Manual: S-tec 55x Installation

Use only the specific S-TEC STC-approved brackets designed for the target airframe.

The S-Tec 55X is a popular autopilot system designed for use in general aviation aircraft. This write-up provides a comprehensive overview of the installation manual for the S-Tec 55X, highlighting key components, installation requirements, and procedures.

The final step of the installation manual is the tracking and performance flight test. In-Flight Calibration

Provides automatic pitch trim adjustments to relieve aerodynamic control pressures. S-tec 55x Installation Manual

A crucial detail often encountered during installation involves the rear connectors and the mounting tray. Technicians should carefully inspect the tray to ensure it is mounted close enough to the radio rack so that the connectors fully engage the faceplate bottoms out against the rack. If the connectors are too long, they will prevent the autopilot computer from seating properly, leading to intermittent connections. Furthermore, the rear connectors on a 55X unit are made of plastic, and the screws securing the backplate to the tray can be prone to stripping. If these plastic backshell screw-holes become stripped, sliding the unit into the tray can push the connectors out, as they are not secured properly, causing a loss of connectivity. Ensuring a robust and secure physical fit is the first step to preventing avionics "squawks."

During the initial test flight in calm air, the technician or test pilot will evaluate:

Engage ALT hold at a level altitude. Check for "porpoising" (vertical oscillations), which usually indicates a loose pitch bridle cable or a static system leak. Use only the specific S-TEC STC-approved brackets designed

Ensure the yoke-mounted Autopilot Disconnect (AP DISC) switch instantly breaks power to the servo clutches.

The information provided in this article is for general information purposes only and should not be considered as a substitute for the S-tec 55x Installation Manual. Installers and operators must always follow the manufacturer's instructions and guidelines to ensure safe and effective operation of the autopilot system.

Each component must be carefully inspected and identified to ensure correct installation. The final step of the installation manual is

Before beginning the installation, ensure that:

Mounts remotely to provide static pressure inputs for altitude hold and vertical speed functions. Mechanical Installation and Servo Rigging