by Julie Carr
Minnesota Department of Transportation
Published in Midwest Flyer Magazine (online) – December 2020/January 2021
Meteorological towers (Met towers) are being built in Minnesota. The towers are used to collect wind data and other weather information, such as temperature, humidity and rain.
Met towers are getting built in large part because they are crucial in the development of modern wind farms. The data collected by Met towers helps developers determine if a site is economically viable for a wind farm. With increased interest in the development of wind energy, comes increased prominence of Met towers.
Met towers are stand-alone towers that range between 50 to 200 feet in height. Many towers are built lower than 200 feet above ground level (AGL) to avoid the Federal Aviation Administration rule requiring coordination for any structure 200 feet or taller. In many areas within the U.S., towers beneath 200 feet AGL require no notification to any unit of government, nor any aeronautics organization, which may result in a pilot first learning of a new tower while flying.
There is growing concern around the country that these towers are hazardous to low flying aircraft. Met towers can readily be moved from one site and erected in another virtually overnight, without warning to aviators. Several fatal crashes have occurred as a result of pilots colliding with unmarked, undisclosed and unlighted Met structures.
General Aviation News put it this way in their July 8, 2019 issue:
“A National Agricultural Aviation Association analysis of accidents from 2008 to 2018 across all sectors of general aviation found there were 40 tower-related accidents and incidents resulting in 36 fatalities. The data also shows many of those general aviation aviators did not collide with the main body of the obstruction itself, but the extremely difficult to see guy wires supporting the structure, illustrating the importance of installing high-visibility guy wire sleeves or spherical ball markers.”
During the 2020 legislative session, the Minnesota Legislature enacted a new law to address these safety concerns. This new law directs the Minnesota Department of Transportation, Office of Aeronautics to track stand-alone meteorological tower installations and locations in the state to ensure this information is available to the public. Met tower marking and lighting requirements are also described in the new law.
Met tower companies must now submit a notification, which includes all contact information, the tower location, tower height, marking and lighting, and the county in which the tower will be erected. There is a $50 fee for each tower notification. Existing tower installations must also submit notification to MnDOT Aeronautics by May 28, 2021.
To learn more, go to www.mndot.gov/aero/meteorological-towers/index.html for information on the new legislation, the notification process, marking and lighting requirements and the location of towers listed by county.