Flight simulation fidelity for rotorcraft design, certification and pilot training

The benefits of using flight simulators for rotorcraft design, certification and pilot training include reduced costs, increased safety, and control over external parameters such as environmental conditions and operational situations. The progression of technology and computing power over recent decades has led to the ability to manufacture highly sophisticated flight simulators that can be used to train complex flight operations and accurately predict the behaviour aircraft. However, such sophistication comes at a cost and there is a need to understand the trade-offs between cost and effectiveness to allow the benefits of flight simulation to be transferred to lower cost applications such as initial skills acquisition training. Assessment of simulator capabilities has traditionally been carried out with focus on the physical similarity of individual components of the simulator systems - motion system, visual system, flight model etc. However, this work is focused on the assessment of the fitness for purpose of the integrated system as a whole. This is referred throughout the thesis as perceptual fidelity, which has been defined as 'The simulator's ability to induce the behaviours known to be essential for operation of the actual aircraft in the performance of a specific task'. The novel contribution of the work in this thesis is the development of new quantitative metrics and a subjective evaluation technique that could be utilised across the simulation industry for quantification of perceptual fidelity of the overall simulation. It is intended that the methods detailed in this work could be used to support simulator development and augment current assessment techniques where appropriate. The quantitative measures of perceptual fidelity are based on comparison of ADS-33E PRF style performance metrics and the Attack metric, a control activity measure developed by Padfield et al. In this work, the utility of these metrics was assessed through correlation analyses with pilot subjective opinion. A lack of correlation in multi-axis tasks was seen and, as a result, novel metrics of pilot control strategy and adaptation have been developed in this work that show significant improvement in correlation with pilot subjective opinion. The subjective assessment methodology developed in this work is based around a new subjective rating scale – the Simulation Fidelity Rating (SFR) scale. The author contributed to the development of the SFR scale along with others at the University of Liverpool and the National Research Council (NRC) of Canada. This scale has been designed specifically to be industry applicable a d to determine the overall perceptual fidelity of the integrated simulation in a specific role. A campaign of piloted simulation and flight test trials has been conducted as the core experimental phase of this work. All the pilots completed a series of controlled experiments where a number of flying tasks were completed with a number of varied simulation models. The pilots rated each simulation against a baseline simulation using the SFR scale and their performance and control activity were recorded. This test campaign generated the pilot feedback for the development of the SFR scale and data for development of the quantitative metrics. The tests were also utilised to demonstrate how this assessment methodology can be used in controlled simulation experiments to provide previously lacking supporting evidence to simulator qualification criteria of individual components. From the analysis of the results, it was found that a more aggressive pilot excites the dynamics of the aircraft to a greater extent, thereby exposing more fidelity issues – leading to poorer SFRs. For similar reasons, an aircraft with degraded HQs was found to cause increased pilot sensitivity to transport delay. Perceptual fidelity was also found to be task dependent, In particular, pilots were found to be more susceptible to changes in off-axis response in the Acceleration-Deceleration manoeuvre than in the Precision Hover manoeuvre. These findings prove that here is a true need for simulation qualification criteria that are based on the intended use of the equipment. Significant spread was seen in the pilot ratings of perceptual fidelity in a number of cases. This was attributed partly to differing interpretation of the terminology within the Simulation Fidelity Rating (SFR) scale and also to pilot selection of task strategy. Therefore guidance material has been developed by the author from lessons learnt throughout the test campaign. This guidance material is intended to ensure best utility of the SFR scale in the future, to mitigate against the effects of differing interpretation of SFR terminology and variation in pilot task strategy through pilot briefing and correct experimental design. The SFR scale has been developed in the context of assessing a simulator for the purpose of rotary wing skills acquisition training. However, the methodologies described throughout the thesis are intended to be transferable to more sophisticated training devices for rotary-wing and fixed-wing pilot and crew training as well as for the quantification of the fidelity of certification and design simulators