Research Objectives The vision for this 3.5-year PhD research is to advance the state of the art in rotorcraft modelling and simulation for Edge/Outside-of-the-Envelope Flight Regimes. The research theme will develop advanced approaches using System Identification (SID) to improve the fidelity of existing rotorcraft simulation models that are applicable for more realistic simulation and training at edge-of-the-envelope and outside-of-the-envelope flight regimes. This represents a step-change in simulator qualification, well-timed making a significant contribution to the initiated NATO STO AVT-296 RTG activity and will have an immediate impact through engagement with Industry partners.
Research Background High fidelity modelling and simulation are prerequisites for ensuring confidence in decision making during aircraft design and development, including performance and handling qualities estimation, control law development, aircraft dynamic loads analysis, and the creation of a realistic piloted simulation environment. The ability to evaluate/optimise concepts with high confidence and stimulate realistic pilot behaviour are the kernels of quality flight simulation, in which pilots can train to operate aircraft proficiently and safely and industry can design with lower risk. Regulatory standards such as CS-FSTD (Helicopter) and FAA AC120-63 (fixed-wing) describe the certification criteria and procedures for rotorcraft flight training simulators. These documents detail the component fidelity required to achieve ‘fitness for purpose’, with criteria based on “tolerances”, defined as acceptable differences between simulation and flight, typically ±10% for the flight model. However, these have not been updated for several decades, while on the military side, the related practices in NATO nations are not harmonised and have often been developed for specific applications. Methods to update the models for improved fidelity are mostly ad-hoc and, without a strong scientific foundation, are often not physics-based. The proposed PhD research, with the significant NATO gearing, will make a contribution for such harmonisation removing the barriers to adopting physics-based flight modelling. The recent research reported by the United States Helicopter Safety Team shows that unrealistic training of manoeuvres such as loss of tail rotor effectiveness (LTE) due to the insufficient fidelity of simulation models was a causal factor in some of the 52 fatal accidents that occurred between 2009-2013. The investigations have shown that current aircraft flight mathematical models are not accurate at edge-of-the-envelope and outside-of-the-envelope flight regimes. These deficiencies can lead to unrealistic training of manoeuvres such as LTE, vortex ring state/settling with power, and autorotation. These also can lead to a negative transfer of training when similar situations are encountered during actual flight. For example, the National Transportation Safety Board (NTSB) investigated 55 accidents involving LTE during the 10-year period from 2004 to 2014. The results revealed that the pilots were unable to recover when the helicopters encountered unanticipated yaw suffered from the LTE. It is obvious that better pilot training can help to reduce these accidents and increased simulator fidelity enables an increase in simulator/flight ratio in training. The proposed research will develop a novel, robust methodology for model enhancements in the Edge/Outside-of-the-Envelope Flight Regimes and LTE will be the focus.
Research Methodology and Management The proposed 3.5-year PhD research will be supervised by Dr Linghai Lu and be conducted in close collaboration between Liverpool John Moores University and The University of Liverpool (UoL). This offers a unique opportunity to conduct inter-disciplinary research with multi-national partners. Research will be conducted using the UoL’s HELIFLIGHT-R flight simulator with the planning and conducting flight simulation trials together with “real-world” flight testing using the National Research Council of Canada’s (NRC) Bell 412 Advanced Systems Research Aircraft (ASRA). The PhD candidate of this proposal research will also work closely with the PDRA1 of the EPSRC-funded project for preparing for Rotorcraft Modelling and Simulation Workshop and dissemination.