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| Date: | Wednesday 13 July 2005 |
| Time: | 19:10 |
| Type: |  Eurocopter EC 120B Colibri |
| Owner/operator: | Sacramento County Sheriff's Department |
| Registration: | N266SD |
| MSN: | 1133 |
| Year of manufacture: | 2000 |
| Total airframe hrs: | 2562 hours |
| Engine model: | Turbomeca Arrius 2F |
| Fatalities: | Fatalities: 2 / Occupants: 3 |
| Other fatalities: | 0 |
| Aircraft damage: | Destroyed |
| Category: | Accident |
| Location: | near Fair Oaks, CA -
 United States of America
|
| Phase: | Manoeuvring (airshow, firefighting, ag.ops.) |
| Nature: | Survey |
| Departure airport: | Sacramento-Mather Airport, CA (MHR/KMHR) |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
On July 13, 2005, about 1910 Pacific daylight time, a Eurocopter EC120B, N266SD, operating as Star 6, experienced a catastrophic engine failure and collided with terrain near Fair Oaks, California. The Sacramento County Sheriff's Department was operating the public-use helicopter under the provisions of 14 CFR Part 91. The commercial pilot and the front-seat observer sustained fatal injuries; the aft-seated observer trainee sustained serious injuries. The helicopter was destroyed during the accident sequence. The local area flight departed Mather, California, about 1815. Visual meteorological conditions prevailed, and a flight plan had not been filed.
The engine experienced an overspeed and catastrophic failure on a law enforcement patrol flight and the helicopter collided with hilly terrain during a subsequent autorotation attempt. Witnesses reported the helicopter began emitting smoke and subsequently descended, impacting terrain near the bottom of a 60-degree sloped hillside. The terrain around the accident site was either steeply sloped hillside with mature trees or bordered by power lines. A post accident examination of the engine and components revealed the constant delta P diaphragm (located in the fuel control unit) had ruptured, resulting in a high and uncontrolled increase of fuel flow to the engine. The power turbine exhibited evidence of a substantial overspeed. All of the turbine blades were separated at their respective shear points. The gas generator turbine exhibited evidence of extreme thermal erosion; the blades were eroded to about 50 percent of their normal height. The centrifugal compressor exhibited evidence of extreme rubbing. A detailed examination of the diaphragm revealed that it had been installed incorrectly (inside-out). The maintenance and engine manufacturer's build records revealed that the diaphragm was last replaced at the engine manufacturer's facilities in France. Recovered Vehicle and Engine Multifunctional Display (VEMD) information supported the evidence of an engine and main rotor revolutions per minute (rpm) exceedance.
Probable Cause: The failure of the constant delta P diaphragm in the fuel control unit, which resulted in an increased fuel flow and subsequent catastrophic failure of the engine. The diaphragm's failure was the result of improper installation by the engine manufacturer. A factor in the accident was the unsuitable nature of the terrain for a successful autorotation.
Accident investigation:
 |
|
Sources:
NTSB
https://data.ntsb.gov/Docket?ProjectID=61966
Location
Images:
Photo: NTSB
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 28-Oct-2008 00:45 | ASN archive | Added |
| 10-Mar-2013 12:14 | TB | Updated [Aircraft type, Source, ] |
| 10-Mar-2013 12:16 | TB | Updated [Time, Location, ] |
| 21-Dec-2016 19:24 | ASN Update Bot | Updated [Time, Damage, Category, Investigating agency, ] |
| 06-Dec-2017 10:43 | ASN Update Bot | Updated [Nature, Source, Narrative, ] |
| 30-May-2023 07:20 | Ron Averes | Updated |
| 16-Jul-2025 16:10 | Captain Adam | Updated [Operator, Phase, Nature, Source, Narrative, Photo, ] |
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