ASN Wikibase Occurrence # 35146
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| Date: | Monday 21 February 1994 |
| Time: | 11:15 LT |
| Type: |  Sikorsky S-58DT |
| Owner/operator: | Air One, Inc |
| Registration: | N581BG |
| MSN: | 58-1487 |
| Total airframe hrs: | 12735 hours |
| Engine model: | P&W PT6T-3 |
| Fatalities: | Fatalities: 3 / Occupants: 3 |
| Aircraft damage: | Destroyed |
| Category: | Accident |
| Location: | near Walnut Creek, CA -
 United States of America
|
| Phase: | En route |
| Nature: | Unknown |
| Departure airport: | Concord, CA |
| San Jose, CA (KSJC) | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
THE HELICOPTER WAS OBSERVED FLYING LOW IN A GRADUAL DESCENT OVER A RESIDENTIAL AREA HEADING TOWARD AN OPEN FIELD. WITNESSES SAID THE HELICOPTER NOISE LEVEL WAS QUIET, BUT NOT SOUNDLESS. AT 200 FEET ABOVE THE GROUND, THE HELICOPTER ROLLED LEFT TO AN INVERTED FLIGHT ATTITUDE AND THEN DESCENDED IN A NOSE-DOWN ATTITUDE. WRECKAGE EXAMINATION DID NOT FIND ANY PREIMPACT MECHANICAL FAILURES WITH THE HELICOPTER'S FLIGHT CONTROL OR DRIVE SYSTEMS. SIGNATURES ON THE INTERNAL ROTATING COMPONENTS OF BOTH ENGINES, THE DRIVE SYSTEM, MAIN ROTOR BLADES, AND TAIL ROTOR BLADES WERE INDICATIVE OF LOW RPM. EXAMINATION OF THE ENGINE FUEL SYSTEM REVEALED EVIDENCE OF FOREIGN PARTICLES IN THE FLOW DIVIDER AND FUEL NOZZLES. POSTACCIDENT FUEL SAMPLES FROM THE REFUELING TRUCK WERE TESTED IN A LABORATORY. ACCORDING TO THE LAB REPORT, THE FUEL HAD A TENDENCY TO ABSORB AND RETAIN WATER, AND A PRESENCE OF MICROBIAL CONTAMINATION WAS NOTED. IN ADDITION TO THE LAB TESTS, FUEL SAMPLES FROM THE OPERATORS REFUELING TRUCKS WERE INDEPENDENTLY TESTED WITH WATER DETECTION PASTE AND TESTED POSITIVE FOR WATER.
Probable Cause: Inadequate fuel quality control procedures by the helicopter operator resulting in fuel contamination and a loss of engine power. The pilot's decision to extend the autorotative glide to avoid striking residential homes, which resulted in low main rotor rpm and a subsequent in-flight loss of control, is also causal in this accident. A factor in the accident was the unsuitable nature of the residential area over which the loss of power occurred for a successful forced landing.
Accident investigation:
 |
|
Sources:
NTSB LAX94FA130
Location
Images:
San Jose Intl Airport, San Jose, CA KSJC/SJC June 1990 apprx photo date. Tom Vance
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 24-Oct-2008 10:30 | ASN archive | Added |
| 15-Jul-2010 02:56 | TB | Updated [Time, Aircraft type, Operator, Other fatalities, Location, Nature] |
| 30-Jun-2018 13:33 | Anon. | Updated [Photo, ] |
| 10-Apr-2024 08:48 | ASN Update Bot | Updated [Time, Operator, Other fatalities, Nature, Destination airport, Source, Narrative, Category, Accident report] |
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