March 08, 2021


MSG 3 Aircraft Inspection Considerations РIntroduction by Sofema Aviation Services (SAS)

What is MSG 3

MSG stands for Maintenance Steering Group (3 is the 3rd version of the process and has been around since 1980).

It provides a process which is used for developing scheduled maintenance tasks and intervals, which will be acceptable to the regulatory authorities, the operators and the manufacturers.

MSG 3 recognises the inherent reliability of aircraft systems and components, moreover it avoids unnecessary maintenance tasks and achieve increased efficiency.

MSG 3 is the process which is used to generate the Maintenance Review Board Report ‚Äď MRBR.

The MRBR is the source document which the Type Certificate Holder (TCH) uses to generate the Maintenance Planning Document (MPD).

The MPD consists of MRB tasks plus special tasks including Airworthiness Limitations and Certification Maintenance Requirements.

The MPD is the source document for Aircraft Maintenance Program.

The following key features of MSG 3 underlying principles are that:

  • Maintenance is only effective if the task applicable
  • No improvement will be achieved in reliability by excessive maintenance
  • Needless tasks can also introduce human error
  • Few complex items exhibit wear out (general failure is random)
  • Monitoring generally more effective than hard-time overhaul – Condition-based maintenance (sometimes known as CBM)
  • Overall Reliability is only improved by modification
  • Maintenance may not be needed if failure cheaper (providing safety is not compromised)

MSG 3 ‚Äď Facts

  • MSG 3 introduced 3 concepts: On Condition (OC), Hard Time (HT) and Zonal Inspection Program (ZIP)
  • MSG 3 Introduced 3 types of Inspections

o   General Visual (Part of the ZIP)

o¬†¬†¬†Detailed Visual (Not part of the ZIP ‚Äď Instead driven be additional task considerations) and

o¬†¬†¬†Special Detailed Inspection ‚Äď typically NDT

  • MSG 3 Introduced 3 types of Structural Maintenance Triggers

o   Environmental Damage

o   Accidental Damage

o   Fatigue Damage

  • MSG 3 Includes the Process known as CPCP Corrosion Prevention and Control Programs (CPCP)

o   The program is expected to allow control of the corrosion on the aircraft to Corrosion Level 1 or better. The CPCP should be based on the Environmental Deterioration (ED) analysis, assuming an aircraft operated in a typical environment.

o   If corrosion is found to exceed Level 1 at any inspection time, the corrosion control program for the affected area must be reviewed by the operator with the objective to ensure Corrosion Level 1 or better.

Quick Questions ‚Äď What is the difference between GVI & DVI

General Visual Inspection (GVI) is a visual examination of an interior or exterior area, installation or assembly to detect obvious damage, failure or irregularity.

This level of inspection is made from within touching distance unless otherwise specified. A mirror may be necessary to enhance visual access to all exposed surfaces in the inspection area.

Detailed Visual Inspection (DVI or DET) is NOT part of the Zonal Inspection Program! ‚Äď It is an intensive examination of a specific item, installation or assembly to detect damage, failure or irregularity.

Note Concerning DVI Inspections  РAvailable lighting is normally supplemented with a direct source of good lighting at an intensity deemed appropriate. Inspection aids such as mirrors, magnifying lenses, etc. may be necessary. Surface cleaning and elaborate access procedures may be required.

Next Steps

Sofema Aviation Services (SAS) & SofemaOnline (SOL) provide regulatory & vocational training offering more than 550 Classroom Training Courses and More than 200 Online Courses. For additional information please email


Aircraft Inspection, Aircraft Maintenance, Aircraft Maintenance Program, Aviation Training, Corrosion Prevention, CPCP, Detailed Visual Inspection, DVI, General Visual Inspection, GVI, Maintenance Planning Document, Maintenance Review Board Report, Maintenance Steering Group, MSG-3