# Disposal and Recycle Economic Assessment for Aircraft and Engine End of Life Solution Evaluation
## 2 Literature Review of Aircraft Disposal and Recycle Analysis  
Recent research on industrial EoL solutions include that regarding rolling stock [13], automobiles [14], ships [15], and aircraft vehicles [8; 16; 17]. The research focus ranges from the macro perspective of EoL strategies [8] to the micro perspective of the disassembly and dismantling process [18], as well as material management methods, i.e., the material recycling [19; 20; 21], and component management [17; 22]. In addition, the economic and environmental impacts of the D&R process are also studied [4; 23; 24]. Another stream of research is relevant to aircraft retirement decision-making [25; 26; 27]. It mainly focuses on the temporal approaches to aircraft decommissioning in order to decide the time at which to retire an aircraft or a fleet with specific strategies. It is noteworthy that the retirement decision is very different from the EoL solution, where the latter considers the time period after the retirement decision has been made. The EoL solution is the focus of the current research and is associated with economic and sustainability of aircraft Life Cycle Analysis (LCA). Aircraft EoL strategies focus on general policies in terms of the priorities of the preferred approach by stakeholders, e.g., the selection of resale or disassembly for an aircraft, which also considers the logistics and supply chain allocations. The goal is to select a D&R strategy for the optimal product usage with the least cost and highest benefit. The model considers stakeholders' benefit, the cost benefit trade-offs among different EoL solutions, the reuse/remanufacturing possibility for the aircraft and its components, and the reverse logistics of the product and material retransformation and redistribution. Most research assumes a fixed task sequence of disassembly & dismantling process. Moreover, methods are provided to generate appropriate EoL solutions. The following techniques are often used for strategy selection: alternative strategy modeling [16; 28], network flow simulation [29], cost-benefit optimization [15], complex system modeling [28], reverse logistics analysis [17; 30], and sustainability considering economic, social, and environmental balances [16; 28; 31]. The detail-level disassembly & dismantling research looks into the characteristic elements of the process steps, viz., the disassembly method, the process steps sequence, the cost of process handling, and material flows. It aims to achieve an optimal process sequence for least cost and maximum revenue. It can be modeled by mathematical programming, heuristics, and artificial intelligence techniques. Methods, such as fuzzy logic [18], mixed-integer linear programming [28], process planning optimization [32], dynamic programming [33], and simulated annealing [34], are utilized. Component management refers to the reuse of components for other aircraft or for other purposes. It also involves the extension of the component lifespan as well as the control of spare parts inventory at EoL stage. The objective is to maximize the reusability and/or the values for the EoL aircraft components. For example, [PERSON] et al. [35; 36] proposed a method of adapting inspection schedule of aero engine welded structures based on defect propagation analysis, and considered the replacement of the welded components by additive manufacturing spare parts in view of improving component life cycle performance. [PERSON] et al. [22] investigated inventory control for aircraft spare parts based on continuous-time Markov chain model at the aircraft EoL phase. A component-oriented approach within a computer-aided system was implemented to integrate assembly and disassembly properties to support component management during the aircraft disposal process [17]. Research on material recycling investigates possible solutions for separating the various material usage in the product and the reuse of the materials in new products [37; 38]. It aims to reduce cost consumption, while considering economic and ecologic impact.