In January, at least three flights over Tennessee experienced altimeter errors at the same time, making them “unable to maintain the designated altitude,” one pilot said. One plane’s autopilot stopped working completely, and a fire truck was on standby when it landed.
In February, a passenger plane approaching Louis Armstrong International Airport in New Orleans issued an unusually low-altitude warning while flying below 1,000 feet. “This type of false warning display would be extremely distracting in more difficult environments, such as poor visibility or icing conditions,” the pilots later wrote.
In March, a commercial jet that landed on autopilot at Los Angeles International Airport suddenly began a violent descent just 100 feet above the ground. The pilot reported, “I took control of the airplane and it landed nose up.” “It was a very alarming pushover by the autopilot. [other] This situation could have caused a collision. ”
All three accidents, and more this year, were linked by pilots to problems with the aircraft’s radio (radar) altimeter. Aircraft radio (radar) altimeters were relied upon by pilots during takeoff and landing to avoid collisions with mountains. These altimeters also feed the critical autopilot, autothrottle, and instrument landing systems.according to IEEE spectrum Complaints about altimeter malfunctions and failures have spiked since high-speed 5G wireless networks using similar frequencies were rolled out earlier this year, according to an analysis of reports received into NASA’s Aviation Safety Reporting System (ASRS).
ASRS is a public database maintained by NASA to encourage U.S.-based air crews, ground crews, and air traffic controllers to anonymously share safety incidents and concerns. Between January and May, there were 93 reports of radar altimeter failures or malfunctions, compared to only a handful in other years. In January alone, there were nearly twice as many complaints about malfunctioning altimeters as in the previous five years combined. In most cases, including the Tennessee and Los Angeles cases mentioned above, reporters mentioned his 5G interference.
The Federal Communications Commission initially downplayed concerns that new cell phone towers and equipment would interfere with radar altimeters on commercial jets, which operate hundreds of megahertz higher in the radio spectrum. In early 2020, the agency wrote: [gigahertz] Service and 220 MHz spectrum separation provides significant protection for services in the 4.2-4.4 GHz band. ”
The U.S. Federal Aviation Administration wasn’t so sure. The company commissioned RTCA, a non-profit organization that researches avionics equipment, to conduct an empirical study to assess the operational risks of 5G interference. The report states that C-band 5G systems could cause harmful interference to radar altimeters on all types of commercial aircraft, and that “this risk is far-reaching, including the potential for catastrophic disasters. could have far-reaching implications for aviation operations.” The failure resulted in multiple fatalities. ”
It was found that the risk arises from intentional false signals from ground-based mobile phone base stations, from accidentally operated 5G mobile phones onboard aircraft, and is further exacerbated by altimeter receivers with poor spectral selectivity. In what now seems prescient, the RTCA report stated:[The] The potential for harmful interference is especially dangerous given that radar altimeter failures have historically been extremely rare. ”
Nevertheless, spectrum auctions continued, with wireless providers led by Verizon and AT&T paying more than $80 billion for spectrum. 5G service was scheduled to launch in 46 markets across the United States on January 5 of this year. However, as deployment approached, the FAA issued an airworthiness directive that significantly restricted air travel to those areas.
In the end, wireless carriers agreed to delay 5G deployments by two weeks, and the FAA announced that certain aircraft (altimeter-sensitive aircraft or those carrying untested aircraft) would not be able to install 5G wireless networks. Landing at low visibility airports is prohibited. The network also agreed to establish “buffer zones” around 50 airports that would reduce 5G C-band signal levels by at least a factor of 10 within one mile of takeoff and landing runways. The mitigation measures were scheduled to continue for six months while the FAA sought to allow more planes into service.
On January 19th, the 5G system was switched on.
Complaints soon started coming in to NASA. On his first flight to San Francisco after 5G was turned on, one pilot was horrified when his brakes activated unexpectedly due to the plane’s speed before landing. “In more than 18,000 hours as a Boeing passenger aircraft captain…the automatic speed brakes were never activated without command prior to ground contact,” they wrote. “I’m operating in his 5G environment, but he’s not going to land on 5G first.”
“I tended to think nothing would happen with the implementation, but I was surprised to experience an actual interference event,” said another who suspected that the plane’s autothrottle was disengaged due to an altimeter failure. the pilot reported.
The ASRS includes at least 40 reports of possible 5G interference near 50 airports with buffer zones. Phoenix Sky Harbor International Airport received the most complaints with six reports.
“I’ve been flying aircraft with radar altimeters for years, and I’ve never seen a failure like this until 5G was turned on,” said one person, who said the altimeter would go from minus 90 feet to 400 feet before takeoff. wrote another pilot in Florida who fluctuated between ft. . “A coincidence? Probably not.”
But is it possible? Chris Rudell is an associate professor in the Department of Electrical and Computer Engineering at the University of Washington. “I want to sleep like a baby.” [on a plane] “We flew over 5G base stations at maximum power,” he said. spectrum. “Perhaps something unusual happens and the pilots attribute it to 5G, but maybe it’s not 5G’s fault. After everything that’s been reported in the news, they now… I’m actually submitting what I saw, and I probably didn’t have the motivation to do that before.”
It is true that the FAA currently has a specific online radio altimeter anomaly reporting form that pilots and other aviation personnel are required to complete. The FAA did not release the full details of these reports, but provided high-level data showing it had received about 550 similar reports since January.
The agency reviewed more than half of the reports, but could not rule out the possibility of 5G interference in about 80 cases. Contrary to the ASRS report, none of the interference events identified by the FAA had an impact on safety-related systems that affect the aircraft’s direct control inputs, such as autothrottle or speed brakes. The FAA concluded that the mitigation measures agreed to with wireless providers are “working.” In June, it reached an agreement with airlines to extend these mitigation measures for another year.
Although altimeter complaints about ASRS seem to be decreasing, many pilots still want tighter controls over 5G technology. AOPA, the world’s largest organization representing general aviation pilots and aircraft owners, said: spectrum: “We call for continued discussions between the public and private sectors to further mitigate the proven safety risks that 5G technology poses to radar altimetry. Further cooperation and coordination will result in solutions that work for everyone. Masu.”
Some pilots were less diplomatic in sharing their opinions anonymously. “shutdown [sic] Don’t use 5G until it’s carefully vetted,” one person suggested. “Please delay the introduction of 5G services until all issues with radar altimeters and transport category aircraft are resolved,” another wrote. A third simply implored: “Please shut off 5G cell phone service near the airport.”
This article has been updated to clarify AOPA’s status as an aviation association.
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