Pilots use radalts to measure an aircraft’s height above the ground. Other safety systems also depend on radalts, making them essential for some operations. This is especially true during final approach and landing in low visibility when pilots rely on instruments.
In Australia, 4G and 5G have been operating in the nearby 3.4 to 3.7GHz band since 2016 and 2019 respectively. ACMA has allocated licences for new 5G operations in the 3.7 to 4.0 GHz spectrum since early 2024. Radalts operate in the radio frequency band between 4.2 and 4.4 GHz.
The risk of interference is greatest when aircraft conduct instrument approach procedures in low-visibility conditions. If 5G interferes with radalts during an approach, aircraft may experience nuisance alerts, a failure to alert, increased flight crew workload, aborted landings (go-arounds) and, in the worst case, accidents.
See radio altimeter requirements for low-visibility operations.
The requirement to upgrade equipment is necessary to ensure radalts operate reliably in the presence of 5G transmissions.
diagram of 5G frequencies and the frequencies used by radalts.