ERA13TA021

The pilot was providing aerial observation for law enforcement activity on the ground when he observed the rotor rpm decaying. He initiated a descending left 180-degree autorotation to a flat, grassy area. As he was lining up for the intended landing area, he noticed that a man on a riding lawnmower was moving toward his intended touchdown point. To avoid a collision, he maneuvered the helicopter to the right to get ahead of the lawnmower. The pilot determined that he could not make his intended touchdown point and landed on uneven terrain. The helicopter impacted the ground, which resulted in damage to the fuselage, main rotor system and separation of the tail boom. The reason for the loss of engine power could not be determined despite a thorough engine examination and test run.

On October 13, 2012, about 1600 central daylight time, a Bell OH-58A helicopter, N40TN, was substantially damaged when it impacted the ground following a loss of engine power near Jackson, Tennessee. The commercial pilot and passenger received minor injuries. Visual meteorological conditions prevailed, and no flight plan was filed for the flight. According to the pilot, he was providing aerial observation for law enforcement activity on the ground when he observed the rotor rpm decaying. He stated he was heading 170 degrees, flying at 80 knots (kts), and at 800 feet agl, when the low rotor rpm horn sounded. He initiated a descending left 180-degree autorotation to land in a flat, grassy area. As he was lining up for his intended landing area he noticed that a man on a riding lawnmower was moving toward his intended touchdown point. To avoid a collision, he maneuvered the helicopter to the right to get ahead of the lawnmower. The pilot determined that he could not make his intended touchdown point and landed on uneven terrain. The helicopter impacted the ground, which resulted in damage to the fuselage, main rotor system and separation of the tail boom. The Director of Maintenance for the Jackson Police Department reported that they recovered about 55 gallons of fuel from the helicopter at the accident site. According to FAA records, the pilot held a commercial pilot certificate, with a rating for a rotorcraft-helicopter. The pilot’s most recent FAA second-class medical certificate was issued on October 12, 2011. On that date, he reported 2,290 total hours of flight experience. The single-engine, single-rotor, helicopter, was a surplus Army helicopter based on Bell’s Model 206A JetRanger. It was powered by a Rolls-Royce AE-406166, 420-horsepower engine. The helicopter was registered to the Jackson Police Department and operated under public use operations. The helicopter’s airframe and engine accrued 8,194 and 2,520 hours total time, respectively. A 100 hour inspection was completed on July 28, 2012 and the engine accrued 89.2 hours since that inspection. On November 7, 2012, under the supervision of the Indianapolis Federal Aviation Administration (FAA) Flight Standards District Office (FSDO), Rolls-Royce conducted an engine functionality test of M250 engine AE-406166 at the Rolls-Royce Indianapolis Plant 5 production test stand. The engine started and functioned per specification during the test run with the following exceptions: the predicted power at the Normal Cruise (370 horsepower (hp), 1360 degrees Fahrenheit Measured Gas Temperature (MGT)) setting was 364 hp, which was 1.6% below specified power. No flame outs were noted during the engine acceleration and deceleration test points and the power turbine governor functioned per specification. The predicted power at the Maximum-Take Off (420 hp, 1490°F MGT) setting was 443hp, which was 5.5% above specification. The 1553 weather observation at McKellar-Sipes Regional Airport (MKL), Jackson,Tennessee, reported winds 190 degrees, 9 knots, 10 miles visibility, broken clouds at 5,500 feet, temperature 27 degrees Celsius, dew point 16 °C, and an altimeter setting of 30.08 inches of mercury. A Garmin GPSMAP 496 and GNC-300XL were recovered from the wreckage and examined at the Safety Board’s recorders laboratory. No accident flight information was captured on either device. The GNC-300XL does not record history and the GPSMAP 496 recorded about a dozen points after October 12, 2012, but they were not indicated in Garmin’s flight logbook function.