# NTSB DEN04LA136: Cessna 182, N2725G, Gillette, WY, September 6, 2004 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: September 6, 2004, 17:45 local (23:45 UTC) - Place: Gillette, WY - Coordinates: 44.174999, -105.635002 - Nearby events: https://openairdocs.org/map.md?lat=44.1750&lon=-105.6350&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report July 7, 2005 - Report: Approved by Office Director - Parties: Teledyne Continental Motors, Casper Flight Standards Field Office - NTSB case key (mKey): 60062 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=DEN04LA136 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/60062/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=60062 - Page: https://openairdocs.org/ntsb/DEN04LA136 ## Probable cause improper engine overhaul performed by the mechanic which resulted in the fractured exhaust valve and subsequent partial loss of engine power. Contributing to the accident was the lack of suitable terrain for a forced landing. ## 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,piston - fractured - engine assembly,valve,exhaust - fractured (cause) - maintenance,installation - not performed, other maintenance personnel - maintenance,overhaul - improper, other maintenance personnel (cause) - Forced landing, descent - emergency - emergency procedure - initiated, pilot in command - On ground/water encounter with terrain/water, emergency landing - terrain condition - none suitable (contributing factor) - terrain condition - rough/uneven - terrain condition - ground ## Analysis The pilot stated he was in cruise flight when the engine began to run rough. He heard sounds of grinding metal and shortly thereafter, the "engine began to shake violently." The pilot shut the engine down and attempted a forced landing to a plowed field. During the forced landing, the nose wheel impacted a small rut, separating the nose landing gear tire from the nose landing gear assembly. The airplane nosed over, causing substantial damage. An internal examination of the engine showed the number 3 piston, piston rings, and tension springs, and the number 3 exhaust valve head had fragmented into numerous pieces. These pieces were located in the oil sump. The inside of the crankcase halves showed impact damage in the areas aft of the number 4 piston and forward of the number 3 piston. The top inside of the number 3 cylinder head showed numerous impact marks including a 7/8 inch long, 1/8 inch wide and 1/8 inch deep indentation at one of the spark plug openings, and a 1/2 inch long, 1/8 inch wide, and 1/8 inch deep indentation at the area of the exhaust valve seat which were consistent with a valve head edge impact. The number 3 exhaust valve seat was not present. The number 3 exhaust valve stem was removed and examined. Fractures observed on the valve stem were consistent with an overload failure. The number 3 exhaust valve guide showed elongating distortion. An examination of the crankshaft, camshaft, other cylinders, pistons, valves, and valve springs showed no pre-existing failures. No evidence of the number 3 exhaust valve seat was found among the fractured pieces in the engine. An examination of the remaining airplane systems revealed no anomalies. ## Factual narrative On September 6, 2004, approximately 1745 mountain daylight time, a Cessna 182, N2725G, piloted by a private pilot, was substantially damaged during a forced landing 8 nautical miles southwest of Gillette, Wyoming. Visual meteorological conditions prevailed at the time of the accident. The personal flight was being conducted under the provisions of Title 14 CFR Part 91 without a flight plan. The pilot reported no injuries. The cross-country flight originated at Casper, Wyoming, at 1700. According to the accident report submitted by the pilot, he was in cruise flight when the engine began to run rough. In a telephone conversation with the pilot, he stated he heard sounds of grinding metal. Shortly thereafter, the "engine began to shake violently." The pilot shut the engine down and attempted a forced landing to a plowed field. During the forced landing, the nose wheel impacted a small rut, separating the nose landing gear tire from the nose landing gear assembly. The airplane nosed over wrinkling the fuselage, crushing the vertical stabilizer and bending both wings. The engine was examined at Mobile, Alabama, on February 22, 2005. An external examination showed no apparent damage. The top and rear seams of the crankcase and the accessory drive housing showed evidence of oil leakage. The crankcase seam at the front portion of the engine, just below the propeller flange gasket, also showed evidence of previous oil leakage. The gasket area between the front crankcase and the front of the oil sump showed oil leakage. Oil covered the bottom of the oil sump. An internal examination of the engine showed the number 3 piston, piston rings, and tension springs, and the number 3 exhaust valve head had fragmented into numerous pieces. These pieces were located in the oil sump. Approximately 2 tablespoons of oil was recovered from the sump. The inside of the crankcase halves showed impact damage in the areas aft of the number 4 piston and forward of the number 3 piston. The inside walls of the crankcase were significantly blackened. The top inside of the number 3 cylinder head showed numerous impact marks including a 7/8 inch long, 1/8 inch wide and 1/8 inch deep indentation at one of the spark plug openings, and a 1/2 inch long, 1/8 inch wide, and 1/8 inch deep indentation at the area of the exhaust valve seat which were consistent with a valve head edge impact. The number 3 exhaust valve seat was not present. The number 3 exhaust valve stem was removed and examined. Fractures observed on the valve stem were consistent with overload failure. The number 3 exhaust valve guide was elongated. An examination of the crankshaft, camshaft, other cylinders, pistons, valves, and valve springs showed no pre-existing failures. The rocker box housings, rockers, and springs, were oil stained. No evidence of the number 3 exhaust valve seat was found among the fractured pieces in the engine. The left and right magnetos were bench-tested. Both magnetos' leads consistently fired within the range of 300 to 3,000 rpm. According to maintenance records, the engine had accumulated approximately 200 hours since the annual inspection when the accident occurred. Previous to the annual inspection, the airplane had not been flown within the previous 10 years. An examination of the remaining airplane systems, conducted by the FAA, revealed no anomalies. ## Aircraft - Registration: [N2725G](https://openairdocs.org/deregistered/N2725G-2012-08-27), registration cancelled 2012-08-27, S/N 52025, built 1959 (OpenAirDocs) - Reported make and model: Cessna 182 - Registry model: [Cessna 182B](https://openairdocs.org/model/cessna-182b) (registry code 2072706) (OpenAirDocs) - Registry engine: [Continental O-470 series](https://openairdocs.org/engine/continental-o-470-series) (registry code 17026, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 52025 - Airframe hours: 3371.8 - Engines: Continental O-479-L 230 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Airworthiness certificate: Standard, Normal - Last inspection: Annual, March 22, 2004, 200 hours before - Departed: CPR, Casper, WY - Destination: GCC, Gillette, WY ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 47; injuries: none; private; airplane ratings: single-engine land; medical: class 3, valid medical--no waivers/lim.; last flight review August 1, 2004; seat: left; flight hours: 1,547 total, 1,547 in this make and model, 122 in the last 90 days, 45 in the last 30 days, 5 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 20° at 12 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 70 °F, dew point 36 °F - Altimeter: 30.20 inHg - Observed at: GCC, 8 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 20040906020939A](https://openairdocs.org/incident/20040906020939A), Sep 6, 2004: Cessna 182B, Gillette, WY, Substantial damage. (-23) While in cruise from casper, WY to Gillette, WY, the engine started to run rough. The pilot turned the magnetos off due to the engine making a very loud… ## Docket (2 files) The files NTSB released with the investigation on April 26, 2005, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=60062. 341 KB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 285 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40422211&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.PDF - Statement of Party Representatives to NTSB Investigation (item 2, .PDF, 56 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40422212&FileExtension=.PDF&FileName=Statement%20of%20Party%20Representatives%20to%20NTSB%20Investigation-Redacted.PDF 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.