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Service Letter 00055

Amadeus

Amadeus

Well Known Member
Garmin sent the exchange GSA 28 autopilot servos and I switched them out on the -12iS today. Van's has Service Letter 00055 that is to be performed following the servo replacement exchange that requires the wire C7042, pin 23 at the AV-60000 main 50 pin D-sub connector, to be severed and the stub heat shrinked to cover.

Does this action render the autopilot disconnect buttons on the sticks and the one on the center console inoperable? If so, then what will be the method for disengaging the autopilot once engaged?

Also does replacing the servos require any new configuration or reconfiguration to make autopilot functional again?

Garmin Service Bulletin: https://support.garmin.com/en-US/?faq=NER5XI3y7C9RT6KIMTkgvA

Van's Service Letter: https://www.vansaircraft.com/service-information-and-revisions/sl-00055/
 
I wish I could help more, but haven’t sent the auto pilot servos in yet.

How long did it take to receive the servos back in the mail?
 
mikefox said:
How long did it take to receive the servos back in the mail?
Click to expand...

Garmin has them ready to go.

You have the option of sending the removed ones in and they return "newly refurbished" replacements immediately or you can pay for the replacements and get refunded as soon as you send in the ones removed.
 
>Does this action render the autopilot disconnect buttons on the sticks and the one on the center console inoperable? If so, then what will be the method for disengaging the autopilot once engaged?

>Also does replacing the servos require any new configuration or reconfiguration to make autopilot functional again?

Everything will work after this change without any config changes required.
 
With C7042 connected, there is a 5K ohm pull-down resistor that I suppose is pulling the signal on the line down too much with these newer servos. Cutting that wire only removes that pull-down resistor from the mix.

Everything works as normal after its cut. I opted to remove the pin from the connector and shrink-wrap it, rather than cut it. A little "cleaner" that way.

The Service Letter was pretty easy, probably spent more time searching for the right sockets.

The only tip I can offer is to attach the control arm to the aileron servo's center hole (in the tailcone) BEFORE mounting the servo. It is impossible to attach the arm to the center hole after the servo has been mounted. And lastly, some people have deferred this Service Letter because they want to use their servos for 5 years (or until something breaks), then trade them in and get "new" (refurb) servos.. maximizing their dollar. I tried to wait, but it was gnawing at me to just do it and get it over with.
 
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Thanks subpar_bucker and Rob.

I, too, planned to wait until closer to the 5 year point to maximize servo lifetimes but on flight to and from Petit Jean the pitch servo began giving an error message.
 
Performing the required action of Service Letter 00055 took much longer than anticipated (but then what doesn't when it comes to aviation maintenance) because I searched through the bundle of wires feeding into the 50 pin d-sub multiple times in every direction possible and could not locate the C7042 wire. After searching online in an attempt to figure out which of the 50 pins is pin 23 proved to be an additional waste of time. I reached out to Tony at Vans who was able to identify pin 23 for me to which I found an unlabeled yellow wire attached that, after a short length had two other wires spliced into it. These were a blue wire labeled C7247 and a yellow wire labeled C7035.

So if you find yourself unable to locate C7042 on your first pass then begin looking for C7247 and C7035 and save yourself some time!

C7042.jpg

C7247.jpg

C7035.jpg
 
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Amadeus said:
Garmin has them ready to go.

You have the option of sending the removed ones in and they return "newly refurbished" replacements immediately or you can pay for the replacements and get refunded as soon as you send in the ones removed.
Click to expand...

I got intermittent pitch servo faults on my last couple of flights. Garmin responded very quickly to my email. I'm opting to replace both servos, with the "advance exchange" option, so I'll pay and get a refund when I send old units back.

My iS was completed in 2019, and the servos have been working as expected until these failures.
 
Amadeus said:
Performing the required action of Service Letter 00055 took much longer than anticipated (but then what doesn't when it comes to aviation maintenance) because I searched through the bundle of wires feeding into the 50 pin d-sub multiple times in every direction possible and could not locate the C7042 wire. After searching online in an attempt to figure out which of the 50 pins is pin 23 proved to be an additional waste of time. I reached out to Tony at Vans who was able to identify pin 23 for me to which I found an unlabeled yellow wire attached that, after a short length had two other wires spliced into it. These were a blue wire labeled C7247 and a yellow wire labeled C7035.

So if you find yourself unable to locate C7042 on your first pass then begin looking for C7247 and C7035 and save yourself some time!


That information was extremely helpful. There was no label on my C7042 wire, either. Trying to find the wire on pin 23 in that fat bundle would have been challenging without your tip. I also chose to simply remove the pin vs cutting the wire, and verified it was the right pin by looking at the front of the connector. All in, this took longer than expected, about 4 hours. As an aside, after we replaced the pitch servo, we turned on the master and got a red X and fault, as we had not removed that wire yet. All was well when the roll servo was in and the wire was removed.
Click to expand...
 
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