Multiple electrical failures - linked?

[JRam]

So I had an interesting flight today. BLUF: Can these all be related to a simple wire crossed?

Let me start with the history:

I've had the plane for a couple months now and prior to picking it up had a GTN 750, GMA35C, GNC 255A and GTX 245. I've had some issues with the pilot PTT on the ground, but could usually solve it by pulling on the yoke and never had a problem in the air. Also had a loose connection at the jacks.

Fast forward to today: Working on my commercial with this instructor for the first time. I call for clearance and get no response. Instructor says he will just make the calls (his headset had issues by the way, where he could talk but only I could hear at times. Solved this by giving him a backup eventually, but it caused further frustrations) and we take off. As we leave the DC SFRA, we constantly are struggling with comms. Pilot PTT still not working and all of a sudden the autopilot registers a TRIM error and my electric trim (located right next to my PTT) isn't working (both tested out on the ground prior to flight and electric trim was used to trim for takeoff) and I'm forced to pull the A/P breaker. Then, instructor asks me to turn off the ATIS, it wasn't on, it was on the #2 Comm which wasn't being monitored. I couldn't hear it, he could. Then I started monitoring #2 and switched the ATIS to the secondary on Comm #2 and ground on the primary. We could still hear the ATIS. 

In summary:

Pilot PTT not working
Electric Trim not working causing autopilot error (I think)
Audio Panel sending #2 Comm to ONLY co-pilot headset when not monitored
#2 Comm sending backup radio frequency comms when #2 monitored

GTN 750 working fine and checked that all audio panel settings set properly.
All other electrical seemed to be working.
Resetting the A/P circuit did not help.
Verified instructor wasn't messing with me, although he got very frustrated when I was trying to switch to VFR freq since he didn't hear the radio call amongst other things.

[DanM20C]

Justin,

First I would crawl under the panel and look closely for any wire bundles that interfere with the flight controls.  The problems may not be related but it sounds like your  ptt wire is partiality broke someplace it is interfering with the flight controls.  If there is a bundle pinched off someplace, moving it and wire  tiying it off may fix the problems temporarily but you will want an avionics guy to get in there an clean everything up.

Remember when I flew with you I thought my Bose X were toast. I haven’t had a problem with them since, over a dozen other airplanes.  So the copilot headset jack problem was likely there the whole time.

Good luck!

Dan

[JRam]

@DanM20C that's right, I forgot about that. 

I'll check out those bundles. It's probably the same bundle as the trim and may be causing issues with that. I could feel some wires tied to the control shaft as well, seemed strange to me but maybe its pulling the wires out somehow.

I'm starting to think I need to just put you on retainer for all my aviation needs! 

[Yetti]

What Audio panel?

Picture of yoke.

Edited November 26, 2018 by Yetti

[JRam]

My audio panel is a behind the panel gma 35C, controlled on the GTN750 reviewing my books to see how to turn off the audio panel.

Included are a couple pictures of the controls. These aren't from my plane, but exactly what it looks like. PTT is on the "trigger" side.

[Yetti]

So I take it that you had these installed prior to picking the plane up?    Should not installer help you with the warranty work?   Separate things out.  

Sounds like there is a wire loose between the GTN750 and the GMA35c.  Which would cause the CoPilot switching to Comm 2

The PTT operates on a signal to ground. Check for a broken wire/ loose ground/ between the PPT switch and audio panel

The Trim switch.   Know to go bad at the switch.   May have just choose to go south to take you off track.  Or it may be a signal to ground and on the same loose ground wire, just follow from the yoke tube.   Seems like the copilot may not have a good ground on the PTT also.    May have forgotten to tighten the airframe ground screw and it is slowly vibrating out.  

[JRam]

2 minutes ago, Yetti said:

So I take it that you had these installed prior to picking the plane up?    Should not installer help you with the warranty work?   Separate things out. 

Yes, I had them installed right after the pre-buy/annual. Very respectable shop and I'm absolutely sure they would jump in and look it over, but it's about a 4 hour flight in the 231 to get there. It's best case annoying to fly as is, worst case is that whatever is going on would continue to degrade and affect more important parts of the electrical system.

Any idea if I could get access to that ground screw without taking off the panel?

[Yetti]

Trace the wires coming out of the yoke tube.  At least one should go to ground.  There should be one wire on each yoke tube that goes to ground.   Some One place to ground things to is the skin.   There might be a bar to mount things to about 3" below where the audio access panels are.   Not sure if you have the little ones below the front edge of the windshield.

I would call and ask the shop where they like to ground things to.

[larryb]

I think some of your problems are related to unfamiliarity with the new radios:

problem:

#2 Comm sending backup radio frequency comms when #2 monitored

Feature, from Garmin description:

With the standby frequency-monitoring feature in the GNC 255, you won’t have to worry about missing an ATC call or other critical transmission.

Many modern radios have the ability to monitor the standby frequency and the active frequency simultaneously. I expect your #2 was in this mode.

I think the audio panel problems could also be a mode issue. I'd sit down with the manuals in the aircraft, with the aircraft on a ground power supply and get familiar with all of the equipment.

The PTT problem sounds like you need to go back to the avionics shop. It often takes a few trips back to the shop after a big install to get all the gremlins figured out. This is why it is best to have a local shop, not 4 hours away. 

Finally, I think the trim problem is unrelated.

Larry

[JRam]

Thanks @larryb , I did think that could be the case and checked my settings. But it wasn't that #2 was being monitored, it was that the second freq on comm #2 was coming through. I had tower and approach freqs in on comm #1 and ground and ATIS freqs on comm #2. ATIS was on on the standby. I could be wrong, but that shouldn't be a feature. I should be able to monitor both comm 1 and comm 2, but the standby freq shouldn't play.

Its confusing to explain via text,  so hopefully that clears it some.

As far as local shops, I miss Texas. So far after taking the plane to anything local to me, it seems like no one in the DC area wants the work. 3 different places so far and none even put forth even a trivial effort in to getting us in to the shop. 

Annnd...I was very wrong. I'm wondering if the keying was actually messed with and it was in monitoring. Still not sure why he was able to hear when not monitoring #2, but you guys may have something on the split comms...

"The MON (Monitor) key will engage the monitor function where the Standby frequency may be monitored while still listening to the Active frequency."

Edited November 26, 2018 by JRam

[Marauder]

I think some of your problems are related to unfamiliarity with the new radios:
problem:
#2 Comm sending backup radio frequency comms when #2 monitored
Feature, from Garmin description:
With the standby frequency-monitoring feature in the GNC 255, you won’t have to worry about missing an ATC call or other critical transmission.
Many modern radios have the ability to monitor the standby frequency and the active frequency simultaneously. I expect your #2 was in this mode.
I think the audio panel problems could also be a mode issue. I'd sit down with the manuals in the aircraft, with the aircraft on a ground power supply and get familiar with all of the equipment.
The PTT problem sounds like you need to go back to the avionics shop. It often takes a few trips back to the shop after a big install to get all the gremlins figured out. This is why it is best to have a local shop, not 4 hours away. 
Finally, I think the trim problem is unrelated.
Larry

I agree with Larry on the #2 radio monitoring. Both radios have a monitoring feature. In order for the co-pilot only to hear the #2 radio, the comms need to be in split mode and the 255’s monitoring feature is turned on. With the 35, check to see if the pilot and co-pilot comms are split. If they are and both radios were set to the same primary frequency and the 255 was set to monitor, he will hear the ATIS and you wouldn’t hear anything.


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[JRam]

Fair enough, I'll recheck. The split mode was what I checked the settings for, but maybe I overlooked it somehow. It's weird that it would have changed all of a sudden, unless the instructor changed things when I was focused on something else which is possible.

[Yetti]

1 hour ago, JRam said:

Fair enough, I'll recheck. The split mode was what I checked the settings for, but maybe I overlooked it somehow. It's weird that it would have changed all of a sudden, unless the instructor changed things when I was focused on something else which is possible.

Not sure if the garmin has it, but some features (like com flip flop or switching to com 2) can be remote controlled.  Usually (with the PS Engineering)  That is done by completing a circuit to ground.

[JRam]

So yeah, after hearing you guys, my guess is that the monitoring switch was hit and something happened with split comms. That's my hope anyway and that would separate that issue from the rest of them making my only concern isolated to that yoke control area. I'll check the grounding and wires as you all pointed out.