Very little changes year to year across the landscape of eastern Maine. The pilots who ply these serene skies can tell you that maintaining 2,000 feet is enough to keep you out of trouble almost everywhere in this area. If you’re headed west toward Bangor and the ceiling starts to come down, pilots pick up the power line just south of the remote Deblois airport, and follow it to their destination. But changes come more quickly than they used to—even here.
The nation is on a quest for diversification of its energy sources, and it has turned to numerous technologies—including wind turbines, which raise the obstruction profile of the usually high terrain on which they are placed.
Not high enough in all cases—as the sectional-chart quadrangle between Deblois and Bangor illustrates—to raise the maximum elevation figure such as the one printed north of Spectacle Pond, from “1.8” (representing 1,800 feet msl to ensure clearing the quadrangle’s highest known feature).
But a pilot who compares a current sectional chart’s depiction of that quadrangle to an older version now finds south and east of that body of water, and straddling the power line pilots follow, a network of wind turbines that each rise 476 feet above the terrain, resulting in a variety of msl values to 1,087 feet. Other hills and ridges in the region also bear the structures, which now have their own specific symbol on aeronautical charts.
If it has been a while since you scanned the charts of your long-familiar home flying area for new obstructions, be sure to do so now that the spring flying season is approaching. Then add some margin to your personal minimum VFR altitudes.
On April 27, 2014, a fatal accident that occurred near Highmore, South Dakota, claimed all four occupants of a Piper PA-32R-300 when the aircraft struck a wind turbine late on a day marked by fog and rainshowers.
By early 2015, no probable cause finding had been published by the National Transportation Safety Board for the accident, which occurred on a return flight from Hereford, Texas, to Gettysburg, South Dakota. A preliminary accident summary noted that “the wreckage of the airplane was scattered in a radius surrounding the base of a wind turbine. The airplane was fragmented. One turbine blade exhibited impact damage and was broken into several large pieces, several of which remained attached to the turbine nacelle. The remaining two turbine blades exhibited impact damage.”
The NTSB noted weather observed 37 miles away at Pierre Regional Airport at 2124Z as “wind 010 degrees at 19 knots, visibility 10 miles, sky condition broken clouds at 1,000 feet, overcast at 1,600 feet, temperature 6 degrees Celsius (C), dew point temperature 5 degrees C, altimeter 29.37 inches; remarks, ceiling variable between 800 and 1,200 feet.”
A local newspaper reported that “the wreckage was found at the South Dakota Wind Energy Center, a group of wind turbines, all approximately 300 feet tall, placed on several parcels of private property.” The group of obstructions is depicted on the Omaha sectional chart, topping out at 2,515 feet msl in a quadrangle with an MEF of “2.7” or 2,700 feet—just south of a Victor airway.
When thinking about obstructions, also keep in mind a unique hazard of the smaller, less regulated obstacles that may precede the appearance of wind turbines on a site. These are the so-called meteorological evaluation towers (METs) that may come and go more quickly than a six-month sectional chart cycle, leaving you to spot them for the first time in the windscreen of your moving aircraft. METs are used to assess a site’s potential for wind turbine installations—and following several mishaps, they have come in for special notice at the NTSB.
In March 2011, the NTSB issued a Safety Alert on METs, “many of which fall just below the 200-foot Federal Aviation Administration threshold for obstruction markings, can be difficult to see from the air, and can be a danger to aircraft conducting low-flight operations—including helicopter emergency services, law enforcement, fire suppression and other low-altitude activities.
“Pilots are urged to maintain vigilance during low-altitude flights and are asked to encourage the markings of METs in their area,” the NTSB said.
Because METs come in below the height of structures the FAA requires to be marked, the task has fallen to states to take action requiring that METs be painted or marked and included in state-run databases of obstructions. AOPA strongly supports state legislative efforts to pass such laws for safety of flight.
For pilots, the obstruction-hazard issue’s wide sweep stands as a reminder to check the charts for changes, add a safety margin, and watch out for any new obstructions that are too low to be published, but high enough to hurt.
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