Philip Perfect

Acceptance testing and commissioning of a flight simulator for rotorcraft simulation fidelity research

The rotorcraft industry faces a number of challenges today regarding the replacement of ageing airframes, an expansion in the operational roles of helicopters and a requirement to improve safety whilst reducing the environmental impact of rotorcraft operations. The quantification of simulation fidelity underpins the confidence required for the expanding use of modelling and simulation to develop solutions to these challenges in a timely and cost-efficient manner. Current simulator certification standards do not provide a fully quantitative method for assessing simulation fidelity, especially in a research environment. This article details the commissioning and acceptance process of the new research flight simulation facility at the University of Liverpool, HELIFLIGHT-R, and its subsequent use in a research project ‘Lifting Standards: A Novel Approach to the Development of Fidelity Criteria for Rotorcraft Flight Simulators’ aimed at developing new predicted and perceptual measures of simulator fidelity. Some initial results from both piloted simulation and flight tests using the Bell 412 Advanced Systems Research Aircraft are reported within the context of the rotorcraft simulation fidelity project.

Objective Fidelity Evaluation in Multisensory Virtual Environments: Auditory Cue Fidelity in Flight Simulation

We argue that objective fidelity evaluation of virtual environments, such as flight simulation, should be human-performance-centred and task-specific rather than measure the match between simulation and physical reality. We show how principled experimental paradigms and behavioural models to quantify human performance in simulated environments that have emerged from research in multisensory perception provide a framework for the objective evaluation of the contribution of individual cues to human performance measures of fidelity. We present three examples in a flight simulation environment as a case study: Experiment 1: Detection and categorisation of auditory and kinematic motion cues; Experiment 2: Performance evaluation in a target-tracking task; Experiment 3: Transferrable learning of auditory motion cues. We show how the contribution of individual cues to human performance can be robustly evaluated for each task and that the contribution is highly task dependent. The same auditory cues that can be discriminated and are optimally integrated in experiment 1, do not contribute to target-tracking performance in an in-flight refuelling simulation without training, experiment 2. In experiment 3, however, we demonstrate that the auditory cue leads to significant, transferrable, performance improvements with training. We conclude that objective fidelity evaluation requires a task-specific analysis of the contribution of individual cues.

Methods to Assess the Handling Qualities Requirements for Personal Aerial Vehicles

This paper describes the development of a methodology to assess the handling qualities requirements for vertical takeoff and landing-capable personal aerial vehicles. It is anticipated that such a personal aerial vehicle would be flown by a “flight-naive” pilot who has received much less training than is typically received even by today’s general aviation private pilots. The methodology used to determine handling requirements for a personal aerial vehicle cannot therefore be based entirely on existing best practice; the use of highly experienced test pilots in a conventional handling assessment limits the degree to which results apply to the flight-naive pilot. Using rotary-wing handling qualities methods as a start point, this paper describes both existing and newly developed alternative methods to subjectively and objectively analyze the performance and workload of flight-naive pilots in typical personal aerial vehicle tasks. A highly reconfigurable generic flight dynamics simulation model that has been...

Rotorcraft simulation fidelity: new methods for quantification and assessment

Flight simulators are integral to the design/development, testing/qualification, training and research communities and their utilisation is ever expanding. The use of flight simulation to provide a safe environment for pilot training, and in research and development, must be underpinned by quantification of simulator fidelity. While regulatory simulator standards exist for flight training simulators and new standards are in development, previous research has shown that current standards do not provide a fully quantitative approach for assessing simulation fidelity, especially in a research environment. This paper reports on progress made in a research project at the University of Liverpool (Lifting Standards), in which new predicted and perceptual measures of simulator fidelity have been developed. The new metrics have been derived from handling qualities engineering practice. Results from flight tests on the National Research Council (Canada) Bell 412 ASRA research aircraft and piloted simulation trials using the HELIFLIGHT-R simulator at Liverpool are presented to show the efficacy of adopting a handling qualities approach for fidelity assessment. Analysis of the new metrics has shown an appropriate degree of sensitivity to differences between flight and simulation.

Handling Qualities Requirements for Future Personal Aerial Vehicles

This paper describes research to develop handling qualities guidelines and criteria for a new category of aircraft: the personal aerial vehicle, which it is envisaged will demand no more skill to fly than that associated with driving a car today. Testing of concept personal aerial vehicle response types has been conducted with inexperienced “pilots” ranging from private pilot’s license holders through to those with no prior flight experience. The objective was to identify, for varying levels of flying skill, the personal aerial vehicle response type requirements that will ensure safe and precise flight. Conventional rotorcraft response types such as “rate command”, “attitude command/attitude hold” are unsuitable for likely personal aerial vehicle pilots. However, response types such as “translational rate command” and “acceleration command, speed hold” permit “flight-naive” pilots to perform demanding tasks repeatably and with the required precision.

A rating scale for the subjective assessment of simulation fidelity

A new rating scale for capturing pilot subjective assessment of simulation fidelity is described in this paper. The scale has been developed through a series of flight and simulation trials using six test pilots from a variety of backgrounds, and is based on the methodology utilised with the Cooper-Harper Handling Qualities Rating scale and the concepts of transfer of training, comparative task performance and task strategy adaptation. The development of the new rating scale has been undertaken using simulations of rotary-wing aircraft on the University of Liverpool’s HELIFLIGHT-R research simulator, in conjunction with the Canadian Flight Research Laboratory’s Bell 412 ASRA in-flight simulator. The utility of the scale applied to locating fidelity boundaries for quantitative metrics is illustrated for an inter-axis coupling criterion. The work described in this paper is preliminary in nature, and research activities are on-going to continue the validation of the fidelity rating scale.

An LPV control law design and evaluation for the ADMIRE model.

This chapter presents the design and evaluation of an LPV control law for the ADMIRE model over a specified wide flight envelope, including subsonic, transonic and supersonic regions. The design of the LPV control law is based on the parameter-dependent Lyapunov function approach with gridding of the parameter space. It is demonstrated that by using a linear piece-wise interpolation of the aircraft model the LPV approach allows the design of a controller for the whole flight envelope (including the transonic region) with satisfactory performance and robustness characteristics. The longitudinal LPV controller provides an automatic transition from the α-demand system at Mach numbers M < 0.58 to the nz-demand system at M < 0.62; in the intermediate region a mixed control principle is implemented. A thorough evaluation of the designed LPV controllers is performed using a number of methods, including time and frequency domain criteria, linear and nonlinear simulation tests, and also piloted simulation in real time on the HELIFLIGHT simulator at the University of Liverpool. The performed evaluation clearly demonstrates that the designed LPV control laws satisfy most of the design requirements. Ways of further improving the performance of the LPV controller are discussed at the end of the chapter.

Objective and subjective evaluations of flight simulator fidelity

There is interest in how pilots perceive simulator fidelity and rate self-performance in virtual reality flight training. Ten participants were trained to perform a target tracking task in a helicopter flight simulation. After training objective performance, the median tracking error, was compared to subjective self-evaluations in a number of flying conditions where the cues available to our pilots were manipulated in a factorial design: the simulator motion platform could be active or static, audio cues signalling the state of the turbine could be those used during training, non-informative, or an obviously different but informative ‘novel’ sound. We tested participants under hard and easy flying conditions. Upon completion of each test condition, participants completed a 12-statement Likert-scale with items concerning their performance and helicopter simulator fidelity. Objective performance measures show that flight performance improved during training and was affected by audio and motion cues. The subjective data shows that participants reliably self-evaluated their own performance and simulator fidelity. However, there were instances where subjective and objective measures of performance or fidelity did not correlate. For example, although participants rated the ‘novel’ turbine sound as having low fidelity, it behaviourally caused no difference with respect to the turbine sound used in training. They were also unable to self-evaluate outcome of learning. We conclude that whilst subjective measures are a good indicator of self-performance, objective data offers a valuable task-oriented perspective on simulator fidelity.

Development of Occupant-Preferred Landing Profiles for Personal Aerial Vehicles

With recent increased interest in autonomous vehicles and the associated technology, the prospect of realizing a personal aerial vehicle seems closer than ever. However, there is likely to be a continued requirement for any occupant of an air vehicle to be comfortable with both the automated portions of the flight and their ability to take manual control as and when required. This paper, using the approach to landing as an example maneuver, examines what a comfortable trajectory for personal aerial vehicle occupants might look like. Based upon simulated flight data, a “natural” flight trajectory is designed and then compared to constant deceleration and constant optic flow descent profiles. It is found that personal aerial vehicle occupants with limited flight training and no artificial guidance follow the same longitudinal trajectory as has been found for professionally trained helicopter pilots. Further, the final stages of the approach to hover can be well described using the Tau theory. For automatic ...

Fidelity enhancement of a rotorcraft simulation model through system identification

High fidelity modelling and simulation are prerequisites for ensuring confidence in decision making during aircraft design and development, including performance and handling qualities, control law developments, aircraft dynamic loads analysis, and the creation of a realistic simulation environment. The techniques of system identification provide a systematic framework for ‘enhancing’ a physics–based simulation model derived from first principles and aircraft design data. In this paper we adopt a frequency domain approach for model enhancement and fidelity improvement of a baseline FLIGHTLAB Bell 412 helicopter model developed at the University of Liverpool. Predictability tests are based on responses to multi–step control inputs. The techniques have been used to generate one, three, and six degree-of-freedom linear models, and their derivatives and predictability are compared to evaluate and augment the fidelity of the FLIGHTLAB model. The enhancement process thus involves augmenting the simulation model based on the identified parameters. The results are reported within the context of the rotorcraft simulation fidelity project, Lifting Standards, involving collaboration with the Flight Research Laboratory (NRC, Ottawa), supported with flight testing on the ASRA research helicopter.