Connect power and ground first. Then connect the gyro, servos, and annunciator. Leave NAV/GPS connections for last.
If you are looking for for an existing unit. S-tec 55x Installation Manual
The manual dedicates an entire subsection to grounding isolation . Autopilot grounds must be isolated from avionics and instrument panel grounds to prevent electrical noise. A single-point ground bus is recommended. Connect power and ground first
The S-TEC 55X installation manual is regarded as a detailed, comprehensive resource for technicians, though it is often described by users as difficult to navigate and restricted to authorized dealers. Community feedback highlights that installation requires aircraft-specific drawing packages provided with the STC kit rather than a generic manual. For user discussions and community insights on the manual, visit the BeechTalk discussion . S-tec 55x Installation Manual Today If you are looking for for an existing unit
Maintain physical separation between autopilot wiring and other avionics to prevent signal bleed.