Federal Aviation

MMEL Policy Letter 124 Revision 0


Jan 20, 2009


All Region Flight Standards Division Managers
All Aircraft Evaluation Group Managers


Manager, Air Transportation Division, AFS-200

Reply To
Attn Of:

Manager, Technical Programs Branch, AFS-260



Damaged Window/Windshield Relief


56 (Windows)


New Policy Letter



The purpose of this policy letter is to provide standardized Master Minimum Equipment List (MMEL) requirements for Damaged Window/Windshield relief.



A review of MMEL documents indicate that a varied assortment of relief and operating criteria is being applied towards damaged windows and windshields in ATA Chapter 56. The appropriateness of such relief in the MMELs is being questioned by the Flight Operations Evaluation Board (FOEB) Chairman. The regulations provide for the MMEL to contain a list of instruments and aircraft equipment that the FAA has determined can be inoperative under certain flight conditions. It also contains conditions, limitations and procedures that are required for operating the aircraft with these items inoperative.


Damaged Windows and Windshields do not qualify as aircraft systems, nor can they be considered for MMEL relief as inoperative components. Damaged windows and windshields are structural components of the aircraft and the airworthiness is determined from limitations in the Aircraft Maintenance Manual (AMM)/Structural Repair Manual (SRM). A cracked/delaminated window or windshield limits described in the AMM/SRM meet the same criteria as a hydraulic leak, fuel leak or dents in the aircraft structure.


It is inappropriate to provide relief through the MMEL for damaged windows/windshields. The validity of relief for damaged windows/windshields in the MMEL may be in conflict with the AMM/SRM when these limits are changed in the maintenance manuals. For these reasons, relief in the MMELs for damaged windows/windshields should be deleted.





Relief for damaged windows/windshields should not be contained in the MMEL, ATA Chapter 56.The AMM/SRM for that particular aircraft contains the acceptable limitations and operating criteria for damaged windows/windshields. For MMEL documents that currently provide relief for damaged windows/windshields, these items should be deleted in the next standard revision with an explanatory note that reads “ REFER TO AIRCRAFT MAINTENANCE MANUAL (AMM), STRUCTURAL REPAIR MANUAL (SRM), or AIRCRAFT FLIGHT MANUAL (AFM) “.


This policy will not restrict the FAA Principal Operations Inspector from approving an Administrative Control Item (Refer to PL-25 definitions) to the operators MEL.





Repair Interval

Number Installed

Number Required for Dispatch

Remarks or Exceptions

XX-X  Windshield, Window











































































  Relief Deleted with Revision  XXXX


Note: Refer to Aircraft Maintenance

          Manual (AMM), Structural

          Repair manual (SRM), or

          other approved documentation.


Flight Operations Evaluation Board (FOEB) chairman should apply the following policy to affected MMELs through the normal FOEB process.






(Gregory Kirkland for)


John Duncan, Manager