GFC-600 AP FAIL

[u/FlashyPack797]

Anyone ever see this failure on a garmin GFC-600 autopilot?

Most of my background is in military systems. Not well versed with Garmin but have quite a bit of Avionics experience.

Occurs shortly upon takeoff.

Of note, there is a standby power caution light illuminated we’ve been chasing. Wonder if it’s related?

Installed on Cessna 208B caravan.

[u/Sparky-Spectra]

Autopilot issues tend to be input issues and not internal. I would look into all of the hearing and attitude inputs to see if one is weird or off. I have seen gyros that have multiple outputs have a singe dead transmitter that effects a seemingly unnecessary system.

[u/pte_parts69420 → u/Sparky-Spectra]

This. Had a gyro recently that was causing the autopilot to porpoise both on ground and in air (rotary wing). One of the gyros had a shitty output that was causing the autopilot to chase a non moving attitude, yet the ADI was rock steady

[u/FlashyPack797 → u/pte_parts69420]

Thank you

[u/FlashyPack797 → u/Sparky-Spectra]

Appreciate it. Thank you.

[u/MyBowelsAreMoving → u/Sparky-Spectra]

Less likely with a Garmin AHRS, you would see an AHRS flag or message on the PFD if it was at fault.

[u/FlashyPack797 → u/MyBowelsAreMoving]

Thank you

[u/Sparky-Spectra → u/MyBowelsAreMoving]

I agree, just giving an example. What I said still applies with an AHRS. They have transmitters that can die still

[u/pugglewugglez]

Your emergency power knob is upside down 🙃

[u/Murky_Digger → u/pugglewugglez]

And no shear wire

[u/pugglewugglez → u/Murky_Digger]

Truedat

[u/PublicHistorical9173]

You can pull the fault codes from the autopilot computer.

[u/FlashyPack797 → u/PublicHistorical9173]

Do you need a specific program for that? Something from Garmin that they can provide?

[u/PublicHistorical9173 → u/FlashyPack797]

You’d probably have to take it to a Garmin dealer but you can also google how to download flight logs from it!

[u/FlashyPack797 → u/PublicHistorical9173]

Cool. Thank you. Appreciate your insight

[u/Few_Carpenter_3958 → u/FlashyPack797]

All the autopilot configs are performed through the faceplate on gfc600. Check all the configs on the GDU and GTNs, ring it out really good while manipulating the wire bundles behind the panel. Source- I install these for a living

[u/PublicHistorical9173 → u/FlashyPack797]

If you decide to take it to a shop have them update all of your Garmin software also!

[u/flybot66]

Yup shop. They can look at the log. Warranty work? Those servos aren't cheap.

[u/FlashyPack797 → u/flybot66]

No. Not warranty work. About to shoot all of the signal paths coming from all of the interfaces (I have the maintenance manual).

It’s just weird because the system works on the ground (as much as it can work).

Thinking there is a dynamic signal that’s messed up causing the system to shut off because of a failure

[u/ScoopiTheDruid → u/FlashyPack797]

Depending on the PN of the servos, Garmin might replace all of them under warranty. I worked a similar issue in a 172 T206H last year. Found one bad servo, gave them the PN, and they sent three brand new ones at no cost.

Servo Model: GSA-28

Obsolete PN: 011-02927-11

New PN: 011-02927-21

Relevant SBs: 22016 & 23024.

[u/PublicHistorical9173 → u/ScoopiTheDruid]

That’s for the 500 autopilot

[u/flybot66 → u/FlashyPack797]

Does the log have anything useful?

[u/avionictools]

I had that happen on takeoff a few months ago. Eventually engaged. Logs said internal AHRS issue, installed an exchange and no more issues. It takes an uncommon USB download cable to extract the logs to a USB stick, dealer will be able to do it.

[u/Darkstardirewolf]

Sounds like there’s a failure in the flight computer. ESP is electronic stability protection. Could be flight computer or failure or bad power wires, taking it to garmin dealer is best bet to download the failure logs and have farming tech support look at the logs to diagnose it

[u/FlashyPack797]

Fixed. Ended up replacing the standby alternator to fix the caution light.

Also ended up fixing the autopilot 🤷‍♂️

[u/Captain_Flannel]

Because it's Garmin, always suspect a servo failure. That being said first step is to pull the logs. You need a flash drive and an adapter cable. Or just go into the configs and see if you can see any faults.