GENESYS Aerosystems , formerly know as S-tec has Stcs for all the autopilots except for the New Arinc models. For nearly All versions of the type certificated Navions . The Palo Alto tail mod or the other equivalent must be installed and you would need to check with your S-tec Dealer to verify particular configuration of Engine type/ tip tanks or not and or specifically which Tip tank install is on your plane.Stec 30 and 50 is available with Altitude hold but Not Vertical control from VSI or Glide slope for altitude changes "coupled" for that type control . They will however couple for approaches on the Roll Mode . Manual electric trim is available for single axis , and system 20 and 50 but NOT Autotrim. Electric trim in that configuration is not really necessary in those situations but is available. SYSTEM 60-2 And Stec 55x are full function 2 axis autopilots and also are available with electric trim/ auto trim. The vertical pitch cam be coupled to VSI rate of climb and also will.provide vertical coupling to approaches that have Vertical guidance for ILS and GPS approaches that does it through Waas GPS Navigators . Also multiple methods are available for altitude preselect with rate of climb set by the pilot.
THE Garmin Autopilots are NOT presently STC approved for Navions , but it appears to be a path to "Field Approval" through the Bracket Purchase with Tech drawings from The Type Certificate Holder . The Autopilot would still require an authorized Garmin Dealer to install it IAW Garmin standards and also brackets for servos to be Installed IAW tech Data of The Type Certificate Holder . Finally the 337s would have to be Field approved. With a Supplementary Operators manual to also approved for the specific plane , much like an STCd one . HOPEFULLY Garmin , or Someone will obtain an STC But it may be hard to get ALL Navions approved under a single STC for gain settings as there are so many different airframe / engine combos . A single gain setting for all variations may not be applicable and there may have to be versions with slightly different gain settings for the variations.
Davis Heath , Heath Aviation .