LAX91LA320 · Sikorsky SK-58
Associated Helicopter Services Sikorsky SK-58 · Accident: partial loss of engine power (mechanical failure) en route
From Barstow Daggett Airport (DAG) to an unrecorded destination
Event
- NTSB case
- LAX91LA320
- 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
- 0 · 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 SK-58
- Aircraft type
- Sikorsky SK-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
- N58WH
- Operator
- Associated Helicopter Services
- Onboard fatalities
- Unknown
- Route
- From Barstow Daggett Airport (DAG), Barstow, CATo not recorded
- 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 133: Rotorcraft Ext. Load
- 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 (mechanical failure)
- DamageDestroyed: beyond practical repair. Substantial: damage that affects the structure, performance or handling and normally needs major repair. Minor: less than that. Glossary
- Substantial
Cause areas
- Engine assembly, connecting rod › Failure, total
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
WHILE RETURNING FROM AN EXTERNAL LOAD OPERATION, THE HELICOPTER'S ENGINE STARTED VIBRATING AND THEN STARTED BACK FIRING. THE PILOT REPORTED HEARING A LOUD 'BANG' AND THEN NOTED A DECREASE IN ENGINE POWER. HE PERFORMED NECESSARY EMERGENCY PROCEDURES AND ENTERED AN AUTOROTATION. HE SAID THAT HE TOUCHED DOWN WITH SOME FORWARD SPEED. THE HELICOPTER HIT A DIRT BERM. THE ROTOR BLADES CONTACTED THE GROUND AND THE AIRCRAFT ROLLED OVER. AN ENGINE TEARDOWN WAS PERFORMED UNDER THE SUPERVISION OF AN FAA AIRWORTHINESS INSPECTOR. A BROKEN ROD WAS FOUND DURING THE TEARDOWN. THE TEARDOWN WAS TERMINATED AT THAT POINT AND THE REASON FOR THE BROKEN ROD WAS NOT DETERMINED.
Probable cause
THE FAILURE OF AN ENGINE CONNECTING ROD CAUSING A REDUCTION OF ENGINE POWER TO THE POINT WHERE LEVEL FLIGHT COULD NOT BE MAINTAINED. A FACTOR IN THE ACCIDENT WAS THE DARK NIGHT CONDITIONS WHICH RESTRICTED THE PILOT'S ABILITY TO SELECT THE BEST LANDING SITE.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record LAX91LA320
- Event ID
- 20001212X17609
- Case number
- LAX91LA320
- 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: local date, investigation status. Values present in the bulk record are kept.
- The date is the local date; the NTSB stores the UTC date 1991-07-22.
- API snapshot SHA-256: aeeb3f8208476fbe40b762d310ec5ba344d5de821492761b9d180f9261af64bc; retrieved 2026-09-23T03:54:56.127Z.