TABLE OF CONTENTS Depending on how you define "Planning Maintenance" and "Scheduling Maintenance," the origin of Planner/Schedulers can vary significantly. Earlier, it was pointed out that pre- and post-flight checks on military, and commercial aircraft had their origins in First World War. The aircraft branches of the military continued to lead the evolving practice of maintenance with their adoption, in the 1930s, of standardized, periodic inspections the 30-, 60-, 90-, 120-hour (flight time) inspections of airframes and aircraft engines. Each increasing hourly-based inspection involved an increasingly detailed level-of-inspection, and ultimately arriving at complete disassembly for individual part inspection and (as required) replacement.
These flight-time based inspections brought about the first requirement for skilled planning and scheduling. Because of the practice of swapping out aircraft engines from planes with heavily damaged fuselages, it was a routine occurrence for the 120-hour inspections of the airframe and engine on one aircraft to come due at different times. This meant that aircraft were taken off-line twice as often as they would have been with coincident airframe and engine 120-hour inspections. Additionally, because the military had this tendency to fly all their aircraft on every mission, most aircraft would come due for their major inspections simultaneously. This, of course, would result in the entire squadron being "off-line" rather than just one or two aircrafts.
The flight-hour-based inspections required some planning skill to keep airframe and engine inspections synchronized and even more skill at maintaining staggered off-line schedules for squadron aircraft. The engine swapping practice had...
