Browsing by Author "Greaves, Matthew J."
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Item Open Access The activated failures of human-automation interactions on the flight deck(Aeronautical and Astronautical Society of the Republic of China, 2016-09-01) Li, Wen-Chin; Greaves, Matthew J.; Durando, D.; Lin, J.J.Cockpit automation has been developed to reduce pilots' workload and increase pilots' performance. However, previous studies have demonstrated that failures of automated systems have significantly impaired pilots' situational awareness. The increased application of automation and the trend of pilots to rely on automation have changed pilot's role from an operator to a supervisor in the cockpit. Based on the analysis of 257 ASRS reports, the result demonstrated that pilots represent the last line of defense during automation failures, though sometimes pilots did commit active failures combined with automation-induced human errors. Current research found that automation breakdown has direct associated with 4 categories of precondition of unsafe acts, including 'adverse mental states', 'CRM', 'personal readiness', and 'technology environment'. Furthermore, the presence of 'CRM' almost 3.6 times, 12.7 times, 2.9 times, and 4 times more likely to occur concomitant failures in the categories of 'decision-errors', 'skill-based error', 'perceptual errors', and 'violations'. Therefore, CRM is the most critical category for developing intervention of Human-Automation Interaction (HAI) issues to improve aviation safety. The study of human factors in automated cockpit is critical to understand how incidents/accidents had developed and how they could be prevented. Future HAI research should continue to increase the reliability of automation on the flight deck, develop backup systems for the occasional failures of cockpit automation, and train flight crews with competence of CRM skills in response to automation breakdowns.Item Open Access Bearing signal separation of commercial helicopter main gearbox(Elsevier, 2017-03-02) Elasha, Faris; Greaves, Matthew J.; Mba, DavidGears are significant component in a multiplicity of industrial applications such as machine tool and gearboxes. An unforeseen failure of gear may result in significant economic losses. Therefore this research propose fault detection improvement throught series of vibration signal processing techuiques. These techniques have been tested experimentally using vibration data collected from the transmission system of a CS-29 ‘Category A’ helicopter gearbox under different bearing damage severity of the second planetary stage. Results showed successful improvement of bearing fault detection.Item Open Access A comparative study of the effectiveness of vibration and acoustic emission in diagnosing a defective bearing in a planetry gearbox(Elsevier, 2016-09-12) Elasha, Faris; Greaves, Matthew J.; Mba, David; Fang, DuanWhilst vibration analysis of planetary gearbox faults is relatively well established, the application of Acoustic Emission (AE) to this field is still in its infancy. For planetary-type gearboxes it is more challenging to diagnose bearing faults due to the dynamically changing transmission paths which contribute to masking the vibration signature of interest. The present study is aimed to reduce the effect of background noise whilst extracting the fault feature from AE and vibration signatures. This has been achieved through developing of internal AE sensor for helicopter transmission system. In addition, series of signal processing procedure has been developed to improved detection of incipient damage. Three signal processing techniques including an adaptive filter, spectral kurtosis and envelope analysis, were applied to AE and vibration data acquired from a simplified planetary gearbox test rig with a seeded bearing defect. The results show that AE identified the defect earlier than vibration analysis irrespective of the tortuous transmission pathItem Open Access Modelling of wreckage trajectories following in-flight breakup(Cranfield University, 2013-04) Greaves, Matthew J.; Braithwaite, Graham R.The study of ballistic trajectories is well-established, with work dating back to the 1940s. More recently, ballistic trajectory analysis has been used by air accident investigators in an attempt to understand events leading up to an accident, with notable examples including the investigation into the Lockerbie bombing. Building on the history of a previous model, this thesis offers an enhanced model for the calculation of ballistic trajectories incorporating altitude dependence for wind, density and gravity. Attempts to solve the model analytically were unsuccessful, and therefore, the model was solved numerically using an implicit scheme, to deal with the inherent stiffness of the equations, and an extrapolation technique. Cubic splines were used to accurately represent the wind proUile in an analytical way. The numerical solution was veriUied against a simpliUied analytical case and results are presented for two simulated breakup cases. Four key parameters were then varied to provide information about the sensitivity of Uinal wreckage location to variation in system parameters. The results indicate that for simulated large aircraft breakups, low ballistic coefUicient items are most heavily affected by breakup altitude, wind magnitude and wind angle whereas large ballistic coefUicient items are most heavily affected by breakup velocity, although to a much lesser extent (around 15% of the distance of low ballistic coefUicient). For small aircraft breakups, wind angle and breakup altitude have the largest effect on low ballistic coefUicient items, with velocity and altitude affecting high ballistic coefUicient items to a larger extent (around 50% of low ballistic coefUicient items). The results will allow investigators to understand better the factors which affect items of differing ballistic coefUicient in different situations. The project as a whole provides a new solution engine for the trajectory problem which can form the basis of a new software package for investigators.Item Open Access Pilot’s attention distributions between chasing a moving target and a stationary target(Aerospace Medical Association, 2016) Li, Wen-Chin; Yu, Chung-San; Braithwaite, Graham; Greaves, Matthew J.Introduction: Attention plays a central role in cognitive processing; ineffective attention may induce accidents in flight operations. The objective of current research was to examine military pilots’ attention distributions between chasing a moving target and a stationary target. Method: Thirty-seven mission-ready F-16 pilots participated in the current research. Subjects’ eye movements were collected by a portable head-mounted eye-tracker during tactical training in a flight simulator. The scenarios of chasing a moving target (air-to-air) and a stationary target (air-to-surface) consist of three operational phases; searching, aiming and lock-on to the targets. Results: The findings demonstrated significant differences in pilots’ percentage of fixation during searching phase between air-to-air (M=37.57, SD=5.72) and air-to-surface (M=33.54, SD=4.68). Fixation duration can indicate pilots’ sustained attention to the trajectory of a dynamic target during dog-fight manoeuvers. Aiming for the stationary target with larger pupil size (M=27105 pixel2, SD=6565 pixel2) reflects higher cognitive loading than aiming to the dynamic target (M=23864 pixel2, SD=8762 pixel2). Discussion: Pilots’ visual behavior is not only closely related to attention distribution, but also significantly associated with task characteristics. Military pilots demonstrated various visual scan patterns for searching and aiming to different types of targets based on the research settings of flight simulator. The findings would facilitate system designers’ understandings of military pilots’ cognitive processes during tactical operations. It will assist human-centered interface design to improve pilots’ situational awareness. The application of an eye-tracking device integrated with a flight simulator is a feasible and cost-effective intervention to improve efficiency and safety of tactical training.Item Open Access Polarimetric imaging for air accident investigation(SPIE - International Society for Optics and Photonics, 2012-09-24) Privett, G. J.; Ashe, M. D.; Greaves, Matthew J.; Holland, D.; Davidson, L.We report a trial wherein a simple 4 CCD visible-band Polarimetric Imaging (PI) camera was fielded against aircraft debris distributed across an arid terrain, a littoral region and a small number of maritime debris targets A debris field realistically simulating an aircrash and a debris grid of aircraft remains were observed from an air platform flying in dry and sunny conditions. We report PI utility in support of air accident investigation by an enhanced ability to successfully locate small targets within the scene via the use of colour enhanced and decorrelated intensity PI products. Our results indicate that handheld PI capability may represent an effective low cost, upgrade and augmentation option for existing and future imaging systems that would support air accident investigators and assist in the cueing of more sophisticated assets and/or analyst attention.