Cessna U206 N8030Z

Summary

On 21 September 2007 at about 23:00 local time, a Cessna U206 registered N8030Z, operated by Vernon Kingsford, was involved in an accident near McGrath, Alaska, United States. 2 people were on board and 2 had minor injuries. The aircraft was substantially damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

21 September 2007 at 23:00

Classification

Accident

Location

McGrath, Alaska, United States

Coordinates

Not recorded

Aircraft

Cessna U206

Registration

N8030Z

Category

Airplane

Engines

1

Operator

Vernon Kingsford

Operating rule

Part 91: General Aviation

Purpose of flight

Positioning

Phase of flight

Not recorded

Route

Galena → Moose Pass

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

ANC07LA104

2 people had minor injuries.

A separation of the engine connecting rod and engine cylinder due to the loss of a connecting rod nut that was stripped from the rod bolt.

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

Read the full NTSB narrative

The airline transport pilot, who was the company owner, and an aviation mechanic, was in cruise flight in a float-equipped airplane when he noticed an engine vibration, followed by a loud bang, and sudden stoppage of the propeller. The pilot described the prop as having suddenly stopped in a feathered position, without windmilling or slowing down. He selected an emergency landing area on a mountain ridge. Just prior to touchdown, the airplane collided with several trees, and nosed over. The pilot had requested and was granted a 100 hour extension beyond the engine overhaul interval of 1,700 hours by his FAA principle maintenance inspector (PMI). The pilot performed 25 hour oil changes and borescoped the engine pursuant to the granting of the 100 hour extension. The number 2 and 6 cylinders were changed about 173.6 hours before the accident, and the number 6 cylinder was changed again, about 60 hours before the accident. At the time of the accident, the engine had about 1,735 hours. Postaccident examination of the engine revealed that one of the number 4 cylinder rod cap bolts was bent 90 degrees, and the bolt threads had been stripped of its retaining nut. The loss of the nut allowed the rod cap to straighten, and then break the opposite cap bolt at its base. The entire number 4 piston and connecting rod departed the engine, breaking the number 4 cylinder away from the engine case. The propeller blade pitch change links within the hub were broken in tension, which the propeller manufacturer indicated was consistent with the blades contacting the ground or striking an object during the accident sequence.

Quoted verbatim from the NTSB record.