Getty Images | Daniel Garrido
The Federal Aviation Administration will give airlines another year to repair or replace altimeters on planes that can’t filter cellular transmissions outside their assigned frequencies. In a Notice of Proposed Rulemaking (NPRM) released today, the FAA has proposed a February 1, 2024 deadline to replace or retrofit faulty altimeters used by aircraft to measure altitude.
Of the 7,993 U.S. registered aircraft, the FAA said, “Approximately 180 aircraft will require a radio altimeter replacement and 820 aircraft will require the addition of a radio altimeter filter to comply with the proposed amendment requirements. We estimate that it will be The estimated total cost of compliance is $26 million.
The requirement finally puts an end to the dispute between the aviation and wireless industries that has prevented AT&T and Verizon from fully deploying 5G on C-band spectrum licenses purchased by wireless carriers for a total of $69 billion. can be hit. The plane’s altimeter relies on the 4.2 GHz to 4.4 GHz spectrum, but some cannot exclude his 5G transmissions from the spectrum of carriers in the 3.7 to 3.98 GHz range.
The FAA said, “Some radio altimeters may exhibit immunity to 5G C-band emissions without modification.” You may need to install a filter between them, and for others, you may need to replace your radio altimeter with an upgraded radio altimeter, as just adding a filter will make it less susceptible to interference.”
“False system warnings” cause problems
The FAA said, “False system warnings due to malfunctioning radio altimeters are expected to desensitize aircrews to system warnings. Such desensitization would negate the safety benefits of the warning itself and could be devastating. It can lead to serious events.”
The FAA said in June 2022 that airlines should replace or retrofit faulty altimeters “as soon as possible.” However, the notice issued today states that February 1, 2024 is “the date the FAA has determined to be reasonably practicable, consistent with FAA policy.”
The FAA will allow 30 days for public comment before finalizing the new proposal. As reported by Bloomberg, lobbying group Airlines for America said airlines “are working hard to ensure their aircraft are equipped with compliant radio altimeters, but global supply chains are lagging behind current demand.” “The government’s deadline must take into account this reality.”
The proposed rule affects aircraft operating under Part 121 certification. According to the FAA, these certificates are for airlines that operate scheduled flights and typically include “major U.S.-based airlines, regional airlines, and all freight forwarders.” .
“To minimize the number of erroneous system messages and the hazardous conditions they create, the FAA is proposing to require all aircraft operating under Part 121 to meet the PSD. [power spectral density] Performance curves operating in the continental United States after February 1, 2024,” the notice states.
Between now and the 2024 deadline, aircraft that continue to use a failed altimeter must comply with some restrictions when landing. December 2021 Airworthiness Directive “Ban[ed] Certain operations requiring radio altimeter data in the presence of 5G C-band interference. ”
Old altimeter “ignore assigned spectral boundaries”
In February 2020, the Federal Communications Commission approved mobile use in the C-band after reviewing complaints from the airline industry. FCC says 220 MHz guard band between 5G and altimeter operations and FCC power limits required for C-band transmission make harmful interference to altimeters unlikely “under reasonable scenarios” concluded.
However, the airline was unprepared for the launch of the C-band, which was due to start in December 2021. AT&T and Verizon have agreed to a nationwide delay of about six weeks and limited deployment near airports. The deployment restrictions around the airport were originally set to expire in July 2022, but the carriers have since agreed to keep the airport area restrictions in place until July 2023.
Altimeters were originally designed decades ago, and the nearby spectral band contained only low-power operations such as satellites. “This led the early designers of altimeters to determine that the assigned spectral boundaries could actually be ignored, thus allowing out-of-band energy to be transmitted to the receiver,” said the expert. Dennis Roberson explained at his February 2022 congressional hearings.
The altimeter issue prompted the FCC to launch an investigation into poorly designed wireless devices that receive transmissions from outside their assigned frequencies. This investigation may result in new regulations for wireless receivers. The FCC has traditionally imposed limits only on transmitters.
