In the bad old days of supporting analog autopilots, there weren’t software updates to dial in their performance and flying characteristics. All that has changed with Garmin’s GSA 28 line of smart digital servos that work with the GFC 500 and GFC 500X (experimental) autopilots.
Learning from the service history, Garmin has been incrementally tweaking and improving its GFC autopilot—a system that’s installed in large numbers in a wide variety of airframes—with software and hardware mods. Since some of these incremental changes were made to the GSA servos, it’s consolidating all past improvements into a single servo that has all the tweaks, creating what it calls the GSA 28 Service-Life Extension Program.
Garmin didn’t say exactly what improvements are built into the latest-version servos, but did say that the goal is better reliability. In the data it say it has “implemented several design and manufacturing process improvements to improve GSA 28 reliability.”
HOW IT WORKS
The Service-Life Extension Program references Garmin’s Service Bulletin 23038 and is a recommended action and not mandatory. This service effort is different than Garmin’s previously issued mandatory Service Alert 22109 for GSA 28 servos used in certain GFC 500 pitch trim applications. Worth mentioning is that the GSA 28 is used as a roll, pitch and trim servo, depending on the configuration of the autopilot. The servos used in the aftermarket GFC 600 and the OEM G1000/3000/5000 integrated autopilots don’t apply.
But for GFC 500/X owners, there’s really no reason not to do the exchange. Garmin is covering parts and labor warranty (through a certified Garmin dealership) for a period of five years, or officially, until May 4, 2028. For experimental/kitplane GFC 500X owners, Garmin covers the servo exchange, but no labor, assuming the builder did the install. There are varying degrees of effort to access these servos, depending on the airframe. The lower left image is a GSA 28 roll servo as installed in a high-wing Cessna. The right image shows what a GSA 28 is made of.
If you have a fairly new GSA 28 servo (within a couple of months) you might have the latest version. For certain, check the data tag/part number. This program applies to all -11 GSA 28s, and all -21 GSA 28s not marked with Mod 1. Worth noting is that -21 servos are compatible with the G3X Touch version 9.00 or later, the G5 version 8.00 or later and the GI 275 version 2.42 or later. Link to more tech data at https://tinyurl.com/5nnc2wx.
