MET Tower Q & A

What are meteorological testing towers?
These towers are typically 60 meters (197 feet), which fall just under the requirements for FAA lighting and marking. They are used for gathering wind data during the development and siting of wind energy conversion facilities. They are also used during wind conversion operations. They are called "met towers" for short.
How are they constructed and when are they used?
The type of met towers used before the construction of a wind site consist of sections of galvanized tubing that are assembled at the site and raised and supported using guy wires. They can be erected or removed in as little as three hours. The tower may be at one location for a short period of time and then moved to a different location, as the wind company checks the area for the best wind conditions for the placement of wind turbines. Since they are lightweight and portable, they do not leave a visible footprint on the ground. They may be found in cropland or non cropland areas.
The type used during the operation of a wind conversion facility is built heavier and may or may not use guy wires; they usually still fall under the height required for FAA lighting and marking.
What is the concern for aerial operations?
Agricultural pilots, EMS operations, Fish & Wildlife, animal damage control, aerial fire suppression and any other low-level flying operation may be affected. The fact that these towers are narrow, unmarked and grey in color makes for a structure that is nearly invisible under some atmospheric conditions conditions. Sadly, aircraft collisions with towers usually result in fatal injuries.
The temporary and mobile nature of the structure makes their location difficult to maintain in a database. There may be a wind company considering an area for a wind site without general public knowledge, as some wind companies do their research and initial development without any public advertising. In some cases, the landowner's contract requires the landowner to keep this information confidential.
The Public Service Commission only regulates wind sites greater than 100mw. The commission may not know about large sites until a siting permit is applied for, which may be several years after a wind company has been researching an area with met towers. Likewise, the commission may never know about smaller sites at all.
Suggested operating procedures regarding meteorological testing towers:
  • Ferry above 500 feet, even in sparsely populated areas.
  • Think inside the box: establish a box that contains the area where you are working plus the turnaround area. Make sure that you inspect that area for obstructions while still at altitude, then stay in that box while conducting operations including entering and exiting the area.
  • When working within or near wind turbine sites, do not become so concentrated on the large turbines that you miss something smaller such as a met tower. Most operating wind conversion facilities have one or more testing towers located within them.
Other ways to mitigate this problem:
  • Ask your customer/landowner to let you know if he signs a contract with a wind developer and find out if he knows of any met towers in the area.
  • Talk to known wind companies and meteorological tower erection companies to see if they will voluntarily mark these towers.
  • Reach out to your local zoning authority and suggest that local zoning laws require the marking of these towers. (Most are willing to consider this, once the danger is explained to them.)