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Top1. Introduction
Aircraft maintenance refers to the periodic inspections that need to be done on all commercial or civil aircraft after a certain amount of flight hours or usage. It is one of the critical aspects as well as a complex activity in the airline and aviation industry. Highly regulated by ICAO (International Civil Aviation Organization) and local airworthiness authorities, maintenance is conducted in order to insure safe and airworthy operations. Conventional aircraft maintenance includes performing maintenance activities based on fixed schedule such as hours, days or weeks (West and Johnson, 2013). For airlines in the United States, FAA (Federal Aviation Administration) has provided recommendations on continuous inspection and maintenance programs (Van Den Bergh et al., 2013).
Aircraft maintenance activities are based on two main metrics, the Total Number of Flying Hours (FH) and the number of cycles (one cycle represents one takeoff and one landing). The most commonly used metric to determine the specific time on which and aircraft needs to receive one of the four types of checks (A, B, C or D) is the number of Flying Hours an aircraft has.
Before an aircraft needs one of the aforementioned checks, carriers perform what is called a daily inspection, also known as line inspection, before the first flight of the day or at each stop while in transit. These inspections consist on a visual inspection of the fuselage, checking the fluid levels, tires, brakes and emergency equipment requiring approximately one hour.
The A checks are considered the lightest maintenance checks and Differ based on the fleet type. B Checks are similar to A with more comprehensive activities. C Checks are structural inspections of the airframe and require opening access panels and detailed checks of individual systems and components. The heaviest types of maintenance are the D Checks, which the aircraft is taken out of service for around a month, disassembled and detailed visual non-destructive tests and inspections of the aircraft structure are made.
According to the Global Maintenance, Repair and Overhaul (MRO 2015) Market Economic Assessment report, civil aviation spent more than $70B on aircraft maintenance in 2014. Aircraft maintenance cost is among the major cost drivers within the airlines. Fuel and crew cost typically rank among the top cost components at the airlines. For comparison purposes, Figure 1 represents the average percentages of total and aircraft operating cost for fuel, flight crew salaries and maintenance for 6 US airlines (Delta, American, United, Southwest, Alaska and US Airways) from 2003-2014.
Figure 1. Average percentages of major cost components in total and aircraft operating costs