Cessna 207 N6312H

Summary

On 10 January 1999 at about 17:30 local time, a Cessna 207 registered N6312H was involved in an accident near Quinhagak, Alaska, United States. One person was on board and one 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

10 January 1999 at 17:30

Classification

Accident

Location

Quinhagak, Alaska, United States

Nearest airport

Quinhagak (AQH)

Coordinates

59.7391, -161.8898

Aircraft

Cessna 207

Registration

N6312H

Category

Airplane

Engines

1

Operator

Not recorded

Operating rule

Part 135: Air Taxi & Commuter

Purpose of flight

Unknown

Phase of flight

Not recorded

Route

Bethel → Unknown

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

ANC99FA021

1 person had minor injuries.

Loss of engine power due to fracture of the engine crankshaft, and the manufacturer's improper manufacturing procedure during engine assembly. Factors associated with the accident were the manufacturer's inadequate quality control standards, trees, and snow-covered terrain.

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

Read the full NTSB narrative

The certificated commercial pilot reported that during the initial descent to land, the engine began to run rough and lose power. He noted that the roughness improved momentarily, followed by a severe engine vibration, and complete loss of engine power. The pilot selected a forced landing area on snow and tree-covered terrain. The airplane sustained substantial damage to the landing gear, fuselage, and wings. Postaccident investigation discovered that the engine crankshaft had sustained a complete fracture of the #2 cheek. A subsequent investigation revealed that on some crankshafts, a crack in the nitride layer that originated from a shallow tool mark, would in some cases ultimately lead to the fatigue failure of the crankshaft cheek. On April 22, 1999, the FAA issued an emergency airworthiness directive (AD) requiring that all TCM 470, 520, and 550 engine crankshafts manufactured in 1998, with less than 300 hours in service, will be inspected in accordance with the TCM critical service bulletin (CSB) within 10 hours of operation.

Quoted verbatim from the NTSB record.