Federal Aviation

MMEL Policy Letter 106 Revision 3


October 7, 2005


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


PL-106 R3 is designated as GC-135

This GC is an approved addendum to all existing MMEL documents.  The operator may seek use of the specific relief contained in the policy letter by revising the Minimum Equipment List (MEL).  In doing so, the sample proviso stating the relief in the policy letter must be copied verbatim in the operator's MEL. Approval of the revised MEL is gained utilizing established procedure, through the assigned Principal Operations Inspector (POI).


High Frequency (HF) Communications MMEL Requirements




PL-106, Revision 2, dated March 16, 2004

PL-106, Revision 1, dated January 18, 2001

PL-106, Original, dated October 18, 2000


The purpose of this policy letter is to provide standards for Master Minimum Equipment List (MMEL) relief for High Frequency (HF) communication systems.


Revision 3 revised proviso (d) to clarify that coordination of Inmarsat Codes is only required when SATCOM Voice is used.

Revision 2 revises DISCUSSION and MMEL provisions to address acceptability of using SATCOM Voice as a backup when one HF is inoperative.

Revision 1 revises the subject title to clarify that more than one HF may be inoperative.  The purpose statement is revised to clarify that the policy letter also addresses HF relief when HF not required by

Title 14 Code of Federal Regulations (14 CFR).  The (O) procedure was deleted in the first proviso since no changes to flight crew procedures are needed.  In the second proviso, the phrase "while conducting extended overwater" was deleted since the requirement for two LRCS can exist over land.  Proviso a) was changed to delete "and ACARS" since the term "data link" includes ACARS and other sub systems on the airplane needed to communicate data.  Proviso b) was revised to clarify that data link communication must be operational, not just SATCOM coverage.

Federal Aviation Administration (FAA) MMEL relief is provided for HF communication systems.  The current proviso states: "Any in excess of those required by FAR may be inoperative."

 In 1996, the FAA recognized technological advances in communications by a rule change that included use of a new term: Long Range Communication System (LRCS).  14 CFR Section 1.1 defines LRCS as "A system that uses satellite relay, data link, high frequency, or other approved communication system which extends beyond line-of-sight." Examples of systems that meet this definition are: HF-voice, HF-data link, SATCOM-voice, and SATCOM-data link.

The regulations, therefore, now address long-range communication requirements in terms of LRCS. With that as a basis, an aircraft on extended range segments unable to utilize line-of-sight systems must have at least two operational LRCSs to honor regulatory communication requirements (unless specifically excepted under the operational rules).

At present most ATS facilities are not adequately equipped to handle SATCOM data or voice as the primary means of communication.  Most however are capable and willing to accept SATCOM data or voice as a backup to normal HF communication systems.  HF-voice is the only LRCS currently available for Air Traffic Control communications in many areas. Therefore, in areas requiring two operational LRCSs, at least one must be HF-voice and in areas requiring one LRCS, that system must be HF-voice.


With the foregoing as a basis, and in order to take advantage of the technology improvements recognized by 14 CFR, the following MMEL policy is established.


Repair Interval

Number Installed

Number Required for Dispatch

Remarks or Exceptions

23-XX High Frequency

(HF) Communications








Any in excess of those required by FAR may be Inoperative.





(O) May be inoperative while conducting operations that require two LRCS provided:

a) SATCOM Voice or Data Link operates normally,

b) Alternate procedures are established and used,

c) SATCOM coverage is available over the intended route of flight, and

d) If Inmarsat coeds are not available while using SATCOM voice, prior coordination with the appropriate ATS facility is required.


NOTE:  SATCOM is to be used only as a backup to normal HF communications unless otherwise authorized by the appropriate ATS facilities.


Each Flight Operations Evaluation Board (FOEB) Chairman should apply this Policy to affected MMELs through the normal FOEB process.


Thomas K Toula Manager,

Air Transportation Division, AFS-200


PL-106, Rev 3 reformatted on Jan 20, 2010 with no change to content.