Cessna TU206 N206J

Summary

On 22 September 2014 at about 18:18 local time, a Cessna TU206 registered N206J, operated by 70 North LLC, was involved in an accident near Deadhorse, Alaska, United States. 4 people were 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

22 September 2014 at 18:18

Classification

Accident

Location

Deadhorse, Alaska, United States

Nearest airport

Badami (AK78)

Coordinates

70.3139, -148.0364

Aircraft

Cessna TU206

Registration

N206J

Category

Airplane

Year built

1967

Engines

1

Operator

70 North LLC

Operating rule

Part 135: Air Taxi & Commuter

Phase of flight

Not recorded

Route

Deadhorse → Deadhorse

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

ANC14LA085

Nobody was injured.

The application of insufficient torque to the engine cylinder through bolts during the replacement of the No. 1 cylinder, which resulted in the displacement of the No. 2 bearing, oil starvation, and a catastrophic engine failure.

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

Read the full NTSB narrative

The commercial pilot was conducting an on-demand air taxi commuter flight. The pilot reported that, during cruise flight, the engine began vibrating violently and lost power and that the throttle and propeller controls were unresponsive. The cockpit subsequently filled with smoke. The pilot conducted a forced landing to the nearest and driest tundra patch, during which the airplane nosed over. Examination of the engine revealed a large hole on the top left side of the crankcase near the No. 2 cylinder. The No. 2 connecting rod had separated from the crankshaft connecting rod journal. The No. 2 main bearing support mating surfaces exhibited fretting damage. The No. 2 main bearing had shed material from its forward side and had shifted. Measurements of the breakaway torque on the cylinder through bolts indicated that the torque on the Nos. 2 and 3 cylinder through bolts was below the engine manufacturer's specification. It is likely that the insufficient torque on the Nos. 2 and 3 cylinder through bolts resulted in the fretting damage and the No. 2 main bearing shifting and interrupted the oil flow to the No. 2 connecting rod bearing. The interruption of oil flow resulted in the bearing becoming starved of oil and overheating and the subsequent separation of the connecting rod from the crankshaft. A review of maintenance records revealed that the No. 1 cylinder was replaced about 403 flight hours before the accident, which would have required the removal and installation of hardware on the Nos. 1, 2, and 3 cylinder through bolts. It is likely that insufficient torque was applied to the through bolts during the replacement of the No. 1 cylinder.

Quoted verbatim from the NTSB record.