| With science and technology developing further and further, the performance and complexity of civil aircrafts are increasing more and more. The maintenance cost of a civil aircraft has grown up to two thirds of the purchase price and 10%-20% of the direct operating cost. The maintain cost has a direct connection with maintenance program, therefore both aircraft manufactures and airlines have paid much attention on maintenance program. The final intention of maintenance program is to design the maintenance tasks of the civil aircraft reasonably. However the maintenance optimal models about the single-unit are more and more perfect and do not fulfill an accurate need for maintenance program. So from the point of the multi-unit maintenance optimization, this dissertation has a deep research on standby system, parallel system, task-group and opportunity maintenance. Then, maintenance program aided system (MPAS) for commercial aircraft maintenance program is developed. The main contain includes as follow:(1) The standby system is to eliminate or relieve abnormal conditions that follow a failure and take over from a function that has failed, so it is very important for the system. The standby system always works at shut-down condition, so its failure is hiden. The operational check policy and functional inspection policy with variant intervals are respectively proposed, according to whether the failure has the characteristics of delay-time. The influence of the protected system on maintenance decision for standby system is analyzed. Then the maintenance optimal model is developed to minimize the maintenance cost rate with the constrain of the availability. Thus the model gets more reasonable.(2) The parallel system is widely used in the civil aircraft in order to enhance the reliability. The redundancy units work together in the two-unit parallel system. The redundancy units have the same physical character and circumstance, and (the failures are found inconveniently), so the imperfect staggered inspection is proposed. Then the failure dependency and modes between these two units are analyzed, and the renewal probability of the parallel system is studied. At last, choosing the inspection interval and number as optimized variables, the maintenance optimal model is developed to minimize the maintenance cost rate with the constrain of the availability. So the maintenance model is more logical.(3) In module systems, opportunistic maintenance on one unit basically refers to the situation in which preventive maintenance on the other units can be carried out at opportunities. Opportunistic maintenance is useful for saving maintenance cost. The opportunistic maintenance policy is proposed considering the minimal maintenance and the different type of failure adopting different type of maintenance. Then, using the renewal theory, the probability density function of opportunity maintenance and the renewal process are analyzed. At last, the optimal maintenance model is developed to minimize the maintenance cost rate, which offers a new method for determining the age of opportunistic maintenance.(4) Because of plenty of tasks and high maintenance cost in aircraft maintenance, the task-group is important in maintenance program. As the existing method of task-group is defective, the new method of task-group is proposed based on group maintenance policy. Considering the real condition of the airlines operation, the influence of task-group on utilization and maintenance cost of the civil aircraft is researched. The optimal maintenance model is developed to minimize the maintenance cost rate, and the model is subject to the reliability and utilization. So it offers a new method of task-group for aircraft manufactures and airlines.(5) MPAS is designed based on the practical requirement of the airlines and the MSG-3. The MPAS applies the theory of decision-making support system and optimal maintenance models. Now, we have handed over this MPAS to ACAC (Avici Commercial Aircraft Co.), and it is of great application.
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