By Bjorn Fehrm

March 1, 2024, ©. Leeham News: We are discussing the Operational phase of a new airliner family. For the operational phase, the airplane must pass scrutiny for Continued Airworthiness. The biggest item in a regulator’s Instructions for Continued Airworthiness is the required Maintenance program to keep an airliner airworthy. We discussed the modern MSG-3 maintenance program for an airliner last week, why it was created, and its main analysis principles.

Now we look at maintenance data designed to the MSG-3 standard, the Maintenance Planning Document (MPD) for the Airbus A318/A319/A320/A321.

Figure 1. The front page of the A318/A319/A320/A321 MPD no 45. Source: Airbus.

Maintenance for the A318/A319/A320/A321

For an aircraft to keep its operational certification, it must be subject to a maintenance program approved by the local regulator. A country regulator, in turn, relies on a proposed maintenance program from the OEM, which is developed in a prescribed procedure called MSG-3 (from Maintenance Steering Group 3^rd version).

An aircraft’s maintenance program is based on the Aircraft OEM’s Maintenance Planning Document, MPD. But it’s only a major help in designing a maintenance program for the aircraft that the Regulator can approve. Here is how Airbus describes the role of the MPD:

The A318/A319/A320/A321MPD is neither a controlling nor an approved document. It is an AIRBUS envelope repository document and covers repetitive maintenance tasks required or recommended by miscellaneous source documents. These are among others:

– Maintenance Review Board Report (MRBR)

– Damage Tolerant Airworthiness Limitation Items (DT-ALI)

– Certification Maintenance Requirements (CMR)

– Ageing Systems Maintenance (ASM)

– Fuel Airworthiness Limitations (FAL)

– Airworthiness Directives (AD)

– Service Bulletins (SB)

– Service Information Letters (SIL)

It is the operator’s responsibility to prepare their scheduled maintenance program after clearance with their regulatory aviation authorities.

MPD revisions

The A320/A321 MPD has been revised about 50 times, with the first version issued at Entry Into Service (EIS) of the A320 in 1988. Today, it contains about 3,000 tasks, but not all tasks apply to all A320 variants.

The tasks can be clustered into a certain pattern, but many tasks do not fit into this pattern. It’s the responsibility of the airline’s maintenance department to do its own grouping of tasks and decide which shall be done during a shorter (typically overnight) hangar event (often called A checks), longer hangar event (B checks), and a dedicated maintenance hangar event (C checks).

For the revision 45 MPD, the A cluster of checks were at 750 Flight Hours (FH), 750 Flight Cycles, or 6 months, whichever was reached first. The B check was folded into the A check, whereas the C check was at 7,500 FH, 5000 FC, or 24 months. This has since increased further as experience is gathered when operating the A320 variants.

Figure 2 shows a page from MPD no 45. The task number is built up of the ATA reference (ATA has built a standardized classification of an aircraft’s parts and systems), followed by a sequence number and an index.

Figure 2. The task page from A320 MPD no. 45 shows inspection tasks for avionics cooling. Source: Airbus.

The first task should be performed every 750 FH or 6 months; thus, it belongs to the A check cluster. The second task shall be done every three years or 10,000FH. It’s a task that does not belong to the typical A or C check schedule. The same goes for the following task on the page. The MPD also lists the source of the tasks, the required workforce (1 person), and the estimated time consumed (M/H, 0.1 for the first task).

A major job for airlines

With around 3,000 tasks to schedule and keep track of when these shall be done and have been done, the management and tracking of the maintenance of an airliner is a major undertaking. There are many specialist consultants, software companies, and maintenance organizations (called MROs, Maintenance and Repair Organizations) that assist airlines in structuring and performing the maintenance of their fleets.

For new airlines, the maintenance of the fleet is often outsourced to specialists, whereas some airlines have spun off their maintenance organizations as divisions, offering their help to other airlines. Examples are Delta TechOps, Lufthansa Technics, and ST Engineering (owned by Singapore Airlines).