Abstract
Background—The visual inspection of aircraft parts such as engine blades is crucial to ensure safe aircraft operation. There is a need to understand the reliability of such inspections and the factors that affect the results. In this study, the factor ‘cleanliness’ was analysed among other factors. Method—Fifty industry practitioners of three expertise levels inspected 24 images of parts with a variety of defects in clean and dirty conditions, resulting in a total of N = 1200 observations. The data were analysed statistically to evaluate the relationships between cleanliness and inspection performance. Eye tracking was applied to understand the search strategies of different levels of expertise for various part conditions. Results—The results show an inspection accuracy of 86.8% and 66.8% for clean and dirty blades, respectively. The statistical analysis showed that cleanliness and defect type influenced the inspection accuracy, while expertise was surprisingly not a significant factor. In contrast, inspection time was affected by expertise along with other factors, including cleanliness, defect type and visual acuity. Eye tracking revealed that inspectors (experts) apply a more structured and systematic search with less fixations and revisits compared to other groups. Conclusions—Cleaning prior to inspection leads to better results. Eye tracking revealed that inspectors used an underlying search strategy characterised by edge detection and differentiation between surface deposits and other types of damage, which contributed to better performance.
Highlights
The inspection accuracy describes the ratio of correct decisions divided by the number of blades and is presented as a percentage
The results show that self-confidence is an unreliable indicator of both inspection accuracy and inspection time
A look at the inspection accuracy for the different defect types revealed that dents had a high false negative rate, which could be the reason for a shorter inspection time
Summary
Engine maintenance, repair and overhaul (MRO) is essential to ensure the continued airworthiness of aircrafts and safe flight operations. Engines are inspected on a frequent basis, either after a certain amount of flight hours or cycles (planned shop visit), or after an unexpected event such as a bird strike or flying through volcanic ash (unplanned shop visit) [1]. The inspection is predominately performed by human operators and there is an inherent risk of human error [2,3,4,5]. According to the International Air Transport Association (IATA), one of the top three causes for aircraft accidents are maintenance and inspection errors, and every third accident chain started with an event caused by incorrect maintenance [6,7].
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