De Havilland DHC-6-300 N178GC

Summary

On 21 May 2011 at about 23:00 local time, a De Havilland DHC-6-300 registered N178GC, operated by Cortez Fisher LLC, was involved in an incident near Peach Springs, Arizona, United States. 17 people were on board and nobody was injured. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

21 May 2011 at 23:00

Classification

Incident

Location

Peach Springs, Arizona, United States

Nearest airport

Boulder City Muni (BVU)

Coordinates

35.1978, -114.0544

Aircraft

De Havilland DHC-6-300

Registration

N178GC

Category

Airplane

Engines

2

Operator

Cortez Fisher LLC

Operating rule

Part 135: Air Taxi & Commuter

Phase of flight

Not recorded

Route

Peach Springs → Peach Springs

Aircraft damage

Not recorded

Weather

VMC

Light

Day

NTSB number

ENG11IA032

Nobody was injured.

A quality control failure in the Sungear, Inc. manufacturing and quality control process allowed sungears with surface finishes of the root fillet radius of the spline that did not conform to the drawing specifications to be released. The surface finish defect caused fatigue cracks to initiate early in the part life.

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

Read the full NTSB narrative

The 1st stage planetary gear assembly was examined by the NTSB laboratory in Washington, DC, and a Materials Laboratory Factual Report, No. 12-100A was issued. A summary of the NTSB laboratory report findings is as follows: The average surface roughness of the root fillet radius surface of the sungear measured 22.68 micro-inches, which is coarser than 8 micro- inches, maximum, specified in the sungear engineering drawing. The fractures of the sungear was the result of a fatigue crack that emanated from the coarse surface finish within the root fillet radius portion of the sungear. The gears were not manufactured in accordance with the engineering drawing. A quality control failure in the Sungear, Inc. manufacturing and quality control process allowed sungears with incorrect surface finishes of the root fillet radius of the spline to be released.

Quoted verbatim from the NTSB record.