Question Avionics Circuit Breaker Switch Fail

[lrobichaux]

2024 NXCub with IFR panel. This past weekend after a 45 min flight in pretty warm weather, avionics circuit breaker switch failed to engage after starting back up to head home. Tried resetting breakers but no joy. On the short flight back to my home field everything driven off the avionics switch was inop, including all comms, transponder, and ADS-B. After plane cooled off overnight, switch worked. We’ve concluded that the CB switch is weak and needs replacing. Let me know if you have any thoughts on that, but it’s not my main question.

After noticing just how many key systems go offline with an avionics switch failure, I became concerned that this is a major risk area. Both comms failed. Transponder failed. ADS-B in and out failed. I understand that most Garmin LRUs can accept multiple power sources, and I further understand that the IBBS can be connected to more than one device. As delivered from CC, the IBBS only drives the G3X and no other LRUs. Has anyone researched connecting the IBBS to additional key systems? I realize that this will theoretically drain the IBBS faster in an actual failure, but frankly the loss of all comms is a major concern. Alternatively, does any know any reason that a second IBBS cannot be installed?

 

[Neal]

Wow, now I wonder if I need to consider breakers in my spares kit. I think I may review the sizes and order a few different sizes. Again, being in the backcountry or a cross-country and having a failure like this could strand you. My mobile snap-on tools cub to the rescue

Sorry to hear you had this. Having the IBBS power more sure seems like a nice idea. First, I hope the failure wasn't caused by something as that's typically why breakers pop as we all know. But replacing it is an easy initial triage from a non AME opinion. Maybe reach out to CC (Pete) and get his opinion but I think you're on the right path.

Another reason I choose not to fly my cub IMC. Too much experimentaling going on here.

 

[Neal]

Okay, so it wasn't a breaker but a switch? I didn't see an AV breaker on my panel in reviewing breaker sizes for spares. Also remove the GDU (G3X) and check the security of all screws going into breakers/switches and all spade connections that you can access. I wire terminal came off of my IBBS breaker that took me 6 months to find the cause of the IBBS alert on my G3X as the screw backed out. I finally found a wire dangling behind the panel. A screw dropped and I found it on the floorboard months prior which I saved but never knew where it came from.

 

[lrobichaux]

Okay, so it wasn't a breaker but a switch? I didn't see an AV breaker on my panel in reviewing breaker sizes for spares. Also remove the GDU (G3X) and check the security of all screws going into breakers/switches and all spade connections that you can access. I wire terminal came off of my IBBS breaker that took me 6 months to find the cause of the IBBS alert on my G3X as the screw backed out. I finally found a wire dangling behind the panel. A screw dropped and I found it on the floorboard months prior which I saved but never knew where it came from.

Correct. The failure was the avionics switch which has an integrated 10A circuit breaker. Great suggestion to check the terminal connections behind the panel. I also think it would be a great idea to buy some spare breakers and CB switches. Would you mind sharing your list of what you intend to order? But the bottom line is that I've got to figure out some modifications to provide some redundancy for the critical systems that went offline when the avionics switch failed (i.e., single point of failure).

 

[Neal]

Right now I have a few breakers in my cart from the link below. I have some spares in the hangar I have to check first as I did some upgrades that required some breaker upsizing so I have to see what I have. I wonder how often these fail though. Your issue may just be the usual crimp or spade issue we all suffer in these planes. I had a wingtip nav light quit working, it was a crimp problem.

Tyco Circuit Breaker W23 Series | Aircraft Spruce ®

Tyco Circuit Breaker W23 Series These bi-metallic single pole breakers weigh less than 2 oz. and are especially suitable for homebuilt aircraft. Used as original equipment in Beech, Cessna and Piper aircraft.

www.aircraftspruce.com

 

[lrobichaux]

Right now I have a few breakers in my cart from the link below. I have some spares in the hangar I have to check first as I did some upgrades that required some breaker upsizing so I have to see what I have. I wonder how often these fail though. Your issue may just be the usual crimp or spade issue we all suffer in these planes. I had a wingtip nav light quit working, it was a crimp problem.

Tyco Circuit Breaker W23 Series | Aircraft Spruce ®

Tyco Circuit Breaker W23 Series These bi-metallic single pole breakers weigh less than 2 oz. and are especially suitable for homebuilt aircraft. Used as original equipment in Beech, Cessna and Piper aircraft.

www.aircraftspruce.com

Thanks! I'll report back after I check the connections later in the week.

 

[lrobichaux]

Right now I have a few breakers in my cart from the link below. I have some spares in the hangar I have to check first as I did some upgrades that required some breaker upsizing so I have to see what I have. I wonder how often these fail though. Your issue may just be the usual crimp or spade issue we all suffer in these planes. I had a wingtip nav light quit working, it was a crimp problem.

Tyco Circuit Breaker W23 Series | Aircraft Spruce ®

Tyco Circuit Breaker W23 Series These bi-metallic single pole breakers weigh less than 2 oz. and are especially suitable for homebuilt aircraft. Used as original equipment in Beech, Cessna and Piper aircraft.

www.aircraftspruce.com

One other question. How do you access the area behind the panel? Is it only accessible by removing the G3X and the other panel mounted units? Or can you also remove the glare shield and access from above?

 

[Neal]

One other question. How do you access the area behind the panel? Is it only accessible by removing the G3X and the other panel mounted units? Or can you also remove the glare shield and access from above?

All I know of is removing the GDU (G3X display). You can see most from there and underneath after some yoga stretching You could use a mirror to inspect as well. The row of switches at the top can all be easily inspected with the GDU removed.