CubCrafters FX-3 issues

[Hunter]

I took delivery of my FX-3 in late March 2023 after the factory accomplished the 40-hour fly-off for me. Since then, I’ve put around 190 hours on the plane, the majority of which being comprised of sandbar and riverbed flying with some extended three to four-hour trips mixed in there.

The plane has been great, and it’s only somewhat recently that I’ve acquired a collection of issues that has me completely stumped. Initially, I thought these were minor isolated issues, but I looked at my g3x data recently, and now I’m concerned I may have a more significant problem.
I live and fly the plane in the southeast, so hot and humid, but it’s always been hangar kept.

Timeline
1. July ‘23- Oil Temp had always remained around 190 degrees; however, at the beginning of a three-hour flight, the oil temp oscillated fairly quickly between 190-225, with no change to oil pressure. I land and reseat the oil temp prope connections. After taking off again, the temp is running high but within limits (maintaining 195-210), about 10-15 degrees above expected but rapid oscillations stop.

2. The mixture cable spring that gives the knob detents when pulling out or pushing in breaks. The mixture knob isn’t freely moving, but it makes precision settings difficult when bumping around.

3. Nov ’23- Condition Inspection goes well. The oil and filter have been changed every 30-40 hours of flying with no issues noted.

4. March-April ’24- I begin noticing that my Strobe switch isn’t on mid-flight. Initially, I thought I was forgetting to turn it on, but it was around this time that I first saw the Strobe switch trip off during climb out. Very rarely, I will notice a brief dip to zero amps, followed by a rapid recovery of amperage (maybe a second at zero, if that).

5. Apr 23 ‘24- Due to the oil temp showing 15 degrees higher than ambient when turning on the IBBS (cold aircraft). I order a new oil temp sensor from Cub Crafters and have it installed by one of their Service Center mechanics. We also perform a thorough inspection of the aircraft and replace the mixture cable (Erroneously high oil temp reading is fixed).

6. Apr 23rd thru 30th- over the course of eight hours or so of flying, everything goes well. Oil Temp is back to 185-190, no oscillations; however, I begin to see the Strobe switch trip off more frequently. This doesn’t happen every flight, nor does it always happen more than once per flight; its highly variable.
I can’t correlate the behavior to anything in particular. It seems to happen in the pattern more often (high AOA, high vibration, frequent movement of throttle, etc.).
*However, I’ve seen the amp behavior with the Strobe switch off, and I’ve seen the Strobes trip without noticing amps dropping. (I’ll confirm this today)

7. April 30th, '24- During my last flight, shortly after liftoff, Oil Temp skyrockets, jumping from 190 to well past the redline in rapid oscillations. 190…280…190…300… blank….260….blank… etc. After completing the flight, the temp shows 195 at shutdown. Strobes didn’t trip.
The day after the flight, I do a runup. Temp shows 150 at a warm idle; however—above 1200rpm, the oil temp resumes the behavior, immediately jumping to the red and returning to expected normal (150 in this case) at low rpm.

8. I reviewed my flight data over the past couple of months) and noticed that amps typically hold at 2, sometimes 1, but occasionally hit zero (after zero, amps jump to 2 but sometimes 5…4….3…2). Looking further into the past, it seems this started quite a while ago (at least Jan). However, occurrences are rare.

****
-Overall, I only saw the amp issue a few times on the g3x, probably because it only lasts a second or so, and most of my flying is eyes outside.
-My data logs at home for review are incomplete, and I’ll have more info once I download a complete history (e.g., when the amp drop began, changes to its frequency, what was happening at the time).
****

Considerations
Presently, I have a second, brand new oil temp sensor from CC in the event there actually is a problem with the sensor itself (this will be the second oil temp sensor replacement), but the amps hitting zero and Strobe tripping worry me.
-Could the Strobe wiring be shorting, causing the switch to trip off and interrupting alternator output (some sort of system surge to which the alternator output reacts)?
-Or is it more likely that I have an alternator issue that is shedding the Strobes?
-Or are they completely unrelated?
-Does the oil temp issue imply a greater electrical system problem?

I apologize for the wall of text, but I am a first-time aircraft owner, brand new to tailwheel and backcountry flying.
Tomorrow, I can follow up with some data logs if anyone has any ideas.

Thanks!

 

[Neal]

Sorry to hear all of this @Hunter and hope someone with experience can chime in. It sure sounds like some electrical issues going on and my initial hunch and where I'd be digging in is checking wires and crimps. When I did my TacAero training prior to the first plane I was told one of the biggest issues were crimps. In fact they had a FX-3 in the shop where wires were completely out of the crimp and they needed to figure out where they go and fix it, and they did.

On my last plane I had a 6 month saga with my IBBS showing an alert "IBBS in use" on the G3X. A screw appeared on the floor board which I saved but never put 2 and 2 together but I had the GDU out many times and checked wires on the GEA24, etc. One day I saw a pink wire dangling, it had separated from the breaker. I was actually thinking of this the other day and in my upcoming first condition inspection on the new plane I plan to pull the GDU and check breaker screws. In my recent landing light upgrade saga I became more familiar with the wiring, switches, etc. and am more comfortable being in there...moral is inspect wires at the breakers as well in your search.

My first plane had a nav light fail within the first few hours and when taking it back to CC from Hood River where I was doing the fly off Blaine found the cause was a bad crimp. So you may want to pull the nav/strobe lights out and inspect those connections as well.

The strobe lights are 12V so I don't believe the alternator is in that loop. Lift the seat and check the battery connection would be a start and then start chasing wires the best you can. I'm not sure what breaker the strobes go through off the top of my head. You may want to look at schematics if necessary, email me and I can send you the EX-3 manuals and I've used those at times to understand wiring and paths.

After talking on the phone with you a week ago I researched the oil temp issue briefly and the Van's forums had some info which pointed to an electrical issue and not a temp sensor itself as the temp won't vary that rapidly, you know this. I hope you can find this culprit, again, my IBBS saga took me 6 months to find the dangling wire even after multiple inquiries to CC for help. It's unfortunate with don't have better support resources around the country but that's the nature of the beast sadly.

 

[Cubonaut875]

I'm just thinking 190 hours in 1 year - I'm moving to
Tennessee and switching jobs to whatever it is you do

 

[FlyBigE]

Wow...any we though Boeing had issues...LOL