Sunday, July 7, 2019

Loss of Engine Power (Total): Beech A36 Bonanza, N36LP, accident occurred May 04, 2018 in Shullsburg, Lafayette County, Wisconsin

The National Transportation Safety Board did not travel to the scene of this accident.

Additional Participating Entities:

Federal Aviation Administration / Flight Standards District Office; Milwaukee, Wisconsin 
Continental Motors Inc; Mobile, Alabama

Aviation Accident Final Report - National Transportation Safety Board: https://app.ntsb.gov/pdf


Investigation Docket - National Transportation Safety Board: https://dms.ntsb.gov/pubdms


Aviation Accident Data Summary - National Transportation Safety Board: https://app.ntsb.gov/pdf
 
http://registry.faa.gov/N36LP


Location: Shullsburg, WI
Accident Number: CEN18LA159
Date & Time: 05/04/2018, 1930 CDT
Registration: N36LP
Aircraft: BEECH A36
Aircraft Damage: Substantial
Defining Event: Loss of engine power (total)
Injuries: 1 None
Flight Conducted Under: Part 91: General Aviation - Personal 

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.

Probable Cause and Findings

The National Transportation Safety Board determines the probable cause(s) of this accident to be: 
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

Aircraft
Recip engine power section - Failure (Cause)
Recip engine power section - Incorrect service/maintenance (Cause)

Personnel issues
Scheduled/routine maintenance - Maintenance personnel (Cause)

Factual Information

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. 

History of Flight

Enroute-cruise
Loss of engine power (total) (Defining event)

Emergency descent
Off-field or emergency landing

Pilot Information

Certificate: Flight Instructor; Commercial
Age: 49, Male
Airplane Rating(s): Multi-engine Land; Single-engine Land
Seat Occupied: Left
Other Aircraft Rating(s): None
Restraint Used: 3-point
Instrument Rating(s): Airplane
Second Pilot Present: No
Instructor Rating(s): Airplane Multi-engine; Airplane Single-engine; Instrument Airplane
Toxicology Performed: No
Medical Certification: Class 1 Without Waivers/Limitations
Last FAA Medical Exam: 02/21/2018
Occupational Pilot: Yes
Last Flight Review or Equivalent: 02/02/2018
Flight Time:  994 hours (Total, all aircraft), 281 hours (Total, this make and model), 942 hours (Pilot In Command, all aircraft), 299 hours (Last 90 days, all aircraft), 111 hours (Last 30 days, all aircraft), 8 hours (Last 24 hours, all aircraft) 

Aircraft and Owner/Operator Information

Aircraft Make: BEECH
Registration: N36LP
Model/Series: A36 UNDESIGNATED
Aircraft Category: Airplane
Year of Manufacture: 1976
Amateur Built: No
Airworthiness Certificate: Utility
Serial Number: E-894
Landing Gear Type: Retractable - Tricycle
Seats: 6
Date/Type of Last Inspection: 08/19/2017, Annual
Certified Max Gross Wt.: 3651 lbs
Time Since Last Inspection: 10 Hours
Engines: 1 Reciprocating
Airframe Total Time: 7951.8 Hours at time of accident
Engine Manufacturer: Continental
ELT: C91  installed, activated, aided in locating accident
Engine Model/Series: IO-520-BB
Registered Owner: On file
Rated Power: 285 hp
Operator: On file
Operating Certificate(s) Held: None 

Meteorological Information and Flight Plan

Conditions at Accident Site: Visual Conditions
Condition of Light: Day
Observation Facility, Elevation: PVB
Distance from Accident Site: 12 Nautical Miles
Observation Time: 1855 CDT
Direction from Accident Site: 307°
Lowest Cloud Condition: Clear
Visibility:  10 Miles
Lowest Ceiling: None
Visibility (RVR):
Wind Speed/Gusts: 9 knots /
Turbulence Type Forecast/Actual: /
Wind Direction: 290°
Turbulence Severity Forecast/Actual: /
Altimeter Setting: 29.98 inches Hg
Temperature/Dew Point: 22°C / 8°C
Precipitation and Obscuration: No Obscuration; No Precipitation
Departure Point: Okmulgee, OK (OKM)
Type of Flight Plan Filed: IFR
Destination: Plainfield, WI (WN09)
Type of Clearance: IFR
Departure Time: 1530 CDT
Type of Airspace: Class E; Class G 

Wreckage and Impact Information

Crew Injuries: 1 None
Aircraft Damage: Substantial
Passenger Injuries: N/A
Aircraft Fire: None
Ground Injuries: N/A
Aircraft Explosion: None
Total Injuries: 1 None
Latitude, Longitude: 42.573056, -90.232222 (est)

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