Beechcraft A36 N36LP

Summary

On 5 May 2018 at about 00:30 local time, a Beechcraft A36 registered N36LP was involved in an accident near Shullsburg, Wisconsin, United States. One person was on board and nobody was injured. The aircraft was substantially damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

5 May 2018 at 00:30

Classification

Accident

Location

Shullsburg, Wisconsin, United States

Coordinates

42.5731, -90.2322

Aircraft

Beechcraft A36

Registration

N36LP

Category

Airplane

Year built

1976

Engines

1

Operator

Not recorded

Operating rule

Part 91: General Aviation

Purpose of flight

Personal

Phase of flight

Not recorded

Route

Okmulgee → Plainfield

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

CEN18LA159

Nobody was injured.

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.

Quoted verbatim from the NTSB record. This site does not paraphrase or interpret it.

Read the full NTSB narrative

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.

Quoted verbatim from the NTSB record.