# NTSB SEA91LA139: Cessna 180G, N4700U, Challis, ID, June 22, 1991

- Type: NTSB accident investigation
- Classification: Accident · Minor injuries · Limited investigation · Final report
- Date: June 22, 1991, 09:45 local (15:45 UTC)
- Place: Challis, ID
- Coordinates: 44.649333, -114.150978 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=44.6493&lon=-114.1510&mi=10
- Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping)
- Highest injury: Minor injuries
- Injuries: 1 minor, 1 uninjured
- Status: Completed, report July 13, 1993
- Report: Approved by Office Director
- NTSB case key (mKey): 41457
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=SEA91LA139
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/41457/pdf
- Page: https://openairdocs.org/ntsb/SEA91LA139

## Probable cause

THAT THE PILOT ENCOUNTERED UNSUITABLE TERRAIN DURING A FORCED LANDING AFTER  A POWER LOSS DUE TO A FRACTURED CYLINDER BOSS AND A BENT ENGINE PUSHROD.

## Sequence of events

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

- Loss of engine power(partial) - mech failure/malf, cruise
  - engine assembly,push rod - bent (cause)
  - engine assembly,cylinder - fractured (cause)
- Forced landing, descent - emergency
- In flight collision with terrain/water, landing
  - terrain condition - none suitable (contributing factor)

## Analysis

THE CESSNA 180 WAS IN CRUISE FLIGHT A FEW MINUTES AFTER DEPARTURE WHEN THE ENGINE BEGAN RUNNING ROUGH AND LOST POWER. THE PILOT WAS UNABLE TO RETURN TO A SAFE LANDING SITE, SO ELECTED TO ATTEMPT A FORCED LANDING NEAR A RIVER. AN ENGINE TEARDOWN REVEALED THAT THE EXHAUST VALVE ROCKER SHAFT BOSS ON ONE CYLINDER HAD FAILED AND THE BROKEN PIECE MIGRATED UNDER THE INTAKE ROCKER SHAFT, WHERE IT CAUSED THE VALVE PUSH ROD TO BEND.

## Aircraft

- Registration: [N4700U](https://openairdocs.org/deregistered/N4700U-1991-09-20), registration cancelled 1991-09-20, S/N 18051400 (OpenAirDocs)
- Reported make and model: CESSNA 180G
- Registry model: [Cessna 180G](https://openairdocs.org/model/cessna-180g) (registry code 2072616) (OpenAirDocs)
- Category: Airplane
- Serial number: 18051400
- Engines: CONTINENTAL O-470R 230 horsepower reciprocating
- Damage: Substantial damage
- Flight: Personal, Part 91
- Operator: Maxl Willis
- Registered owner: Maxl Willis
- Departed: FLYING B RANCH, ID
- Destination: CAMAS CREEK, ID

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 46; flight instructor, commercial; airplane ratings: single-engine land; instrument ratings: airplane; medical: unknown, unknown; flight hours: 3,570 total, 201 in this make and model, 3,070 as pilot in command, 56 in the last 90 days, 16 in the last 30 days, 1 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Visibility: 40 statute miles
- Temperature: -0 °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 19910622023369A](https://openairdocs.org/incident/19910622023369A), Jun 22, 1991: Cessna 180G, Challis, ID, Substantial damage. Engine roughened and popped on leveling off. Turned back but crash landed. Cylinder rocker arm boss failed.

## Other investigations on N4700U (1)

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 SEA73DYA33](https://openairdocs.org/ntsb/SEA73DYA33), Jun 22, 1973: Cessna 180 (N4700U), Boise, ID, 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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