GTN 750 Froze in flight

[William Munney]

All:

 

Anyone with experience or hear a tale of the Garmin GTN 750 freezing in flight?  We were VFR.  Tried to switch frequencies and the touch screen was completely un-responsive.  So, Com 1, Nav 1, Audio panel and transponder……Kaput!  Tried everything on the touchscreen.  Even HOME.  Nothing.

Pulled the CB for Nav1/ Audio.  Reset it.  No problems the remainder of the day.

 

 

[Ragsf15e]

49 minutes ago, William Munney said:

All:

 

Anyone with experience or hear a tale of the Garmin GTN 750 freezing in flight?  We were VFR.  Tried to switch frequencies and the touch screen was completely un-responsive.  So, Com 1, Nav 1, Audio panel and transponder……Kaput!  Tried everything on the touchscreen.  Even HOME.  Nothing.

Pulled the CB for Nav1/ Audio.  Reset it.  No problems the remainder of the day.

 

 

Yikes.  I just started flying with a 750xi and only recently learned that you “can’t turn it off”.  I have located the CBs and they are actually pulled right now so next time I start it shouldn’t come on.  I want to make sure I know which ones turn it off.  The scary thing to me isn’t losing the gps, but I also have the remote audio panel.  I actually wish I had a normal audio panel and a remote transponder as I think that’s easier to deal with if you lose it. I’m glad it reset for you, and that you weren’t ifr or in a class B/C!

[toto]

17 minutes ago, Ragsf15e said:

Yikes.  I just started flying with a 750xi and only recently learned that you “can’t turn it off”.  I have located the CBs and they are actually pulled right now so next time I start it shouldn’t come on.  I want to make sure I know which ones turn it off.  The scary thing to me isn’t losing the gps, but I also have the remote audio panel.  I actually wish I had a normal audio panel and a remote transponder as I think that’s easier to deal with if you lose it. I’m glad it reset for you, and that you weren’t ifr or in a class B/C!

This is the biggest reason I decided to burn the real estate on a non-R GTX and a non-R GMA.

I didn’t have exactly the same situation as OP, but my GTN once went blank and rebooted while on a long XC flight. It probably took about 10 seconds total, but it felt like 10 minutes. It never happened before or since, and the avionics shop kind of shrugged. I chalked it up to a dodgy software release, and felt better with the next one. 

[Ragsf15e]

13 minutes ago, toto said:

This is the biggest reason I decided to burn the real estate on a non-R GTX and a non-R GMA.

I didn’t have exactly the same situation as OP, but my GTN once went blank and rebooted while on a long XC flight. It probably took about 10 seconds total, but it felt like 10 minutes. It never happened before or since, and the avionics shop kind of shrugged. I chalked it up to a dodgy software release, and felt better with the next one. 

Yeah, im really happy with the panel the previous owner put in, but a physical audio panel seems like a good thing.  Losing gps and transponder is fine if you can tell atc about it, heck, I have com/nav 2!  But the inability to select comm/nav2 would be frustrating.

[Oscar Avalle]

9 hours ago, William Munney said:

All:

 

Anyone with experience or hear a tale of the Garmin GTN 750 freezing in flight?  We were VFR.  Tried to switch frequencies and the touch screen was completely un-responsive.  So, Com 1, Nav 1, Audio panel and transponder……Kaput!  Tried everything on the touchscreen.  Even HOME.  Nothing.

Pulled the CB for Nav1/ Audio.  Reset it.  No problems the remainder of the day.

 

 

Yes, happened to me too. I pulled the CB and it came up again. Since then no issues. Scared the heck out of me. Must be a software issue. 
 

[Pinecone]

I have my two GTN CBs collared to quickly ID.

One thing I have hear of people doing is wiring the audio panel so that Com 2 is wired as Com 1.  The panel defaults to connect the pilot to Com 1 when there is an issue.  So you would actually be on Com 2.

[76Srat]

48 minutes ago, Pinecone said:

I have my two GTN CBs collared to quickly ID.

One thing I have hear of people doing is wiring the audio panel so that Com 2 is wired as Com 1.  The panel defaults to connect the pilot to Com 1 when there is an issue.  So you would actually be on Com 2.

Interesting theory, PC.  I'd be curious, however, to see how many annuals would get that wiring setup squawked by an IA for not being "i/a/w certification", etc.  I could see several not signing off on that setup unless there's an approved published alternative in the installation process.  Just thinking out loud here . . .

[William Munney]

All good ideas.  I thought the remote transponder and audio was fantastic until a few days ago.  I didn’t get to fully explore what was available for coms with the frozen screen because I quickly tried everything on the screen……(No OFF button on the unit)…..and the pulled the CB and reset.  I did 3 different approaches that day to different airports so lots of comm changes, flight plan changes, VNAV profiles etc.  No problems through the rest of a busy day that gave it a real workout..

I was VFR practicing multiple instrument approaches with a new GFC-500.  IFR would be a bigger deal. The GPS was still working in there, I had a magenta line and a GPS roll mode but I was unable to do anything on the touchscreen.  That’s flight plan, Com 1, Nav1, Audio Panel, Transponder.

Next time in there, i will pull the CB on the ground and see if it auto-fails to comm 2….which would be nice.  If not, I will have to look into seeing how that can be done.  I always have the handheld radio and a bunch of batteries.

 

Edited March 25 by William Munney

[Pinecone]

On 3/25/2025 at 9:27 AM, 76Srat said:

Interesting theory, PC.  I'd be curious, however, to see how many annuals would get that wiring setup squawked by an IA for not being "i/a/w certification", etc.  I could see several not signing off on that setup unless there's an approved published alternative in the installation process.  Just thinking out loud here . . .

Where does the approved info say which radio is Com 1 and which one is Com 2???????

[jetdriven]

That’s obvious,, COM 1 is always the one with the biggest screen 

[Pinecone]

????

Both of mine are on the REALLY big screen.

 

[Max Clark]

On 3/25/2025 at 7:29 AM, Pinecone said:

I have my two GTN CBs collared to quickly ID.

One thing I have hear of people doing is wiring the audio panel so that Com 2 is wired as Com 1.  The panel defaults to connect the pilot to Com 1 when there is an issue.  So you would actually be on Com 2.

Just went through this on my install (GTN 750xi, GNC 215, GMA 35c)

The coms are wired to the GMA "backwards" (com 2 to GTN, com 1 to GNC) and then in the configuration on the GTN inverted for the display.

If the GTN fails the GMA failsafe connects the pilot to com 1.

This is the normal installation.

[EricJ]

The latest, Mar 2025, issue of IEEE Spectrum magazine, the professional society magazine for Electrical Engineers, has an article on "Bring Back Buttons", about how the trend in user interfaces is now swinging back to having buttons instead of solely touch-screen controls.  I think a decade or two of touch screens has taught us some things.   I've never liked the idea of being dependent on a single touch screen for controlling an integrated system, so maybe the interface design pendulum swinging back to buttons to will solve some of these issues.  Of course, that doesn't eliminate the possibility of software failures, but I think it'll help some things.

 

[Pinecone]

On 3/27/2025 at 10:34 AM, Max Clark said:

Just went through this on my install (GTN 750xi, GNC 215, GMA 35c)

The coms are wired to the GMA "backwards" (com 2 to GTN, com 1 to GNC) and then in the configuration on the GTN inverted for the display.

If the GTN fails the GMA failsafe connects the pilot to com 1.

This is the normal installation.

I will have to check with my shop.  I don't have a GMA but I think the PS 450B will do the same

[Max Clark]

Good reminder for me to test this with the CB next flight.

[TCC]

When it happened to me on a night flight, the unit was actually heat soaked and it overtemped. Avionics fan failed.

Luckily, this was shortly after takeoff and before established on flight following. Did the CB pull thing once; didn’t solve the problem. We just stayed VFR and went back home.

[76Srat]

On 3/26/2025 at 8:50 PM, Pinecone said:

Where does the approved info say which radio is Com 1 and which one is Com 2???????

I know, I know.  I cringed right after I posted that.  I was (stupidly) trying to think like an installer and forgot its as simple as designating which is which.  My bad for overlooking a simplicity amidst what is usually Medusa's headdress of compliance BS.  

 

 

[Pinecone]

NP, it happens.

 

[moosebreath]

Once on an IFR departure, never happened again in ten years.  Always good to have alternatives setup and operating in critical phases of flight.

[Ragsf15e]

On 3/27/2025 at 7:34 AM, Max Clark said:

Just went through this on my install (GTN 750xi, GNC 215, GMA 35c)

The coms are wired to the GMA "backwards" (com 2 to GTN, com 1 to GNC) and then in the configuration on the GTN inverted for the display.

If the GTN fails the GMA failsafe connects the pilot to com 1.

This is the normal installation.

I was interested in this, and it deserves a bit of investigation…

The previous owners installer did a very nice wiring diagram, so I can see that my gtn 750xi is in radio 2 on the gma 35.  My gnc255 is wired into radio 1 like yours.  So far, so good.  However, when I simulated the gtn “freezing” by pulling the circuit breakers, nothing happened (I was stuck on the inop gtn comm radio) and I had no comm and no way to select “comm 2” (wired as comm 1).  Now I’m thinking (but haven’t tested), that if the gtn freezes, you might need to pull the gma35 cb in order to get it to “fail” back to comm 1 (which is actually your other radio).

Have you tried this on your setup?

[Max Clark]

I have not, but I will when I have time

[Ragsf15e]

On 6/3/2025 at 1:04 PM, Max Clark said:

I have not, but I will when I have time

So i tried this morning after flying.  I selected comm 1 and set comm 2 radio on atis.  I then pulled the CBs for comm 1 (gtn750).  The audio panel didn’t auto switch to comm 2.  So I pulled the audio panel cb… no luck.  Can someone else who has comm 1 wired as comm 2 see if their remote audio panel will switch over when the GTN fails?