Why 5G Is Now a Problem for Airports: An Analysis

The concept of 5G has been around for over two years, yet airports around the world are only now grappling with the challenges it poses. This surprising timing can be attributed to the convergence of older technologies and emerging wireless capabilities. In this article, we delve into the technical aspects, safety concerns, and legal implications that have brought 5G and airport operations to a critical juncture.

Understanding the Problem: Radar Altimeters and 5G

The issue lies in the close relationship between radar altimeters and C-band 5G technology, both of which use C-band frequencies. Radar altimeters, introduced in the 1960s, were designed without the need for adjacent channel rejection as there were no terrestrial users at that time. The absence of interference control mechanisms has now become a point of contention with the introduction of 5G.

Many airlines, particularly budget U.S. carriers, still rely on older radar altimeters. These devices play a critical role in instrument approaches during adverse weather conditions. A CAT-II (Category II) approach allows the aircraft to descend as low as 100 feet without visual contact with the runway, while a CAT-I approach caps the descent at 200 feet. Without a properly functioning radar altimeter, only CAT-I approaches are permissible, leading to a higher decision height and potentially increased go-around maneuvers.

The operation of radar altimeters falls under stringent regulatory control. The Federal Aviation Administration (FAA) has taken a cautious approach, stipulating that if there is any potential for interference, legal protections require operators to seek specific clearance. This preventative measure, often necessitated by the fear of legal repercussions, can halt operations pending further approval and evaluation.

Quantifying the Risk: Real-World Implications

Despite concerns, the practical impact of 5G on radar altimeters is limited. Fog or clouds so low as to necessitate CAT-I operations are exceedingly rare. In 25 years of flying, the author has encountered such conditions only once. This makes the risk of full-fledged CAT-II approach failure due to 5G interference relatively low.

However, the legal and reputational risk of an accident occurring during an instrument approach is significant. Airport operators and aviation authorities are therefore being more cautious, especially in areas with high-density 5G deployments.

The Broader Context: Technological Ignorance and Public Perception

The issue extends beyond technical challenges; it touches on a broader narrative of technological ignorance and conspiracy theories in the United States. While technical expertise exists globally, the cultural and regulatory environment in the U.S. has led to heightened sensitivity to new technologies.

Even removing 5G from airport areas addresses only the need for precise radar altimeter (RA) functionality during CAT-3B autoland operations. RAs are critical components of ground proximity warning systems (GPWS) and enhanced ground proximity warning systems (EGPWS). Accidents caused by controlled flight into terrain (CFIT) can occur well outside airport boundaries, making the broader system's reliability paramount.

Additionally, some aircraft have replaced the squat switch, which signals to the aircraft that it is on the ground, with RAs. A failed RA could mislead pilots about the aircraft's state, preventing them from executing a proper engine reverse and leading to extended idle speed, making aircraft more difficult to stop before reaching the runway end.

Conclusion: Moving Toward a Solution

The challenges posed by 5G to airport operations are multifaceted but not insurmountable. With a better understanding of the technical issues, the aviation industry can work with regulators and technology providers to mitigate risks. This collaborative approach is essential in ensuring that the benefits of 5G technology can coexist with the safety requirements of aviation.