MSG 2 was introduced in 1970 primarily as a result of the Lockheed Tristar L1011 and the Douglas DC10 aircraft.
A primary consideration was given to further development of the MSG1 methodology which introduced the new concept of condition monitoring, to the existing Hard Time and on condition.
Essentially with this concept no specific maintenance task was introduced however the component is monitored in respect of it is physical performance.
So MSG-2 consisted of the following elements HT, CM & OC:
Components are monitored and as long as their behaviour is in line with expectations regarding the trends and behaviours, no action is taken, should the behaviour deviate from what is considered the norm then the component will be replaced.
Condition Monitoring should not be considered a preventative maintenance activity, as the process does allow failures to occur, It is an important consideration that the failure modes of condition-monitored items should not have a direct adverse effect on operating safety.
Many western aircraft had maintenance programs which were developed using either MSG-2 or the European version of MSG-2.
Driven by a new generation of aircraft led by the Boeing 757 and Boeing 767 Air Transport Association (ATA) task force sought to improve on MSG-2.
By the end of the 1970’s it was apparent that a number of shortcomings were identified in respect of the MSG2 process.
MSG-2 did not differentiate between maintenance being done for safety reasons versus economic reasons.
Components were tracked individually in the MSG-2 program, which added both cost and complexity to the process.
MSG-2 did not effectively deal with the increased complexity of aircraft systems.
Structural Significant Inspection SSI & Corrosion Prevention Corrosion Protection CPCP – MSG-2 did not address regulations related to damage tolerance and fatigue evaluation of Structures.
Under MSG-3 logic, activities are assessed at the system level rather than the component level – The major difference with MSG-3 is that it is a task-oriented approach to maintenance using a methodology which looks at the various failure modes from a system level, or “top down”.
In addition economic considerations play a role – Maintenance tasks are performed for safety, operational, or economic reasons.
The MSG-3 process provide for both preventative maintenance as well as considering tasks to expose potential failures.
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