# NTSB SEA92LA196: Piper PA-12, N78599, Cokeville, WY, September 6, 1992

- Type: NTSB accident investigation
- Classification: Accident · No injuries · Limited investigation · Final report
- Date: September 6, 1992, 09:00 local (15:00 UTC)
- Place: Cokeville, WY
- Coordinates: 42.079898, -110.949218 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=42.0799&lon=-110.9492&mi=10
- Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping)
- Highest injury: No injuries
- Injuries: 2 uninjured
- Status: Completed, report September 14, 1993
- Report: Approved by Office Director
- NTSB case key (mKey): 42893
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=SEA92LA196
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/42893/pdf
- Page: https://openairdocs.org/ntsb/SEA92LA196

## Probable cause

FATIGUE FAILURE OF THE CRANKSHAFT.  FACTORS INCLUDE NON SUITABLE TERRAIN FOR A FORCED LANDING AND AN IMPROPER PROPELLER.

## 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, maneuvering
  - engine assembly,crankshaft - fatigue (cause)
  - propeller system/accessories - improper (contributing factor)
- Forced landing, descent - emergency
- Nose over, landing
  - terrain condition - none suitable (contributing factor)

## Analysis

THE PILOT OF THE PIPER PA 12 REALIZED THAT HE WAS EXPERIENCING A POWER LOSS WHILE MANEUVERING, LOOKING FOR MISSING SHEEP.  HE TURNED TO LOWER, FLATTER TERRAIN.  THE ENGINE CONTINUED TO LOSE POWER, SO HE MADE A FORCED LANDING IN UNSUITABLE TERRAIN.  THE AIRCRAFT NOSED OVER AFTER TOUCHING DOWN.  METALLURGICAL TESTING REVEALED THAT THE CRANKSHAFT HAD EXPERIENCED FATIGUE FAILURE.  THE ENGINE HAD BEEN INSTALLED ON A FIELD APPROVAL.  THE PROPELLER/ENGINE COMBINATION INSTALLED IN THIS AIRCRAFT HAD NOT BEEN TESTED OR APPROVED FOR THIS, OR ANY OTHER, INSTALLATION.

## Aircraft

- Registration: [N78599](https://openairdocs.org/deregistered/N78599-1996-09-05), registration cancelled 1996-09-05, S/N 123961 (OpenAirDocs)
- Reported make and model: PIPER PA-12
- Registry model: [Piper PA-12](https://openairdocs.org/model/piper-pa-12) (registry code 7101202) (OpenAirDocs)
- Category: Airplane
- Serial number: 12-3961
- Airframe hours: 4777
- Engines: LYCOMING O-340-A1A 170 horsepower reciprocating
- Damage: Substantial damage
- Flight: Personal, Part 91
- Operator: John I Ritter
- Registered owner: John I Ritter
- Airworthiness certificate: Special, Restricted (Special)
- Last inspection: Annual, May 16, 1992, 68 hours before
- Departed: KEMMERER, WY

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 51; private; airplane ratings: single-engine sea, single-engine land; medical: class 2, valid medical--no waivers/lim.; seat: front; flight hours: 861 total, 824 in this make and model, 821 as pilot in command, 70 in the last 90 days, 29 in the last 30 days, 2 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: calm
- Visibility: 40 statute miles
- Lowest ceiling: none
- Temperature: 50 °F, dew point -0 °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 19920906035469A](https://openairdocs.org/incident/19920906035469A), Sep 6, 1992: Piper STCPA12, Cokeville, WY, Substantial damage. Rough engine seized en route. Nosed over landing. Had large engine installed. Not approved. Crankshaft broke.

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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