Garmin’s new GFC 600 and GFC 500 autopilots are retrofit systems that bring modern autopilot capabilities at a relatively low cost to the fixed-wing general aviation market, from the Cessna 172 and Piper PA-28 series through high-performance piston twins and turbine aircraft. The systems are solid-state attitude-based (AHRS-derived) autopilots, according to Garmin, with performance that is not available from traditional mechanical-attitude or rate-based autopilot systems, but similar to its GFC 700 series autopilots. Both autopilots feature brushless DC motor servos.

Both the GFC 600 and 500 include Garmin’s electronic stability and protection (ESP), which works even when the autopilot is switched off. ESP nudges the flight controls to lessen pitch attitude or bank angle when the aircraft exceeds pre-determined pitch, roll or airspeed limitations. The new autopilots also include the level mode, which can be engaged with a button to return the airplane to straight-and-level flight or engages automatically in case a pilot becomes incapacitated, when ESP detects no activity for an extended time. The autopilots also feature underspeed and overspeed protection.

The GFC 600 is designed for airplanes equipped with Garmin G500 and G600 displays, but it can also integrate with other manufacturers’ displays, instruments and navigation sources. It includes a self-contained controller with its own status and mode selection display as well as a wheel for adjusting pitch, airspeed and vertical speed modes. The controller fits into normal radio stacks.

According to Garmin, the GFC 600 is already STC’d in the A36 Bonanza and B55 Baron. The Model 58 Baron will be next, followed by more high-performance piston singles and twins and turbines.

Both the GFC 600 and 500 can be fitted with an optional autopilot annunciator panel that can be installed in the pilot’s field of view. Control wheel steering is optional on the G600.

The GFC 500 is integrated with Garmin’s G5 electronic flight instrument, which “provides input and display of altitude preselect, heading, vertical speed target, airspeed target and flight director command bars for the GFC 500,” Garmin said. An optional adapter is available to interface the GFC 500/G5 to certain Garmin GPS or VHF navigators. The first GFC 500 STC will be in the Cessna 172 in the fourth quarter this year, followed by the Cessna 182 and Piper PA-28 series.

Both the GFC 600 and 500 offer altitude hold, vertical speed and heading modes plus altitude preselect and indicated airspeed hold mode (Vnav for appropriately equipped airplanes will be added later).

Coupled instrument approaches can be flown with both autopilots, including GPS, ILS, VOR, LOC and back course approaches when the appropriate navigator is installed. Pilots can also fly coupled go-arounds by pushing a remotely installed go-around button. This commands the flight director to display the correct pitch attitude for the missed approach and also activates a loaded missed approach (when paired with a GTN 650/750 navigator), according to Garmin.

The flight director command bars are available on the G5 when installed with the GFC 500, and for the GFC 600, on G500/600 displays and certain third-party displays. Other features include GPS roll-steering and optional yaw servo and pitch-trim servo. The only feature that is available on the GFC 600 but not the GFC 500 is control wheel steering.

The GFC 500 starts at $6,995 for aircraft equipped with the G5 or less than $10,000 for both, for a two-axis autopilot. The GFC 600 starts at $19,995 for the A36 Bonanza and $23,995 for the B55 Baron, and these include the two-axis autopilot with electric pitch trim.