Avionics Digital Edition
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Clearing the Skies for Satvoice

High-frequency radios have been in use by airlines for decades, and their fuzzy connections have been annoying pilots and air traffic controllers for almost as long. Clearer, more reliable voice-over-satellite communications might soon solve that problem around the world — If some obstacles can be overcome.

It was only an hour after Avionica COO Anthony Rios’ 2007 flight with now-defunct Guam-based Continental Micronesia launched into the pitch-black night that it became clear they were heading into a major storm.

The pilot used the Boeing 737’s high-frequency radio to call into Oakland Air Traffic Control Center, which oversees air traffic for the entire oceanic region, to request a deviation from their planned route. He didn’t hear back, so he made an unplanned, unapproved deviation of his own. Five minutes after that, Oakland called him back, and the pilot basically just filled the controller in on what had already happened.

“Those are the kinds of things that satcom voice is geared to solve,” said Rios, who is also a member of the FAA’s performance-based operations advisory and rule-making committee communications working group (PARC CWG).

ICAO regulations, as well as those of local regulations such as the FAA, require two long-distance radios for all trans-oceanic flights; historically, that has always meant high-frequency (HF) radios. As satellite coverage fills out and data transmission rates increase, there’s an argument that satellite-based voice communications (satvoice) could replace one — or both — of the HF radios on new and future aircraft and do their job better. Being a good idea isn’t’ all that’s required for that kind of switch, though; there are all sorts of obstacles to getting a global industry like aviation to adopt new standards.

There are reasons to pursue it, though.

The average response time from controllers over an HF system is about 400 seconds, according to Inmarsat VP of Aviation Safety and Cybersecurity Joseph Texeira. Testing shows that over satvoice, that figure could drop as low as 10 seconds.

“Everybody wants to do this because this is a game changer,” Texeira said. The biggest reason is that call identification allows for prioritization.

The staunchest satvoice advocates include the two big satellite companies, Inmarsat and Iridium, service providers such as SITAONAIR, equipment developers such as Avionica and integrators such as L2 Aviation. In the near term, Rios and other proponents have their eyes on replacing one of the two communications systems planes are required to carry with a satvoice system.

Ultimately, though, they want planes to be able to forego HF radios altogether in favor of two “dual-dissimilar” satvoice solutions—one leveraging Inmarsat’s satellite network and one leveraging Iridium’s. The two systems need to be on separate networks to create the redundancy that the regulators are seeking with the requirements.

The reasons to get there are compelling, according to L2 President Mark Lebovitz.

“If you were just to say to our customers, ‘You can pick between a short-wave radio and a high-tech cell phone — and, by the way, [the latter] one is cheaper and lighter — which do you want?” the answer would be obvious, Texeira said.

“The idea of having HF radios that our grandparents were using… They’re not very clear and at times they’re not usable,” he said.

HF radios “have been the bane of operators” because of how heavy and unreliable they are, often requiring that airlines keep backup units at hubs, according to Rios.

Outside of some impact from ionospheric activity and sunspots that doesn’t impact HF radios, satvoice should always be clearer and faster than HF. And there has been wide support—everyone agrees that it’s a better situation.

But there are hold-ups.

As always, regulatory change is slow. Companies have to show rulemakers that, in practice, satvoice is just as reliable as HF. They’re working on that: In one effort last summer, Rios chaired a committee that brought Hawaiian Airlines, Jet Blue and UPS together to measure how long it takes to set up the call between an aircraft and air traffic control and what the quality is of that call. They advised the FAA that satvoice is a viable safety tool for long-range communications, which the FAA took into consideration for some new equipage rules for certain regions, which, Rios said, will make the U.S. the first region to let airlines replace one HF system with a satvoice system.

The big one is ICAO, though. Other bodies tend to follow ICAO’s lead and since the primary use case for HF and satvoice is transcontinental flights, the international body’s ruling is especially important.

“We don’t know when ICAO will be satisfied,” Texiera said, but that is where all of Inmarsat’s efforts are focused. The hope is that within the next year, the organization will adopt new language to facilitate satvoice.

When regulations do move to allow satvoice, though, they won’t likely do so explicitly; rather, the wording that requires HF radios will be changed so that instead of requiring certain equipment, the regulation will require certain capability. That way, any certified equipment that meets that capability can be used. That’s the way regulations are being written more often now, according to Rios, and that’s part of the effort to keep regulation from stifling technological advancement.

“The first part is removing any wording in the regulation that might hint toward HF, making it more generic and then making sure our products meet those regulations,” he said.

Another obstacle is infrastructure. While everyone might agree that satvoice is good in theory, not every country is set up to handle it, Lebovitz said, pointing to Australia as a prime example.

“They’re not set up to support two satcom calls. They don’t have the phone switch set up,” he said. “If a whole bunch of people started calling them, they wouldn’t have the people to support it.”

That’s something that Inmarsat is working on addressing in a partnership with Airservices Australia and SITAONAIR. SITA provides datalink services in Australia, and the air navigation service provider (ANSP) contracted Inmarsat earlier this year to evaluate the country’s connectivity infrastructure and ultimately use satvoice to enable direct controller-to-pilot communications beyond the reach of very high-frequency (VHF) radio, which is typically not more than 50 or 60 nautical miles.

If an airline does business in a region without the necessary infrastructure, its aircraft would need to have two HF radios onboard even if regulations don’t explicitly require it. Just because North America and Europe could support the switchover doesn’t mean it would work globally, and major transcontinental carriers want aircraft equipped to fly in any airspace.

It’s also a big investment on the part of airlines and manufacturers to add new satvoice systems in addition to or in place of an existing HF radio. The lifecycle of an airliner is measured in decades. There are tens of thousands of airliners in service, and Airbus and Boeing have combined to produce around 1,500 per year recently. As such, it takes a long time for new technology to proliferate the industry without costly retrofits.

Some newer aircraft may come with a satvoice system instead of dual HF systems. The Boeing 777X and the Airbus A350 come standard with a satvoice system and are capable of dual dissimilar satvoice, Rios said.

“They will not install dual HF systems very much in the future,” Lebovitz said. “But if you already have HF, why take it off?”

He suggested that some operators are interested in how the data transmission rates can be used for other things as a way to make the business case.

“Most of our customers… look at satvoice as kind of a given,” he said. “They realize they need that capability. Where they’re getting excited about is what kind of higher data speeds they can get with Iridium or Certus. If they can get 150 kbps or faster, they’re looking at what they can do to justify it to their operational finance people.”

Engine manufacturers, for example, “are looking for easier ways to obtain data regularly for trend monitoring of their components and these systems are an easy way to do so,” he said.

While satcom isn’t new as a technology, the newest high-throughput satellites can make that a possibility. Iridium Next will increase data speeds up to 176 kbps for active low-gain antennas and up to 1.4 Mbps for high-gain antennas is on the way through the company’s core transceiver, per Iridium.

For now, most airlines flying transcontinental flights that add satvoice systems will add them in a “two-plus-one” configuration; adding a satvoice system and using it and one HF radio, but keeping the second, inactive HF radio onboard as well. First, as Rios said, why take off an HF system that works? It can be kept as a backup if nothing else. And second, engineers might be loath to stick their necks out recommending a relatively unproven technology in lieu of something that has been used for decades and meets requirements all over the world. That way, if there would be problems or the aircraft finds itself in a location that strictly requires HF systems, it doesn’t risk grounding.

Then, if the single HF system and satvoice system do the job reliably, Lebovitz said, customers will likely start taking advantage of the minimum equipment list and only installing those in the first place.

The FAA is expected to adopt satvoice-friendly regulations in early 2019 that allow one HF radio and a satvoice system without a second HF radio on board, according to Rio. He anticipates “pretty good worldwide coverage by 2020,” though full proliferation is hard to predict since it depends on infrastructure changes in some places.

Avionica, which recommends one-plus-one installations to customers, has an Iridium system is provides and is on the path to developing one for Inmarsat as well. With a future of dual-dissimilar satcom systems, airlines will need to have one of each, so Avionica wants to be prepared to meet that demand.

The company is in talks with one customer that may soon be the first major operator to run the two-plus-one setup and disable the second HF system on its Boeing jets in regions where that is allowed, Rios said, but the customer’s identity is not yet available.

L2 Aviation offers certifications and does field-installs for both Iridium and Inmarsat systems. To this point, the lack of minimum operational performance standard approval for satvoice equipment has prevented L2 from getting certification for satvoice installs, but Lebovitz said those are now being accomplished, notably by the newly rebranded Collins Aerospace. As such, L2 is now adding approval for satvoice services to its Iridium STCs.

Inmarsat’s customers have mostly been ANSPs so far. The ones investing in space-based ADS-B are primarily the ones investing in satvoice, according to Texeira. That should expand as regulations facilitate it.

There’s a cycle of regulation making companies feel that it’s worth investing in technologies which enable technological advancement that facilitates regulation change. That full suite is coming together at the right time now for relatively rapid change.

“This was never possible several years ago. The availability of voice-over-IP, digital switches, the necessary infrastructure of satellite service providers,” Texeira said. “How confident are we ATC facilities are going to prefer this method? I’m sure they’ll absolutely want to have the ability to intervene when something goes wrong. They do so in the VHF world on a regular basis.”