Is It Time for a Revolution in Aircraft Maintenance Programs?

February 14, 2024

Commencing the implementation or revision of an Aircraft Maintenance Program (Fixed-wing and/or rotary-wing) is a responsibility that must be assumed accordingly. Through this action, control over scheduled, unscheduled, and recommended maintenance for an aircraft is granted. It is acknowledged that the program will subsequently undergo scrutiny by figures such as the operator's Quality Control (QC) or the local Civil Aviation Authority (DGAC). However, it is crucial to ensure, before this approval, that it complies with the minimum standards set by the manufacturer, design authority, and local regulations.

It is noteworthy that since 2013, with the publication of Annex 19 by ICAO, the Aeronautical Industry has framed Operational Safety as its primary focus. The effective control of an aircraft maintenance program plays a significant role in this regard. To implement effective Aircraft Maintenance Program Control, there is much to grasp. In this post, I will begin based on my experience with what I personally consider essential – the starting point – and detail it by addressing three key questions:

What is the manufacturer's manual or document that will provide guidelines for controlling my aircraft?

It is imperative to understand that every aircraft has a Maintenance Manual (AMM - Aircraft Maintenance Manual). This is not the sole manual for an aircraft; there is a list that can be accessed through technical publications for the fleet. This is where navigation begins to execute a proper Maintenance Program. It is also essential to note that manufacturers typically structure their maintenance manuals consistently, regardless of the aircraft model.

For instance, Boeing utilizes the Maintenance Planning Document (MPD) under the structure of Volumes to segregate instructions for various checks.

Similarly, Airbus (for fixed-wing aircraft) imparts maintenance program instructions through an MPD, usually organized into sections such as systems, zones, structures, and airworthiness limitations. Manufacturers like Bombardier have their maintenance planning manual (MPM), while smaller aircraft manufacturers like Cessna or Diamond use the Aircraft Maintenance Manual (AMM) or the Service Manual (SM) for instructions, with specific focus on Chapters or Sections 04, 05, and 12.

This consistent philosophy can also be observed with Bell helicopters (rotary-wing), where the manufacturer typically directs us to Chapters 04, 05, and 12 of its Maintenance Manual (MM).

Defining precisely how each manufacturer operates is impossible, but as we become familiar with their philosophies, navigation through their manuals becomes more seamless. A good analytical ability is crucial to cross-reference details in the manual, as they often refer to documentation separate from the manual we are extracting information from. Access to up-to-date technical publications is also essential for effective program control.

What should I know before taking on the responsibility of a Maintenance Program analysis?

Personally, I define this in four simple items:

  1. Understanding that regulations set by FAA, EASA, ICAO, and local DGAC are fundamental guidelines. They design the structure or specify minimum items to be addressed in a maintenance program. The checklist primarily consists of regulations from these entities, depending on the aircraft being operated and the regions in which the aircraft will fly.
  2. After identifying the manual to use, whether or not we have experience in maintenance program analysis, it is crucial to understand that the manufacturer provides instructions for scheduled and unscheduled services. These are often termed as Service Checks. Regardless of the aircraft model, search for instructions on controlling airworthiness limitation items, control for aircraft components (Life Limit, Component Inspection, Time Limits Components, etc.), and structural inspections, typically labeled as Structural Inspection, Corrosion Program, etc.The organization of the maintenance program's structure is the template for effective control. It can be structured into sections, volumes, or chapters, but the crucial aspect is to separate different types of controls by category. For example, segregating fuselage inspections from component inspections and having a separate section for structural inspections. I usually suggest keeping the engine inspection program completely separate and including routine controls, bulletin listings, Life Limited Parts (LLP), QEC, etc., in that section.
  3. Also, for proper interpretation of a maintenance program, it is vital to note that the items listed usually indicate whether they are applicable to the aircraft being controlled. Information such as effectiveness number, model, series, configuration, among others, are crucial and must be known for each aircraft under control.
  4. It may seem obvious, but knowing the definition of Flight Hours, Cycles, Landings, and other types of controls such as calendar times, RIN, External Load Time, External Load Event, NG Cycles, NF Cycles or NTL, Engine Start, Operating Hours, among others, is necessary. These are detailed by the manufacturer in the maintenance program manual to correctly track these items and project future compliance with scheduled maintenance.

In addition to the control items detailed in the manufacturer's maintenance planning manual, what other controls should I consider?

There is a defined set of controls for aircraft, and while I can't detail tips for the analysis and control of each in this post, I will share my experience in subsequent weekly publications. However, as mentioned earlier, the manufacturer's manual typically guides us to the following necessary documents for a proper maintenance program. Paying attention to local and design authority regulations is crucial.

At this point, to avoid extending the post, we could initiate a small list to provide an overview of the universe we need to be familiar with to properly control our aircraft.

  1. Airworthiness Directives (AD): These are rules from the Design and/or local Aviation Authority, and it is mandatory to control the ADs for each aeronautical product under our responsibility.
  2. Service Bulletins: These are mandatory or recommended items defined by the manufacturer of the aeronautical product, and we must list and control them.
  3. Supplemental Type Certificate (STC): These are mandatory or recommended modifications made to the aircraft that could affect its configuration. They must be listed and controlled, accompanied by Instructions for Continued Airworthiness (ICA), which are the instructions to control the STC.
  4. Dent, Buckle or Repair: Every impact or repair that the aircraft undergoes should be recorded in a Structural Mapping, typically supported by the Aircraft Repair Manual. Each of these must be monitored over time, even when referring to a Permanent Repair.
  5. OCCM (On-Condition Component Maintenance): A list of components installed in the aircraft that do not have maintenance limits, but proper control of these components could help develop a very mature reliability program for the organization.
  6. There are more documents that provide scheduled maintenance instructions, such as CMR, ALI, SFAR88, which vary depending on the size or model of the aircraft. Still, their correct interpretation and control are mandatory.

With these three questions, I conclude my post, hoping that these tools are helpful to our community.

Holymar Ruiz, Chief Engineer at SOMA Software