# NTSB LAX91LA358: Beech J35, N3028C, San Jose, CA, August 14, 1991

- Type: NTSB accident investigation
- Classification: Accident · No injuries · Limited investigation · Final report
- Date: August 13, 1991, 18:15 local (Aug 14, 1991, 01:15 UTC)
- Place: San Jose, CA
- Coordinates: 37.329006, -121.829399 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=37.3290&lon=-121.8294&mi=10
- Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping)
- Highest injury: No injuries
- Injuries: 1 uninjured
- Status: Completed, report March 10, 1993
- Report: Approved by Office Director
- NTSB case key (mKey): 27327
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=LAX91LA358
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/27327/pdf
- Page: https://openairdocs.org/ntsb/LAX91LA358

## Probable cause

THE FAILURE OF THE CRANKSHAFT COUNTERWEIGHT RETAINING CLIP DUE TO IMPROPER MAINTENANCE INSTALLATION OF THE PART.

## Sequence of events

In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf).

- Loss of engine power(total) - mech failure/malf, cruise
  - eng assembly,crankshaft counterweights/vib damper - failure,total (cause)
  - maintenance,installation - improper, other maintenance personnel (cause)
  - engine assembly,connecting rod cap - failure,total
- Forced landing, descent - emergency
- In flight collision with terrain/water, landing
  - terrain condition - rough/uneven

## Analysis

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.

## Aircraft

- Registration: [N3028C](https://openairdocs.org/deregistered/N3028C-2012-09-05), registration cancelled 2012-09-05, S/N D-5693, built 1958 (OpenAirDocs)
- Reported make and model: BEECH J35
- Registry model: [Beech J35](https://openairdocs.org/model/beech-j35) (registry code 1151522) (OpenAirDocs)
- Registry engine: [Continental I0-470 series](https://openairdocs.org/engine/continental-i0-470-series) (registry code 17027, reciprocating) (OpenAirDocs)
- Category: Airplane
- Serial number: D-5693
- Airframe hours: 3685
- Engines: CONTINENTAL IO-470-C 250 horsepower reciprocating
- Damage: Substantial damage
- Flight: Personal, Part 91
- Operator: Dtb Aviation
- Registered owner: Dtb Aviation
- Airworthiness certificate: Special, Experimental (Special)
- Last inspection: Annual, February 13, 1991, 26 hours before
- Destination: 307, HOLLISTER, CA

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 33; commercial; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 2, valid medical--w/ waivers/lim; seat: left; flight hours: 676 total, 71 in this make and model, 572 as pilot in command, 30 in the last 90 days, 8 in the last 30 days, 2 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: 300° at 12 knots
- Visibility: 25 statute miles
- Lowest ceiling: none
- Temperature: 90 °F, dew point 68 °F

## FAA reports on this event (1)

The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs).

- [Accident 19910813033929A](https://openairdocs.org/incident/19910813033929A), Aug 13, 1991: Beech J35, San Jose, CA, Substantial damage. Engine quit on test flight. Connecting rod failed. Modified engine had cir-clips on counter weight installed wrong.

## Other investigations on N3028C (2)

From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model.

- [NTSB CHI68D0246](https://openairdocs.org/ntsb/CHI68D0246), Aug 23, 1967: Beech J35 (N3028C), Chicago, IL, substantial damage
- [NTSB CHI67D0574](https://openairdocs.org/ntsb/CHI67D0574), Mar 4, 1967: Beech J35 (N3028C), Polo, IL, substantial damage

From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model.

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