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  #21  
Old 09-13-2022, 04:57 PM
FireMedic_2009 FireMedic_2009 is offline
 
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Mark’s plane has an xCruse and the electric elevator trim is not controlled by the AP. After he recovers he finds the elevator trim is in the full up position. Not sure why it’s happening but maybe it has to do with what was mentioned regarding the problem with the blackhawks. Is it possibly 5G interference which I think came online earlier this year?
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Last edited by FireMedic_2009 : 09-13-2022 at 05:04 PM.
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  #22  
Old 09-13-2022, 05:13 PM
kovacjd kovacjd is offline
 
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There is an interesting Lockheed facility in the vicinity. I don’t know what it is. Probably just a coincidence thing. It’s ‘pointed’ at DEARY…
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  #23  
Old 09-13-2022, 05:46 PM
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RV7A Flyer RV7A Flyer is offline
 
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Quote:
Originally Posted by FireMedic_2009 View Post
Mark’s plane has an xCruse and the electric elevator trim is not controlled by the AP. After he recovers he finds the elevator trim is in the full up position.
OK, so the A/P is on, 2-axis mode, holding altitude via the pitch servo, right?

So what is he "recovering" from?

ETA: Never mind, I think I get it...something ran his pitch trim full nose up while on A/P, the A/P couldn't hold it anymore and disconnected, at which point the plane shot upwards, as one would expect.

The original post was just poorly written, that's all...I had trouble figuring out how many times this happened, what was going on with the A/P, etc. I see it now.

As to *why* the trim tab was run to full or nearly full nose down, heck, I dunno...your guess is as good as mine, but I'd look for simple things first: chafed wire or bad switch.
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Last edited by RV7A Flyer : 09-13-2022 at 05:56 PM.
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  #24  
Old 09-13-2022, 05:57 PM
Canadian_JOY Canadian_JOY is offline
 
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Quote:
Originally Posted by RV7A Flyer View Post
OK, so the A/P is on, 2-axis mode, holding altitude via the pitch servo, right?

So what is he "recovering" from?
He is recovering from a runaway trim condition. The trim in some aircraft can overcome the strength of the autopilot servos and cause them to disengage. We don't have a full enough description of symptoms to know if this is the case, but we do know the pitch trim ends up being in the full-nose-up position. Since the autopilot and trim systems are not interconnected in any way we can remove the autopilot from our consideration of potential causes.

I also have an XCruze - or rather Trutrak Vizion 385 autopilot and Ray Allen electric trim motor in my aircraft. I have very carefully wired my aircraft, paying particular attention to shielding, BUT the 5-wire trim cable is not shielded, thus I am very, very wary of any potential for externally-induced trim movement.
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  #25  
Old 09-13-2022, 06:18 PM
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Quote:
Originally Posted by Canadian_JOY View Post
He is recovering from a runaway trim condition. The trim in some aircraft can overcome the strength of the autopilot servos and cause them to disengage. We don't have a full enough description of symptoms to know if this is the case, but we do know the pitch trim ends up being in the full-nose-up position. Since the autopilot and trim systems are not interconnected in any way we can remove the autopilot from our consideration of potential causes.

I also have an XCruze - or rather Trutrak Vizion 385 autopilot and Ray Allen electric trim motor in my aircraft. I have very carefully wired my aircraft, paying particular attention to shielding, BUT the 5-wire trim cable is not shielded, thus I am very, very wary of any potential for externally-induced trim movement.
Yeah, I got it...it was just a badly written description...even confused some others when he talked about pulling the trim motor CB...it read like he pulled it *before* the next event, and that had no effect. (see post #13 para 2).
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  #26  
Old 09-13-2022, 09:25 PM
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Quote:
Originally Posted by kovacjd View Post
There is an interesting Lockheed facility in the vicinity. I don’t know what it is. Probably just a coincidence thing. It’s ‘pointed’ at DEARY…
That's an odd-looking building and I can't find any information on it. As much as I love a good conspiracy theory, I think that building is shaped more as a firing range than some odd antenna. Next time I fly back from Melbourne I'll definitely have video rolling and figure out everything I can about the "event". At least pinpoint the location.
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  #27  
Old 09-13-2022, 09:43 PM
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Quote:
Originally Posted by FireMedic_2009 View Post
Is it possibly 5G interference which I think came online earlier this year?
5G comms are way too low power to induce currents powerful enough to run a trim motor, even if the wires were tuned to the right length to receive the signals.
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  #28  
Old 09-13-2022, 10:51 PM
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fl-mike fl-mike is offline
 
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Quote:
Originally Posted by kovacjd View Post
There is an interesting Lockheed facility in the vicinity. I don’t know what it is. Probably just a coincidence thing. It’s ‘pointed’ at DEARY…
Antenna test range.
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  #29  
Old 09-14-2022, 10:21 AM
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RV7A Flyer RV7A Flyer is offline
 
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I'm going to make another observation here that is going to seem harsh, but is not intended to be, so bear with me.

It seems that the OP wasn't adequately knowledgeable about his A/P and trim systems. He didn't know that the A/P had no autotrim function, so doesn't "know" anything about the trim settings, and he didn't know that his trim system used a RAC motor with a pushrod but instead thought there was a spring. And, he probably didn't realize the amount of force necessary in an RV to overcome a full pitch up or down trim setting at cruise speeds, nor the proper recovery from such a scenario.

All of this points, IMO, to a lack of training in the type of aircraft, the specific aircraft, and the aircraft systems.

I don't mean to bag on anybody, but I've been thinking about this a bit. His trim went to full nose up for whatever reason TBD while the A/P was on during cruise, and the A/P did precisely what it was designed to do, which is to disconnect the pitch servo when it exceeds the torque limit. The resulting nose up could have been easily corrected by simply trimming back to level flight (perhaps after slowing down), but instead he fought the system for some time, even going so far as to pull the breaker which then *removes* the ability to restore trim (it had already run away to the limit, it can't go any further, so pulling the breaker is ineffective at best).

Granted, it was a new airplane to him, but I suggest some time with an instructor and some serious digging into the avionics manuals is in order, along with diagnosing the root cause here.

Sorry if this sounds harsh...as I said, it's meant to be helpful, not critical.
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  #30  
Old 09-14-2022, 09:18 PM
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markserbu markserbu is offline
 
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Quote:
Originally Posted by fl-mike View Post
Antenna test range.
I assume you're just kidding around? I mean, the "event" has happened to me 3 or 4 times in the same location so it's obviously not a coincidence. On the other hand, it could be a time thing...climbing Westbound out of Melbourne for a given amount of time would tend to put me in the same area. But then why doesn't it happen climbing out of every other airport?
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