# NTSB SEA02LA187: Mooney M20J, N4232H, Oakley, ID, September 30, 2002 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: September 30, 2002, 16:30 local (22:30 UTC) - Place: Oakley, ID - Coordinates: 42.244998, -113.879447 - Nearby events: https://openairdocs.org/map.md?lat=42.2450&lon=-113.8794&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed, report April 8, 2003 - Report: Approved by Office Director - Parties: Boise FAA FSDO - NTSB case key (mKey): 55814 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=SEA02LA187 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/55814/pdf - Page: https://openairdocs.org/ntsb/SEA02LA187 ## Probable cause Failure (fracture) of the two number four piston compression rings, leading to the erosion of a section of the piston sidewall, resulting in the exhaustion of the engine's oil supply during cruise flight, followed by a forced landing on a country road. Factors include mail boxes mounted on metal poles immediately adjacent to the side of the road. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Loss of engine power, cruise - engine assembly,ring - fractured (cause) - engine assembly,piston - eroded (cause) - fluid,oil - exhaustion (cause) - Forced landing, descent - emergency - On ground/water collision with object, landing - roll - object - other (contributing factor) ## Analysis During cruise flight, the aircraft began to lose oil pressure, and the propeller rpm stopped responding to the position of the propeller governor control lever. Eventually the engine oil pressure dropped to zero, and the pilot elected to attempt a forced landing on a country road. Although the touchdown was successful, during the landing roll, the aircraft's wings collided with mailboxes mounted on steel poles situated immediately adjacent to the side of the road. It was later determined that both compression rings on the number four piston had failed (fractured), and that a portion of the piston outer wall near the piston dome had eroded away allowing loss of a majority of the engine's oil through the engine exhaust system. ## Factual narrative On September 30, 2002, approximately 1630 mountain daylight time, the wings of a Mooney M20J, N4232H, collided with mail boxes mounted on steel posts during the landing roll after the pilot successfully executed a forced power-off landing on a country road. The private pilot and his passenger were not injured, but the aircraft, which is owned and operated by the pilot, sustained substantial damage. The 14 CFR Part 91 personal pleasure flight, which departed Walker Field, Grand Junction, Colorado, about two hours earlier, was being operated in visual meteorological conditions. The ELT was not activated. According to the pilot, while en route, the aircraft began to lose oil pressure and eventually the propeller failed to respond correctly to the movement of the propeller rpm governor control lever. Eventually the oil pressure dropped to zero, and the pilot elected to make an emergency landing on a country road. Although the pilot was able to maneuver the aircraft to a successful touchdown on the road he selected, during the landing roll, the wings of the aircraft collided with mail boxes situated immediately adjacent to the edge of the road. A post-accident inspection of the engine revealed that both compression rings on the number four piston had fractured, and a 3/8 inch wide section of the piston surface had been eroded away. The eroded area extended from the land of the bottom compression ring, through the land of the top compression ring, to within 1/16 inch of the piston dome. The depth of the erosion was approximately 1/8 inch (level with the bottom surface of the ring land). In addition, according to the FAA inspector who looked at the engine after the number four cylinder was removed, except for a small residual amount, the engine had lost all of its oil supply, and the number three connecting rod bearing was beginning to extrude from between the rod end and the crankshaft journal. The investigation also revealed that the number four cylinder exhaust pipe was contaminated with both oily soot and a coating of unburned oil. In addition, the fuselage skin in the area aft of the exhaust pipe for the number two and number four cylinders was coated with what appeared to be relatively fresh oil. ## Aircraft - Registration: [N4232H](https://openairdocs.org/aircraft/N4232H), registered now, S/N 24-0671, built 1978 (OpenAirDocs) - Reported make and model: Mooney M20J - Registry model: [Mooney M20J](https://openairdocs.org/model/mooney-m20j) (registry code 5870219) (OpenAirDocs) - Registry engine: [Lycoming I0360 series](https://openairdocs.org/engine/lycoming-i0360-series) (registry code 41515, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 24-0671 - Airframe hours: 3971 - Engines: Lycoming IO-360-A3B6D 200 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Registered owner: James H. Sharman - Airworthiness certificate: Standard, Normal - Last inspection: Annual, September 16, 2002, 12 hours before - Departed: GJT, Grand Junction, CO - Destination: BOI, Boise, ID ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 74; injuries: none; private; airplane ratings: single-engine land; instrument ratings: airplane; medical: class 3, valid medical--w/ waivers/lim; last flight review August 24, 2001; seat: left; flight hours: 5,647 total, 3,707 in this make and model, 5,516 as pilot in command, 20 in the last 90 days, 14 in the last 30 days, 6 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: calm - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 55 °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 20020930026799A](https://openairdocs.org/incident/20020930026799A), Sep 30, 2002: Mooney M20J, Oakley, ID, Substantial damage. (-23) On September 30, 2002, at approximately 16:30 MDT, while in cruise flight from grand junction Colorado to boise Idaho, the engine lost oil pressure. The… 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.