S-tec 55x Installation Manual -

The is the definitive technical reference for certified avionics installers and maintenance personnel responsible for integrating the S-TEC 55X two-axis autopilot into general aviation aircraft. Originally developed by S-TEC and now supported by Genesys Aerosystems, this manual provides comprehensive, FAA-acceptable data for the physical and electrical installation of one of the most popular rate-based autopilots in the industry.

Upon completion of the physical and electrical installation, ground and flight testing are required to verify the STC conditions are met.

This manual is for reference only. Actual aircraft installation of the S-TEC 55X requires appropriate technical training, test equipment, and regulatory approvals. Installation errors (e.g., reversed servo polarity, improper torque) can lead to autopilot-induced oscillations or loss of control. Always follow the latest FAA-approved data. S-tec 55x Installation Manual

Connects to the localized radio magnetic indicator (RMI) or HSI via a standard standard AC bootstrap or DC analog heading error signal.

Before beginning the installation process, it is essential to ensure that you have the following: The is the definitive technical reference for certified

Unlike modern software-only configurations, the System 55X computer unit often utilizes internal DIP switches for configuration (depending on the revision of the manual and the unit P/N).

To return the aircraft to service, the installing FAA-certified A&P mechanic or authorized repair station must document the work. This includes updating the aircraft equipment list, filing an FAA Form 3337 (Major Repair and Alteration), and placing the S-TEC 55X Airplane Flight Manual Supplement (AFMS) into the aircraft cockpit. This manual is for reference only

The S-TEC 55X control head utilizes a high-density D-subminiature connector. Key wiring runs detailed in the manual include:

An autopilot installation is not a generic project. It requires strict adherence to legal and engineering boundaries. STC and Approved Model List (AML)

: External switches for AP Disconnect, CWS (Control Wheel Steering), and Trim Master. 🔌 Wiring & Pinout Essentials

The manual includes a flow chart titled “System Fails BIT – Rate Gyro LED Red.” Follow it religiously—90% of BIT failures are bad grounds or incorrect gyro orientation.