This research explores optimal sequencing of aircraft engine maintenance events. Due to the high ongoing maintenance costs and large capital investments required for supporting an aircraft engine fleet, the timing and associated costs of maintenance events are key to minimizing overall costs for an airline. This paper examines a novel application of particle swarm optimization techniques in order to create a decision tool which may be easily implemented by the practitioner. Numerical experiments demonstrate the quality of this solution method under multiple maintenance pricing structures and operational constraints.

The aim of this research is to propose an alternative approach to determine the maintainability prediction for aircraft components. In this research, the author looks at certain areas of the maintainability prediction process where missteps or misapplications most commonly occur. The first of these is during the early stage of the Design for Maintainability (DfMt) process. The author discovered the importance of utilising historical information or feedback information. The second area is during the maintainability prediction where the maintenance of components is quantified; here, the author proposes having the maximum target for each individual maintainability component. This research attempts to utilise aircraft maintenance historical data and information (i.e. feedback information systems). Aircraft feedback information contains various types of information that could be used for future improvement rather than just the failure elements. Literature shows that feedback information such as Service Difficulty Reporting System (SDRS) and Air Accidents Investigation Branch, (AAIB) reports have helped to identify the critical and sensitive components that need more attention for further improvement. This research consists of two elements. The first is to identity and analyse historical data. The second is to identify existing maintainability prediction methodologies and propose an improved methodology. The 10 years’ data from Federal Aviation Administration (FAA) SDRS data of all aircraft were collected and analysed in accordance with the proposed methodology before the processes of maintainability allocation and prediction were carried out. The maintainability was predicted to identify the potential task time for each individual aircraft component. The predicted tasks time in this research has to be in accordance with industrial real tasks time were possible. One of the identified solutions is by using maintainability allocation methodology. The existing maintainability allocation methodology was improved, tested, and validated by using several case studies. The outcomes were found to be very successful. Overall, this research has proposed a new methodology for maintainability prediction by integrating two important elements: historical data information, and maintainability allocation. The study shows that the aircraft maintenance related feedback information systems analyses were very useful for deciding maintainabilityeffectiveness; these include planning, organising maintenance and design improvement. There is no doubt that historical data information has the ability to contribute an important role in design activities. The results also show that maintainability is an importance measure that can be used as a guideline for managing efforts made for the improvement of aircraft components.

The aim of this study is to propose an alternative approach in prognostics for airborne avionics system in order to enhance maintenance process and aircraft availability. The objectives are to analyse the dependency of avionic systems for fault propagation behaviour degradation, research and develop methods to predict the remaining useful life of avionics Line Replaceable Units (LRU), research and develop methods to evaluate and predict the degradation performances of avionic systems, and lastly to develop software simulation systems to evaluate methods developed. One of the many stakeholders in the aircraft lifecycle includes the Maintenance, Repair and Overhaul (MRO) industry. The predictable logistics process to some degree as an outcome of IVHM gives benefit to the MRO industry. In this thesis, a new integrated numerical methodology called ‘System Level Airborne Avionic Prognostics’ or SLAAP is developed; looking at a top level solution in prognostics. Overall, this research consists of two main elements. One is to thoroughly understand and analyse data that could be utilised. Secondly, is to apply the developed methodology using the enhanced prognostic methodology. Readily available fault tree data is used to analyse the dependencies of each component within the LRUs, and performance were simulated using the linear Markov Model to estimate the time to failure. A hybrid approach prognostics model is then integrated with the prognostics measures that include environmental factors that contribute to the failure of a system, such as temperature. This research attempts to use data that is closest to the data available in the maintenance repair and overhaul industry. Based on a case study on Enhanced Ground Proximity Warning System (EGPWS), the prognostics methodology developed showed a sufficiently close approximation to the Mean Time Before Failure (MTBF) data supplied by the Original Equipment Manufacturer (OEM). This validation gives confidence that the proposed methodology will achieve its objectives and it should be further developed for use in the systems design process.

The aim of this research is to propose an alternative approach to determine the maintainability prediction for aircraft components. In this research, the author looks at certain areas of the maintainability prediction process where missteps or misapplications most commonly occur. The first of these is during the early stage of the Design for Maintainability (DfMt) process. The author discovered the importance of utilising historical information or feedback information. The second area is during the maintainability prediction where the maintenance of components is quantified; here, the author proposes having the maximum target for each individual maintainability component. This research attempts to utilise aircraft maintenance historical data and information (i.e. feedback information systems). Aircraft feedback information contains various types of information that could be used for future improvement rather than just the failure elements. Literature shows that feedback information such as Service Difficulty Reporting System (SDRS) and Air Accidents Investigation Branch, (AAIB) reports have helped to identify the critical and sensitive components that need more attention for further improvement. This research consists of two elements. The first is to identity and analyse historical data. The second is to identify existing maintainability prediction methodologies and propose an improved methodology. The 10 years’ data from Federal Aviation Administration (FAA) SDRS data of all aircraft were collected and analysed in accordance with the proposed methodology before the processes of maintainability allocation and prediction were carried out. The maintainability was predicted to identify the potential task time for each individual aircraft component. The predicted tasks time in this research has to be in accordance with industrial real tasks time were possible. One of the identified solutions is by using maintainability allocation methodology. The existing maintainability allocation methodology was improved, tested, and validated by using several case studies. The outcomes were found to be very successful. Overall, this research has proposed a new methodology for maintainability prediction by integrating two important elements: historical data information, and maintainability allocation. The study shows that the aircraft maintenance related feedback information systems analyses were very useful for deciding maintainabilityeffectiveness; these include planning, organising maintenance and design improvement. There is no doubt that historical data information has the ability to contribute an important role in design activities. The results also show that maintainability is an importance measure that can be used as a guideline for managing efforts made for the improvement of aircraft components.

The aim of this study is to propose an alternative approach in prognostics for airborne avionics system in order to enhance maintenance process and aircraft availability. The objectives are to analyse the dependency of avionic systems for fault propagation behaviour degradation, research and develop methods to predict the remaining useful life of avionics Line Replaceable Units (LRU), research and develop methods to evaluate and predict the degradation performances of avionic systems, and lastly to develop software simulation systems to evaluate methods developed. One of the many stakeholders in the aircraft lifecycle includes the Maintenance, Repair and Overhaul (MRO) industry. The predictable logistics process to some degree as an outcome of IVHM gives benefit to the MRO industry. In this thesis, a new integrated numerical methodology called ‘System Level Airborne Avionic Prognostics’ or SLAAP is developed; looking at a top level solution in prognostics. Overall, this research consists of two main elements. One is to thoroughly understand and analyse data that could be utilised. Secondly, is to apply the developed methodology using the enhanced prognostic methodology. Readily available fault tree data is used to analyse the dependencies of each component within the LRUs, and performance were simulated using the linear Markov Model to estimate the time to failure. A hybrid approach prognostics model is then integrated with the prognostics measures that include environmental factors that contribute to the failure of a system, such as temperature. This research attempts to use data that is closest to the data available in the maintenance repair and overhaul industry. Based on a case study on Enhanced Ground Proximity Warning System (EGPWS), the prognostics methodology developed showed a sufficiently close approximation to the Mean Time Before Failure (MTBF) data supplied by the Original Equipment Manufacturer (OEM). This validation gives confidence that the proposed methodology will achieve its objectives and it should be further developed for use in the systems design process.

Aircraft maintenance is viewed as a critical safety component in general and military aviation industries, and thus it is crucial to identify the factors that may affect aircraft maintenance. Because the safety climate is considered as a leading indicator of safety performance and safety outcomes, this study utilized this safety climate approach to develop a model which can explain the relationships between employee turnover, safety motivation, self-reported unsafe acts, reporting unsafe behaviors, incidents, and injuries in the aviation maintenance environment. This study included a sample of 283 technicians in military aircraft maintenance units who participated in a cross-sectional random survey. Data collected were analyzed using Exploratory Factor Analysis (EFA) and Structural Equation Modeling (SEM) techniques. A structural model that fitted the data was developed which predicted 64% of the variance in employee turnover, 7% of the variance in safety motivation, 20% of the variance in unsafe acts, 41% of the variance in reporting unsafe behavior, and 21% of the variance in workplace injuries. The results indicate employees who report a perception of high turnover exhibit decreased safety motivation and increased unsafe acts which lead to higher levels of workplace injuries. The perception of safety climate was identified as an antecedent to safety performance and safety outcomes. Additionally, the effects of control variables such as age and education were tested. The implications for safety management in aircraft maintenance were also discussed. This study provides directions for future research on the turnover of aircraft maintenance technicians, safety performance, and safety outcomes.

Detta examensarbete utfördes på Saab AB, Support & Service, i Tannefors, Linköping, samt vid Institutionen för datavetenskap på Linköpings universitet. Ett moment i kvalitetsarbetet för komplexa industriprodukter, som till exempel flygplan, är att skifta från tvådimensionellt konstruktionsunderlag till tredimensionellt. Tredimensionella modeller har funnits i flera år. Nackdelen med dessa modeller är att de inte kunnat bära någon extra information, förutom den information som krävs för att de ska vara uppritade. Tekniken har gått framåt och nu går det att lagra teknikinformation i modellerna samt göra simuleringar som inte gått att göra förut. I och med att teknikinformation finns i modellerna, går det även att använda denna information till de olika publikationer som skrivs. Syftet med denna studie är att analysera hur teknikinformationsflödet mellan modeller och användare kan komma att se ut vid användning av modellbaserat konstruktionsunderlag, samt att föreslå exempel på hur tekniska publikationer för Gripen NG kan komma att se ut i framtiden. När all information finns i modellen, behövs inte lika mycket personal som redigerar bilder eller skriver text. Detta kommer innebära ekonomisk vinst och efter ett tags användning, kommer det även ge en ytterligare ekonomisk vinst, eftersom användarna har lärt sig hur produkten fungerar och på så sätt blivit effektivare på att använda den än de nuvarande dokumenten. / This thesis was carried out at Saab AB, Support & Service, in Tannefors, Linköping, and at the Department of Computer Science at Linköping University. One item in the quality work for complex industrial products, such as aircrafts, is to shift from two-dimensional design data to three-dimensional. Three-dimensional models have been around for years. The disadvantage of these models is that they could not carry any extra information, in addition to the information necessary for them to be plotted. The technology has moved on and now it is possible to store technical information in the models and do simulations that didn't work before. As the technical information is contained in the models, you can also use this information to the various publications that are printed. The purpose of this study is to analyze how the technical information flow between models and users, and also to propose examples of how technical publications for the Gripen NG may be in the future when using model-based design documents. Once all information is in the model, it is not needed to have as much staff employed for editing pictures or writing text. This will involve a financial gain, and after some time, it will also provide an additional financial benefit, because the users have learned how the product works and will be more efficient in using it than the current documents.

This study investigates the influence of unscheduled maintenance activities on delays and disruptions during the execution of aircraft heavy maintenance services by developing a simulation model based on Systems Dynamics (SD) and supported by an Evidential Reasoning (ER) rule model. The SD model studies the complex interrelationship between scheduled and unscheduled tasks and its impact on delays during a maintenance service execution. It was found that the uncertain nature of the unscheduled maintenance tasks hinders the planning, control and allocation of resources, increasing the chances to miss deadlines and incur in cost overruns. Utilising causal loop diagrams and SD simulation the research explored the relevance that the resource allocation management, the precise estimation of the unscheduled tasks and their prompt identification have on the maintenance check duration. The influence that delays and attitudes in the decision-making process have on project performance was also investigated. The ER rule model investigates the uncertainty present during the execution of a maintenance check by providing a belief distribution of the expected unscheduled maintenance tasks. Through a non-parametric discretisation process, it was found that the size and array of distribution intervals play a key role in the model estimation accuracy. Additionally, a sensitivity analysis allowed the examination of the significance that the weight, reliability and dependence of the different pieces of evidence have on model performance. By analysing and combining historical data, the ER rule model provides a more realistic and accurate prediction to analyse variability and ambiguity. This research extends SD capabilities by incorporating the ER rule for analysing system uncertainty. By using the belief distributions provided by the ER model, the SD model can simulate the variability of the process given certain pieces of evidence. This study contributes to the existing knowledge in aircraft maintenance management by analysing, from a different perspective, the impact of uncertain unscheduled maintenance activities on delays and disruptions through an integrated approach using SD and the ER rule. Despite the fact that this research focuses on studying a particular problem in the airline industry, the findings and conclusions obtained could be used to understand and address problems embodying similar characteristics. Therefore, it can be argued that, due to the close similarities between the heavy maintenance process and complex projects, these contributions can be extended to the Project Management field.

Many aircraft owners in the general aviation industry do not possess maintenance and facility technicians of their own. They shop around to get the lowest possible price to maintain their aircraft. Mississippi has taxes on both labor and parts for aircraft maintenance at the rate of seven percent. The state government repealed these taxes in 2006, a question posted by local decision makers might be: what the economy would likely be after tax repeal? In response to this question, the study first developed an econometric model to estimate aircraft ownership. Then, the Impact Analysis for Planning model (IMPLAN model) was used to estimate the effect of repealing the aircraft maintenance labor and parts tax in Mississippi. The results showed the state output, employment, and labor income would increase substantially if the labor and parts taxes were repealed.

En god säkerhetskultur är avgörande för att flygunderhållsfunktionerna i Försvarsmakten ska kunna leverera luftvärdiga flygfarkoster. Personalbrist råder i flygunderhållsfunktionerna och därför undersöks om och hur personalbristen inverkar på säkerhetskulturen. I arbetet undersöks flygunderhållsfunktionen på en skvadron inom Helikopterflottiljen. På grund av att Försvarsmakten ålägger ansvaret för säkerhetskulturen på chefer i organisationen samt att forskning på ämnet pekar på att ledarskapet är den största inverkande faktorn på säkerhetskultur så undersöktes ämnet utifrån ett ledarskapsperspektiv. Fyra chefer från flygunderhållet på Helikopterflottiljen intervjuades om faktorer som påverkar säkerhetskulturen och om personalbristen i deras organisation. Slutsatserna i arbetet är att personalbristen bland chefer leder till att chefer inte har tillräckligt med tid för att planera arbetsuppgifter och svårigheter med att visa närvaro i hangarerna. En medvetenhet om personalbristen i organisationen leder till att chefer engagerar sig mycket i personalens välmående. Personalbristen bland tekniker leder till, i kombination med två andra faktorer, att rapporteringskulturen försämrats. / Safety culture is a critical factor within aircraft maintenance organizations for delivering air-worthy aircrafts for the Swedish Armed Forces. There is a problem with insufficient manpower within the aircraft maintenance organizations, and therefore this paper aims to examine the implications this might have on safety culture. An aircraft maintenance function within the Armed Forces Helicopter wing was studied. The Swedish Armed Forces regulations inflict the responsibility for safety culture upon commanding officers. And this together with the research on the subject safety culture that says that it is leadership that inflicts on safety culture the most, dictates this paper to examine the subject from a leadership point of view. Four officers from the aircraft maintenance function was interviewed about leadership factor that inflicts with safety culture and the insufficient manpower problems. This paper concludes that commanding officers have problem finding time for planning for the workforce and making frequent tours in the hangars. Due to awareness of the problems with insufficient manpower commanding officers pay extra attention to the workforce’s wellbeing. Due to lack of manpower within the workforce, together with two other factors, the reporting culture has declined.