WEST LINN, OR, USA
N2784D
Fairchild Hiller FH-1100
The pilot reported that while northbound along the Willamette River at 700 feet above ground level (AGL), the helicopter yawed left and the ENGINE OUT light came on. The pilot stated he put the helicopter into autorotation, told his passengers to brace for a hard landing, gave a Mayday call and put the helicopter in what he thought was the safest place to land. The helicopter landed hard on the river bank, seriously injuring the pilot, but the passengers were not injured. During post-accident engine examination, a red sealer, which appeared as high temperature RTV, was noted to be applied extensively and heavily on several areas of the engine. Disassembly examination of the engine revealed red sealant adhered to the engine interior surfaces, as well as at various points in the engine oil system. Subsequently, the spur adapter gearshaft (SAG, a shaft that joins the gas producer turbine to the engine compressor) was found fractured, heat-distressed, and dry of lubrication. During an oil flow test of the oil delivery tube servicing the SAG, no oil flowed from the oil jet targeted for the SAG. Closer examination of the oil delivery tube revealed that this oil jet was clogged. Since complete maintenance records were not provided to investigators, a full service history for the engine could not be established.
On July 2, 2000, approximately 1615 Pacific daylight time, a Fairchild Hiller FH-1100 helicopter, N2784D, registered to Hurst Aviation of Coulterville, Illinois, and being operated by Helitours, Inc. of Seaside, Oregon (a non-certificated operator) on a 14 CFR 91 local sightseeing flight, was substantially damaged in a forced landing attempt on the bank of the Willamette River near West Linn, Oregon. The commercial pilot-in-command of the helicopter was seriously injured in the accident, but three passengers riding aboard the aircraft were uninjured. The flight had departed from the parking lot of an Elks lodge in Milwaukie, Oregon, approximately 5 minutes prior to the accident. Visual meteorological conditions existed and no flight plan had been filed for the flight. Passengers reported that as the helicopter, flying over the river, descended from approximately 700 feet above ground level (AGL) to 500 feet AGL, they heard a "popping" sound come from either the engine or the main rotor area and observed a red warning light illuminate on the instrument panel (they did not know which warning light illuminated.) The pilot then called Mayday and banked hard to the left, descending for an emergency landing on the river bank. The passengers reported that the landing was hard. In the landing, one of the helicopter's skids was broken and its tail boom was severed. In an accident report submitted through counsel to the NTSB, the pilot reported that he took off with 30 to 35 gallons of Jet A fuel for a 6- to 7-minute sightseeing flight. He reported that while northbound along the Willamette River at 700 feet AGL and a speed of 100 knots or greater, the helicopter yawed to the left and the ENGINE OUT light came on. The pilot stated that he put the helicopter into autorotation, told his passengers to brace for a hard landing, gave a Mayday call and put the helicopter in what he thought was the safest place to land. The pilot indicated that the helicopter had last received an annual inspection on March 10, 2000, 46.8 flight hours prior to the accident, and that the helicopter's airframe total time was 2,447.0 hours. An engine disassembly examination report prepared by the engine manufacturer, Rolls-Royce Corporation (formerly Allison) ("Accident Investigation & Engine Disassembly Examination Report, Rolls-Royce Allison Model 250-C18B Engine CAE 802368B", report date July 9, 2000, textual excerpts attached), reported that the engine was overhauled by APSI on March 27, 1974, and installed on the accident helicopter on April 26, 1974, at 1,395 hours airframe total time and 715.0 hours engine total time. The Rolls-Royce report stated that complete records were not made available to establish times for all the components installed on the engine, but gave the engine total time at the time of the accident (as derived from the airframe Hobbs meter and available records) as 1,768.0 hours, and the engine time since overhaul as 1,053.0 hours. Since complete maintenance records were not available for review, a full service history for the engine, engine modules and accessories could not be established. The accident helicopter was equipped with a 317 shaft horsepower (SHP) Allison 250-C18B turboshaft engine. The helicopter wreckage was viewed by FAA and Rolls-Royce investigators at the West Union Shop of Danielson Developers, Inc., Hillsboro, Oregon, on July 7-8, 2000. The engine was subsequently removed from the helicopter and shipped to Rolls-Royce facilities at Oakland, California, for further examination. This examination, consisting of a disassembly/teardown examination, was conducted on July 25, 2000, under supervision of an inspector from the FAA's Oakland Flight Standards District Office (FSDO). Upon completion of the disassembly examination, selected components of the engine were shipped to Rolls-Royce Corporation's Materials and Processes Department in Indianapolis, Indiana, for failure analysis. The Rolls-Royce engine investigation report stated that during engine examination at the recovery site, a red sealer, which appeared as high temperature RTV, was noted to be applied extensively and heavily on the exterior of the engine, diffuser scroll, N1 and N2 tachometer generator mating surfaces, power shaft output seal, and other areas. Subsequently, during the disassembly examination, the spur adapter gearshaft (SAG, a shaft that joins the gas producer turbine to the engine compressor) was found failed at the juncture of the aft splines. The Rolls-Royce report stated that the SAG was heat-distressed and dry of lubrication. The failed section of aft splines from the SAG was engaged in the forward end of the compressor-to-turbine coupling. Further disassembly examination revealed red sealant adhered to the interior surfaces of the gearbox at the power shaft seal opening. An oil flow test of the gearbox and the oil delivery tube (part number 6874672) was conducted. According to the Rolls-Royce report, with 60 PSI oil pressure applied, no oil flowed from the oil jet targeted for the SAG. Closer examination of the oil delivery tube revealed that the oil jet of the oil delivery tube, targeted for the SAG, was clogged. Red sealant was also found on the inlet and outlet sides of the oil filter screen upstream of the oil delivery tube. Subsequent disassembly examination of the oil pump revealed red sealant in three of the four scavenge pump gear chambers. Metallurgical investigation conducted at Rolls-Royce disclosed that the SAG had failed due to torsional fatigue, initiated in the aft splines, which the Rolls-Royce report stated "were heavily worn from inadequate or restricted oil flow." The Rolls-Royce report stated that the red sealant specimens found throughout the gearbox, oil passages, and oil pump were determined to be the same material, which a Rolls-Royce Metallurgical Investigation Report identified as "a rubberized sealant (referred to as 'Proseal')".
Improper maintenance (excessive/improper sealant application) by an unknown person, and subsequent fracture of the spur adapter gearshaft resulting in a total loss of engine power. Factors included foreign material/substance in the engine oil, a blocked oil delivery tube oil jet, and oil starvation in the area of the spur adapter gearshaft.
Source: NTSB Aviation Accident Database
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