Bell BHT-206L-1 N27591

Summary

On 7 July 1997 at about 00:03 local time, a Bell BHT-206L-1 registered N27591, operated by Usda Forest Service, was involved in an accident near Highland, California, United States. One person was on board and one died. The aircraft was destroyed. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

7 July 1997 at 00:03

Classification

Accident

Location

Highland, California, United States

Coordinates

34.1302, -117.1507

Aircraft

Bell BHT-206L-1

Registration

N27591

Category

Helicopter

Engines

1

Operator

Usda Forest Service

Operating rule

Public Use

Purpose of flight

Unknown

Phase of flight

Not recorded

Aircraft damage

Destroyed

Weather

VMC

Light

Day

NTSB number

LAX97GA235

1 person died.

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.

Quoted verbatim from the NTSB record. This site does not paraphrase or interpret it.

Read the full NTSB narrative

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.

Quoted verbatim from the NTSB record.