WPR13LA215

The pilot reported that, at the time of the accident, he had been awake for about 14 hours. The accident flight occurred about midnight as he was completing his 15th agricultural application to a field in dark night conditions with no moon and a cloud layer. Forward-projecting flood lights had been mounted on the helicopter to illuminate the terrain directly in front of it. The pilot stated that, while in a left turn to align with a narrow field that had a row of power lines running along one side, he applied left cyclic until it hit the stop. The helicopter continued to drift toward the power lines, so he increased the collective and left pedal to maneuver over them. Although the helicopter cleared the power lines, it started to rotate to the right in an uncommanded fashion and subsequently collided with terrain. The pilot reported no preimpact mechanical malfunctions or failure with the helicopter that would have precluded normal operation. The pilot had accumulated 40 hours of night-time flying experience, and this was his first season being employed as a pilot for agricultural application operations. However, due to his working at a time when he normally would be asleep and a relatively long time since awakening, the pilot was most likely fatigued at the time of the accident.

HISTORY OF FLIGHT On May 4, 2013, at 0012 mountain standard time, an Arrow Falcon Exporters OH-58A+ helicopter, N911RN, collided with terrain during crop application operations near Somerton, Arizona. The commercial helicopter pilot was not injured. The helicopter came to rest on its right side resulting in substantial damage. The helicopter was registered to Morris Equipment LLC, and operated by Morris Ag Air as a 14 Code of Federal Regulations Part 137 aerial application operator. Night visual meteorological conditions prevailed, and no flight plan had been filed. The flight originated from Yuma International Airport, Yuma, Arizona, and was destined for Somerton. The pilot stated that he was applying product to a field and was completing his 15th load of the night. The target field was a narrow field with tall power lines along one side. The pilot approached the field made a right turn to parallel the field then a wide left turn to align the helicopter with the length of the field. The helicopter was in the left turn, and the pilot continued to apply left cyclic until it hit the stop. The helicopter continued to drift right towards the power lines. The pilot applied up collective and left pedal to maneuver over the power lines when the helicopter started to rotate to the right in an uncommanded fashion. The helicopter collided with terrain as the pilot attempted to regain directional control. The pilot stated that the helicopter and engine had no mechanical failures or malfunctions during the flight. PERSONNEL INFORMATION The pilot, age 36, held a commercial pilot certificate for helicopters with an instrument helicopter rating issued on June 6, 2009, and a flight instructor certificate with ratings for helicopter and instrument helicopter, issued on February 2, 2012. He held a second-class medical certificate issued on February 6, 2013, with no limitations. The pilot reported having 650 total flight hours, all in rotorcraft, and 250 hours in the OH-58. He had a total of 40 night hours, accumulating 18 hours of night time within the previous 30 days. This was the first season he had been employed as a pilot for crop application operations. He reported that on the day of the accident he flew a practice flight at 0730, went home at 0900, took a 1-hour nap, returned at 1500, went home at 1700, and returned at 2030. He tookoff at 2130, which commenced his working flight. At the time of the accident it had been 14 hours since the pilot's last sleep period. AIRCRAFT INFORMATION The conventionally configured helicopter, serial number 69-16273, was manufactured in 2006. It was powered by a Rolls Royce T63-A-720 turboshaft engine rated at 420 horsepower. The operator reported that the most recent annual inspection was completed on February 27, 2013, at a total airframe time of 6,729.3 hours. Engine total time was 5,058.1 hours, time since major overhaul (TSMO) was 4,964 hours, and time since inspection was 94.1 hours. The helicopter was equipped withwork flood lights that were aimed out ahead of the helicopter and are used while performing crop application work at night. An Arrow Falcon Exporters, Inc., model 3900-OH58 Spray System was installed on the helicopter, Supplemental Type Certificate (STC) SR00268LA. The model 3900-OH58 Spray System consists of two 70-gallon cylindrical chemical tanks attached by quick disconnect pins on the left-hand and right-hand side of an "H" frame support that is bolted to the hard points of the landing gear attach fittings. The tanks are connected together through a cross feed tube so that they can be filled from either side by pressure or gravity fill provisions. The chemical is routed through the cross feed tube to a center outlet on the tube to the chemical pump. The center spray boom is 70" long and is mounted at airframe station 22 on the "H" frame support. It has provisions for mounting 12 spray nozzles or down tubes. Each outboard spray boom is connected to the center boom through a connector and to the "H" frame by one each vertical and horizontal strut for support. METEOROLICAL INFORMATION Marine Corps Air Station Yuma meteorological report for May 3, 2013, at 2357 was 10 statute miles visibility, broken cloud layer at 18,000 feet, broken cloud layer at 25,000 feet; temperature 26° Celsius; dew point 2° Celsius; and an altimeter setting of 29.73 inHg. Astronomical data provided by the US Naval Observatory for the location Latitude N32° 36', longitude W114° 43' (Somerton, AZ), mountain standard time, on May 4, 2013, show that sunset was at 1932, moon rise was at 0233, and moon set was at 1441. Fraction of the moon that was illuminated was 31% (after moon rise). WRECKAGE & IMPACT INFORMATION The helicopter was found on its right side by first responders. A small fire was observed in the engine compartment and was extinguished a few minutes later by the Fire Department. The main rotor was attached to the drive transmission, both rotor blades were attached to the rotor hub, and both rotor blades extended about half span from the hub with the outboard half of each blade not attached. Both chemical product tanks were attached to the airframe, and the deformed spray boom remained attached to the airframe. The tail boom aft of the fuselage transition splice has separated and was lying next to the fuselage upper deck. The tail rotor had been severed from the end of the tail boom. A Federal Aviation Administration (FAA) inspector examined the wreckage and did not identify any evidence of a mechanical failure or malfunction.