USAF High Frequency Global Communications System
The USAF High Frequency Global Communications System is a worldwide network of 15 high-power HF stations providing command and control communications between ground agencies and US military aircraft and ships. Allied military and other aircraft are also provided support IAW agreements and international protocols as appropriate. The HFGCS is not dedicated to any service or command, but supports all DoD authorized users on a traffic precedence/priority basis.
General services provided by the HFGCS are:
- General Phone Patch and Message Relay Services
- Automatic Link Establishment (ALE)
- HF Data Support
- Command and Control Mission Following
- Emergency Assistance
- HF Direction Finding Assistance
- ATC Support
- E-Mail connectivity to NIPRNeT and SIPRNeT
SCOPE (System Capable Of Planned Expansion) Command replaces older high power Global HF (GHFS) equipment. SCOPE Command incorporates Automatic Link Establishment (ALE) to automate communications. All HFGCS station transmit and receive equipment is remotely controlled from the
Centralized Network Control Station (CNCS) at Andrews AFB, MD.
Aircrews use a preliminary call as outlined in ACP-121 US Supp 2 using the collective callsign "MAINSAIL" or the HFGCS station call sign (example: Sigonella Global this is Dark 86 on 11175, OVER). HFGCS operators require approximately 10 seconds (for automated equipment configuration) to respond to calls for service. The HFGCS operator may request the aircraft change to a discrete frequency for improved and/or extended service.
(a) PUBLISHED FREQUENCY LISTING - HFGCS stations operate on “core�?
frequencies to provide increased "Global" coverage. The published frequency listing does not
reflect complete system frequency authorizations. These published frequencies will be used for
initial contact, EAM broadcasts, and short-term C2 phone patch and message delivery. Other
extended or special services will be moved to each station’s available "discrete" frequencies.
(b) FREQUENCY GUIDE - The frequency guides are designed to optimize air/ground communications.
Primary HFGCS Frequencies 24 Hours: 8992 and 11175
Back up HFGCS Frequencies Day: 13200 15016
Back up HFGCS Frequencies Night: 4724 6739
200-750 NM 750-1500 NM More than 1500 NM
0000L 4724 6712-6739-8992 6712-6739-8992-11175
0400 L 4724 4724-6712-6739 6712-6739-8992
0800 L 4724-6712-6739 6712-6739-8992-11175 11175-13200-15016
1200 L 4724-6712-6739 8992-11175-13200 13200-15016
1600 L 4724-6712-6739 8992-11175-13200 13200-15016
2000 L 4724-6712-6739 6712-6739-8992-11175 11175-13200-15016
1. When less than 200 NM any frequency
2. Local time at ground station.
FREQUENCIES - SUMMER (Apr-Sep)
STATION 4724 6712 6739 8992 11175 13200 15016
Andrews 0500-1330Z 0300-1600Z 24 hours 24 hours 1330-0500Z 1600-0300Z
Ascension 2300-0700Z 2200-0900Z 24 hours 24 hours 0700-2300Z 0900-2200Z
Croughton 2300-0600Z 2100-0800Z 24 hours 24 hours 0600-2300Z 0800-2100Z
Dieg Gar 1400-0100Z 1200-0200Z 24 hours 24 hours 0100-1400Z 0200-1200Z
Elmendorf 0600-1500Z 0400-1700Z 24 hours 24 hours 1500-0600Z 1700-0400Z
Guam 1300-2200Z 1100-2400Z 24 hours 24 hours 2200-1300Z 2400-1100Z
Hawaii 0800-1700Z 0700-1800Z 24 hours 24 hours 1700-0800Z 1800-0700Z
Lajes 2200-0800Z 2000-1200Z 24 hours 24 hours 0800-2200Z 1200-2000Z
Offutt 0400-1330Z 0200-1700Z 24 hours 24 hours 1330-0400Z 1700-0200Z
Puerto R 0400-1200Z 0100-1400Z 24 hours 24 hours 1200-0400Z 1400-0100Z
Sigonella 2200-0530Z 1900-0900Z 24 hours 24 hours 0530-2200Z 0900-1900Z
West Coas 0600-1400Z 0300-1800Z 24 hours 24 hours 1400-0600Z 1800-0300Z
Yokota 1300-2200Z 1100-2200Z 24 hours 24 hours 2200-1300Z 2200-1100Z
FREQUENCIES - WINTER (Oct-Mar)
STATION 4724 6712 6739 8992 11175 13200 15016
Andrews 2400-1200Z 2200-1400Z 24 hours 24 hours 1200-2400Z 1400-2200Z
Ascension 2200-0800Z 2100-1000Z 24 hours 24 hours 0800-2200Z 1000-2100Z
Croughton 1800-0600Z 1700-0900Z 24 hours 24 hours 0600-1800Z 0900-1700Z
Diego Gar 1600-2300Z 1400-0200Z 24 hours 24 hours 2300-1600Z 0200-1400Z
Elmendorf 0330-1630Z 0200-1800Z 24 hours 24 hours 1630-0330Z 1800-0200Z
Guam 1300-2030Z 0800-2200Z 24 hours 24 hours 2030-1300Z 2200-0800Z
Hawaii 0700-1600Z 0400-1800Z 24 hours 24 hours 1600-0700Z 1800-0400Z
Lajes 1800-0730Z 1700-0900Z 24 hours 24 hours 0730-1800Z 0900-1700Z
Offutt 0030-1330Z 2300-1400Z 24 hours 24 hours 1330-0030Z 1400-2300Z
Puerto R 0100-1100Z 2300-1200Z 24 hours 24 hours 1100-0100Z 1200-2300Z
Sigonella 1700-0500Z 1600-0800Z 24 hours 24 hours 0500-1700Z 0800-1600Z
West Coas 0130-1400Z 0030-1500Z 24 hours 24 hours 1400-0130Z 1500-0030Z
Yokota 0900-2100Z 0800-2200Z 24 hours 24 hours 2100-0900Z 2200-0800Z
Unclassified Phone Patch and Message Relay Services
(a) Phone Patch Service. Phone patching allows direct voice communications between ground agencies and aircraft by electronically connecting telephone circuits to radio transmitters and receivers. Phone patch service is reserved for official unclassified business only and shouldn’t exceed 5 minutes. Patches of more than 5 minutes or of a sensitive nature should be run on a discrete frequency. Users requesting a phone patch must include all information necessary for HFGCS operators to complete the call, such as the identity or location of the called parties and telephone number if known. Phone patches are monitored by HFGCS operators. If radio reception
isn’t of sufficient quality to complete the patch, they will attempt to copy the traffic and relay it to addressees.
(b) Message Relay Service. HFGCS operators transcribe encoded or plain-text messages for aircraft or ground stations and forward them to the addresses by radio or landline. The text of the messages can be in the form of alpha-numerics, code words, plain text, acronyms, and/or numerical sequences. Aircrews may use "READ BACK" procedures when the message data is critical, or when an incomplete transmission is suspected due to poor radio reception. All messages received by Global stations will be accepted and delivered by the fastest means available according to precedence and priority.
(c) ALE - For ALE radios to operate properly, the radio must have a loaded datafill, be turned on in the “automatic�? mode and remain there the duration of the flight. If the radio is removed from the ALE mode, history tables will require time to rebuild and initial communications may be slightly degraded.
ALE Address and Frequency Chart
Station ALE Frequency
Address 3137 4721 5708 6721 9025 11226 13215 15043 18003 23337
Andrews ADW x x x x x x x x x x
Ascension HAW x x x x x x x x x
Croughton CRO x x x x x x x x x
Diego Garcia JDG x x x x x x x x x x
Elmendorf AED x x x x x x x x x x
Guam GUA x x x x x x x x x x
Hawaii HIK x x x x x x x x x
Lajes PLA x x x x x x x x x x
McClellan MCC x x x x x x x x x x
Offutt OFF x x x x x x x x x x
Salinas JNR x x x x x x x x x x
Sigonella ICZ x x x x x x x x x
S Atlantic MPA x x x x x x x x x x
West Coast MCC x x x x x x x x x x
Yokota JTY x x x x x x x x x
(d) HF Data Service. All HFGCS stations have HF data access to AUTODIN/NOVA and SACCS. HF Radio Teletype requirement has been removed by Joint Staff J6.
(e) Command and Control Mission Following. C2 agencies can use the HFGCS for mission tracking/control of their aircraft. Aircraft responsible to a C2 agency for mission tracking/control should transmit an initial contact/departure report to a Global HF System station after takeoff. The following information should be included:
- Aircraft Call Sign
- Departure point and time
- Destination point and ETA
- Relay Instructions for C2 Agencies
- Remarks: DV codes, special instructions, etc.
d. EMERGENCY ACTION MESSAGE (EAM) BROADCASTS - Most HFGCS stations transmit high priority EAMs on published frequencies during specific broadcast periods. During EAM broadcast periods, aircraft may only transmit In-Flight Emergency traffic.
e. EMERGENCY ASSISTANCE - Distress and urgency situations should be clearly identified by the words "MAYDAY" or "PAN" as appropriate (refer ACP 121 US Supp 2, Ch 8 for definitive usage). Users should transmit present position and heading when encountering grave or serious emergency situations.
f. HF DIRECTION FINDING (DF) ASSISTANCE - HFGCS stations are capable of coordinating DF efforts between aircraft and direction finding facilities for both emergency situations and suspected spectrum interference location efforts.
(1) Emergency DF Requests. Aircraft requiring DF support should advise the HFGCS station of the nature of the emergency, a bearing (steer) or a position (fix). The HFGCS operator will arrange the support and ask the aircraft to transmit a slow count from 1 to 10 and back, followed by the aircraft call sign. The aircraft should then standby for further instructions and/or results of the service. DF facility response time will vary, depending on operating conditions, location of the aircraft, nature of request, prevailing DF facility operating commitments, type of DF facility providing the service and coordination of all concerned. The average response time is estimated at four minutes for bearings and ten minutes for positions after the slow count.
(2) DF Support for Suspected Spectrum Interference. Aircraft experiencing spectrum interference may obtain DF fix information on source of interference by calling the nearest HFGCS station and requesting Spectrum Interference DF support. The aircraft will advise the Global stations of the frequency affected, type of interference (Voice, Morse Code, Printer, Noise, etc.) and request a read-back of the information passed. A report will be filed in accordance with AFI 10-707 by the aircrew upon landing. The Andrews CNCS will report
Spectrum Interference DF results via message to the AF Frequency Management Agency and the aircraft unit command post.
g. ATC SUPPORT - HFGCS is not configured to meet ATC communications routing requirements and cannot provide ATC flight following service. This service can be obtained through the appropriate Civil/ICAO ATC communications agency such as the AREA CONTROL CENTER, SECTOR RADIO, or FLIGHT INFORMATION CENTER (see section B, ICAO HF Aeronautical Station List). Global HF stations will accept emergency ATC traffic and provide phone patch or message relay support as required.
- The 2015 Digital Digest has information on the US Air Force Global HF ALE Network - see the HF Appendix for the link to this document, which is very inexpensive.
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