There has been a lot of news recently involving two of the three big US Wireless (cellular phone) providers, AT&T and Verizon in regards to fully activating their 5G networks and impact on commercial aircrafts worldwide. First off a little background on ‘5G’. 5G or fifth generation is the newest technology standard for broadband cellular networks. It was introduced as a standard in July 2016 with deployment beginning in 2019 and full implementation planned by AT&T and Verizon for early December 2021. Speeds are up to 100 times faster than that of the previous generation (4G,) with a maximum speed of 10 gigabits per second (not that any provider is currently offering such speeds at this time). In addition to the increased speed comes much increased bandwidth (amount of data which can be transferred). This is great as more and more devices from cell phones, tablets, PCs/laptops, TV’s to Internet of Things (IoT) devices such as Amazon Echo/Alexa, Nest thermostats, video doorbells, baby cameras, etc. are connected to the Internet. The expanded bandwidth capacity of 5G allows for all these devices not having to compete with each other for access to an allotted chunk of network space (bandwidth). So far 5G sounds like a wonderful thing, especially as we become more “connected”. So what’s the issue with commercial aircraft?
The “issue” has to do with the frequency at which these providers (AT&T and Verizon) are operating their 5G networks. Their 5G spectrum of frequencies is on the C-Band between 3.7 and 3.98 GHz (note prior to the 2020 FCC Auction 107, C-Band was designated as the range between 4 and 8 GHz). These frequencies were approved and auctioned off by the Federal Communications Commission in December 2020. If C-Band sounds familiar it is because it was used in the past for older Satellite TV systems (think back to the 80’s Big Ugly Dish the size of a Volkswagen) before the introduction of direct-broadcast satellite (DBS) (DiSH/direcTV). T-Mobile/Sprint operates their 5G network on a different band at 2.5 GHz (very close to the 2.4 GHz frequency used by landline cordless telephones made from 1998-2003). Commercial aircraft (though primarily Boeing’s 777) have radar altimeters which operate between 4.2 and 4.4 GHz. A radar altimeter simply described is radar which measures the distance between the bottom of the aircraft and the ground. These combined with the other aeronautic systems on commercial aircraft allow for “automatic landings”. It is important to understand this is not an issue with all 5G base stations, just those located close to major airport approaches. This is because the 5G signal strength dissipates with distance, so the farther aircraft are from the ground the less of an issue this becomes.
If you lived in a large metro area and used an over-the-air television antenna prior to the digital television transition in June 2019 you likely have had experience interface from other TV stations, weather, microwaves, cordless phones, CB radios and more. While this interface was just an annoyance for you; potential inference with radio altimeters could cause ‘bad data’ which could lead to potentially catastrophic consequences. Older models radar altimeters lack RF Filters, a type of resistor-capacitor circuit. RF Filters are designed to remove or accept signals that fall in certain areas of the radio spectrum. In this case accepting signals only from the 4.2 to 4.4 GHz range while removing ‘interference’ from the neighboring 3.7 to 3.98 GHz frequencies. There are a couple cavoites; First, in Europe the 5G spectrum is between 3.4 and 3.8 GHz, so there is less chance of interference; Second, pilots typically utilize radar altimeter when line of sight on approach is not possible (low visibility cased by weather or nighttime).
Now, if you have made this far you might be confused as to why this is suddenly an issue. Again the 5G standard was introduced some six and half years ago and deployment began within the last 3-years. Per the FCC guidelines AT&T and Verizon planned to be fully operational in 46 major metropolitan areas of the U.S. on December 5, 2021. Simply put the Federal Communications Commission or FCC (an independent agency of the United States federal government that regulates communications by radio, television, wire, satellite, and cable across the United States) and Federal Aviation Administration or FAA (transportation agency of the U.S. government and regulates all aspects of civil aviation) have their own competing interests. The FCC claims there is little to no risk of issues while the FAA (as well as the US Department of Defense) tend to think otherwise. If you were to pick sides on this issue, one would be wise to side with the FAA. Furthermore, this became more of an issue when the FCC auctioned off portions of the C-Band spectrum (the ‘new’ 3.7 to 3.98 GHz range) in December 2020 to AT&T and Verizon. The FCC netted over $80 Billion USD from Auction 107. On November 2nd, 2021 (about a month before the planned ‘activation’ of AT&T and Verizon’s new 5G networks), the FAA issued a Special Airworthiness Information Bulletin warning that “action might be required to address potential interference with sensitive aircraft electronics.”
There are three ways the problem can be minimized:
- Replacing existing altimeters.
- Changing 5G frequencies.
- Reducing the power output of cellular base stations.
The first two are impartial and would be extremely costly (both in time and modifying/replacing technology). The Boeing 777 or Triple Seven as it is commonly known is the largest twin-engine jet transport in service, a role that was briefly held by the Airbus A330 prior to the Boeing 777s introduction into service in 1995. There are around a total of 1657 Boeing 777’s delivered as of February 2021. This figure based from the first delivery in 1994/1995) but not this many are still in service as most of the older generations have since been retired and some aircraft which have been delivered may not yet be in service. While the Boeing 777 is the most commonly used (especially for International travels), there are other models of commercial aircraft in service in the US using the same altimeters. From Forbes “Replacing altimeters on thousands of aircraft currently operating within U.S. airspace would take the better part of a decade.” This wouldn’t even include the years needed just to develop a new standard for radio altimeters.
Well, that wouldn’t work, so how abut charging the frequencies of the 5G Phones/Network? Also noted by Forbes “Changing the frequencies of AT&T and Verizon’s 5G networks would be similarly difficult.” Remember, AT&T and Verizon spent tens of BILLIONS of dollars in the FCC Auction 107 to purchase their spectrums of the C-Band from the FCC. Imagine the costs and time involved in not only replacing/adjusting the radio transmitters on every 5G cell tower in the US, but very likely having to replace every AT&T and Verizon customer who has purchase a 5G phone is the last couple years. Between these two carriers there are almost 171 million subscribers (as of 2nd quarter 2020). Not all these subscribers have 5G phones (though throughout 2021 both companies ran aggressive trade-in campaigns allowing new and existing customers to upgrade to a new 5G phone (mostly the Apple iPhone 12 or 13) for little or no cost )especially as these carriers began phasing out their outdated 3G networks).
So, this leads to last option of reducing power output of the cellular base stations or in the case of Canada imposing restrictions on locating new 5G cell towers near the runways of large airports. Australia, France and other nations have taken steps to limit the chances of aircraft interference. There has been talks of AT&T and Verizon temporarily reducing power output of the base stations in the US by 50% located near major airports. However, the biggest airports and most heavily used approach paths are located near the biggest concentrations of base stations, because that’s where the people are. But, reducing the power would severely cripple the benefits of 5G. Major telecoms in Canada have protected the restrictions imposed by Canadian radio spectrum authority., saying it will keep them from offering the latest wireless services to many businesses and private customers in the heavily industrialized and populated areas around major airports. Any similar restrictions here in the US would likely would lead to AT&T and Verizon having to install more (lower-power) towers to compensate. Again, very costly in both time and new equipment.
As of late several international commercial carriers including Germany’s Lufthansa. Japan Airlines, Air India, Korean Air, Hong Kong’s Cathay Pacific and Austrian Airlines are canceling flights with the Boeing 777 to some or all US Airports. They are either swapping out to a different plane (mainly Airbus which I am guessing uses a radar altimeter that is not susceptible to 5G interference) or canceling these flights all together. However, recent news reports indicate airlines are being instructed by the FAA to avoid automatic landings at affected U.S. airports during bad weather conditions, regardless of plane type. I don’t see a simple fix and have to wonder why the FAA didn’t say anything when the FCC issued a release in early March 2020 for Expanding Flexible Use in the 3.7-4.2 GHz Band. Turns out they did. From this Defense News article from December 21, 2020 (less than two weeks after FCC Auction 107 concluded)
“But, in the weeks leading up to the auction, more than a dozen commercial aviation groups warned the sale could, as one study put it, lead to “catastrophic failures” with the potential for “multiple fatalities.”
According to a memo obtained by Defense News, those concerns are shared by the head of the Federal Aviation Administration and the number two at the Department of Transportation, who are calling on the FCC to pause the sale so the safety issue can be studied more closely. The FCC, in turn, has said its own technical studies show little to no risk involved and it intends to continue moving forward.
Unfortunately, it seems this issue is going to continue to playout over the next serveral weeks if not months and once again (as usual) the consumers are the ones who are caught in the middle. From either having to suffer from reduced/canceled flights within (or to) the US or for AT&T and Verizon subscribers, a 5G network that might not be at its fullest protentional.