Most of the Trimmable Horizontal Stabilizer Actuators (THSA) feature a dual structural load path, the primary load path being loaded, the secondary load path being normally unloaded, or both load paths sharing in parallel the Horizontal Stabilizer load. This document describes existing methods for detecting rupture or disconnection of loaded load paths as an overview for those specifying or designing Horizontal Stabilizer Trim Actuators in order to compare existing solutions as reference for implementation in new aircraft programs.
Rationale: In the recent past years many different solutions have been designed and implemented to cope with possible failures of Trimmable Horizontal Stabilizer Actuator primary load paths. There is a need for a general overview of these solutions as a source of information both for aircraft manufacturers specifying this type of equipment as for systems suppliers designing them. This document provides this overview and a summary of examples of successful developments to serve as a guideline.