Introduction to Aircraft Maintenance – EASA Compliant Maintenance Program Development

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Aircraft Maintenance Program Development – Considerations by Sofema Aviation Services (SAS)


When dealing with the complex technical systems involved in air transport, the consequences of unreliable services become critical and may include:

       » A high cost of operation
       » A loss of productivity
       » Incidents
       » Potential exposure to accidents

Hard Time Primary Maintenance

The early attempts at delivering a more effective maintenance approach (in the early 1960s) saw hard time limits developed which resulted in aircraft being progressively dismantled, in what became known as Hard Time primary maintenance.

      » All hard time components were then routed through an overhaul process and after an appropriate restoration process was considered as zero time.
      » Essentially this meant that they were considered as zero life and good to go again for a full life – (The problem was that the overhaul process did not necessarily impact the eventual life of the component)

Reality Check ****

In reality performing schedule overhaul on a complex component does not have a particular impact on the overall reliability*

             *Unless there was a dominant failure mode evident.

(Thus, calling into question the associated rationale in performing the overhaul).

A second understanding concerns the fact that there are many items for which there is no “effective maintenance activity” for scheduled hard time maintenance.

On Condition (OC) Maintenance

The findings of the FAA Led task force led to the development of a second primary maintenance process defined as On-Condition (OC).
      » On-Condition requires that an appliance or part be periodically inspected or checked against some appropriate physical standard to determine whether it can continue in service.
      » Note – The purpose of the standard is to remove the unit from service before failure during normal operation occurs.

From the regulatory perspective, it is of primary importance to deliver effective oversight of aircraft operators’ maintenance programmes. Together with a viable assessment of the management of the continuing airworthiness process.

General Introduction – Objectives of an AMP:

      » To ensure the inherent safety & reliability levels of the equipment
      » To restore safety and reliability to their levels when deterioration has occurred.
      » To obtain the information necessary for the adjustment and optimization of the maintenance program when these inherent levels are not met.
      » To obtain the information necessary for design improvement of those items whose inherent reliability proves adequate.
      » To accomplish these objectives at a minimum total cost, including the cost of maintenance and the cost of residual failure.

The Essential Purpose of Aircraft Maintenance is to:

      » Either return a defective system or component to serviceability or to
      » Maintain the aircraft system, component or structure in airworthy condition.

Primary Objectives:

      » To keep the aircraft in a serviceable and reliable condition so that may continue to serve its useful purpose.
      » To ensure that all regulatory requirements remain fully in compliance with the concept of delivering continuing airworthiness.
      » To ensure that the asset value is protected.

Considering Methods, Procedures and Tasks Necessary to Maintain the Aircraft:

Early in the development of a new type, an INDUSTRY STEERING COMMITTEE (ISC) is formed to manage maintenance program development activities.

General Introduction – ISC

      » The committee is composed of members from a representative number of operators and a representative of the prime airframe and engine manufacturer.

Responsibilities of the ISC include:

      » Directing the activities of the MRB Working Groups
      » Carrying out all liaison with the manufacturer and other operators
      » Preparing the final program recommendations
      » Coordinating any future revisions
      » Representing the operators during contact with the authority of the State of Design

Initial Aircraft Maintenance Program – AMP

A new operator is responsible for producing his own maintenance program tailored for his specific operation.

This program must be based on the MPD and not based on another operator's experience.

Next Steps

Sofema Aviation Services ( and SofemaOnline ( provide EASA Compliant Maintenance Planning Regulatory & Vocational Training – please see the websites or email

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