# NTSB CHI87LA037: Mooney M20K, N3691H, Watertown, WI, November 28, 1986

- Type: NTSB accident investigation
- Classification: Accident · No injuries · Limited investigation · Final report
- Date: November 28, 1986, 17:35 local (23:35 UTC)
- Place: Watertown, WI
- Coordinates: 43.189785, -88.719375 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=43.1898&lon=-88.7194&mi=10
- Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping)
- Highest injury: No injuries
- Injuries: 2 uninjured
- Status: Completed
- Report: Approved by Office Director
- NTSB case key (mKey): 13703
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CHI87LA037
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/13703/pdf
- Page: https://openairdocs.org/ntsb/CHI87LA037

## Sequence of events

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

- Airframe/component/system failure/malfunction, cruise - normal
  - engine assembly,cylinder - fatigue (cause)
  - engine assembly,cylinder - failure,total (cause)
- Forced landing, descent - emergency
- On ground/water encounter with terrain/water, landing - roll
  - object - vehicle (contributing factor)
  - remedial action - not possible, pilot in command (contributing factor)
  - terrain condition - ditch (contributing factor)

## Analysis

FOLLOWING AN ENGINE POWER LOSS DUE TO FATIGUE OF THE #1 CYLINDER, THE PLT FORCE LANDED THE ACFT ON A HIGHWAY. THE HIGHWAY WAS THE ONLY AVAILABLE LANDING AREA, ACCORDING TO THE PLT. ON LANDING ROLLOUT, THE PLT WAS FORCED TO SWERVE THE ACFT OFF THE PAVED SURFACE TO AVOID ON COMING VEHICULAR TRAFFIC. THE ACFT STRUCK TWO TRAFFIC SIGNS AND SUBSEQUENTLY WENT INTO A DITCH ALONG THE SIDE OF THE ROAD. ALTHOUGH THE SYLINDER APPEARED TO HAVE BEEN PROPERLY MANUFACTURED, ACCORDING TO TELEDYNE CONTINENTAL METALLURGICAL DATA THE ISOLATED LOCATION OF THE FATIGUE POINTS AND THE ABSENCE OF OTHER POSSIBLE CAUSES OF THE CYLINDER FAILURE INDICATE THAT A MANUFACTURING DEFECT EXISTED.

## Aircraft

- Registration: N3691H (not matched to a registry record)
- Reported make and model: MOONEY M20K
- Category: Airplane
- Serial number: 250431
- Airframe hours: 1332
- Engines: CONTINENTAL TSIO-360-GB1 210 horsepower reciprocating
- Damage: Substantial damage
- Flight: Instructional, Part 91
- Registered owner: David C Flemming
- Airworthiness certificate: Standard, Normal
- Last inspection: Annual, January 6, 1986, 7 hours before
- Departed: OSH, OSHKOSH, WI
- Destination: RFD, ROCKFORD, IL

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 23; commercial, flight instructor; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 1, valid medical--no waivers/lim.; seat: right; flight hours: 500 total, 6 in this make and model, 365 as pilot in command, 122 in the last 90 days, 1 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Night/dark
- Wind: 250° at 5 knots
- Visibility: 10 statute miles
- Lowest ceiling: none
- Temperature: 36 °F, dew point 30 °F
- Altimeter: 30.00 inHg
- Observed at: MSN, 25 nm away

## 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 19861128062379A](https://openairdocs.org/incident/19861128062379A), Nov 28, 1986: Mooney M20K, Watertown, WI, Substantial damage. The engine failed in flight. The aircraft hit a post during landing. Nr 1 engine cylinder failed in fatigue.

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.

---
OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.