MRO, Line Maintenance and Base Maintenance

Maintenance is one of the pillars that supports the entire aviation industry. Similar to how all machines require time to time maintenance, even aircraft require regular maintenance to maintain its airworthiness. Airworthiness is the quality check of various aircraft components and structure which determine its suitability for a safe flight. A certificate of airworthiness is conferred from a local governing aviation authority and is maintained by performing the required regular maintenance checks.

Maintenance, Repair, and Overhaul (MRO)

The Maintenance, Repair, Overhaul refers to organizations involved with the maintenance, repair, and overhaul of aircraft and associated systems and components and continues throughout the life of an aircraft from its initial entry into service through to its ultimate disposal.
The MRO organizations carry out activities include the following activities:

Maintenance that relates to the process of preserving a complete aircraft in an airworthy condition.
Repair or replacement of damaged items that are inoperable
The overhaul that relates to reconditioning a system that has degradation in performance or strength.

Line Maintenance

Line Maintenance comprises of any maintenance that is carried out before the flight to ensure that
the aircraft is fit for the flight. The aircraft is visually inspected and its aircraft
logbook is checked for various entries relating to system problems, failures or other maintenance. It includes troubleshooting, defect rectification and component replacement of an aircraft and requires 2 man hours to complete the checks.

Base Maintenance

Base Maintenance is carried out in a hanger and covers a series of checks and MRO activities. Every airline has different maintenance schedules and procedures that relate to their specific aircraft. Base maintenance is classified into 4 categories each denoted by a letter.

A Check: Carried out after every 100 flight hours.
B Check: Carried out after 2 months or 500-600 flight hours. It involves a more thorough check than A Check.
C Check: It involves a very comprehensive and thorough check. Carried out after every 2 years. Some operators carry out a "3C Check" which is a subcategory of C Check and includes light structural maintenance, corrosion check, replacement of seats, etc.
D Check: It is the most comprehensive check-in Base Maintenance. Carried out after every 6 years and can take up to 2 months to complete. An aircraft on average undergo 2 to 3 D Checks before it retires.

Unscheduled Maintenance and Aircraft Recovery

If there is a need to repair an aircraft is stranded at an airport away from the base airport, the operator may declare the aircraft as “Aircraft on Ground”. Repair to the damaged aircraft may require a specialist team to travel on site and carry out the repair.

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MRO, Line Maintenance and Base Maintenance