Does Periodic Maintenance Cause Unscheduled Outages?

Abstract

It has been suspected for some time that unscheduled outages of National Airspace System equipment increase during core working hours; to date, however, no research has been done to determine their cause. First, aggregate trends in scheduled periodic maintenance (PM) activities and unscheduled outages are examined for calendar years 2000 through 2004. The reported increase in unscheduled outages is postulated to be due to increased levels of maintenance activities that may occur during this period. A detailed analysis is presented, and the individual pieces of equipment that suffer unscheduled outages after receiving PM are examined. If PM activities have an effect on unscheduled outages, then higher levels of unscheduled outages would be expected to occur in the first hours after the completion of a PM task. Further data analysis shows evidence for this hypothesis.