Background
Refueling is a critical and costly part of aircraft operation and maintenance. There are two methods to conduct land-based aircraft refueling: hot and cold. In hot refueling, the aircraft’s engines are still operating, which means that the aircraft must be equipped with a closed-circuit refueling receiver and single-point pressure refueling receiver that incorporates an automatic fuel shutoff capability. In cold refueling, the aircraft must shut down its engines, turn off all switches, and conduct a turnaround inspection prior to the refueling. The Naval Air Systems Command (NAVAIR) aircraft refueling manual 00-80T-109 provides definitions and guidelines for hot and cold refueling (NAVAIR, 2002). Although cold refueling is more fuel efficient, it is also more time consuming; hot refueling provides a much quicker turnaround. It would be easy to assume that the preferred method is hot refueling because it is faster than cold refueling; however, because fuel is consumed while refueling or waiting to refuel, hot refueling is costly. A squadron requests and schedules an aircraft to receive hot refueling if the aircraft needs to immediately fly another mission. Thus, achieving a balance between these two refueling methods and avoiding unmanageable peak demands are keys to maximizing the effectiveness of a refueling facility.
Naval Air Station (NAS) Lemoore is the home base of 16 fighter squadrons. A number of squadrons are deployed away from NAS Lemoore at any given time. Each of the remaining at-home squadron generates a flight schedule with its respective events a day prior to the actual flying date. Each event includes, among other information, the takeoff and landing times, the number of aircraft, the range where the aircraft will go, and the estimated fuel that will be burned in that event. The events of all squadrons are independently scheduled with the exception of joint missions in which multiple events from one or more squadrons will fly to the same range at the same time.
Because the squadrons do not communicate their schedules among themselves, and because the times when aircraft take off and land are not taken into account as a whole, there are times when the number of aircraft landing exceeds the capacity of the refueling system. The large number of aircraft coinciding in their landing time, in addition to the first-come, first-served distribution of the refueling resources, creates a backlog during some peak hours while leaving refueling resources underused in other times.
Additionally, NAS Lemoore’s aircraft population will grow in the coming years, particularly in 2017 and 2018. This growth will be due to the introduction of the Joint Strike Fighters (JSF) F-35 and relocation of one or more F/A-18 E/F squadrons. Given the current bottleneck experienced by the aircraft waiting to be refueled during peak operational periods, the additional future demand will likely increase wait times for refueling if a new approach to scheduling is not developed. Optimizing the flying and refueling schedules in order to operate the refueling system more efficiently will improve the available flying time of the aircraft.