This thesis focuses on obtaining better estimates of remaining life for on-condition (OC) parts in aircraft engines. Aircraft engine components are commonly classified into three categories, life-limited parts (LLP), OC-parts and consumables. Engine maintenance typi-cally accounts for 10% to 20% of aircraft-related operating cost. Current methods to esti-mate remaining life for OC parts have been found insufficient and this thesis aims to devel-op a method that obtains better life estimates of OC part. Improved life estimates are es-sential to facilitate more reliable maintenance plans and lower maintenance costs. In the thesis, OC parts that need a better life estimates are identified and suitable prognosis methodologies for estimating the remaining life are presented. Three papers are appended to the thesis. The first paper lays out the main principles of air-craft engine maintenance and identifies the potential for improving maintenance planning by improving the remaining life estimation for the OC parts. The paper concludes that re-search is needed to find better estimates so that the right amount of maintenance is per-formed at each maintenance occasion. The second paper describes the aircraft and its engine from a system of system perspective. The aim of the paper is to show that no system is stronger than its weakest part and that there is a potential to increase the availability and readiness of the complete system, the aircraft engine, by introducing better life estimates for OC parts. Furthermore, a review of all engine parts, no matter if they are life-limited or on-condition, which needs to be incor-porated in a replacement model for maintenance optimization, is given. The paper con-cludes that the reliability of the complete aircraft engine would be increased if better life estimates are presented also for the OC parts. The third paper includes an evolved analysis of the subject and the analysis moves deeper in to a subsystem/module of the engine, the low pressure turbine. The specific subsys-tem/module is further analyzed to show the potential of increased reliability for the subsys-tem/module and the complete system, the aircraft engine, if better life estimates for the OC parts are obtained. Methods on how to estimate remaining life is discussed in this paper. It is stated that life estimates can be based on visual inspections, available testing methods (e.g. non destructive testing ) or new techniques that may be need to be developed based on remaining useful life estimations. To estimate the remaining life for the OC parts well es-tablished prognostic techniques such as physic-based, data-driven, symbolic, hybrid, or context awareness approaches that combine contextual/situation information awareness will be considered.

The content of customer-perceived value has in this study been explored with the aim of providing an understanding of the concept. The evolving service-centered logic for marketing puts an emphasis on value, especially the value perceived and determined by the customer. Concurrently, a development is recognized within the industrial business-to-business sector where goods and services are packaged into total service offerings – with an increasing prominence for services. This is the background of the study. The study itself was conducted in order to elucidate the concept of customer-perceived value in a context where total service offerings are provided within dyadic business-to-business relationships. The conceptual framework, guiding the empirical study, has its points of departure in the field of service research. A case study conducted in the commercial aircraft engine maintenance industry has provided a description – depicted in value maps – of context-specific attributes forming the dimensions of customer-perceived value. It is suggested that customer-perceived value is created at three levels; at a product level, at a partnership level, and at a psychological level. Furthermore, the value maps clarify the double nature of customer-perceived value, which is found to have both an origin side – how the service provider should act to deliver value – and a side illuminating the more or less monetarily quantifiable effects of value. The origin and effect of customer-perceived value are proposed to be explained by a model where the notion of “flow” is central. Flows of goods, information, risk, involvement, and money intersect the value features and provide the sources of value on the origin side of customer-perceived value. The effects can be traced to the flows of revenue benefits, cost benefits, interest effects, and costs to use. Concurrently, flows both build, and are filtrated by, “trust” during the process in which the customer’s perception of value comes into being. On the effect-side of value, the concepts stochasticity and substantiality are introduced in order to capture the uncertainties that make translations into monetary terms difficult. The outcome of the abductive reasoning in the final phase of the investigation is a conceptual model – proposed as the main contribution of the study – summarizing aspects of customer-perceived value. My definition of customer-perceived value, together with a list clarifying the many facets of the concept, concludes the study.