Aircraft Maintenance Control Centre (MCC) Recurrent Defect Control

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SofemaOnline (SOL) considers best practices related to the management of Recurrent Defects within the Maintenance Control Centre

Introduction - How To Ensure That Outcomes Of Repeated Defect Analysis Provide Meaningful Results

Maximization of fleet availability depends in part on having the ability to identify potential repeating defects on either individual or fleet aircraft and to expedite the necessary maintenance action.

» Being able to identify such repeating defects is dependent on a number of  variables

o   Has the defect been correctly recorded into the reliability system?

o   Can we rely on Engineering to ensure that outcomes of repeated defect analysis provide meaningful results?

» Repetitive defect analysis requires analysis of the technical event/issue complaints information of each individual aircraft in the fleet and determining if specific complaints keep reappearing on individual aircraft or across a certain fleet of the same aircraft type.

» Being able to address potential issues before they cause a significant impact may help to reduce unnecessary downtime thus increasing the overall aircraft availability.

Concerning Pilot Reports (PIREPS) - MCC Reliability and Defect Control Considers

MCC Reliability and Defect Control consider specific issues/defects which re-appear over a given period on each individual aircraft.

» Such repeated defects could be an identification of any number of issues and should be subjected to a thorough root cause analysis process.

Development of a Defect Control Procedure – Example

A description of the defect rectification and control procedures, including details of:

o   The methods used to detect and report recurring defects

o   The procedures for scheduling the rectification of defects whose repair has been deferred..."

o   Procedures for recording and rectification of defects, including the identification of recurring defects.

o   The complexity of the system used to control defects, including rectification and deferral, as well as identifying and handling recurring defects will vary according to the type of aircraft operated and the size and nature of the operation. It may include policies and procedures for the use of an approved Minimum Equipment List (MEL).

o   The pilot in command must know the status of the aircraft in order to make an informed decision on its serviceability for the intended flight.

o   Additional crew workload must be taken into consideration if defects are deferred.

Definition of a Recurring Defect

A recurring defect is one that is repeated 3 times on a particular aircraft within 15 flight segments.
» The purpose of specific procedures for identifying recurring defects is to avoid ineffective methods of repair and to ensure the defect will not reoccur.
» The final authority to reject an unsafe aircraft rests with the pilot.

Use of Minimum Equipment List (MEL)

For aircraft operated with a MEL the following procedures apply:

» Any defect identified prior to departure will be recorded in the Technical Log immediately.
» The pilot will notify MCC If the item can be deferred, as identified in the MEL, the pilot will ensure that the "O", "M" & "M#" procedures in the MEL are followed and ensure the appropriate entries are made in the Technical Log.
» If the defect occurs in flight the defect will be recorded in the Technical Log as soon as practical but before the next flight.
» The pilot in command (PIC) will consult the MEL and defer the item, if permitted, following the appropriate MEL procedures. The PIC will notify MCC as soon as possible;
» MCC Control will ensure the defect is registered into the Maintenance Planning and Control Program and include the date and time by which the MEL applicable limit must be addressed.
» MCC will ensure all defects are rectified in a timely manner

Next Steps

Sofema Aviation Services ( and Sofema Online ( offer EASA Regulatory Compliant and Vocational Training across a range of Aviation Areas – please see our Websites or email

 Sofema Aviation Services provides a 3-day course to implement your own MCC – please see the following

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