MSG-3 reliability-based maintenance method

This article, aimed at readers with a basic knowledge of industrial maintenance, presents the contents of the ATA (Air Transport Association of America) MSG-3 standard applicable to scheduled aircraft maintenance. This standard and its revisions have been in force since 1968 in American regulations. Since 2003, the European Aviation Safety Agency (EASA) has played a similar role in Europe. This article focuses solely on the technical aspects of maintenance programs. Organizational and regulatory aspects related to American or European certification issues are briefly described.

The first section outlines the origins and development of the maintenance approach that began with the commissioning of the first jumbo jet, the Boeing 747, and led to the first document, MSG-1, drawn up by the Maintenance Steering Group. Feedback led to the drafting of MSG-2. The work carried out by Nowlan and Heap on RCM (Reliability-Centered Maintenance) and the difficulties encountered in applying MSG-2 led ATA to develop a third version, MSG-3, in 1980. This standard has undergone eleven revisions to take account of new technologies: the latest was published in 2013.

The second section presents the objectives and development principles of the MSG-3 maintenance program, which is intended to provide assistance to regulatory authorities in developing an initial program of scheduled maintenance tasks and intervals for new aircraft and their propulsion systems. As mentioned as early as 1978 by Nowlan and Heap, the major purpose of MSG-3 is to maintain the inherent levels of safety and reliability of an aircraft. It then briefly describes the organization defined by the FAA (Federal Aviation Administration) in Information Circular AC 121-22C for drawing up scheduled maintenance programs: the Maintenance Review Board (MRB). Validation of the content of maintenance programs drawn up by MRB working groups depends on the regulatory authorities.

The third section describes the approach and objectives for the development of the MSG-3 programmed maintenance program, and presents the two groups of maintenance tasks with definitions of their technical content.

The fourth section deals with the content of the analysis procedure for propulsion systems and equipment. The criteria for classifying an item as a Maintenance Significant Item (MSI – Maintenance Significant Item) are described in detail, together with the steps involved.

The fifth section describes the analysis procedure for aircraft structures. It specifies the definitions of structural elements and their modes and sources of degradation: accidental damage due to the environment and fatigue. The criteria defining the SSI ( – Structural Significant Item) to be maintained...