April 21, 2015
South Dakota

NTSB factual report released in collision with wind turbine

NTSB Factual Report Released In Collision With Wind Turbine; Pilot Had Previously Expressed Concerns To The FAA About The Wind Farm | Aero News Network | Apr 21, 2015 | www.aero-news.net

The NTSB has released a factual report from an accident which occurred 10 miles south of Highmore, South Dakota in which the commercial pilot and three passengers were fatally injured. The airplane was registered to and operated by a private individual. Dark night instrument meteorological conditions prevailed for the flight, which operated without a flight plan. The airplane collided with a wind turbine, and it was reported to the NTSB IIC that the light on tower #14, which the aircraft struck, was not functioning at the time of the accident and had been inoperative for an undefined period. The actual witness to the inoperative light did not return telephone calls in attempt to confirm or verify this observation.

The flight originated from Hereford Municipal Airport (KHRX), Hereford, Texas, approximately 1700, and was en route to Highmore Municipal Airport (9D0), Highmore, South Dakota. According to the report, a fixed base operator employee at KHRX witnessed the pilot fuel the accident airplane at the self-serve fuel pump just prior to the accident flight. He reported that the fuel batch report showed 82.59 gallons of fuel had been dispensed. The pilot commented to the employee that he was going to “top it off” as he had “pushed his luck on the trip down.” The pilot also discussed the weather conditions in South Dakota, noting that it was raining there. The pilot also added that the only reason they were leaving was because one of the passengers was anxious to get home.

Several witnesses in the area reported seeing an airplane fly over their homes the evening of the accident. The first witness, located near the shore of the Missouri River, near Fort Thompson, South Dakota, reported seeing an airplane about 200 feet above the ground, flying to the northeast, about 2045. He stated that the airplane was low and was moving quickly. The second witness, located a few miles southwest of the accident site, reported seeing an airplane flying at a very low altitude, headed north, about 2115. Neither witness reported hearing problems with the engine.

Wind turbine tower #14, part of the South Dakota Wind Energy Center owned by NextEra Energy Resources, was damaged during the accident sequence. One of the three blades was fragmented into several large pieces. One large piece remained partially attached to a more inboard section of the turbine blade. The inboard piece of this same turbine blade remained attached at the hub to the nacelle. The outboard fragmented pieces of the wind turbine blade were located in a radius surrounding the base of the wind turbine tower. The other two wind turbine blades exhibited impact damage along the leading edges and faces of the blades.

The closest official weather observation station was Pierre Regional Airport (KPIR), Pierre, South Dakota, located 35 miles west of the accident location. The elevation of the weather observation station was 1,744 feet mean sea level (msl). The routine aviation weather report (METAR) for KPIR, issued at 2124, reported wind from 010 degrees at 19 knots, visibility 10 miles, light rain, 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.

The wind turbine farm south of Highmore, South Dakota, was constructed in 2003. There are 27 towers in the entire farm oriented from east to west across highway 57. It was reported to the NTSB, on scene, that each turbine tower is about 213 feet tall (from the ground to the center of the hub) and the blade length is 100 feet long. Each tower is equipped with three blades and FAA approved lighting. The blades are constructed from carbon fiber.

On June 2, 2003, the FAA issued a Determination of No Hazard to Air Navigation, regarding the installment of wind turbine tower #14 near Highmore, South Dakota. The document identified that the wind turbines would be 330 feet agl and 2,515 feet msl. A condition to the determination included that the structure be marked and/or lighted in accordance with FAA Advisory Circular 70/7460-1K Change 1.

The wind turbine tower #14 was located to the west of highway 57, and was the 5th wind turbine tower in a string of wind turbine towers, oriented from east to west. Wind turbine tower #14 was 0.3 miles to the west of the 4th wind turbine tower and 0.5 miles to the west of the 3rd wind turbine tower. The string of wind turbine towers changed direction after wind turbine tower #14 and continued to the south and south west for about 2 additional miles with 13 additional wind turbine towers in the string. The next closest wind turbine tower to #14 was 0.5 miles south.

The wind turbine tower #14 recorded an alert in the system when the airplane and the turbine blade collided and the turbine went offline. The impact was recorded at 2116:33. The blades were pitched at -0.5 degrees and the nacelle was at 112 degrees yaw angle (not a compass heading, rather nacelle rotation). There were no employees at the wind farm maintenance facility when the accident occurred. The NextEra control center in Juno Beach, Florida, received an immediate alert when the collision occurred. The company response would have been to send an employee to the wind turbine the next morning to determine why the turbine had gone offline.

Maintenance records for wind turbine tower #14, for 5 years prior to the accident, were submitted to the NTSB investigator in charge for review. These records included major and minor inspection sheets for 2010 and 2011 in addition to work management records for general maintenance, repairs, and fault troubleshooting that occurred between June 2010, and October of 2014 (after the accident). The major and minor inspection sheets for 2010 and 2011 indicated that the FAA lighting was inspected and found to be “normal” or “OK.” No other maintenance records were provided which illustrated maintenance that was conducted or performed on the FAA lighting system between 2010 and the accident.

The family provided investigators the pilot’s flight logbook. The logbook covered a period between April 22, 2010, and April 20, 2014. He had logged no less than 3,895.8 hours total time; 100.7 hours of which were in the make and model of the accident airplane and 95.1 hours of which were in the accident airplane. This time included 76.2 hours at night, 1.1 hours of which had been recorded within the previous 90 days. The pilot was current for flight with passengers at night. He successfully completed the requirements of a flight review on January 18, 2013. He successfully completed an instrument proficiency check in a PA-32R on February 7, 2014.

According to the FAA, the pilot was familiar with the accident area. Specifically, the pilot was familiar with the wind turbine farm and had expressed his concern about the wind turbine farm to the FAA Flight Standards District Office in Rapid City, South Dakota. The details of his concerns were not available.