# NTSB CEN18LA159: Beech A36, N36LP, Shullsburg, WI, May 5, 2018 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: May 4, 2018, 19:30 local (May 5, 2018, 00:30 UTC) - Place: Shullsburg, WI - Coordinates: 42.573055, -90.232223 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=42.5731&lon=-90.2322&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Defining event: [Enroute-cruise: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report May 29, 2019 - Report: Approved by Office Director - NTSB office: Central Region - Parties: Continental Motors Inc., FAA Flight Standards - NTSB case key (mKey): 97174 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN18LA159 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/97174/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=97174 - Page: https://openairdocs.org/ntsb/CEN18LA159 ## Probable cause A catastrophic engine failure due to improper torque on the engine through-bolt nuts, which resulted in relative movement between the crankcase halves, damage to a main journal bearing, and a loss of oil lubrication. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Engine (reciprocating): recip engine power section](https://openairdocs.org/ntsb-findings/01058520): Aircraft › Aircraft power plant · Failure (probable cause); cases with it: [Beech A36, 6 cases](https://openairdocs.org/ntsb-findings/01058520/cases.md?model=1151604), [All aircraft, 233 cases](https://openairdocs.org/ntsb-findings/01058520/cases.md) - [Engine (reciprocating): recip engine power section](https://openairdocs.org/ntsb-findings/01058520): Aircraft › Aircraft power plant · Incorrect service/maintenance (probable cause); cases with it: [Beech A36, 6 cases](https://openairdocs.org/ntsb-findings/01058520/cases.md?model=1151604), [All aircraft, 233 cases](https://openairdocs.org/ntsb-findings/01058520/cases.md) - [Maintenance: scheduled/routine maintenance](https://openairdocs.org/ntsb-findings/02062010): Personnel issues › Task performance · Maintenance personnel (probable cause); cases with it: [Beech A36, 2 cases](https://openairdocs.org/ntsb-findings/02062010/cases.md?model=1151604), [All aircraft, 320 cases](https://openairdocs.org/ntsb-findings/02062010/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Enroute-cruise: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341) (defining event); cases with it: [Beech A36, 56 cases](https://openairdocs.org/ntsb-events/341/sequence.md?model=1151604), [All aircraft, 3,820 cases](https://openairdocs.org/ntsb-events/341/sequence.md) - [Emergency descent: Off-field or emergency landing](https://openairdocs.org/ntsb-events/440); cases with it: [Beech A36, 47 cases](https://openairdocs.org/ntsb-events/440/sequence.md?model=1151604), [All aircraft, 3,365 cases](https://openairdocs.org/ntsb-events/440/sequence.md) ## Analysis The commercial pilot reported that he heard an unusual noise from the engine during cruise flight and shortly afterward, the engine experienced a total loss of power. The pilot performed a forced landing to an open field. Visual examination of the engine revealed a hole in the crankcase. A teardown examination revealed fretting on the crankcase mating surfaces, shifting of the No. 2 main bearing within the journal support, thermal damage consistent with a loss of oil lubrication, and separation of the crankshaft. The observed fretting damage was consistent with relative movement of the crankcase halves during operation due to a lack of through-bolt torque. The main journal bearing damage, the separation of the crankshaft, and the crankcase damage were secondary and a result of the loss of lubrication. An engine overhaul was completed in about 11 years 5 months before the accident; about 849 flight hours had accumulated since the overhaul. Two cylinders were replaced 6 years before the accident, and one cylinder was replaced during the most recent annual inspection about 9 months before the accident. It is likely that improper torque of the through-bolt nuts was applied during one of the cylinder replacement events, though it could not be determined which event. ## Factual narrative On May 4, 2018, about 1930 central daylight time, a Beech A36 airplane, N36LP, was substantially damaged during a forced landing following a loss of engine power near Shullsburg, Wisconsin. The pilot was not injured. The airplane was registered to and operated by a private individual as a Title 14 Code of Federal Regulations Part 91 personal flight. Visual meteorological conditions prevailed, and the flight was operating on an instrument flight rules flight plan. The flight originated from the Okmulgee Regional Airport (OKM), Okmulgee, Oklahoma, about 1537. The intended destination was Bucky's Airport (WN09), Plainfield, Wisconsin.The pilot reported that the airplane was in cruise flight at 7,000 ft mean sea level when he heard an unusual noise from the engine. Shortly afterward, the engine lost power and he executed a forced landing to an open field. He recalled thinking that oil may have escaped from the engine because he observed smoke. The airplane sustained substantial damage to the lower fuselage/nose landing gear wheel well structure. A postaccident engine examination revealed a hole in the crankcase above the no. 1 cylinder. A teardown examination revealed wear on the mating crankcase surfaces consistent with fretting of the case halves. The no. 2 main journal bearing was shifted within the bearing support, the lock tab was elongated, and the bearing was extruded. Bearing fragments were recovered from the oil sump. The crankshaft was separated between the no. 2 main bearing journal and the no. 2 connecting rod journal. The crankshaft was discolored adjacent to the separation consistent with thermal damage due to a lack of oil lubrication. The remaining portions of the crankshaft displayed normal operating and lubrication signatures. The no. 2 connecting rod bearing exhibited damage consistent with lubrication distress. The oil pump housing and impellers exhibited scoring consistent with hard particle passage. Airplane maintenance records indicated that an engine overhaul was completed in November 2006. The no. 2 and no. 4 cylinders were replaced in June 2012. The most recent annual inspection was completed in August 2017. The no. 5 cylinder was replaced during the annual inspection. At the accident site, the airplane recording hour (Hobbs) meter and tachometer indicated 4,698.4 hours and 7.951.79 hours, respectively. At the time of the accident, the engine had accumulated 848.9 hours since overhaul and 9.8 hours since the annual inspection. The time between overhaul (TBO) interval recommended by the engine manufacturer was 1,700 hours or 12 years, whichever came first. In October 2016, the NTSB issued a safety alert regarding improper torque of engine fasteners during maintenance activities. ## Aircraft - Registration: [N36LP](https://openairdocs.org/aircraft/N36LP), registered now, S/N E-894, built 1976 (OpenAirDocs) - Reported make and model: BEECH A36 (UNDESIGNAT) - Registry model: [Beech A36](https://openairdocs.org/model/beech-a36) (registry code 1151604) (OpenAirDocs) - Registry engine: [Continental IO-520 series](https://openairdocs.org/engine/continental-io-520-series) (registry code 17032, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: E-894 - Year built: 1976 - Airframe hours: 7951.8 - Engines: Continental IO-520-BB 285 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Airworthiness certificate: Standard, Utility - Last inspection: Annual, August 19, 2017, 10 hours before - Departed: OKM, Okmulgee, OK - Destination: WN09, Plainfield, WI - Flight plan: IFR - Equipment: Stall warning system, ADS-B, Auto-pilot, Electronic flight bag or handheld device ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 49; injuries: none; commercial, flight instructor; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 1, without waivers/limitations; last flight review February 2, 2018; seat: left; restraint: 3-point; flight hours: 994 total, 281 in this make and model, 942 as pilot in command, 299 in the last 90 days, 111 in the last 30 days, 8 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 290° at 9 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 72 °F, dew point 46 °F - Altimeter: 29.97 inHg - Observed at: PVB, 12 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 20180504004629A](https://openairdocs.org/incident/20180504004629A), May 4, 2018: Beech A36, Shullsburg, WI, Substantial damage. Airplane lost all engine power and pilot saw smoke coming from the engine Cowling and entering the cabin. He declared an emergency and asked air Traffic… ## Docket (4 files) The files NTSB released with the investigation on September 12, 2018, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=97174. 21.0 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 10.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40466579&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Master.PDF - Engine Examination Report w/photos (item 2, .PDF, 6.0 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40466580&FileExtension=.PDF&FileName=Engine%20Examination%20Report%20w%2Fphotos-Master.PDF - Maintenance Records (item 3, .PDF, 4.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40466581&FileExtension=.PDF&FileName=Maintenance%20Records-Master.PDF - NTSB Safety Alert - Take Time to Torque (item 4, .PDF, 462 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40466582&FileExtension=.PDF&FileName=NTSB%20Safety%20Alert%20-%20Take%20Time%20to%20Torque-Master.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.