News from the US that telecommunications companies AT&T and Verizon have opted to delay turning on 5G mobile towers located near US airports has stirred concerns from Australia's airports and air authorities, prompting some to ask the question: are 5G towers a possible safety issue for Australian aircraft?
5G and airports: What's the issue in the US?
To recap what's been happening in the US, airports and aviation authorities have for months now feared that 5G signals from 5G towers planned for installation this month near US airports, will interfere with sensitive airplane instrumentation - so much so, that they have been actively negotiating with telecommunications companies to halt their installation.
Their concerns may be justified, too. That's because in the US 5G towers can operate at a frequency range of between 3.7-3.89 GHz, which is very similar to the frequency range used by radio altimeters used by airplanes to measure how far they are off the ground. These altimeters operate at frequencies of between 4.2-4.4 GHz.
While it's true that the altimeter frequencies are just "similar to" 5G signals in the US and that there's still a gap of 220 MHz between the top end of the 5G frequency range and the lower end of the altimeter range, reports indicate that there may still be some interference.
The ABC, for example, cites a report from the Radio Technical Committee for Aeronautics (RTCA) dated October 2020, that found there is "a major risk that 5G telecommunications systems in the 3.7-3.98 GHz band will cause harmful interference to radar altimeters on all types of aircraft."
Concerns about interference mainly revolve around the possibility that 5G interfering with an aircraft's altimeter could prevent engine and braking systems from transitioning to landing mode, which according to the US Federal Aviation Authority (FAA), "could prevent an aircraft from stopping on the runway."
Earlier this month the FAA and 5G companies were at loggerheads to come to an agreement on the issue, a stalemate that was, up until this week, expected to cause massive disruption to flights and passengers.
However, since then negotiations between the FAA and the telecommunications companies have made some headway, with the wireless companies agreeing to delay turning on 5G towers, to create buffer zones for six months around airports where transmitters are in close proximity - a decision that should at least allow some time to find further solutions to the problem, and at the same time, allow air traffic to continue.
Are Australian aircraft at risk?
The quick answer is: no current risk has been found. While the debate rages on in the US, Australia's Civil Aviation Authority (CASA), released a statement, saying it has seen "no evidence that 5G transmissions are currently affecting aircraft" in Australia.
The main reason for this, CASA says, is that Australian 5G transmissions don't currently extend into the part of the spectrum that account for the worrying US transmissions. CASA says, Australian 5G transmissions top out at 3.7 GHz which is far below the low end of the 4.2-4.4 GHz range that airplane altimeters use.
Although no reports of 5G interference with airplane altimeters have yet been reported, CASA and the Australian Transport Safety Bureau (ATSB) have advised pilots to report any altimeter anomalies (while flying below 2500ft), which they can do via an online form at the ATSB website.