Autopilot went on strike

[dkkim73]

Hi All,

While down at the Mooney Pilot Proficiency Program last weekend, my AP went offline early on (during the VFR part) and wouldn't come back on despite recycling multiple times. I get a PTRM red flag on the PFD, and the aux page seems to show no comms or a problem with the pitch trim servo. Please see attached screenshots. Unit is a GFC 700. 

While it made for hours of great training (including on the IFR flight home :|), the AP is a big safety element in this plane so I'm eager to get it fixed.

Other data:

- I found the switch cluster on the left horn of the pilot yoke quite loose recently, in fact I tightened it a day before all this (the AP worked in the meantime). I went back and took it apart (no way the tightening affected the trim switches, they click normally, esp. after some contact cleaner). 

-when I first got the plane, the factory annual/pre-buy found the clutch untis on PITCH TRIM
and ROLL out of spec (despite adjustment) and so they installed "new old" stock GSM 85's they had that were lightly used off an engineering bird, part described as GSM 85 PITCH TRIM/ROLL SERVO MOUNT 011-00894-09. So the servo unit itself remains original, high 1500 hrs right now. 

- also went back and checked the bayonet connector (to pitch trim servo), cleaned and re-seated. 

No joy. The local avionics shop is going to come by this week (they're kinda busy) and troubleshoot; specifically their Garmin-whisperer. Sounds like they can interrogate the servo unit for more particulars than I can see from the Aux page. 

 

Thinking I'm headed towards a servo unit swap/overhaul/replacement, but would appreciate any recent experiences or insights. 

Thanks,
David

 

Edited June 10 by dkkim73
fixed image rotation

[Fritz1]

I had a sticky trim switch in the KFC225 a couple of weeks ago, the left half that energizes the trim servo clutch did not zero by itself any more, easy to check, wiggle the trim switch up and down after the error message comes up, a stuck AP disengage switch or a stuck CWS switch may cause that error, too, not familiar with the GFC700 though 

[dkkim73]

Hey all, 

Quick update and urgent question: 

Servo tested bad, the local Garmin dealer got an overnighted unit (GSA-81) but apparently when they went to get 401.37 software from the Garmin dealer site, it wasn't available. I got an email just now "when I went to the Garmin DRC to grab this system’s S/W, I saw that Garmin only has up to v 401.34.  Apparently, last April, Mooney rescinded S/W v401.37, making Garmin take it OFF the DRC." He's looking for a release letter from Mooney to allow him to get the SW from Garmin, or someone to send him that software. 

I reached out to a Mooney avionics guy in TX, wondering if any of you have dealt with this problem and why in the world Mooney would restrict Garmin's general distribution of this SW? I can see steering business to Mooney centers, but limiting only certain SW versions seems a recipe to unnecessarily AOG planes...

Thanks for any help,

David

Edit to clarify: The plane's already at 401.37, done at the Mooney factory service center in Feb 2024. So it's a matter of updating the servo to "fit in". I've never heard of a recall of the 401.37 software, so no idea why this is an issue at all. 

[dkkim73]

Nevermind. Talked to Brian Kendrick, who straightened me out. Turned out that the paid upgrade involves access including an SD card placed with the AFM (POH). It's coming back to me now. Still odd that authorized dealers don't have separate access for maintenance, but oh well. 

[dkkim73]

Update (since it sounded like the above was confusing to at least one person): 

The update to 401.37 was paid (by me) and they put a copy of the loader files for all the Garmin LRUs on an SD card with the AFM. So we found what we needed today after a little digging. 

What is apparently strange (and relevant) is that many manufacturers do not restrict this, so Garmin can provide up-to-date software directly to the dealers. But some manufacturers, incl. Mooney, and apparently recently Textron, do not. Apparently Mooney told Garmin last April to not include this on the dealer resource site.  Which dealer resource site can be used by authorized servicers, E.g. my local dealer today who was trying to update the servo to match my existing installation. 

So.... the issue my installer pointed out is that, if the card isn't available or gets lost, it requires the manufacturer in the loop to sell (or in my case generate) a new. He had the same problem a few years ago when Mooney were inactive. FWIW no one picked up the phone when I called for technical support today. So a potential snag, FYI for others. 

Luckily, all is now updated and installed and tested. No post-mortem as the old servo didn't respond electrically at all, and it's on its way back to the mystical place called "Olathe" where it  will judged by the Great LRU and be reborn again. Or that's what I recall from my Garmin course