Airbus continues to target 2026 for delivering aircraft factory-fit with Ku-band multi-orbit inflight connectivity under its supplier-furnished Airspace Link HBCplus program. But the airframer admits it’s still immersed in “intensive studies” about how to address heat dissipation for the large dual-beam electronically steerable antenna (ESA) and whether true gate-to-gate connectivity, as we define it today, needs to be supported.
“So, we want to have a Ku solution and ESA-based as early as possible, ideally 2026. So, we keep that ambition, even though I mean we see that of course as you go in and design it, you need to make some trade-offs but yes, we keep that ambition,” Airbus head of connected aircraft Tim Sommer told RGN at the APEX Global Expo in Long Beach.
But in terms of heat dissipation, he said, this “is becoming a key factor and I would say the bigger and the more performing an ESA antenna becomes, the bigger that question becomes. So, we have been doing quite intensive studies in the frame of HBCplus, but also in terms of the general observation of what is happening on the market on the technology side.
“There are essentially two things. I mean, one is on the antenna itself. How hot can it get? And then the second thing is what kind of heat load can the aircraft take, the fuselage of the aircraft? And that again is different between a metal fuselage and a composite fuselage. And it’s adding another level of complexity.”
ThinKom’s Milroy and Seamless’ Lemme weigh in
For the Ku-band side of HBCplus, Airbus is using a terminal from Safran Passenger Innovations, based on the Thales/Get SAT dual-beam ESA. On the Ka-band side, it is using an SPI terminal based on ThinKom’s Ka2517 VICTS antenna (mechanically steered phased array as opposed to electronically steered). HBCplus Ka-fitted aircraft are now being delivered to customers, with Emirates the first to receive an A350 line-fitted with the system. And so, we tapped ThinKom CTO Bill Milroy for color.
Stressing that ThinKom has “never had a problem with LEO-only ESAs” — as evidenced by its ThinAir Plus mix-and-match package (which can pair VICTS with a LEO-only ESA) — Milroy suggested that the power and ergo heat issue comes into play when you’re talking about hybrid ESAs that can talk to both LEO and GEO (with full GEO coverage), in what the Seamless Air Alliance would categorize as Type 4.
“Well, you’re going to need to get to 1,000 or 1,200 Watts if you want to be a Type 4 or even get close to truly what we can do already with our [VICTS] system. You’re really pushing up towards the 1,500-2,000 Watt range,” he suggested.
“And Boeing and Airbus have both told us they’re not too comfortable with that both literally and figuratively. And particularly putting that like close to a composite fuselage, that’s problematic.”
Peter Lemme, an industry veteran and thought leader at Seamless Air Alliance, of which Airbus is a founding member, said that when looking specifically at hybrid ESAs, the heat factor is not just a concern for composite aircraft.
“Aluminum is just as much a concern for us. And this is an activity on the AEEC side that we worked at for several years trying to develop a standard between Boeing and Airbus as far as how an antenna supplier could assess their skin temperature because the antenna is sitting above a section of the skin and we purposely put a gap in there,” he told RGN in reference to AEEC’s standards work (Lemme was instrumental in ARINC 791/792 work…793 is now coming down the pike).
“And so, there’s heat transfer and of course the skin itself has a certain thermal coefficient as far as how that heat is absorbed and translates to temperature rise. And it’s very difficult to model. And we went back and forth around this and ultimately, we were able to come to some understanding of what the maximum skin temperature should be. But how to model heat transfer as it relates to skin temperature rise was something that we could not come to an open standard.”
Interestingly, he suggested that a cooling fan “is not necessarily a good solution” to the problem “because you have to get into, what if the fan’s not working? Can you detect it and how you prevent it from overheating and those kinds of failures. And again, it’s not a casual exercise. It’s a fairly serious exercise that has to occur.”
Whilst LEO-only ESAs that support the likes of Eutelsat OneWeb and Starlink connectivity do not really pose a heat issue, he said, hybrid LEO/GEO terminals represent a more demanding, heat-intensive solution. “So, yeah, it’s a problem and I just want to make sure [you understand] it’s not limited to composite airplanes by any means. It’s a problem on any airplane that you do this,” said Lemme.
That may be so, but Airbus’ Sommer said the airframer has been studying heat dissipation “intensively and notably for the A350 obviously, which is a composite fuselage as well” [i.e. in the context that this is not just a Boeing 787 consideration].
The airframer is, however, “confident that there is a solution which can be found for that. Obviously, I mean, we haven’t made up our choice exactly on how the final design will look like, which technology exactly we’re going to use, etc [for heat dissipation]. So, we’re still in the phase of kind of finalizing that design at the moment. But yes, we’ve done the studies on all the aircraft platforms. And yes, there are solutions for that.”
Airbus is also asking the question: is true gate-to-gate connectivity really necessary?
“We are also, as I said, looking at the ESA solutions which are out there. And sometimes it’s a question also of what kind of operational limitation can you accept or not,” confided Sommer.
“So, everybody’s speaking of gate-to-gate connectivity at the moment, but you really need to look in detail, what does that exactly mean? So, is it really necessary that the thing works with full power when the aircraft is still standing at the gate, or is it enough if the aircraft is starting to be pushed back and starting to move? Because that makes a whole lot of difference.”
There are discussions right now about the “design trade-off”, he said, “how important is that really for an airline customer to have that moment when the thing is still standing at the gate, and everybody anyway is still connected on the 5G network? Do you really need a solution which is working full power on the top of the aircraft and then that drives maybe an active cooling system in the antenna, which makes it more expensive, more complex.”
Like Lemme, Sommer does not think there’s a case for an active cooling system. “That’s the kind of discussion we’re in a bit at the moment to find that sweet spot on the design.”
The SPI ESA terminal being used for Ku-band Airbus HBCplus will have a 5G solution to be able to accommodate connectivity on the ground, but Sommer said “that’s not for passenger connectivity” it’s more for software updates and the operational side.
So, Airbus is studying what temperature limit is acceptable when an aircraft is standing in a desert airport “fully heat soaked at the gate” and whether it’s necessary for passengers to connect via the ESA in that scenario or if it’s enough to say, you can connect “when the aircraft is pushed back”, and then of course climbing and flying in cruise, and being cooled by the airflow.
On an aside, your author is a residential user of SpaceX’s Starlink service, and has a Starlink LEO-focused phased array antenna in her backyard for over a year. During the first few months of service, the Wi-Fi was bizarrely hit or miss and overall not consistent. But it got much better thereafter, and the performance has been solid including on hot days (Pennsylvania weather doesn’t hit the antenna’s temperature limit of 122 degrees…at least not yet!) The antenna is warm to the touch (similar to a laptop) and when the weather cools down, flies start congregating on it. Service does degrade immensely, and can become inoperable, if there is a heavy snow that then melts into slush.
Cold day? Flies congregate.
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Featured image credited to Mary Kirby
