The Transition to True North in Air Navigation from the Avionics Perspective

In azimuth sensing, aviation relies on the magnetic compass or magnetic sensors (flux valve, magnetometer) because the azimuth reference is Magnetic North. Maritime navigation completed the transition to True North. In October 2023, ICAO established the True North Advisory Group (True-AG) to consider the possibility of the same transition in aviation, as proposed by the International Association of Institutes of Navigation’s AHRTAG Group. There are significant benefits of this transition (accuracy, stability). Still, there are also some concerns and risks to be mitigated: the transition itself is a major change at the scale of the history of aviation, the need for an inexpensive basic sensor for True North, and other operational aspects. This paper analyses the azimuth sensing technology with a view on the transition to True North. This study comprises both general aviation and commercial aviation and concerns the integrity, accuracy, availability, and continuity of the azimuth flight parameter. The main True North sensors are the inertial reference system and the GNSS receiver. For a basic navigation sensor, the GNSS resilience is essential, and this is currently being challenged in many parts of the world in regions proximate to conflicts.