WPR09LA471

The helicopter was equipped with aerial application equipment, however, the chemical tanks were empty at the time of the accident. As the helicopter departed the landing zone, the pilot sensed that more power than usual was being required to clear the 10- to 12-foot trees at the edge of the takeoff zone. He checked the engine instruments, which indicated normal readings, and 100 percent torque. Following his instrument check he heard "popping sounds coming from the engine." The pilot said that once over the trees, between 20 and 30 knots airspeed, the helicopter would not accelerate and settled into the trees despite applying full collective. On scene documentation of the rotor blades indicated leading edge damage and upward bending of the blades, indicative of low rotor energy at the time of rotor blade impact with the trees and terrain. Examination of the engine identified leading edge damage to the compressor blades; however, a functional test cell run of the engine revealed it was capable of producing rated horsepower. No airframe anomalies were identified during the airframe examination that could explain the loss of power.

HISTORY OF FLIGHT On September 27, 2009, at 1900 Pacific daylight time, an Arrow Falcon Exporters OH-58A+, N298CP, collided with trees during takeoff from a landing zone in a field, 24 miles west of Myrtle Creek, Oregon. Reforestation Services, Inc., operated the helicopter under the provisions of Title 14 Code of Federal Regulations Part 137. The commercial pilot received minor injuries, and the helicopter sustained substantial damage to the tailboom, tail rotor blades, and main rotor blades. Visual conditions prevailed, and no flight plan had been filed. The pilot stated to the Safety Board investigator that the helicopter was equipped with agriculture application equipment, however, the chemical tanks were empty at the time of the accident. The purpose of the flight was to survey the area to be sprayed. As the helicopter departed the landing zone, the pilot sensed that more power than usual was being required to clear the 10- to 12-foot trees at the edge of the zone. He checked the engine instruments, which indicated normal readings, and 100 percent torque. Following his instrument check, he soon heard ‘popping sounds coming from the engine.’ Once over the trees, between 20 and 30 knots airspeed, the pilot said the helicopter would not accelerate and settled into the trees despite applying full collective. The pilot reported that the wind was about 2 knots from the west; field elevation was about 3,000 feet mean sea level; and the temperature was 74 degrees F. PERSONNEL INFORMATION The pilot, age 46, held a commercial pilot certificate with rotorcraft-helicopter, and instrument-helicopter ratings, issued May 22, 2008. He held a second-class medical certificate issued on June 12, 2009. The pilot reported in the NTSB Pilot Accident Report, that he has 14,250 hours of total flight time, and 1,500 hours in the accident helicopter’s make and model. His most recent flight review was on June 4, 2009, in a Bell 206B helicopter. AIRCRAFT INFORMATION The five-seat, single engine helicopter, serial number (S/N) 71-20532, was originally owned and operated by the US Army. In 1996 it was transferred to the Baltimore County Police. On April 26, 2007, Dakota Air Parts International purchased the helicopter from the Baltimore Police. The helicopter was subsequently purchased by Reforestation Services, Inc., on July 18, 2007. Arrow Falcon Exporters, Inc., refurbished the helicopter with an extended range fuel system, chemical spray system, and a VHF/FM radio. The helicopter was registered as an Arrow Falcon Exporters Inc OH-58A+, N298CP, on September 13, 2007, with a restricted category special airworthiness certificate. The operator reported that the total time on the airframe was 6,705.6 hours, and its most recent maintenance inspection was performed on September 16, 2009. The engine maintenance logbook recorded that the Allison T63-A-720 gas turbine engine had been installed on the helicopter since new, and engine total time was approximately 1,336.2 hoursat the time of the accident. WRECKAGE AND IMPACT INFORMATION On-scene observations were provided by the FAA inspector and the technical representative from Rolls-Royce. The accident site was in a forest area 24 miles west of Myrtle Creek. The site was approximately 1/2 mile from the departure area. The trees in the area were approximately 10 to 12 feet high and were a mixture of hardwoods and pines. The wreckage path was approximately 75 feet long. Several of the trees, in a linear and descending pattern leading to the main wreckage, showed evidence of main rotor and airframe impact damage to the trees or to broken off limbs. There were pieces of airframe wreckage dispersed through the area, from the first tree strike to the main wreckage. Damages to the helicopter included: tail rotor blades bent 90 degrees upwards; the tail rotor gearbox fractured from tail boom; the tail boom was fractured forward of the tail rotor attachment point to the empennage; the right side windscreen was broken; the left side chin bubble was broken; one main rotor blade was bent at a 90-degree angle chordwise at the doubler; one main rotor blade trailing edge was damaged from tree impact; the mast was bent slightly forward; and the transmission mounting structure surface was fractured. TESTS AND RESEARCH The engine was removed from the helicopter under the supervision of an FAA inspector and shipped to Rolls-Royce, Indianapolis, Indiana, for a detailed examination and functional test. On October 20, 2009, the engine was examined and tested under the supervision of an FAA inspector. The upper and lower chip detectors were clean and free from debris. Approximately 200 cubic centimeters (cc) of clean oil was drained from the accessory gearbox. The gas generator turbine and power turbine rotated freely. A pneumatic system air leak check was performed at 50 psi, and no leaks were detected. Damage was noted on several of the first and second stage compressor blades and vane leading edges. The engine was installed in a test cell. The engine was functionally tested to an abbreviated version of the factory production test specification procedure and found to meet all test parameters, producing 439 shaft horsepower. The manufacturer rating for the engine is 420 horsepower.