The Challenge of Developing Objective and Subjective Metrics for Rotorcraft Flight Simulators

Flight simulation regulatory standards such as CS-FSTD(H) and FAA AC120-63 describe the criteria and certification procedures for rotorcraft flight training simulators. These documents are central to the certification process, detailing the component fidelity required to achieve “fitness for purpose”. Typically, they define criteria based on “tolerances”, defined as acceptable differences between simulation and flight, typically ±10% for the flight model, defined here as predicted fidelity requirements. Methods to update the models for improved fidelity are mostly ad-hoc and, without a strong scientific foundation, are often not physics-based. Furthermore, there are no quantitative methods used to assess the fidelity of the overall system and determine the perceptual fidelity requirements for a training simulator. The paper will present work that has been undertaken to start to address the development of objective measures for predicted fidelity, complemented by objective and subjective measures of perceptual fidelity. Results from simulator trials will be compared against “benchmark” data obtained during flight tests to illustrate the need to develop a coherent approach to defining fidelity requirements for rotorcraft simulators across a range of applications. The challenges of designing test manoeuvres that can “expose” flight simulator deficiencies, what makes a “good” simulator evaluation pilot and the fidelity requirements for simulating helicopter operations in non-standard operations that are not covered by existing standards e.g. helicopter-ship operations, will be presented to encourage discussion towards the development of new fidelity criteria.