ASN Wikibase Occurrence # 181558
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| Date: | Tuesday 3 November 2015 |
| Time: | 11:30 LT |
| Type: |  Hughes 369D |
| Owner/operator: | Olympic Air Inc |
| Registration: | N510PA |
| MSN: | 811073D |
| Year of manufacture: | 1981 |
| Total airframe hrs: | 9329 hours |
| Engine model: | Rolls Royce 250-C20B |
| Fatalities: | Fatalities: 0 / Occupants: 1 |
| Aircraft damage: | Substantial |
| Location: | near Sedro-Woolley, WA -
 United States of America
|
| Phase: | Manoeuvring (airshow, firefighting, ag.ops.) |
| Nature: | External load operation |
| Departure airport: | Arlington, WA (AWO) |
| Arlington, WA (AWO) | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
According to the pilot, he was conducting longline operations using a 50-foot line to gather cedar pieces. After completing work at an initial jobsite, he flew to the second jobsite. Between jobs, the helicopter was refueled. Before beginning the second job, a safety briefing was conducted. The pilot then completed about 30 to 40 slings and as he was positioning the helicopter to lift a load from a slope, the helicopter suddenly lost engine power and he entered an autorotation. The pilot attempted to land at the bottom of a hill because of the flat terrain, but the helicopter touched down on the slope and the tailboom impacted the side of a hill, followed by the skids. The helicopter came to rest on its right side. Prior to the loss of engine power, the pilot did not receive any warning lights during the flights.
During postaccident examination of the airframe and engine, debris was found throughout the fuel system. The start pump was removed, and the fuel bypass valve inlet port screen was found covered with a brown, spongelike debris. Normal operation is with the start pump off (except when using alternate fuel mixtures or emergency fuels). When the start pump is not in use, fuel passes through the fuel bypass valve inlet port screen. The debris located on the fuel pump bypass valve inlet port screen, throughout the inside of the pump, and embedded in the centrifugal pump prevented the pump from producing sufficient fuel flow, which starved the engine of fuel and resulted in the power loss. Although the operator reported that it monitored for fuel contamination in the accident helicopter and its other company helicopters in accordance with the helicopter manufacturer’s maintenance procedures, these procedures did not require that the fuel bypass valve inlet port screen be checked unless a cockpit warning indication light was activated. The light had not activated in the accident helicopter; therefore, the operator had not checked the screen. Following the accident, the helicopter manufacturer revised its procedures to require that the screen be checked whenever fuel contamination was identified.
Testing of the debris was consistent with naphthenates, which are surfactants that reduce the surface tension between the fuel and free water and allow the two liquids to mix. Refinery processing should remove all traces of naphthenic acid and its corresponding metal salts; however, in some refining processes, small amounts of the naphthenates can get carried through with the jet fuel, which can lead to microbial growth in the fuel. About 1 month before the accident, the operator found microbial growth in company fuel and treated the fuel with a microbiocide to destroy biological growth. However, there is no evidence that the microbiocide used by the operator contributed to the dissolution of the naphthenates, and the reason for the separation of naphthenates from the fuel could not be determined.
Probable Cause: The loss of engine power due to fuel starvation as a result of naphthenate fuel contamination, which blocked the fuel flow through the start pump.
Accident investigation:
 |
|
Sources:
NTSB
https://flightaware.com/resources/registration/N510PA
History of this aircraft
Other occurrences involving this aircraft
| 30 July 1999 | N103FW | Alpine Helicopters, Inc. | 0 | Petersburg, AK | |
sub |
| Fuel exhaustion | ||||||
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 21-Nov-2015 16:25 | Aerossurance | Added |
| 21-Dec-2016 19:30 | ASN Update Bot | Updated [Time, Damage, Category, Investigating agency] |
| 08-Sep-2017 19:47 | ASN Update Bot | Updated [Operator, Other fatalities, Nature, Departure airport, Destination airport, Source, Narrative] |
| 10-Sep-2017 13:07 | Aerossurance | Updated [Time, Other fatalities, Location, Nature, Source, Narrative] |
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