ASN Wikibase Occurrence # 42596
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| Date: | Sunday 6 July 1997 |
| Time: | 17:03 |
| Type: |  Bell 206L-1 LongRanger II |
| Owner/operator: | U.S. Forest Service |
| Registration: | N27591 |
| MSN: | 45273 |
| Year of manufacture: | 1979 |
| Total airframe hrs: | 7705 hours |
| Engine model: | Allison 250-C30P |
| Fatalities: | Fatalities: 1 / Occupants: 1 |
| Aircraft damage: | Destroyed |
| Category: | Accident |
| Location: | Highland, CA -
 United States of America
|
| Phase: | Manoeuvring (airshow, firefighting, ag.ops.) |
| Nature: | Fire fighting |
| Departure airport: | Patton Helibase, CA |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
On July 6, 1997, about 1703 hours Pacific daylight time, a Bell BHT-206L-1, N27591, operating with the call sign H-520, crashed in the San Bernardino mountains north of Highland, California. The pilot was conducting water dropping operations as part of an ongoing forest fire fighting effort. The aircraft was destroyed and the commercial rated helicopter pilot, the sole occupant, received fatal injuries. The aircraft was being operated by the USDA Forest Service under contract as an exclusive public-use aircraft when the accident occurred. The flight originated about 1630 from the Patton Helibase in Highland, California. Visual meteorological conditions prevailed with localized smoke in the fire areas. No flight plan was filed.
The pilot was conducting water dropping operations as part of an ongoing forest fire fighting effort. A firefighter reported that the helicopter made two water drops before the accident. A battalion fire chief, who was directing the effort, reported that he saw the helicopter making water drops on a slope. After a water drop which involved an abrupt pull up and turn after the water was released from the bucket, he reported hearing the words 'May Day,' 'I have a flame out' and finally 'I'm going down'. Several other people who were monitoring the common frequency also reported hearing a transmission with the phrase 'flame out.' The helicopter impacted the bottom of the canyon. An inspection revealed that the lines from the engine fuel nozzle to the fuel control and the airframe fuel filter contained fuel. The lines and in-line filters contained both fuel and particulate matter in the bottom of both filter housings. Testing revealed that the manifold check valve leaked from both inlet ports. When the valves were disassembled additional foreign material was found. The material was found to be a combination of organic and inorganic materials. A 5-gallon fuel sample was taken from the refueling truck on the day of the accident. The analytical report stated that the sample submitted was that of aviation turbine fuel. No contamination was noted. According to historical records, there have been a series of engine flameout related accidents and incidents related to this engine make and model. Controlled tests have demonstrated that should entrapped air migrate through the fuel system to the engine, an engine flame out can occur.
Probable Cause: Loss of engine power due to fuel contamination. Also causal was the ingestion of entrapped air that occurred during an abrupt maneuver and fuel-borne contamination that caused the fuel system check valves to leak, resulted in a lower than expected fuel level in the main fuel cell. A related factor was mountainous terrain.
Accident investigation:
 |
|
Sources:
NTSB: http://www.ntsb.gov/ntsb/brief.asp?ev_id=20001208X08415
Images:
Photo: NTSB
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 24-Oct-2008 10:30 | ASN archive | Added |
| 21-Dec-2016 19:24 | ASN Update Bot | Updated [Time, Damage, Category, Investigating agency] |
| 01-May-2022 08:32 | Ron Averes | Updated [Operator] |
| 18-Oct-2022 17:37 | Captain Adam | Updated [Operator, Nature, Departure airport, Narrative, Accident report, Photo] |
| 12-Nov-2022 01:30 | Ron Averes | Updated [Operator] |
| 12-Nov-2022 01:35 | Ron Averes | Updated [Operator] |
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