An aircraft maintenance program is certified at the time of the airworthiness certification acquired by the aviation regulatory authority. A certified maintenance program lists the manufacturer's and operator's responsibilities in keeping the aircraft within serviceable limits.

The aircraft operators follow an Operator's Approved Maintenance Plan (OAMP) that includes thousands of maintenance tasks, Service Bulletins (SBs), Airworthiness Directives (ADs), and is approved by the regulatory authority.

The OCMP tasks must be clustered based on the time limits of various component groups. The tasks are clustered across multiple maintenance checks at different times during the aircraft’s operational life. Some maintenance checks are more frequent than others.

Line checks

Tasks performed during a pre-flight walk-around or on an overnight maintenance line are part of line checks. Checking the outer probes, sensors, vents, tires, lights, and any apparent damage to the aircraft surface are examples of a pre-flight check.

All Nippon Airways Boeing 787-9 Dreamliner JA839A
Photo: Vincenzo Pace | Simple Flying

Line-maintenance mechanics perform relatively heavier tasks such as engine oil and hydraulic checks, cabin emergency equipment, tire pressure, and brakes.

Ramp checks

Ramp checks may be done every week at the home base of the operator. A Minimum Equipment List (MEL) provided by the OEM is followed during the ramp check to ensure the continued operability of the aircraft. During a ramp check, a more extensive inspection is performed.

Oil checks, fluid top-ups, crew emergency equipment, and sensor redundancies are checked. Non-urgent but critical items found during pre-flight checks are handled during a routine ramp check.

A-checks

The A checks are typically performed after approximately every 500 flight cycles or 700 flight hours. A narrowbody Airbus A320 goes through an A check at 400 cycles. With an average of four daily cycles, an A320 may be scheduled for an A check every three months.

 Air France Airbus A320 during a ramp check
Photo: Getty Images

Numerous inspection and maintenance tasks on an A320 have a 100-day limit, which keeps it right around the three-month maintenance cycle. During an A check, lubricating critical systems, changing filters, and a more detailed emergency equipment inspection is performed. An A check can take between six and 24 hours for a narrowbody jet and up to 72 hours for a widebody jet.

C-checks

The C-checks, also known as base checks, are heavy system maintenance performed every 18 months to two years. For an A320, a C-check kicks in at around 5,000 flight cycles or approximately 24 months.

During a C check, complex systems such as pumps, actuators, and functional assemblies are tested for performance and failure. Load-bearing components such as the fuselage structure, wings, and engine pylons are examined for wear and stress.

An aircraft mechanic checks the door of an Airbus A380
Photo: Getty Images

Moreover, the entire cabin is removed, inspected, repaired, and put together during a C-check. With up to 6,000 labor hours for a C check, the aircraft may spend up to four weeks in the shop, costing several million dollars.

D-Checks

The D-check, also known as one of the heavy maintenance checks, comprises further teardown of the aircraft. The D-checks are costlier and require 6-8 weeks to complete.

Extensive repair of control surfaces and repainting of the fuselage may be part of the D-check. Landing gears are also dismantled, inspected, repaired, and tested during the check.

What do you think about aircraft maintenance tasks and checks? Tell us in the comments section.