Physics-Based Detection of the Proximity to Loss of Tail Rotor Effectiveness Within the Helicopter Flight Data Monitoring Program

Loss of tail rotor effectiveness (LTE) is a critical helicopter flight characteristic and a major factor in numerous fatal accidents. To support LTE risk mitigation, the Helicopter Flight Data Monitoring (HFDM) program provides pilots with constant flight evaluation reports. Nevertheless, the existing LTE safety metric used within the HFDM environment presents several pitfalls that hinder the reliability of the results, contributing to a misleading pilot's training and low LTE awareness during flights. This paper is part of a larger ongoing effort that aims to develop an expanded safety metric to enhance the detection of proximity to LTE within the HFDM program. While LTE has been defined to include different complex flight conditions, this work focuses on the phenomenon of running out of pedal (tail rotor collective) for trim, a critical event that may lead to LTE behavior. A parametric surrogate model for the detection of proximity to running out of pedal events is formulated by combining results from physics-based simulations with machine learning techniques. The new safety metric allows for operator fine-tuning of proximity to critical boundaries, and hence, it provides flexibility in risk management from post-flight analyses. The results confirm the accurate prediction of running out of pedal for trim, providing an improved detection of the proximity to LTE within flight data. This aims to promote better awareness of LTE within the pilot community and support the proactive mitigation of LTE accidents.