FAA’s AD escalates the technical battle with FCC over 5G

FAA v. FCC on 5G
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FAA and aviation industry – 5G will affect Altimeter accuracy

FCC and communications carriers– 5G has not disturbed aircraft navigation in other countries

AD issued prohibiting flights depending on altimeter for SAFETY

How can 2 technically expert agencies disagree?

Trade issues involved?


The battle over the 5G implementation is unique in recent public policy debates. The FCC and the FAA both can claim high levels of expertise about radio interference; yet, they absolutely disagree on whether the newly approved 5G deployment will or will not interfere with the aviation safety provided by radio altimeters.

As well explained by an aviation safety expert—

 Heidi Williams, NBAA director for air traffic services and infrastructure. While such networks will ultimately operate across more than 50 distinct C-Band frequencies, the range from 3.7 to 3.98 gigahertz overlaps radio frequencies used by radar altimeters, “the only sensor onboard civil aircraft that provides a direct measurement of the clearance height of the aircraft over the terrain for other obstacles,” noted Heidi Williams, NBAA director for air traffic services and infrastructure.

Roy likened 5G networks sharing bandwidth with radar altimeters to placing “a karaoke bar next to a monastery [that] has taken a vow of silence. You really need to figure out how those different applications can work together.”



The FAA ruled on Tuesday that those thousands of US planes (and some helicopters) won’t be able to use many of the guided and automatic landing systems that are designed to work in poor visibility conditions, if they’re landing at an airport where there’s deemed to be enough interference that their altimeters aren’t reliable. “Landings during periods of low visibility could be limited due to concerns that the 5G signal could interfere with the accuracy of an airplane’s radio altimeter, without other mitigations in place,”

“In areas of 5G interference identified by notams, the related AD would prohibit the following operations: “Performing approaches that require radio altimeter minimums for rotorcraft offshore operations. (Barometric minimums must be used for these operations instead.) Engaging hover autopilot modes that require radio altimeter data. Engaging search and rescue (SAR) autopilot modes that require radio altimeter data. Performing takeoffs and landings in accordance with any procedure (Category A, Category B, or by Performance Class in the Rotorcraft Flight Manual or Operations Specification) that requires the use of radio altimeter data.”

On the other side of this debate, Verizon said Tuesday “there is no evidence that 5G operations using C-band spectrum pose any risk to aviation safety, as the real-world experience in dozens of countries already using this5G map spectrum for 5G confirms,” and added it was confident the FAA ultimately will conclude C-Band 5G use “poses no risk to air safety.

The FCC maintains it has developed suitable limits to prevent such interference, such as “guard frequencies” between the spectrums used by 5G and radar altimeters. Other suggested mitigations include “protection areas” from 5G signals near airports and along typical glideslope paths, though such actions would not address potential interference to helicopter and UAS operators.

Each agency seems set in its opinion about 5G and altimeters.

Their debate started several years ago:

A Technical Battle FCC V. DOD, FAA, Etc. May Involve Much More


Round Three In The 5G V. GPS FCC Battle


Two Attacks On GPS Navigation Integrity Could Cause An Aviation Disaster


BREAKING NEWS High Level Game Of Chicken- 5G V. GPS 12.05.21-DEFERRED–WHY

There is no transparent reason for this technical disagreement; however, one cognoscenti posited that the 5G proponents have heavy political clout (both Democratic and Republican Members have supported the FAA safety position.) More cynical commentators attribute the FCC lean to global competition with the PRC 5G industry.  5G clash in a trade context


U.S. Aviation Industry Pans AT&T, Verizon 5G Precautions

By Reuters

Dec. 6, 2021, at 5:37 p.m.

U.S. Aviation Industry Pans AT&T, Verizon 5G Precautions

By David Shepardson

5G and altimeter potential


WASHINGTON (Reuters) -The U.S. aviation industry said on Monday new precautionary measures offered by AT&T and Verizon Communications were insufficient to address air safety concerns raised by the planned use of C-Band spectrum for 5G wireless.

AIA logoThe Aerospace Industries Association said in a letter to Federal Communications Commission chair Jessica Rosenworcel that the telecom plans “are inadequate and far too narrow to ensure the safety and economic vitality of the aviation industry.”

The industry and the Federal Aviation Administration (FAA) have raised concerns about potential interference of 5G with sensitive aircraft electronics like radio altimeters.

The FCC, FAA and Verizon did not immediately comment. AT&T declined comment.

On Friday, an aviation coalition including major airlines and airplane manufacturers met with the White House and other agencies and presented the National Economic Council with a proposal for additional safeguards.

The letter said the aviation proposal “provides additional safeguards in, around, and on the approach to airports and heliports.”

The FAA is expected as soon as Tuesday to issue two airworthiness directives highlighting safety issues that may arise from 5G interference.

“This AD was prompted by a determination that radio altimeters cannot be relied upon to perform their intended function if they experience interference from wireless broadband operations in the 3.7-3.98 GHz frequency band (5G C-Band). This AD requires revising the limitations section of the existing airplane/aircraft flight manual (AFM) to incorporate limitations prohibiting certain operations requiring radio altimeter data when in the presence of 5G C-Band interference as identified by Notices to Air Missions (NOTAMs).”

Final instructions to airlines about potential impacts and ways to comply are not expected until later when the FAA issues notices that will take into account AT&T and Verizon mitigation efforts.5G implementation

AT&T and Verizon said on Nov. 24 they had committed for six months to take “additional steps to minimize energy coming from 5G base stations – both nationwide and to an even greater degree around public airports and heliports.”

AT&T and Verizon in November agreed to delay commercial launch of C-band wireless service until Jan. 5 after the FAA issued a Nov. 2 bulletin warning action may be needed to address the potential interference.

Wireless groups argue that there have been no C-Band aviation safety issues in other countries using the spectrum.

(Reporting by David ShepardsonEditing by Sonya Hepinstall and David Gregorio)

5G interference graph

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