High Frequency Data Link (HFDL)
Frequently Asked Questions
- What Is HFDL?
- What avionics support HFDL?
- What areas of the world are covered by HFDL?
- How long has HFDL been in use?
- Isn’t HFDL becoming an obsolete technology?
- How has the HFDL service grown over the years?
- How many ground stations are operational, and what is their coverage?
- With such explosive growth, won’t the system get overloaded?
- If HF voice is unusable, won’t this be the case for HFDL as well?
- Like HF voice, do the pilots have to dial in the HFDL frequencies?
- We fly to airports that are not currently covered by VHF, how can HFDL help us when it cannot be used on the ground?
- How is the service performing with regard to message uplink success?
- I have new aircraft on order, what should I be considering for the avionics specification?
- With the near-term viability of some long-distance communication media questionable, how does ARINC ensure the continued operation of the HFDL Service?
- What Is HFDL? High Frequency Data Link (HFDL) is an ACARS® communications medium used to exchange data such as Airline Operational Control (AOC) messages, Controller-Pilot Data Link Communication (CPDLC) messages and Automatic Dependent Surveillance (ADS) messages between aircraft end systems and corresponding ground-based HFDL ground stations. Using the unique propagation characteristics of high-frequency radio waves, the ground stations provide data link communications to properly equipped aircraft operating anywhere in the world. The result: pilots can always communicate with someone on the ground.
- What avionics support HFDL? To use the service, an aircraft only needs a Communications Management Unit (CMU) or equivalent, and an HFDL data radio. The CMU is an airborne communications router that interfaces with many aircraft communications systems, including SATCOM, VHF, HFDL, FMS, and others.
- What areas of the world are covered by HFDL? Today, HFDL is an air/ground data link standard with coverage in virtually every corner of the globe. That’s nearly 168 million square miles where aircraft are never out of touch both in the air and on the ground.
- How long has HFDL been in use? HFDL is entering its second decade of operation. In fact, ARINC was the first to provide it in the aviation industry.
- Isn’t HFDL becoming an obsolete technology? Far from it.The HFDL network and avionics are continually evolving. For instance, recent innovations in avionics software developed by both Honeywell and Collins have enhanced performance and contributed to the service’s outstanding message success rates. ARINC continues to invest in its HFDL infrastructure and has a long-term strategy in place to ensure its success.
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- How has the HFDL service grown over the years? HFDL usage rates have grown more than 20% for each of the past ten years. It now supports 73 airlines with well over 1,600 aircraft sending more than 1 million messages a month. Over the last two years, ARINC’s focus on growth has resulted in the addition of eight new operating frequencies, bringing our total to 167 worldwide. In addition, more new short- and long-haul air transport aircraft are being built with HFDL as a customer option than ever before.
- How many ground stations are operational, and what is their coverage? ARINC currently has 15 HF ground stations (HGS) available today and like a canopy within a jungle, the stations provide overlap and redundancy in the unlikely event of an HGS failure. These 15 stations provide nearly complete global coverage, including both poles, and system availability in 2009 is 100 percent.
- With such explosive growth, won’t the system get overloaded? The design of the system allows for 4 channels per ground station. Currently, 13 stations are only using 1/2 of the designed capacity. Two others are using 3 of the 4 designed channels. We actively monitor the traffic load and can determine when another channel needs to be added. There is plenty of extra capacity.
- If HF voice is unusable, won’t this be the case for HFDL as well? Not at all! Data link uses between 1/3 and 1/2 of the bandwidth that voice uses. So data can continue to be decoded when voice is unusable. This was proven during the 2003 Halloween Solar storm in which aircraft were still using HFDL on polar routes when voice was unusable.
- Like HF voice, do the pilots have to dial in the HFDL frequencies? No. The data radios constantly scan and select the most efficient frequency to use, all seamlessly to the crews.
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- We fly to airports that are not currently covered by VHF, how can HFDL help us when it cannot be used on the ground? Provided basic HF transmission precautions are made, the HFDL can be used on ground. In fact, many aircraft have a Ground Transmit Inhibit Override installed for this very purpose.
- How is the service performing with regard to message uplink success? Uplink success rates are comparable to those on other air/ground data link services such as VHF and Inmarsat data link.
- I have new aircraft on order, what should I be considering for the avionics specification? To ensure true diversity of ACARS® communications, ARINC recommends that when specifying HF radios for any new aircraft, request that the data link function be available on delivery.
- With the near-term viability of some long-distance communication media questionable, how does ARINC ensure the continued operation of the HFDL Service? HFDL has been ARINC owned and operated since its inception with no dependency on outside companies or third parties for end-to-end operation. And, ARINC continues to invest in HFDL infrastructure with a commitment to continued service well into the future.
For more information, e-mail globalink@arinc.com.
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