The U.S. government said last month that it does not plan to delay the current July 1, 2023 retrofit deadline for aircraft that may be subject to interference from 5G emissions. The piece of equipment in question is called a "radar altimeter" which measures the distance between an aircraft and the ground, among other critical functions. Radar altimeters are especially important in low visibility takeoffs and landings.
The impact of the July 1, 2023 deadline for operators will depend on, (1) the aircraft type [including its radar altimeter model]; (2) the operating environment [e.g., the existence of potential interference from 5G signals, and airport characteristics], and (3) any other mitigating or aggravating factor. On its website, the Federal Aviation Administration sheds light on these factors with an interactive map. Using the interactive map, operators can see airports in low visibility scenarios where certain aircraft have been approved for takeoff and landing. However, all operators must also follow FAA's published Notice to Air Missions (NOTAM), which provide information on restrictions or procedures that pilots need to follow. The issuance of a NOTAM supersedes the interactive map and may render an operation impermissible.
How did we get here?
Potential conflict between radar altimeters and 5G emissions first arose several years ago, prior to 2020. Significantly, in 2021, the FCC finalized the auction of a portion of the radiofrequency spectrum that is near spectrum used for aircraft radar altimeters. A number of telecommunications companies with plans to use the auctioned spectrum for 5G telecommunications services bid on the spectrum. The auction garnered approximately $80B USD, which was generally allocated to the U.S. Treasury, resulting in a significant economic impact for the U.S. The result of the auction meant that 5G telecommunications signals would be transmitted in a frequency band very close to the band used for radar altimeters. The question arose whether interference from 5G emissions could be tolerated by radar altimeters, or whether 5G emissions may cause the radar altimeters to malfunction.
Likelihood of interference and voluntary mitigations
To address the interference question, an aviation standards setting organization and a telecommunications organization conducted studies about the potential impact of emissions produced by the 5G tower on radar altimeter signals operating in a nearby spectrum band. Differing opinions about the likelihood and severity of the interference resulted in delayed deployment of certain 5G towers, especially near airports with low visibility operations. Parties on all sides of the issue, telecommunication companies, the aviation industry, and government regulators, took actions to avoid potential interference, such as a voluntary reduction in power levels by certain telecommunications companies. The FAA, for its part, issued airworthiness directives and NOTAMs to limit operations where interference was of significant concern.
During 2022, many aircraft were able to retrofit their radar altimeters with new equipment that is more tolerant of the 5G emissions, thanks in part to the swift action of radar altimeter manufacturers. Nevertheless, airlines also faced significant challenges in attempting to retrofit aircraft due to supply chain challenges and the significant cost of retrofitting, among other challenges. In an effort to provide aircraft owners/operators with more time to retrofit, many telecommunications companies also continued to voluntarily reduce the emissions produced by their 5G towers into 2023. This is slated to change July 1. After all, telecommunications companies are eager to end mitigations, since their impact is lesser power for 5G signals, and a resulting diminution in service.
July 1, 2023 represents a deadline by which operations may be limited for those aircraft that have not been retrofitted with new radar altimeters. In preparation, on May 24, 2023, the FAA issued a Special Airworthiness Information Bulletin (SAIB) for radar altimeter and aircraft manufacturers, as well as operators and pilots. In the SAIB, the FAA makes recommendations to mitigate impacts and request information from interested parties relating to their equipment and encountered interference.