PTRM failure on GFC700

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agmolnar
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PTRM failure on GFC700

Post by agmolnar »

Hi all,

I am getting a PTRM (pitch trim) failure (red box) on my GFC700. According to the GFC700 manual, this can be cleared by running the pitch trim through its range of motion. However, this is not clearing the error message...

Due to the PTRM failure, the AP won't engage. (I have pulled the AFCS circuit breaker, but that hasn't helped.)

Any thoughts or suggestions before I have an expert take a look at it?

Many thanks,
Arpad
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Chris B
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Re: PTRM failure on GFC700

Post by Chris B »

Hi Arpad -

Does the trim move smoothly with the wheel, or does it "stutter"? The action should be very smooth, with no jumpiness.

A dirty friction rod/sleeve will create problems for the pitch servo, possibly inducing damage.

Chris
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T Mac
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Re: PTRM failure on GFC700

Post by T Mac »

Arpad,

I believe this is may be simply the trim switch sticking. Located under it's cover on the control stick.

T
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agmolnar
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Re: PTRM failure on GFC700

Post by agmolnar »

Hi Chris, thanks -- the wheel is spinning freely and not only that but the electric trim is working well and controlling the wheel smoothly and well.

Hi T, I suspect it may be something like this -- can the cover me easily removed, do you have further instructions on this procedure?

Many thanks,
Arpad
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Re: PTRM failure on GFC700

Post by T Mac »

Good Morning Arpad,

Very easy. From memory as I no longer have my DA40, there are two small Phillips head screws that hold the Electric Trim Switch. This switch is only the "rocker" the real switch is under this. Remove the screws and gently pull this assembly out of its pocket. The wires soldered to the switch will keep the assembly from falling out. Once you see what's going on I believe that you will be able to free up whatever is binding or preventing the proper travel of the limit (micro) switch. Then powering up your avionics will quickly confirm if the alarm is gone or not.
I hope this helps!

T
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Re: PTRM failure on GFC700

Post by agmolnar »

Well, I removed the assembly but there were no blockages or issues with it -- the trim is working properly. Oddly, the error message is now "PTCH" instead of "PTRM" - not sure of the significance of this.

Checking the AUX page of the G1000, it shows that the GSA PTCH CTL and GSA PTCH MON now have red X's (photo below). When the issue first manifested itself, these were all working properly, with is odd.

The avionics folks are advising a software re-load but that makes me nervous as I understand other issues can pop up after a re-load. I am considering monitoring this issue for a bit of time, since I have seen other G1000 gremlins come and go.

If anyone else has any advice or experience on/with this, I'd be grateful.

Best,
Arpad
pitch control.jpg
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agmolnar
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Re: PTRM failure on GFC700

Post by agmolnar »

Hi all, just following up on this. Checked the wiring harness for shorts, etc, and also had some advice that this may be a software issue but the culprit was neither of these issues.

It turned out to be a simple a pitch servo failure -- the tricky part was that it was a fault in the electronics of the pitch servo, otherwise the servo (motor, etc) was working just fine.

The frustrating part is that exactly one year ago, a new (or rather, refurbished) pitch servo was installed just before I bought the plane (during pre-buy). Garmin, bless their souls, only warranties the servo for six months. Really?

An experience like this does not make one a happy Garmin customer, at a minimum they should offer some sort of credit or at the very least let you know why the servo they just sold you failed.

If anyone has any thoughts or suggestions here vis-a-vis Garmin, I'd be all ears!

Best,
Arpad
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Re: PTRM failure on GFC700

Post by smoss »

Agreed that their warranty sucks. At least it is quick and easy to swap any Garmin item for a "new" refurbished one, and the rates are transparent. https://fly.garmin.com/fly-garmin/suppo ... f-warranty

You can either send yours in for fixing, or have a "new" one immediately sent to you, then you send them yours, same rate. I assume you got the $700 swap rate shown for the GSM 85. Actually, the Garmin repair page shows warranty as only 90 days!
Steve
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Re: PTRM failure on GFC700

Post by agmolnar »

Thanks Steve, useful Garmin link, thanks for sending. The GSA 81 was that was swapped for my GFC700 cost $900 plus markup (since you have to buy through a dealer). I hope I don't go through one of these a year, like popcorn...

Best,
Arpad
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