LAX91LA358 · Beech J35
DTB Aviation Beech J35 · Accident: total loss of engine power (mechanical failure) en route
From an unrecorded airport to 307 · Hollister, CA
Event
- NTSB case
- LAX91LA358
- 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
Beech J35
- Aircraft type
- Beechcraft 35
- Category
- Airplane
- 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
- N3028C
- Operator
- DTB Aviation
- Onboard fatalities
- Unknown
- Route
- From not recordedTo 307 · Hollister, 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
- Total 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
- Eng assembly, crankshaft counterweights/vib damper › Failure, total
- Other maintenance personnel › Maintenance, installation, improper
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
THE ENGINE WAS OVERHAULED AND MODIFIED ABOUT SIX OPERATING HOURS PRIOR TO THE ACCIDENT WITH A NEW TYPE OF CAM SHAFT UNDER THE PROVISIONS OF A SUPPLEMENTAL TYPE CERTIFICATE. THE PILOT SAID HE WAS IN LEVEL CRUISE WHEN HE HEARD A LOUD BANG EMANATE FROM THE ENGINE CONCURRENTLY WITH IT STOPPING. AN INITIAL INSPECTION OF THE AIRCRAFT ON SITE BY FAA INSPECTORS REVEALED THAT OIL COVERED THE WIND SHIELD. THE NUMBER TWO CYLINDER ROD WAS OBSERVED TO BE PROTRUDING FROM A HOLE IN THE TOP OF THE ENGINE CASE. ONE COUNTER WEIGHT ASSEMBLY WAS FOUND MISSING FROM THE CRANKSHAFT COUNTERWEIGHT BLADE. THE MISSING COUNTERWEIGHT, COVER PLATES, RETAINING CIR-CLIPS, AND ASSOCIATED BUSHINGS WERE FOUND IN THE OIL PAN. OPTICAL EXAMINATION OF THE RECOVERED PIECES REVEALED THAT THE RETAINING CIR-CLIP FAILED, ALLOWING THE COUNTER WEIGHT PIN AND THE WEIGHT ITSELF TO SEPARATE FROM THE CRANKSHAFT. THE INSPECTOR DETERMINED THAT THE CIR-CLIP HAD BEEN INSTALLED BACKWARDS.
Probable cause
THE FAILURE OF THE CRANKSHAFT COUNTERWEIGHT RETAINING CLIP DUE TO IMPROPER MAINTENANCE INSTALLATION OF THE PART.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record LAX91LA358
- Event ID
- 20001212X17900
- Case number
- LAX91LA358
- 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 1991-08-14.
- API snapshot SHA-256: 2bb277a5d8f8cb184d882e634c01862f3962d855942b0c7d8ad69bd27daf3e6a; retrieved 2026-09-23T03:48:06.010Z.