May 30, 2013
By Dan Namowitz
As the wind-energy industry grows, the towers it uses to evaluate the potential of sites for power generation pose a growing hazard to aviation, the National Transportation Safety Board said, issuing six safety recommendations to stakeholders.
Citing three fatal accidents in which aircraft collided with meteorological evaluation towers (METs), the NTSB said the time has come for all such towers to be registered, marked, and lighted where feasible.
That recommendation, addressed to the FAA for possible amendment of Part 77 regulations—which now pertain only to structures more than 200 feet high—was accompanied by a recommendation that the FAA create and maintain “a publicly accessible national database for the required registration of all meteorological evaluation towers.”
“The NTSB notes that the deployment of METs will continue to increase in support of the wind energy industry in the United States and anticipates that, without a change in requirements, this hazard to aviation safety will increase accordingly,” said the May 22 recommendation, addressed to FAA Administrator Michael Huerta.
Although some states have passed or proposed legislation, the NTSB said, action is needed on a nationwide basis.
The NTSB also addressed recommendations to the American Wind Energy Association, urging it to “revise the Wind Energy Siting Handbook to clearly indicate the hazards that meteorological evaluation towers (MET) pose to low-altitude aviation operations and encourage voluntarily marking them to increase their visibility by reference to Advisory Circular70/7460-1, ‘Obstruction Marking and Lighting.’ (A-13-018).”
The American Wind Energy Association also should inform its members about the circumstances of aircraft accidents involving METs—emphasizing the hazard to aviation, the NTSB said.
The NTSB also recommended that the U. S. Department of the Interior, Defense Department, and Department of Agriculture direct applicants seeking permission to build METs to the advisory circular on obstruction marking and lighting.
In a recommendation to 46 states, the District of Columbia, commonwealths, and territories, the NTSB urged enactment of legislation requiring that METs be marked and registered in a directory.
In 2011, the FAA released voluntary guidelines for the marking and lighting of METs, which, if less than 200 feet high, are not subject to Part 77 requirements for obstruction marking and lighting. AOPA supported the FAA’s policy, noting in formal comments that the difficult-to-see towers located in rural or remote areas pose a “significant hazard” to many aviation operations.
Many METs are portable, and can be erected and installed with guyed wires in a matter of hours, the FAA said.
Dan Namowitz is an aviation writer and flight instructor.
Wind and Gusts,
Safety and Education,
FAA Information and Services,
Department of Transportation
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