Potential 5G Interference to Radar Altimeters

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 civil aircraft—including commercial transport airplanes; business, regional, and general aviation airplanes; and both transport and general aviation helicopters.

RTCA Article – Potential 5G Interference to Radio Altimeters

Radio Altimeter (RADALT) measures an aircraft’s altitude above the terrain.

The above-ground level (AGL) altitude of the aircraft is measured by transmitting a radio frequency (RF) signal down to the ground and receiving a portion of this energy back through reflection from the terrain or other obstacles to determine the time taken and, therefore, the height.

The receive power levels from the RF reflections are very low, and thus the RAD ALT receiver is highly sensitive.

RADALT devices operate in the 4.2–4.4 GHz band, which is internationally recognised and protected by the International Telecommunications Union (ITU).

However, radar altimeters could be susceptible to RF interference received within this operation band or adjacent or nearby frequency bands.

During testing, we have observed the following;

Un-annunciated Errors – PILOT UNAWARE

Incorrect altitude output
  • Deviation of actual altitude, positive or negative.
  • No Fault warning
  • No NCD error.
Altitude frozen
  • Altitude remains fixed even when the aircraft descends.
  • No Fault warning
  • No NCD error.

Here at Frequencia we are working a solution for this problem, get in touch and see how we can help.

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