Low-altitude, rural Class G airspace is considered by the broader public a space of negligible aviation activity. Due either to lack of awareness or understanding of the unique nature of Part 137 operations, structures are often erected in these spaces without consideration to their impact on the aerial application of crop protection products, and agricultural productivity.

While the Federal Aviation Administration (FAA) requires all structures exceeding 200 feet above ground level (AGL) to be marked with tower lights or tower paint, the rules vary for structures below that height. Unmarked towers are extremely difficult for aerial applicators to see as they conduct their work at speeds up to 160 mph just 10 feet off the ground, and accidents (too many, fatal) occur every year as a result.

The FAA Modernization and Reform Act of 2012 – §219 directed the FAA to consult with affected industries and carry out a feasibility study for developing a publicly searchable, web-based resource that provides information regarding the height and latitudinal and longitudinal location of guy-wire and free-standing tower obstructions.

The FAA Extension, Safety and Security Act of 2016 – §2110 directed the FAA to issue regulations to require marking (consistent with AC 70/7460-1) for all towers 10 feet or less in diameter and 50-200 feet AGL located in rural/agricultural areas. In addition, the FAA was directed to develop a database to log the location and height for each tower to be used for aviation safety purposes.

To appease the telecommunications industry, the FAA Reauthorization Act of 2018 – §576 amended the 2016 act to allow applicable towers to be either marked or logged, however meteorological evaluation towers (METs) must still be marked and logged.

The FAA was expected to address this safety concern by issuing a Notice of Proposed Rulemaking (NPRM) in 2020. However, several years later, no action has been taken and the issue remains unresolved.

Language in the enacted House of Representatives 2023 FAA Reauthorization bill again urges FAA to develop this rule and, if not, to report why it hasn’t and to list the “fatal aircraft accidents associated with unmarked towers that have occurred over the 5 years previous to the date of submission of the report.”

There were 20 accidents, 10 of which were fatal, involving towers in Part 137 operations between 2010 and 2022.

METs present an especially pronounced risk to aerial applicators. Many are erected only temporarily to test sites for wind farm suitability, and they can be put up in what was a familiar field in a very short period of time. In addition, METs placed within and near operational wind farms can be difficult to spot as an aerial applicator is focused on avoiding other obstacles, sometimes the wind turbines themselves.

The National Transportation Safety Board (NTSB) issued a Safety Alert (SA-016) in 2011 on the hazards of unmarked METs. In 2018, they revised and reissued it urging pilots to be vigilant for unmarked GPS and telecommunications towers, in addition to METs. The Safety Alert reads, in part, “FAA published AC 70/7460-1L, which recommends the marking of METs and provides marking guidance. However, the NTSB is concerned that the application of the AC is voluntary and, without mandatory application and marking requirements for METs and other kinds of towers less than 200 feet tall, many of these towers will continue to be constructed without notice to the aviation community and will fail to be marked appropriately.”

In 2014, the wrongful death action filed by the family of a California agricultural aviator was settled in the amount $6.7 million against a group of defendants representing tower manufacturing, wind energy, land-owning and farming interests for not marking or making aware the location of an unmarked MET to protect the pilot. The settlement establishes a standard of care as to the use of METs for wind prospecting in agricultural areas. (Read Full Article)

This safety issue is also being addressed at the state level: tower marking has been mandated in 15 states including Kansas, North Dakota, Idaho, Missouri, Mississippi, California, Colorado, Montana, Nebraska, North Carolina, Oklahoma, South Dakota, Texas, Washington, and Wyoming.

NAAA has actively engaged aviation stakeholders over its concerns with unmarked towers for decades. In short, unmarked towers are incredibly hard to see for aerial applicators, particularly in the task saturated low-altitude environment they work in. As demand for wind energy and higher frequency telecommunication networks fuels further proliferation of unmarked towers, the risk only increases. It is paramount, then, that all towers be properly marked and logged to prevent loss of life through collisions with them.

NAAA is pursuing action through House Transportation & Infrastructure Committee Chairman Sam Graves (R-MO), pressuring the FAA to expedite their completion of the tower marking/logging rule. In a September 28th , 2021, letter to the FAA, Representative Graves reminded the FAA in no uncertain terms that the FAA is “blatantly ignoring this congressionally directed and long-overdue safety-critical rulemaking.”

Given the gravity of the situation, and after many fruitless inquiries with FAA as to the status of this issue, NAAA sent a letter to FAA Administrator Whitaker in November 2023 requesting a meeting to discuss strategies and potential actions that can be taken to ensure FAA’s compliance with the 2018 statutory requirements stated above.

Here are some communications on this topic from the last several years:

Tired of towers being erected in your area without any type of notification to fight back?  Using the FAA’s Obstruction Evaluation / Airport Airspace Analysis (OE/AAA) website, users can now be notified when a structure is proposed in an area that might impact operations allowing you to petition the local zoning authority to build the tower(s) elsewhere or mark it to ensure it will be easily visualized for low-flying aviators.

To receive these notifications, simply complete the following steps:

Once your account is created:

  • Under “My Account and Email Notifications” click “Subscription Preferences”
  • Add a new subscription, and set a radius of your choosing from your home airport

You will then be notified anytime the FAA’s OE/AAA conducts a study for a proposed obstacle in that area. You can then work with your city or county governments and the entity constructing the obstacle to ensure it doesn’t affect your operations.

While no national database of low level towers has been constructed just yet per federal legislation NAAA was instrumental in urging Congress to enact, there are some resources ag aviators can utilize. The FAA’s Digital Obstacle File (DOF) can provide you information about potential obstacles in your flight path before you even take off.

The FAA receives obstacle information from a variety of sources both inside and outside the FAA. The FAA then evaluates the obstacle data based on their analysis of supporting documentation and assigns an accuracy code. The DOF is updated every 56 days, but you can alternatively download the Daily DOF to get more up-to-date information.

These include many obstacles of interest to aviation users above 200 feet as well as lower obstructions mainly near airports. Structures below 200 feet not near airports are only submitted to this database voluntarily. The FAA’s Obstacle Team is working on new techniques to improve the accuracy of obstacle data accessible to the public.  The FAA is interested in learning about obstacles (include the coordinates and height if known) not in the DOF, of interest for flight safety.  If an obstacle is listed as existing in the database when that is not the case, please notify their office.

For more information, email 9-AJV-532-OBSTData-REQ@faa.gov.

The University of Nebraska Lincoln Extension program and the Nebraska Aviation Trades Association (NATA) produced this video in 2012 to highlight the importance of marking METs. The FAA/FCC has since mandated the marking of METs, however, the video still provides helpful insight into why NAAA believes that all towers should be marked and the hazard they pose to aerial applicators.

In another move to ensure proper marking of towers under 200 feet, NAAA sent letters to the American Wind Energy Association and dozens of U.S. meteorological evaluation tower (MET) manufacturers warning them that ignoring an FAA Advisory Circular (AC) providing guidance on the marking of METs and other government warnings on the risks posed by unmarked METs would very likely result in legal liability for a tower company whose tower resulted in an accident due to improper marking. NAAA is making this information available to U.S. aerial applicators in the form of two draft letters.

Prompt Letter to Tower Entities (Template) – May be used to prompt those responsible for erecting unmarked towers in an applicator’s area to abide by FAA AC 70-7460-1 and existing federal and state law.

Thank You Letter to Tower Entities (Template) – May be used to thank entities responsible for properly marking towers for low-level aviators.

This policy page was updated 2024-01-08 and is not intended for publication. NAAA requests that should any party desire to publish, distribute or quote any part that they first seek the permission of the Association.