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Federal Aviation Administration
Washington, DC

MMEL Policy Letter 119, Revision 4

Date:                                        12/04/2017

To:                                           Manager, Aircraft Evaluation Division (AFS-100)
   All Aircraft Evaluation Group Managers

From:                                      Manager, Air Transportation Division (AFS-200)

Reply to Attn of:                    Manager, New Program Implementation Branch (AFS-240)

SUBJECT:                     Two-Section MMELs (Parts 91, 125, and 135)

MMEL CODE:                      00 (GENERAL)

REFERENCE:                       PL-119, Revision 3, dated October 17, 2011
  PL-119, Revision 2, dated February 10, 2008
  PL-119, Revision 1, dated February 14, 2008 (Cancellation Notice)
  PL-119, Original, dated September 12, 2006


The purpose of this Policy Letter is to establish a standard Master Minimum Equipment List (MMEL) policy regarding the use of two-section MMELs. These MMELs are for aircraft equipped with self-diagnostic technology which provide Crew Alerting System (CAS) messages for determining aircraft airworthiness status. This Policy Letter applies to Title 14 of the Code of Federal Regulations (14 CFR) parts 91, 125, and 135 operations only.

This policy is for Aircraft Evaluation Group (AEG) MMEL development and review.


Revision 4: Adds 14 CFR part 125. Revision 3 did not consider 14 CFR part 125, and thus prohibited use of two‑section MELs by part 125 operators. Revision 4 now allows this policy to be applied for operations under 14 CFR part 125.

Revision 3: Added part 135 operations. Clarified crew procedure limits when inspecting compartments and using external access equipment.

Revision 2: Revised and clarified this PL policy and guidance for standardized formatting of the two-section MMELs. Section Two CAS message relief was also clarified.

Revision 1: Withdrew original PL policy and guidance due to confusion over who (crew or maintenance) can accomplish CAS self-diagnostic actions.


Two-section MMELs are authorized by FAA Policy Letter PL-119. Section Two of two-section MMELs may grant relief for failure indications presented as CAS messages on Engine Indicating and Crew Alerting Systems (EICAS) or Electronic Centralized Aircraft Monitoring (ECAM), rather than the traditional relief (Section One) for failed equipment. New technology self-diagnostic tests eliminate the need for failure isolation procedures by maintenance personnel for many CAS messages. By using (O) procedures, the crew can complete selected system/component deactivation/reconfiguration from the cockpit for which the crew has been trained. Section Two will only contain CAS message relief if the crew can act on the item. CAS message relief must ensure safe operation of aircraft. Flight Operations Evaluation Boards (FOEB) will use the normal FOEB processes for determining which CAS messages go into each section.


Modern technology CAS MMELs shall be divided into two sections.

A.  Section One. Items which either require maintenance actions (this may include some CAS messages) or caution/advisory information. Section One will continue to use the existing Line Replaceable Units (LRU) oriented MMEL format and should address the following type of equipment failures:

1.   Failures which are not annunciated to crew; and

2.   Failures which are annunciated, but the failure indication by itself is not considered sufficient to determine the aircraft airworthiness status.

B.  Section Two. Includes only items where flight members may act on CAS messages. MMEL items where CAS messages can be used to determine the aircraft airworthiness should be formatted as follows:

1.   It should have only two columns:

a.   Column one should list the failure indications (messages) for which relief is given (if desired, the messages may be listed in alphabetical order with no ATA breakdown).

b.   Column two should include the corresponding MMEL limitations and/or procedures. The format of this column should be in line with the format requirements of the “Remarks or Exceptions” column of the conventional “LRU oriented” MMEL.

NOTE: In many cases, CAS messages will not require maintenance to perform fault analysis. Relief provisos for these CAS items are expected to be more restrictive in content and repair interval, as compared to Section One relief provisos.

2.   Section Two CAS message relief items require flightcrews to accomplish one or more steps to deactivate/reconfigure the affected system prior to flight. The “(O)” indicates the need for these tasks. Tasks include, but are not necessarily limited to, the following duties:

a.   Procedures accomplished using cockpit (or cabin) system controls;

b.   Deactivation of affected systems (by pulling system breaker or use of remote electronic system isolation);

c.   Visual confirmation of remote gauge indications or valve positions, as provided by integral external indicators; and

d.   Visual inspection behind panels (internal or external).

1)  These panels must be accessible without tools via quick-release latches and must clearly indicate their unlocked or unsafe state (red/green safe window; flush fit latches - candidates to be verified at FOEB).

2)  The visual inspection of compartments accessed by the panels is within the normal crew duty requirements for which they have been trained; and

3)  The crew may use an external ladder for visual inspection behind panels as long as this procedure is within the normal crew duty requirements for which they have been trained. Special equipment, such as maintenance stands and hydraulic lifts, may not be used by the crew to perform visual inspections.

C.  The following statement will be included on page 1 of Section Two in all two-section MMELs:

1.   Section Two of the MMEL will list only Crew Alerting System (CAS) messages meeting the following requirements:

a.   Equipment failure indications(s) that can be used to determine the airworthiness status of the airplane.

b.   Messages that the crew can act upon from the cockpit with simple troubleshooting procedures without the assistance of a mechanic, and for which the crew has been trained.

c.   Messages using the new self-diagnostic technology (virtual) actions for which the crew has been trained.

2.   CAS message relief items not meeting these requirements will be listed in Section One of the MMEL.

Each FOEB Chair should review the specific aircraft configuration(s) and apply this policy to affected MMELs through the normal FOEB process.


/s/ Stephen C. Moates for

Manager, Air Transportation Division