the GX60's plan. I usually do that by punching up "Direct" to that waypoint on the 496, which is enough to make it think it has a flight plan, I'm pretty sure.

--Paul

Garage Guy said:

I have different flight plans in my 496 vs. my GX60 all the time. These won't cross-feed anyway

Click to expand...

Are you sure? I believe Dan Checkoway has his 496 following his GX60.

mcb

mburch said:

Are you sure? I believe Dan Checkoway has his 496 following his GX60.

Click to expand...

Matt --

Actually I've never tried it, and my 496 has a broken Data In pin so I'm not able to try it, but the documentation on the 496 just talks about input in NMEA format, and the GX60 documentation just shows flight plan data output in non-NMEA format, so...

Maybe Dan will check in and clarify. If this actually works, I might have to fix that Data In pin.

--Paul

Garage Guy said:

the documentation on the 496 just talks about input in NMEA format, and the GX60 documentation just shows flight plan data output in non-NMEA format, so...

Click to expand...

Take a look at the "Aviation" format. That seems like it ought to work.

mcb

Matt

OK, got me looking into the manuals for the 430W and the GX60, and sure enough the flight plan serial data output formats are exactly the same. I did not know that... So anyway then yes certainly the GX60 should crossfeed to the 496.

Now I wonder if I can fix that data in pin on my 496 without paying Garmin $400 for the flat rate out of warranty repair...

--Paul

Garage Guy said:

So if you lose GPSS from the 430, and there is a flight plan on the serial pin because you have that connected to your 496 and the 496 has a flight plan, the TruTrak won't follow that flight plan, but instead will just track the current course?

Click to expand...

If the 496 HAS an active flight plan, the TruTrak will attempt to correct to course on the active leg. If it has NO flightplan, it will revert to true course. If the 496 dies too, it will revert to Magnetic Heading.

I have different flight plans in my 496 vs. my GX60 all the time. These won't cross-feed anyway, but I find the 496 useful for checking bearing and distance to some waypoint that isn't the next waypoint on the GX60's plan. I usually do that by punching up "Direct" to that waypoint on the 496, which is enough to make it think it has a flight plan, I'm pretty sure.

--Paul

Click to expand...

Hehe - then in the event your GX60 fails you're cleared direct, whether you intended that or not...

Seriously, if you are doing that then you are doubtless monitoring your current heading and track relative to your primary GPS. You will notice such a change, and can then take corrective action to restore your course to what it should be.

Know what your systems do, and make your own decision based on how you fly the plane.

breister said:

Hehe - then in the event your GX60 fails you're cleared direct, whether you intended that or not...

Click to expand...

I'm trying to figure out what you mean there, but I don't see the connection between my IFR GPS failing and being cleared direct. Sorry!

Know what your systems do, and make your own decision based on how you fly the plane.

Click to expand...

Right, well, I was interested in finding out what the TruTrak does in those cases. The Trio ProPilot we have will basically do the same thing, if it loses GPSS, it will fall back on its "Avlink/NMEA" input. If I had that hooked up to my 496, with a different flight plan, I think it would be more obvious that something had changed, since the Trio autopilots display a lot of flight plan information (identifier of next waypoint, etc.). But instead I have a locking toggle switch on the panel to select between nav sources for the autopilot, so it's really unlikely that it will switch sources on its own without me telling it to.

Cheers,

--Paul

Garage Guy said:

I'm trying to figure out what you mean there, but I don't see the connection between my IFR GPS failing and being cleared direct. Sorry!

Click to expand...

I was responding to the scenario presented where there was a DIFFERENT flight plan (or simply a DIRECT TO course) programmed in the 496 than in the primary GPS. In that case, if the primary fails the autopilot will begin attempting to intercept the active leg of the x96 flight plan.

I'll write this as a series of if-then-else statements:

If TT receiving data from <ARINC GPS connection> and <ARINC GPS> has active flight leg then TT follows ARINC steering

- else -

If TT receiving data from <serial GPS connection> and <serial GPS has active flight leg then TT follows Serial steering

- else -

if NEITHER GPS connection has an active flight plan leg AND (EITHER <ARINC GPS connection> OR <serial GPS connection> is receiving valid GPS data) then TT reverts to last TRUE heading

- else -

TT reverts to internal magnetic compass and flies MAGNETIC heading

Right, well, I was interested in finding out what the TruTrak does in those cases. The Trio ProPilot we have will basically do the same thing, if it loses GPSS, it will fall back on its "Avlink/NMEA" input. If I had that hooked up to my 496, with a different flight plan, I think it would be more obvious that something had changed, since the Trio autopilots display a lot of flight plan information (identifier of next waypoint, etc.). But instead I have a locking toggle switch on the panel to select between nav sources for the autopilot, so it's really unlikely that it will switch sources on its own without me telling it to.

Cheers,

--Paul

Click to expand...

Don't know what the Trio would do if it had different sources providing ARINC and serial. You'll have to contact them or experiment.

Anyway, the gist of this is that for TT owners there exists an "undocumented feature" that can act as an automatic failover backup if you choose to wire it that way. At the moment I'm a bit burned out on wiring having just finished a 2 year restoration, but I'll probably circle back at some point and make that change.

Cheers,

Bill

Hello all,

I'd like to clarify just a little. Sometimes my fingers type muttled words like my mouth speaks, so I apologize if I was misinterpreted. If an ARINC 429 steering signal is present as well as an RS232 flightplan, pushing the MODE button will engage GPSS mode following the ARINC steering commands. If your ARINC source is lost, the autopilot will revert to TRK mode, not GPS NAV. So, having a different flightplan in your 430 vs. your 496 will not cause any funky conditions. Whatever ground track you are on when your GPSS source signal disappears is what the AP will hold that track. It will not automatically begin following the flightplan from the RS232 source, you will have to push the MODE button again to engage the GPS NAV mode.

I hope this makes everything clear as mud!

Ah well, perhaps I was too optimistic in reading your response on your forum.

At least learning that now saves me from re-wiring to get a feature that doesn't exist.

Any possibility this behavior could be changed with a software release? It does make sense to do it that way...

breister said:

Ah well, perhaps I was too optimistic in reading your response on your forum.

At least learning that now saves me from re-wiring to get a feature that doesn't exist.

Any possibility this behavior could be changed with a software release? It does make sense to do it that way...

Click to expand...

Whoa, I seem to becoming good at this missing questions in posts thing.

I doubt this is particular feature will ever be real for the exact reason that was laid out here. If the AP automatically started following the flight plan in your backup GPS without pilot prompting, there could potentially be a hairy situation arise. What if your backup GPS flightplan is completely different and has you going the opposite direction? Defaulting to the track mode is the safest method.

Thanks Lucas,

I saw a note on the TT boards a day or two ago that said the newer Digiflight IIs will no longer contain an internal magnetometer. Is that true? If so, then if you lose all GPS info you are completely up the creek with respect to autopilot!

Will you be adding an external magnetometer?

breister said:

Thanks Lucas,

I saw a note on the TT boards a day or two ago that said the newer Digiflight IIs will no longer contain an internal magnetometer. Is that true? If so, then if you lose all GPS info you are completely up the creek with respect to autopilot!

Will you be adding an external magnetometer?

Click to expand...

You aren't up the creek! It now has the same bank angle backup mode that our Sorcerer autopilot has had its entire life. Using your compass and the AP, you can get anywhere and get anywhere reliably.

Lucas,

If I am in town can you "upgrade" me to this functionality? the compass in mine is worthless and if I lose GPS (for whatever reason) it takes off on a tangent everytime....

Tailwinds,
DougR

B25Flyer said:

Lucas,

If I am in town can you "upgrade" me to this functionality? the compass in mine is worthless and if I lose GPS (for whatever reason) it takes off on a tangent everytime....

Tailwinds,
DougR

Click to expand...

Sure can Doug. Just give me a heads up before you get here. Thanks!