N 8900.507


National Policy

Effective Date:



Cancellation Date: 4/9/20



Operator Use of Engineering Change Authorizations (EA), Engineering Change Orders (EO), and/or Other Acceptable Maintenance Methods Applicable to Minimum Equipment List (MEL) Items

1.    Purpose of This Notice. This notice provides guidance to Flight Standards Service aviation safety inspectors (ASI) for oversight of an approved minimum equipment list (MEL) and MEL management program.

2.    Audience. The primary audience for this notice is Flight Standards Service ASIs who have certificate management oversight responsibilities for operators utilizing an MEL. The secondary audience includes Flight Standards divisions and branches and the Aircraft Evaluation Groups (AEG).

3.    Where You Can Find This Notice. You can find this notice on the MyFAA employee website at Inspectors can access this notice through the Flight Standards Information Management Systems (FSIMS) at Operators can find this notice on the Federal Aviation Administration’s (FAA) website at This notice is available to the public at

4.    Background. Operators are required to accomplish Maintenance (M) and Operations (O) procedures contained in their FAA-approved MEL prior to dispatch and operation of the aircraft. Operators commonly perform additional maintenance procedures to disable and/or troubleshoot inoperative equipment or systems in accordance with Engineering Change Authorizations (EA), Engineering Change Orders (EO), or other acceptable methods during the MEL deferral period.

5.    Guidance.

a.    Maintenance on Inoperative Instruments or Equipment. The presence of an (M) or (O) procedure symbol indicates a specific M or O procedure is required to be accomplished. The operator may perform additional maintenance for troubleshooting or increased safety of the inoperative MEL item. The additional maintenance may be more restrictive, but must not be less restrictive than the MEL. Such maintenance may be performed in accordance with the operator’s MEL management program, which may include the use of an operator-produced EA, EO, or other methods acceptable to the Administrator. The procedures developed by the operator must include detailed instructions.

b.    Components of MEL Items and Warning/Caution Systems. Defective components of an MEL item (e.g., chafed or broken wiring, inoperative switch, or worn electrical connector) that are directly associated with and have no function other than supporting the MEL item, component or system being “MEL’d” can be inoperative as part of the MEL action. Defective components of an MEL item (e.g., engine or auxiliary power unit (APU) bleed duct systems with chafed hole(s) or leaking) that are directly associated with and have function(s) other than supporting the MEL item, component, or system cannot be MEL’d. However, warning or caution systems associated with the inoperative system must be operative unless relief is specifically authorized in the Master Minimum Equipment List (MMEL).

c.    Securing and Deactivating Inoperative MEL Items. The certificate holder’s procedures should describe the methods for securing, labeling, identifying, and deactivating an inoperative MEL item. Procedures for these methods should be clearly documented in the certificate holder’s manual system. Such tasks must be performed in accordance with instructions contained in the certificate holder’s maintenance manuals. Such tasks include, but are not limited to:

    Disconnecting and securing an electrical connector;

    Draining and/or capping hydraulic, fuel, water, or pneumatic lines;

    Pulling and collaring circuit breakers; and

    Capping and stowing electrical wires (provided there is no effect on another system or component).

d.    Maintenance Instructions. An EA or EO produced in accordance with the certificate holder’s MEL management program is an acceptable method for establishing maintenance instructions for securing, labeling, identifying, and deactivating a defective component or inoperative system.

e.    Approval or Acceptance of Maintenance Procedures. FAA certificate management oversight Flight Standards District Office (FSDO)/certificate management office (CMO) approval or acceptance of such procedures is only necessary at the level of the certificate holder’s MEL management program and does not extend to the review and acceptance of engineering documents. All MMEL M and O procedure symbols are required to be included in the operator’s MEL. All such maintenance must be documented in the aircraft records, such as the aircraft logbook. During the deferral period, the operator may work/repair/diagnose/analyze the deferred MEL item in accordance with the related manual requirements or engineering EAs or EOs. The MEL repair category will remain as the control for the time limits in the MEL deferral process.

6.    Action. Provide operators with guidance for additional maintenance action(s) when disabling equipment and/or systems in conjunction with an MEL.

7.    Disposition. We will incorporate the information in this notice into FAA Order 8900.1 before this notice expires. Direct questions concerning the information in this notice to the Air Carrier Maintenance Branch (AFS‑330) at 202-267-1675.


/s/ Robert C. Carty

Deputy Executive Director, Flight Standards Service