No fatalities

2009-09-15: Cessna 208A Caravan (N336DN) — North American Flight Services — Sheffield, United States of America

Sheffield, United States of AmericaFlight

On September 15, 2009, a Cessna 208A Caravan (registration N336DN) operated by North American Flight Services was involved in an aviation accident near Sheffield, United States of America in flight. No fatalities were reported. Investigators recorded the probable cause as: A total loss of engine power due to a failure of the 1st stage sun gear output splines for unknown reasons, which resulted in a power turbine overspeed condition, with subsequent blade distress/release. This summary draws on records from the Bureau of Aircraft Accidents Archives (B3A).

Sourcesthe Bureau of Aircraft Accidents Archives (B3A)Primary reportUpdated 1781196567Data APIEditorial standards

A climb at 8,500 ft ended with a forced landing after a catastrophic engine failure. The aircraft struck a tree, separated a wing, and burned. All six occupants evacuated without injury.

Event Summary

While climbing through 8,500 feet, the airplane experienced a catastrophic engine failure. The pilot declared an emergency and conducted a forced landing to a field. During the landing roll, the right wing struck a tree and separated from the airframe. The airplane subsequently became fully engulfed in fire, which consumed the majority of the structure. All six occupants—the pilot and five passengers—exited the aircraft without injury. The passengers were employees of an industrial services company returning from a job site with hazardous materials used for blasting operations.

Aircraft and Engine Details

The airplane was equipped with a turbine engine. At the time of the accident, the engine had accumulated approximately 7,620 hours since new and 65 hours since its last overhaul, which had been performed about 19 months earlier.

Post-Accident Examination

Examination of the engine revealed impact damage to the interior of the exhaust duct. The duct also contained portions of a fractured power turbine blade. Further disassembly showed damage consistent with a distressed first-stage sun gear, along with associated damage to the compressor turbine and power turbine. The sun gear’s output splines exhibited extensive damage, preventing determination of the original cause of deterioration. Investigators noted that the sun gear had been previously removed from another engine about seven years prior due to "spalled gear teeth"; its condition at the time of installation on the accident engine could not be established. The fire consumed the majority of the airframe, leaving only fragments for examination.

Probable cause

A total loss of engine power due to a failure of the 1st stage sun gear output splines for unknown reasons, which resulted in a power turbine overspeed condition, with subsequent blade distress/release.