## 4 Case Study  
### Industrial Problem Description  
The primary concern of maintenance, repair, and overhaul (MRO) companies is the prevention of Aircraft on the Ground (AOG) events, which negatively impact airlines and MROs, especially in terms of their economic relationships. AOG events always involve a degree of risk. When they are related to repairs that are not included in the aircraft maintenance manual, the risk of an AOG event increases exponentially because non-standard methods are used to ensure airworthiness, which typically increase repair time. The need for these repairs began with lifecycle extension programs motivated by developments in the crude oil market, where lower crude oil prices encouraged the return of parked aircraft to airline fleets. These aircraft were fully restored with maintenance programs ranging from structural maintenance to cabin overhauls. One way to mitigate AOG risk in the case of aircraft repairs not included in maintenance manuals is to design and develop these aircraft repairs. MRO companies can be certified to develop these types of repairs, but several issues have been raised, primarily because these types of activities are not part of the MROs' core business. One of these issues is the long time required to develop repairs, which in some cases can take up to 2 years. This delay is usually due to the fact that there are not enough staff for development, and technical resources are limited. In order to perform development activities in repairs design, MRO companies need what is known as a Design Organization Approval Certificate (DOA), which is issued by regulatory agencies such as the FAA or EASA. This certificate allows not only the development of new repairs, but also the development of Supplemental Type Certificate(STC) projects, i.e., major changes to an existing type-certificated aircraft, i.e., major changes to the original design. In many cases, these changes bring enormous economic benefits. Therefore, it is useful to evaluate the ability of a particular MRO to perform the mechanical design activities of aircraft repairs. The evaluation of MRO performance in mechanical design can be quantified by assessing the risk that the design activities will not be performed well on a particular project. This assessment brings several benefits, such as the ability to create project portfolios and optimize resource allocation (technical and human). To develop new repairs or changes to the original design of an aircraft, MROs must overcome a number of mechanical design challenges. The first and biggest challenge is the lack of information about the original design. The original design is proprietary and not available outside of OEMs. Typically, MROs start from scratch on this type of project without OEM support. As a result, MROs know nothing about the materials, surface treatments, bonding technology and its curing parameters, and other design variables used in the OEM's original design. Another limitation is the human resources available for design. Typically, the skills required for maintenance are quite different than those required for design. As a result, maintenance personnel tend to be more technically oriented than scientifically oriented, which can lead to a lack of design knowledge and experience. In addition, the lack of scientifically oriented personnel can lead to a heavy reliance on a small number of experts, which can lead to a number of management limitations. In addition, maintenance and design activities are typically performed by the same staff, so design activities tend to take second place, which negatively impacts productivity and encourages project delays. Another limitation is the lack of required technologies in MRO hangars. In many cases, different kinds of technologies are needed for repairs than for building a component from scratch. MRO companies are struggling to survive economically, due to airline requirements and demands, so they rarely invest in technologies that are not used in their core business. This fact severely limits design activities.