Mounted on the forward cabin bulkhead or radio rack.
Technicians must check for service bulletins (SB) or required revisions, such as those related to AP Steering Information Kits (e.g., Kit No. 767-316/317/318/319/320), which may modify the standard installation procedure for specific aircraft models.
The S-tec 55x autopilot system consists of several components, including:
Installation of the 55X is a major alteration requiring strict adherence to the manufacturer’s Installation Manual (IM). This paper summarizes the critical phases of that manual, highlighting the technical challenges and safety requirements involved in the integration process. S-tec 55x Installation Manual
Before physical installation begins, the installing agency (typically an FAA Part 145 Repair Station or holder of an Inspection Authorization) must determine the certification basis.
During the initial test flight in calm air, the technician or test pilot will evaluate:
Weaknesses
With the aircraft perfectly level on the ground and the controls centered, the installer must perform a "null adjustment." This ensures that when the autopilot commands zero movement, the servos receive exactly zero volts, preventing the system from drifting or creeping on its own. 6. Ground Testing and Pre-Flight Checks
Provides automatic pitch trim adjustments to relieve aerodynamic pressure on the primary pitch servo.
This paper serves as a technical overview and procedural guide for the installation of the S-TEC System Fifty Five X (55X) autopilot system. As one of the most prevalent General Aviation autopilot systems, the 55X requires precise integration with an aircraft’s existing pitot-static, electrical, and flight control systems. This document outlines the regulatory framework, physical installation considerations, electrical interfacing, and the mandatory post-installation testing protocols required for airworthiness certification. Mounted on the forward cabin bulkhead or radio rack
Mechanical geometry is the most critical factor in preventing autopilot binding or control surface jam conditions. Servo Bridle Cable Rigging
Use bridle cables and extension attachments to connect servos to the aircraft's primary flight control and trim systems.
If the system fails its ground test or behaves erratically, look for these common installation pitfalls: The S-tec 55x autopilot system consists of several
Once the installation is complete, the system must be tested and calibrated to ensure proper operation. To do this:
Connect the system to the avionics master switch, ensuring proper circuit protection (fuse or circuit breaker). Phase C: System Integration
