Effect of Inspection Strategies on the Weight and Lifecycle Cost of Airplanes

Inspections of aircrafts fuselage panels are performed periodically, at scheduled intervals, to repair damage that can threaten the safety of the structure. Recently, structural health monitoring techniques have been developed that use sensors and actuators to detect damage, paving way for condition-based maintenance. This paper quantifies the effect of inspection strategies on the safety and lifetime cost of an airplane. The lifecycle of an airplane was modeled as blocks of damage propagation interspersed with inspection. The Paris model with uncertain parameters is used to model fatigue damage growth, and the detection process by inspections is modeled by the Palmberg equation. Two inspection strategies are compared based on their effect of optimal weight and lifecycle cost of the panel, while maintaining a desired level of reliability. Direct integration procedure computes the reliability for a given set of maintenance parameters. It is found that the better inspection model leads to about 15% savings in weight of airplane and about 35% savings in lifecycle cost of an airplane over scheduled maintenance.

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