A Pilot’s Guide to Using HFDL Prepared July 2016

HFDL Propagation Ionosphere Refraction of signal works by bouncing signals off the ionosphere. Aircraft might be one hop or more away. This bouncing allows HFDL to provide worldwide coverage with only 15 stations. Ionosphere Refraction of signal One hop Multi-hop

Does Solar Activity Affect Propagation? Propagation is affected by solar events. How do we compensate? We need less bandwidth than voice. Full Fidelity Voice 7-8 kHz Intelligible voice 3.3 kHz Data 2.4 kHz We monitor for solar events and change the operating frequencies.

Worldwide Coverage HF Ground Stations Alaska Bahrain Bolivia California Canary Islands Guam Hawaii Iceland Ireland New York New Zealand Panama Russia South Africa Thailand Legend HFDL ground station Areas of Primary coverage Areas of Secondary coverage

HFDL Flights - Positions reported through HFDL automated performance packets

Connectivity between HFDR and HF ground station When not transmitting or receiving data, the HFDR (HF data radio) will check other HF data frequencies to keep a current list of frequencies to use. The HFDR will tune to the next frequency/ground station if the connection fails. The ground station also polls the HFDR to make certain that the aircraft has a good connection. The aircraft periodically sends performance data that gives the lat/long of the aircraft and UTC. This allows for route tracking/mapping without bothering the crew for position reporting.

Airborne Architecture HF Antenna HF Coupler (x2) Multi-functional Cockpit Display Unit ACARS MU/CMU/ATSU Flight Management System HF Data Radio (x2)

Flight Crew Operational Use - Preflight Radio tuning panel is always placed in ON position One HFDR is tuned to DATA mode during pre-flight prior to push back The HFDR will passively listen for HF stations. Both Boeing and Airbus inhibit HFDL transmission on-ground unless the override switch (GTIO) is “ON”. HF SENS VHFL VHFC VHFR HFR HFL AM OFF P N L ACTIVE 13.348 STANDBY DATA

HFDL Use On The Ground – when outside VHF coverage Ground Transmit Inhibit Override (GTIO) – The “ON” position enables HFDL send/receive Always follow company policy and procedure for use of this switch. present in most Boeing and Airbus aircraft. Our recommendations: When on-ground at an airport without VHF coverage. Put the GTIO in the ON position after pushback (when refueling/defueling is complete) When no ground personnel are within 10 feet of the vertical stabilizer during transmission When outside VHF coverage, this will allow the OUT message and any pre-flight messages to be sent and received. Put it back to the OFF position before landing in VHF coverage - anytime during the flight. Upon approach to an airport with no VHF coverage Put the GTOI in the ON position before landing This will allow the ON and IN reports to be sent. Turn it to the OFF position in the gate (for fueling or when ground personnel are near the aircraft).

Flight Crew Operational Use - Inflight Keep the same HFDR in DATA mode for the entire flight (pre-flight to post-flight) If no VHF ground coverage is available, it is essential to leave the HFDL equipment on so that OOOI messages (ON/OFF/OUT/IN) can be transmitted. Do not switch between left and right HFDRs This will cause the HFDR to begin frequency search which can last several minutes, possibly interrupting message transmission Do not tune the data frequency on the radio tuning panel. The HFDR will automatically tune to the proper HF data frequencies. Be patient. HF is slower than VHF, where VHF might deliver a large message in seconds, HF might require a few minutes.

Flight Crew Operational Use - Inflight HF voice use will pre-empt DATA use since they share an antenna. Do not key or tap the mic prior to voice use to “tune the antenna” This is not needed and can interrupt data. Do not key the mic when “HF in PROG” is displayed. This will interrupt data transmission. Be patient after a voice exchange. Once the mic is released, the HFDR will stay locked in voice for 60 seconds which prevents data transmission Use of the mic for more than 3 minutes requires the HFDR to log back onto a ground station, so data will take a few minutes.

Questions or Problem Reports Carolyn Bray – HFDL Technical Project Manager CBRAY@ARINC.COM + 1 410-266-2147 Helpdesk@arinc.com US & Int’l Access (Sprint) 1-800-633-6882 HDQHDXA