Design of an enhanced FOD inspection system for the aircraft assembly process

Foreign object debris is any object alien to an aircraft assembly component, examples include screws, fasteners, bottle caps, tools, and trash. Currently, visual inspection techniques are used to detect FOD. These methods, relying on line-of-sight, are time consuming (5- 10% shift time), costly ($13B direct costs annually) and subject to errors (i.e. 50% FOD remains undetected after inspection). Analysis of production data shows that a typical fighter jet production line with 26 assembly stations will experience one FOD event on average every 5.46 hours. An enhanced FOD detection system (FODXSYS) proposed combines X-ray imaging technology with differential imaging software. This system aims to improve efficiency and decrease production costs. A discrete event simulator [FODSIM] was developed to estimate the effect of FOD on aircraft production time, cost, and quality. There are 26 assembly processes modeled station-by-station. Historical FOD data was used to derive an inter-arrival time of FOD occurrences [Exponential (λ=0.0102 hours)],), and FOD rework times [Exponential (λ=9.51 hours)]. Analysis of FODSIM output indicates a savings of $8M; 5 years post implementation, and $18M after 10 years. A break-even analysis shows that an initial investment of $2M for 5 X-ray machines requires 5.5 years to reach a break-even point.