Moisture under the antenna hood? It’s not just deicing fluid

Rotation

It may still seem like magic that GORE-TEX jackets are able to stop rain from getting in while letting the wearer’s perspiration out, but the same kind of concept could be used to protect aircraft antenna systems from moisture, according to W. L. Gore & Associates.

“You have to vent them somehow,” notes Gore’s global product manager – civil air cabling and aircraft connectivity products, Adrian Milne, in reference to the large radomes atop aircraft fuselages that house terminal equipment to support inflight connectivity.

Milne explains: “So, if you think of the same context of how your GORE-TEX jacket stops rain water coming in but allows vapor moisture to come out, the vents work in a very similar fashion, where if you do get moisture within the enclosure it is actually expelled through the vent.”

Gore has been selling protective vents into many different industries for years, including for telecommunication infrastructure and in automotive. “We sell tens of millions of vents in those industries, and pretty much [to] every car manufacturer in the world,” says Milne.

While the company is in the exploratory phase of applying the technology in aerospace, Milne sees opportunities to add Gore content to antenna radomes, specifically. “When you’re talking about materials which are coming into your radomes, those can [include] moisture which can be driven by altitude changes – if you have pressure changes – so having these vents can help equalize pressure and you can expel moisture that you don’t want inside your dome,” he tells Runway Girl Network.

The problem of moisture inside antenna radomes gained attention after deicing fluid seeped under Gogo 2Ku radomes last winter, creating Internet outages for airline passengers and prompting Delta to assume a greater share of maintenance work on the structures. Gogo later discovered that the issue was not relegated to deicing fluid alone, noting in a 10Q filing with the SEC that moisture can enter during aircraft cleaning and or by humidity or condensation.

But the predicament of condensing water is not uncommon; indeed, it plagues virtually all antennas under a radome. Even long-defunct Connexion by Boeing faced these sorts of challenges on entering the market nearly two decades ago. Effectively, the radome creates a micro environment, which traps humidity and can collect water.

Industry consultant and “satcom guru” Peter Lemme, who chairs the subcommittee that developed the ARINC 791 spec for Ku- and Ka-band antennas for aircraft, as well as the 792 spec for nextgen aero antennas, notes that radome designs “must provide channels to drain away water collection, else corrosion sets in. Cold-soaked assembly flying into warm humid air will suffer dripping water.”

He adds, “[The] radome is not a pressure vessel, it must breathe. Vents typically are covered with a fabric to promote egress and to block contamination. Decompression requirements may include other features for rapid venting.”

To be clear, radome vents can’t take deicing fluid away because it is a “very caustic, aggressive material and that does different things because it’s quite sticky” but for regular moisture issues that can affect the reliability of the antenna system, venting works, says Gore’s Milne.

As Gore eyes fresh venting opportunities in aerospace, it is already vapor-sealing some of the cables used to provide power or transmit data for inflight connectivity systems. “We are talking a lot about sealing in the electronic components and sealing the domes themselves, but our cables, like the ones we are using on the EAN [European Aviation Network], they are actually vapor-sealed themselves. And that’s a huge issue, I would say, in the industry is around the liabilities of cables,” says Milne.

Jeremy Moore, who works as product manager, civil aerospace cabling at Gore says the cable reliability problem is “only going to get worse as the installations are increasing, and [as] time goes on and planes are going up and down. Every time you have a change in atmosphere like that and altitude, the pressure difference is going to cause the ingress of the moisture down the cable and if it’s not sealed, that’s going to happen.”

Rotation
Lemme notes that ARINC 791/792 provides ample documentation of the challenges and testing necessary for dealing with fluids, including sprays, though there is no specific requirement for sealing cables beyond the testing criteria.

“While qualification does not drive reliability, the marketplace has not vocalized a need for any special cable covering other than for bonding issues,” he says.

But Milne believes the market is starting to get more educated on the matter. “I would say there are probably more enlightened customers, obviously, that are starting to appreciate true value and understand what’s important. And they are learning from the experiences they are having within their own installations and also with information that Gore [provides]. We are providing a lot of test data, things that back up the claims that we are making and I think those two things are starting to come together and we are having people come back and say ‘we want to go vapor seal now’ because, you know, engineers have worked on previous projects and previous installations and learned the hard way, and they don’t want to go back to that place again.”

Related Articles:

Leave a Reply

Your email address will not be published. Required fields are marked *