SUBJECT: Supplemental Type Certificate (STC) MMEL Relief Process

PL-109                                                                                                                     December 13, 2001

SUBJECT:                 Supplemental Type Certificate (STC) MMEL Relief Process

MMEL CODE:         00 (GENERAL)

REFERENCE:           Original

FROM:                      Acting Manager, Air Transportation Division, AFS-200

TO:                             All Regional Flight Standards Division Managers All Aircraft Evaluation Group Managers

REPLY TO ATTN OF: Manager. Program Management Branch, AFS-260

The purpose of this policy letter is to provide guidance on how to obtain Master Minimum Equipment List (MMEL)/Minimum Equipment List (MEL) relief for items associated with STCs.

Clarification is necessary for MMEL relief for items covered by STCs. MMEL relief is not granted through STC documents, but is granted only through the Flight Operations Evaluation Board (FOEB) process. Passenger convenience items installed by STC may not have to go through the following process. For administrative control items, the STC is not the basis for an approved FAA document for MEL relief.

Aircraft modifiers (STC holders) and operators should consider the following for obtaining MMEL relief:

* Contact the responsible Aircraft Evaluation Group chairman.
* Submit to the FOEB chairman the MMEL proposals in accordance
    with the MMEL Agenda Proposal and Coordination Process.
* Ensure the STC identifies minimum certification requirements
    for continued dispatch.
* Development of appropriate Definition 23 in the MMEL (if
    required) to allow for continuous dispatch.
* Appropriate AFM limitations
    Identify the minimum requirements for continued dispatch,
    to include:

*   Hard failures.
*   Crew actions (O) are identified.
*   Maintenance actions (M) are identified (MMEL).
*   Deactivation procedures (non-MMEL).

*   Soft failures (do or do not affect MMEL).
*   Degraded modes/maintenance level messages or normal
      inspection procedures are addressed in the STC.
*   Crew actions (O) are identified.
*   Maintenance actions (M) are identified (MMEL).
*   Maintenance actions, continued dispatch (non-MMEL).
*   Deactivation procedures (non-MMEL).
*   Continued MMEL relief may be affected by issuance
      of Airworthiness Directives, Service Bulletins, NTSB.
      Recommendations, AFM Limitations, modifications to
      the system, etc. Modifications to the system may nullify MMEL relief.


Some inertial Navigation Systems annunciate soft failures, which is an indication of a future maintenance requirement. Others have redundancies built in that permit operation in Class 1 airspace provided altitude and heading information are available to each pilot position.

Modern Fuel Quantity Indication Systems annunciate minor inaccuracies (soft errors) within the certification limits of the system. (A soft error may be annunciated if the quantity error is in excess of 1 per cent but within the 4 per cent certification limit.

Relief for inoperative systems/components installed by STC other than provided in AFM supplements, coordinated with and approved by the FOEB chairman, will be granted in accordance with the FOEB process. Relief for this equipment must be included in the MMEL prior to inclusion in the operator's MEL. STC relief may be considered outside the normal FOEB schedule. The goal of the process is to provide appropriate MMEL relief upon certification of the STC.

The operator involved in the certification of an STC should submit a request for MMEL relief in accordance with the "MMEL Agenda Coordination Process". This submission should be made early in the certification process to allow MMEL evaluation concurrent with the certification process.


Matthew J. Schack