Why Is 5G Still Interfering With Radar Altimeters?

By John Oncea, Editor

5G deployment began in January and, within days, pilots began reporting instances of aircraft system interference.

Earlier this year, we reported the Federal Aviation Association (FAA) issued a historically high 1,462 flight notices detailing the potential interference 5G may have on aircraft altimeters. Let’s take a look at what has changed since then.

According to Yahoo, things are looking up in Europe where “airplane mode will become a thing of the past in the European Union (E.U.) starting next year, following the European Commission’s decision to allow airline passengers to use data and even perhaps make calls while in the air. The ruling will allow airlines to provide 5G technology rather than offering historically slow free Wi-Fi or requiring passengers to pay for data access.” *

But 5G in the air isn’t coming to the U.S. anytime soon, at least if the Federal Aviation Administration (FAA) has its way. According to Reuters, the FAA wants the U.S. telecommunications regulatory agency to ensure a delay in some 5G C-Band transmissions from smaller operators.

Acting FAA Administrator Billy Nolen said back in October that he wants the Federal Communications Commission (FCC) to mandate voluntary mitigations that AT&T and Verizon agreed to earlier this year mandated for 19 smaller telecoms and other spectrum holders.

Why is Nolen making his ask? Because of complaints about altimeter failures jumping after consumer C-band deployment dating as far back as January.

* Why is the E.U. forging ahead with 5G usage while the U.S. is taking a more cautious approach? According to Dai Whittingham, chief executive of the U.K. Flight Safety Committee, “There is much less prospect of interference” because Europe has “a different set of frequencies for 5G, and there are lower power settings than those that have been allowed in the US. The traveling public wants 5G. The regulators will open up that possibility, but there will be steps that will be taken to ensure that whatever they do is safe.”

A Look Back At A Year’s Worth Of Incidents

As reported by IEEE.org, “At least three flights above Tennessee simultaneously experienced altimeter errors that made it ‘impossible to maintain assigned altitude,’ according to one of the pilots. One jet lost its autopilot completely, and reportedly had fire trucks waiting for it on landing.” This all happened in January.

Then, in February, a passenger plane on approach to the Louis Armstrong International Airport in New Orleans experienced erratic low-altitude warnings as it flew below 1,000 feet. In March, a commercial jet landing on autopilot at Los Angeles International Airport suddenly went into an aggressive descent just 100 feet above the ground.

The pilots of these aircraft linked the incidents to “problems with the aircrafts’ radio (radar) altimeters, which pilots rely on during takeoff and landing, and to help avoid crashing into mountains.” A possible cause of these problems? The rollout of high-speed 5G wireless networks which use similar frequencies that began in January.

The IEEE article provides more detail – please check it out – and concludes with these anonymous pilot quotes:

• “Shutdown [sic] 5G until carefully vetted.”
• “Delay implementation of 5G service until all issues with radar altimeters and transport category aircraft have been dealt with.
• “Turn off 5G cell service near airports.”

Retrofit The Altimeters!

An early effort at fixing the problem was to retrofit radio altimeters, a piece of equipment that has been a successful part of aircraft operations for the past 50 years. According to Simple Flying, “One of the main functions of the radio altimeter is to show the altitude of the aircraft, but this is just one small function of it. It is connected to many other critical aircraft systems. Consequently, an erroneous radio altimeter can be a major safety issue.”

Back in June, the FAA – according to Ars Technica – the FAA announced “a plan for the industry to replace or retrofit airplane altimeters that can't filter out transmissions from outside their allotted frequencies.” It further reports the FAA issued a statement saying, in part, that “airlines and other operators of aircraft equipped with the affected radio altimeters must install filters or other enhancements as soon as possible.”

Well, that hasn’t gone as planned with Simple Flying reporting the aviation industry is not on track to meet two crucial deadlines – one this month and the other in July 2023. The FAA, “several major U.S. carriers, and other aviation stakeholders have been pushing for an extension to the deadlines previously given for all airlines to retrofit for new 5G altimeter requirements,” notes Simple Flying. “The ask for an extension comes as these parties feel that there isn't enough time for all airlines and aircraft manufacturers to make such changes.”

Reuters also reported on the delay, writing, “Air carriers will be unable to fully meet deadlines to retrofit planes to avoid interference from the latest generation 5G C-Band wireless service. A letter signed by Airlines for America, Boeing, Airbus, Embraer, aviation unions, and others backed the FAA’s request to mandate an extension of mitigation by wireless carriers as airlines retrofit radio altimeters.”

The letter went on to say that “the FAA has documented over 100 FAA incidents of potential 5G interference” since the January incidents noted above. It also notes that “Unfortunately, the U.S. government agencies do not appear to be on the same page with respect to these safety issues.”

The FAA has a page dedicated to this situation, noting it is “working to ensure that radio signals from newly activated wireless telecommunications systems can coexist safely with flight operations in the United States, with input from the aviation sector and telecommunications industry.”

While it doesn’t appear to have been updated since June, the page does contain a map showing the percentage of the U.S. commercial fleet and aircraft types that can land at U.S. airports with low-visibility approaches or a high-volume of aircraft with systems that could be adversely affected by 5G. It also notes to check back for information and updates as its work continues, so it may be worth bookmarking.