NAAA continues to address aviation concerns with cellular network services that have developed over the last couple of years. In recent months the following three separate issues, all related to 5G networks, have warranted attention from NAAA.

5G Interference with Radio Altimeters

This situation has been very prominent in the news media recently. The good news is that this does not affect aerial application. The cellular industry’s proposed rollout of the 5G system has caused concern primarily for the airline industry and others who need to perform category III and some category II instrument approaches. It also affects aircraft that have auto-land features. A radio altimeter, also called a radar altimeter, is the only system that provides direct measurement of height above the ground. The frequency of 5G is close enough to what a radio altimeter uses that interference is expected. Concern was great enough that the FAA issued NOTAMs regarding Category II and III approaches. Verizon and AT&T recently agreed to temporarily limit some 5G services near key airports.

NAAA is not aware of any aerial application that uses radio altimeters. Some application aircraft do use laser altimeters to determine application height above the ground, but this is not affected by 5G.

Ligado’s L-Band Spectrum 5G System’s Interference with GPS

Of great concern to the aerial application industry is Ligado Networks’ L-band 5G system. Ligado (formerly LightSquared) plans to use the L-band frequencies, which are next to the frequency band in which GPS operates. Ligado’s 5G technology would interfere with aviation and other GPS receivers when the receivers get close to a Ligado 5G tower. A study by the Department of Transportation revealed that most non-IFR-certified GPS equipment, such as that used for general aviation, would experience interference at close to a mile from a Ligado tower.

As early as May 7, 2020, and as recently as July 15, 2021, NAAA has been reporting on efforts to prevent Ligado from moving ahead. Last week, NAAA participated in an aviation briefing for the National Academy of Sciences (NAS) committee responsible for conducting the independent technical review of the Federal Communications Commission’s decision to authorize Ligado to develop a network in the L-band radio spectrum. Agricultural aviation was used as a case study on how Ligado’s proposed network will negatively impact non-certified GPS receivers.

NAAA provided an overview of how agricultural aviators rely on GPS for all facets of an application mission, ensuring every pass is precisely made. The NAS was also briefed on the airspace utilized by agricultural aircraft, in particular the fact that they would operate well within a 250-foot radius around any tower in or adjacent to an application site. Ligado has designed its system to minimize interference outside the 250-foot radius to its towers but falsely assumed that no aircraft commonly operate within 250 feet of towers. NAAA corrected the record for the NAS committee on this matter.

NAAA also provided the NAS committee with some figures for how important the aerial application industry is to the U.S. food supply and the environment. These figures included that:

• Aerial application treats 127 million acres, or 28%, of U.S. cropland.
• The speed, timeliness and precision of aerial application protect 27.4 million acres of wildland from being converted into cropland annually.
• The aerial application industry adds $37 billion to the U.S. economy for just corn, soybean, wheat, cotton and rice crops.
  

A video of the committee meeting in which NAAA spoke can be found here. Scroll to the bottom of the page to find the 1/20/22 committee meeting. Dr. Scott Bretthauer, NAAA’s director of education and safety, spoke on behalf of the aerial application industry and his comments may be found starting at the 2:28:48 point.

Obstruction Issue Caused by 5G Towers