LAX94FA130 · Sikorsky S-58T
Air One Sikorsky S-58T · Accident: partial loss of engine power (non-mechanical) en route
From Concord, CA to Mineta San Jose International Airport (SJC)
Event
- NTSB case
- LAX94FA130
- Event typeAccident: someone killed or seriously injured, or the aircraft substantially damaged (NTSB definition). Incident: an occurrence that affected or could have affected safety, short of that. Glossary
- Accident
- InvestigationHow far the investigation had got when the record was published: preliminary, ongoing, final or completed. Unknown where the source does not say. Glossary
- Completed
- API-reported fatalities
- 3 · all aircraft and ground
- Ground fatalities
- 0
- OperationWhat kind of flying it was, grouped by the rules it flew under: airline (US Part 121), air taxi and commuter (Part 135), general aviation (Part 91 and similar), military or government. Glossary
- General aviation
- WeatherVisual meteorological conditions (VMC): good enough to fly by looking outside. Instrument conditions (IMC): cloud or low visibility, flying by instruments. Glossary
- Visual Meteorological Cond
Sikorsky S-58T
- Aircraft type
- Sikorsky S-58
- Category
- Helicopter
- RegistrationThe aircraft's tail number, such as N12345 or G-ABCD. Registrations are reissued, so the same one years apart can be a different aircraft. Glossary
- N581BG
- Operator
- Air One
- Onboard fatalities
- Unknown
- Route
- From Concord, CATo Mineta San Jose International Airport (SJC), San Jose, CA
- Aircraft age
- Not recorded
- Flight rulesThe regulations the flight operated under: in the US, Part 91 (general aviation), Part 121 (airlines), Part 135 (air taxi and commuter) and others; for flights abroad, the NTSB's coarser commercial or non-commercial code. Glossary
- Part 91: General Aviation
- Phase of flightThe stage of the flight when things started to go wrong: standing, taxi, takeoff, initial climb, en route, maneuvering, approach or landing. Glossary
- En route · cruise
- First occurrenceThe single coded event the NTSB judges best describes what happened (records from 2008 on). Older records name the first occurrence in the sequence instead. Glossary
- Partial loss of engine power (non-mechanical)
- Also codedOther events the NTSB coded in the sequence, such as a wire strike after a loss of power. Flight Findings uses them for its kinds of event. Glossary
- Fuel contamination
- DamageDestroyed: beyond practical repair. Substantial: damage that affects the structure, performance or handling and normally needs major repair. Minor: less than that. Glossary
- Destroyed
Cause areas
- Company maintenance personnel › Inadequate quality control
- Company maintenance personnel › Maintenance, service of aircraft/equipment, inadequate
- Fluid, fuel › Contamination
- Fuel system › Flow restricted
- Fuel system, fuel flow divider/distributor › Foreign material/substance
- Fuel system, nozzle › Foreign material/substance
- Pilot in command › Autorotation, delayed
- Pilot in command › Maneuver to avoid obstructions, intentional
- Pilot in command › Rotor RPM, not maintained
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
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.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record LAX94FA130
- Event ID
- 20001206X00756
- Case number
- LAX94FA130
- Dataset
- historical-pre2008
- Source SHA-256
- 89e2df6d848e7ab3b42e7d7c7a03ff403303057a26ca04c95b3ea67201c3ce74
Source notes (4)
- Unreviewed is an editorial label, not an investigation status. API-sourced is not report-checked or human-reviewed. Explicit event totals are used without summing aircraft injury tables; onboard allocation is withheld. Unknown values remain unknown. The operation category is mapped from the NTSB-reported FAR part and has not been reviewed.
- Filled from the NTSB case API where the bulk record had no value: investigation status. Values present in the bulk record are kept.
- The date is the local date, which is the same as the UTC date the NTSB stores.
- API snapshot SHA-256: 3ae75239396134be5fd2573a784bbd99cef1fe338aeb8e907342201e4eabe82e; retrieved 2026-09-21T00:14:32.202Z.