The periodic aviation maitenance stochastic schedule model (PAM-SS)

Abstract

Aircraft accidents are the most horrible accidents in modern society. It is proved that aircraft maintenance errors form 40% of the causes of accidents, while 35% of maintenance errors is caused by poor scheduled maintenance. Planning of aircraft maintenance isnt about planning and scheduling only, its about management, leadership, communication, and supervision. It is the act of planning, controlling and executing materials, resources, and activities. With the continuous introduction of new aircrafts with advanced technology, aircraft maintenance is becoming more complicated. Aircrafts were built to fly, so the purpose of the aircraft maintenance program is to maintain the aircraft performance, serviceability, and readiness to stay in the air. Aircraft maintenance consists mainly of scheduled maintenance and unscheduled maintenance. Scheduled maintenance is due relevant to operating hours, calendar, or number of cycles. Existing researches used regular project management techniques, or even integrated them in order to produce a plan and a schedule for scheduled aircraft maintenance. However, these researches failed to (i) incorporate uncertainty in the schedule, and (ii) consider all resources in the schedule. Thus, a new model is required that considers uncertainty and delays in the maintenance schedule, and considers all resources, such as work force and work zones. This research develops the Periodic Aviation Maintenance Stochastic Schedule (PAM-SS) model. The PAM-SS model evaluates the stochastic schedule of an aviation 50- hours maintenance program using the Cyclone model. Cyclone is very powerful in showing the bottlenecks in the maintenance schedule, and indicating which resources are mostly idle or in queue. The PAM-SS model (1) identifies the different inspection tasks of the maintenance schedule, (2) allocate the resources required for each task, (3) evaluate a stochastic duration of each inspection task, (4) evaluate probability of occurrence for each breakdown or repair, (5) develop the cyclone model of the stochastic schedule, (6) simulate using Monte Carlo Simulation the Cyclone model, and (7) evaluate the total stochastic duration of the overall maintenance program. Data were collected from military aircraft experts, mainly engineers and inspectors, through interviews and questionnaires. The PAM-SS model is applied to the PUMA SA330SM helicopter of the Lebanese Air Forces (LAF). The schedule showed a 50-hours maintenance duration of 323 minutes after steady state is reached. Except the pilot and the electrical team (~ 90% idle), all other teams range between 10% and 50% idle. A sensitivity analysis is also performed, and yielded that the PAM-SS model is not sensitive to the number of technicians in each team, however it is highly sensitive to the probability of occurrence of the breakdowns/repairs. The PAM-SS solves the problem of stochastic periodic scheduling of aircraft maintenance, both in academic and industry circles.