All maintenance, whether base or line in nature and complexity, must be conducted in accordance with the regulations of the national aviation authority (NAA) of aircraft registration, the operator (or owner, if an internal flight department) being ultimately responsible for maintenance compliance.
National regulations apply to different jurisdictions.
Aircraft are required to undergo regular scheduled inspections and servicing in accordance with an approved maintenance programme determined for the precise type and model established by the manufacturer and accepted by the NAA responsible. Major components, including, for example, engine and engine accessories, the auxiliary power unit (APU), and other major and minor parts each have defined overhaul hard lives with flight hour, flight cycle and/or calendar limits which are routinely computer-tracked.
Some manufacturers and component manufacturers offer ‘power by the hour’ schemes to better predict maintenance costs, though there are differences between products offered, coverage, terms and conditions, and all are impacted by area and type of operation, the aircraft’s utilisation, previous maintenance history and projected future maintenance.
Typically, an aircraft will undergo a daily or pre-flight check, most likely performed by the crew to defined procedures. Further regular checks at flight time or calendar intervals will be performed at an approved maintenance facility.
Away from base, while certain defects will ground the aircraft immediately, others may be carried over to the next inspection or more likely for an otherwise limited period. The operator-specific minimum equipment list (MEL) is an approved document stating which on-board equipment may be unserviceable while still permitting safe flight. Operating outside the authority of the MEL, created with a broad input of maintenance experience and historic fleet reliability experience way outside that of the pilots on the day, will negate the aircraft’s certificate of airworthiness (CofA) and hence its insurance.
The oversight of hangar visits for inspection, man-hours employed, parts replacement, warranty and power by the hour or similar programme provisions and reclaims, and other maintenance performed requires a deep scrutiny for contract and cost control, and quality. Yet, this is a specialist area of expertise often beyond the scope and ability of many aircraft managers, benefitting from external and independent oversight of these maintenance events.
The use of expert advice in contracting maintenance, rather than simply a known engineer or an operator’s maintenance manager, while necessarily and importantly in close cooperation with an operator’s technical personnel, negotiating power by the hour agreements, reviewing parts replacement and warranty provisions, overseeing maintenance and quality while actually performed, cost control and billing audit, will likely save many hundreds of thousands of dollars during a period of ownership.