The Australian Civil Aviation Safety Authority (CASA) has recently released an airworthiness bulletin stating that “CASA has not confirmed any RA (radar altimeter) system failure from 5G interference but continues to monitor this situation.” This is despite the international attention of 5G telecommunication interference with radar altimeters, with Boeing 737s being singled out.

The bulletin, released on March 4, 2022, reasons Australian telecommunications companies are currently operating at frequencies and power levels lower than those in the United States, with Australian licenses permitting frequencies no higher than 3.7GHz at power levels of 63 Watts. By contrast, 5G towers in the US can operate at frequencies between 3.7Ghz and 3.98GHz at power levels of 1584 Watts. This means that Australian 5G frequencies do not operate at those of many radar altimeters. This is in contrast to those in the US,

Regarding the future of Australian 5G networks, CASA and the Australian Communications and Media Authority (ACMA) are aiming to pursue a policy of “co-existence” between radio frequency services. At this point, CASA will not publish NOTAMs for Australian airspace restricting operations due to 5G interference.

Multiple Causes for Radar Altimeter Interference

Although CASA finds no evidence of 5G radio altimeter interference, it acknowledges some reported discrepancies could be caused by Terrain Awareness Warning Systems (TAWS) or factors other than 5G. Following up on several of these reported issues, CASA says that these types of failures are “generally not repeated again through ground testing.”

One such occurrence, with the aircraft type withheld, involved the disengagement of an Autopilot A on a final approach at 2300 feet when the Captain’s RadAlt1 froze at an altitude of 2640 feet for 11 seconds. This prompted the Captain to fly until Autopilot B was engaged and operations continued normally.

Another incident, again with the aircraft type withheld, occurred on approach passing 400 feet when a radar altimeter froze at 547 feet for 47 seconds, only returning to normal after touchdown.

Despite the suspected interference of these and other occurrences, CASA believes that “smaller commercial operations, general aviation and rotorcraft” may be more susceptible to such radar altimeter interference, making particular reference to the possibility of older radar altimeter systems as the primary victims of interference.

CASA Continues to Monitor US Interferences

CASA  says it hasn’t been ignorant of potential 5G interference in the US, requiring Australian pilots and aircraft to comply with Federal Aviation Administration (FAA) directives when operating in US airspace.

Additionally, CASA and the Australian Transportation and Safety Bureau (ATSB) have encouraged Australian pilots to report any suspected 5G radar altimeter interference through its online form on CASA’s official website.

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Mike Mangano

Mike’s love affair with flight and mechanical objects in the sky began at an early age, fascinated by space documentaries and the vintage Flight Simulator ’95. He currently works as an instructor for UAVs and is training to receive his Private Pilot Licence with the goal of working in manned flight instruction. An avid reader of all things aviation and manned space flight, Mike stays close to developments in aerospace while reminiscing and sharing the rich history of flight with others. He loves writing, engineering and science.

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