Garmin GFC 500 AP AD

[Brandt]

https://www.avweb.com/aviation-news/ad-mandates-garmin-autopilot-software-fix/?MailingID=1527

From Avweb:

On Oct. 6, the FAA proposed a new airworthiness directive requiring operators of thousands of aircraft to update Garmin autopilot software to address a flaw causing the autopilot to make unintended flight-control inputs.

According to the agency, the AD was issued in response to an incident involving an F33A Bonanza experiencing “an un-commanded automatic pitch trim runaway when the autopilot was first engaged.”

The proposed rule states: “The affected autopilot system software does not properly handle certain hardware failures of the pitch trim servo. This could result in an automatic uncommanded pitch trim runaway and loss of control of the airplane.”

The FAA estimates the AD would affect 5,900 aircraft equipped with the autopilot system— including Beechcraft Bonanzas, Commander Aircraft 112s and 114s, Cessna 172s, 182s, 206 and 210s, along with Daher TB20s and TB21s, Mooney’s M20 series and Piper Cherokees. However, the FAA estimates a fix will be relatively cheap for operators at around $85.

The agency is proposing operators complete the installation of the updated Garmin autopilot software within a one-year time frame. The proposed rule will be published on Oct. 10, and the FAA will accept public comment until Nov. 24.

[PT20J]

The most interesting part is that it confirms what my Garmin dealer told me that there was only on instance of a trim runaway. Even more interesting is that Garmin has sold 5900 GFC 500s. That is a LOT of autopilots.

I wonder where the FAA came up with $85? Most shops charge an hour for updating software, printing out the AFMS and completing the logbook entry. I don’t know any good shops that only charge $85/hr.

Skip

[AdamJD]

So I'm assuming those of us who have the separate issue of the GSA-28 servo warranty extension to replace impacted servos (https://support.garmin.com/en-US/aviation/faq/yG9YhFImtt8XiNr8uLLUA6/) will now be motivated to go get those taken care of.  I was waiting until the next time I needed something from the avionics shop as mine don't oscillate that much outside of IAS mode.  I'm hopeful the software update for this new AD can be done at the same time and on Garmin's dime.  The servo replacement is a warranty item.  I guess it's up to the shop to include the software update, but I know my guy will likely include that in the visit.

[Pinecone]

1 hour ago, PT20J said:

I wonder where the FAA came up with $85? Most shops charge an hour for updating software, printing out the AFMS and completing the logbook entry. I don’t know any good shops that only charge $85/hr.

Skip

That seems to be the FAA's "average" shop hour cost.  IIRC, it was the same in the Continental crank counter weight AD

[PT20J]

There are several GFC 500 issues:

1. Trim runaway

2. Servo upgrade

3. Pitch oscillations

This AD is for the trim runaway for which Garmin has already issued a software update. The AD would just make that update mandatory.

The servo upgrade is covered by the extended warranty/replacement program

Last I heard, Garmin was still looking for someone with the pitch oscillations to loan them an airplane so that they could test a fix. 

Skip

[ricardo-sf]

If you complied with the Garmin SB from a year ago regarding pitch trim on the GFC500 then you are already compliant with this AD afaict.

The shops I use charged me nothing to make the software upgrade .. took them about 15 minutes. .. (ok maybe 20 because they had to print the log entry)

Edited October 11, 2023 by ricardo-sf

[Greg Ellis]

On 10/9/2023 at 9:40 AM, AdamJD said:

So I'm assuming those of us who have the separate issue of the GSA-28 servo warranty extension to replace impacted servos (https://support.garmin.com/en-US/aviation/faq/yG9YhFImtt8XiNr8uLLUA6/) will now be motivated to go get those taken care of.  I was waiting until the next time I needed something from the avionics shop as mine don't oscillate that much outside of IAS mode.  I'm hopeful the software update for this new AD can be done at the same time and on Garmin's dime.  The servo replacement is a warranty item.  I guess it's up to the shop to include the software update, but I know my guy will likely include that in the visit.

When I did my servo exchange earlier this year (my servos fell under the exchange parameters) the shop also updated the software at the same time.  Charged me for neither.

[AdamJD]

On 10/9/2023 at 12:31 PM, PT20J said:

Last I heard, Garmin was still looking for someone with the pitch oscillations to loan them an airplane so that they could test a fix. 

I thought the servo upgrade was supposed to help with oscillations.  That's not the case?

[ArtVandelay]

I thought the servo upgrade was supposed to help with oscillations.  That's not the case?

No, it fixed the runaway trim issue.