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High Frequency (HF) Requirement


WARNING: you may not want to read this. The world changed in 2014 and nobody told you (or me) and the news was passed along in an obscure policy letter about master minimum equipment lists. But if your airplane only has one HF, doesn't have CPDLC, and doesn't have a qualified SATVOICE system, you might not be able to fly where you once could.


Required for Oceanic?

U.S. Requirement

AC 91-70A, ¶3-3.c.] Notwithstanding the fact that pilots must comply with all regulations applicable to their flight, all aircraft operating over the high seas must equip suitable instruments and navigation equipment appropriate to the route to be flown (§ 91.703, ICAO Annex 2, section 5.1.1, and this chapter). The aircraft must also equip a functioning two-way radio to maintain a continuous listening watch on the appropriate radio frequency and establish two-way radio communications with the appropriate ATC unit (ICAO Annex 2, section It is not acceptable to depend on radio relay operations to satisfy this requirement.

ICAO Requirement

[ICAO Annex 2, §] An aircraft operated as a controlled flight shall maintain continuous air-ground voice communication watch on the appropriate communication channel of, and establish two-way communication as necessary with, the appropriate air traffic control unit, except as may be prescribed by the appropriate ATS authority in respect of aircraft forming part of aerodrome traffic at a controlled aerodrome.

  • Note 1. SELCAL or similar automatic signalling devices satisfy the requirement to maintain an air-ground voice communication watch.
  • Note 2. The requirement for an aircraft to maintain an air-ground voice communication watch remains in effect after CPDLC has been established.

[ICAO Annex 2, §5.1.1] Aircraft shall be equipped with suitable instruments and with navigation equipment appropriate to the route to be flown.

North Atlantic Requirement

ICAO Doc 7030, §NAT, ¶3.4.1] Within the NAT Region, aircraft equipped for SATCOM voice shall restrict the use of such equipment to emergencies and non-routine situations. An unforeseen inability to communicate by voice radio constitutes a non-routine situation. Since oceanic traffic typically communicates through aeradio facilities, a SATCOM call due to an unforeseen inability to communicate by other means should be made to such a facility rather than the ATC centre unless the urgency of the communication dictates otherwise. Dedicated SATCOM telephone numbers (short codes) for aeradio facilities and air traffic control facilities are published in national AIPs.

Yes, you can use your SATCOM for position reporting if you really needed to, and yes, you do make position reports with CPDLC. But the requirement remains: you need the HF when beyond VHF coverage.

How Many HF's Do I Need?

[FAA MMEL Policy Letter (PL)106] The regulations 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).

This is the first document from the FAA that says you need two long range communications systems. You could get away with just one HF as your only means of long range communications until this came out. Now, if you don't have a qualified SATVOICE or CPDLC, you need two HFs.

More about this: LRCS to be Carried on Board.

The "unless specifically excepted under the operational rules" gives you an out if the region you are flying in specifically says only one is needed. Nobody, to my knowledge, has done that.

So what just makes a SATVOICE system qualified?

Is my Satellite Phone Qualified to be a Long Range Communications System?

With an MEL Statement

You cannot assume a satellite telephone installed in your aircraft qualifies as a suitable LRCS that can take the place of one HF. The satellite telephone must pass several security and Required Communications Performance (RCP) tests. The easiest way for you, the pilot, to tell if your system qualifies is to check your MMEL. The GV series MMEL, for example, was modified as follows:


Figure: GV MMEL HF Systems, (GV MMEL, page 23-14)

Gulfstream has stated SATCOM Voice or Data Link can substitute as a backup to normal HF communications, so with this series of aircraft we are good to go, for now. I say "for now" because the ICAO is refining its rules and there are rules that say you cannot simply call a commerical number (country code, area code, etc.) and make a position report. The number has to be a direct link, such as with the INMARSAT short codes. I don't know how you would do that with Iridium. The G650 MEL might have a view of the future because it changes a few things:


Figure: GVI MMEL HF Systems, (GVI MMEL, page 23-15)

Without an MEL Statement

What if you don't have such a statement in your MEL?


Figure: DA-2000 MMEL HF Systems, (DA-2000 MMEL, page 1-23-1)

This is an older copy of the DA-2000 MMEL for sake of illustration, they might have a qualified system and this may have changed. But for the purpose of this discussion, if what you see is something that doesn't mention your satellite phone system or an LRCS at all, you might not have a qualified system. You should ask your aircraft manufacturer for guidance. If they are clueless, send them the Appendices to the ICAO Satellite Voice Guidance Material, available for download below.


Iridium has presented another option over the years and that option went from "yeah, but it isn't good enough" to "hey, this actually works!" The world hasn't caught up yet and the rules are supposed to be rewritten to specifically allow some Iridium SATVOICE systems. The deciding factor is what is called "safety voice services." I think this has to do with the unit's Required Communications Performance, but I am not sure. There is nothing written about safety voice services in ICAO literature other than proposed rule making from five years ago. So what to do if you have an Iridium SATVOICE but no specific mention in your manuals that it is a suitable HF backup?

[InFO 15008] With this policy change, operators will need to modify Iridium SATVOICE aircraft installations, operations centers, and service accounts, as necessary. This policy change and timeframe would be aligned with the November 2016 applicability date for the ICAO SATVOICE provision. Directors of safety and directors of operations (part 121); directors of operations (part 125 and 135); training managers; and pilots must ensure these safety services are being used in lieu of commercial services, and that flightcrews and operations personnel (dispatchers) are knowledgeable in the new communication procedures.

As with many things in international operations, the rules are struggling to keep up with technology. But we, as pilots, are ill-equipped to make these kinds of decisions. My advice: get something from your aircraft manufacturer that says your Iridium SATVOICE is good enough. If you end up without the necessary communications performance over the North Atlantic you are probably okay, but the air traffic service unit may to have to move a lot of airplanes out of your way and they aren't going to be happy about that. As a corporate aviation operator they may decide to come after you and being able to fall back on the manufacturer improves your odds.


Advisory Circular 91-70A, Oceanic and International Operations, 8/12/10, U.S. Department of Transportation

FAA InFO 15008, Iridium Satellite Voice (SATVOICE) with Safety Services, 8/4/15, U.S. Department of Transportation

FAA MMEL Policy Letter (PL)106, Revision 5 GC, June 6, 2014

Falcon 2000EX EASy Series Master Minimum Equipment List (MMEL), Revision 9, March 11, 2013

Gulfstream GV Master Minimum Equipment List (MMEL), GV GV-SP (G550), GV-SP (G500), GIV-X (G450), GIV-X (G350), Revision 8, 11/07/2014

Gulfstream GVI Master Minimum Equipment List (MMEL), GVI (G550), GVI (G650ER), Revision 1b, 09/12/2015

ICAO Satellite Voice Guidance Material (SVGM), International Civil Aviation Organization, First Edition, 24 July 2012

Revision: 20160402