ASN Wikibase Occurrence # 314497
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| Date: | Saturday 21 May 2011 |
| Time: | 16:00 LT |
| Type: |  de Havilland Canada DHC-6 Twin Otter 300 |
| Owner/operator: | Grand Canyon Airlines |
| Registration: | N178GC |
| MSN: | 697 |
| Year of manufacture: | 1980 |
| Engine model: | Pratt & Whitney Canada PT6A-27 |
| Fatalities: | Fatalities: 0 / Occupants: 17 |
| Aircraft damage: | None |
| Category: | Serious incident |
| Location: | Peach Springs, Arizona -
 United States of America
|
| Phase: | En route |
| Nature: | Passenger - Scheduled |
| Departure airport: | Boulder City Municipal Airport, NV (BLD/KBVU) |
| Boulder City Municipal Airport, NV (BLD/KBVU) | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
A DHC-6-300, registration number N178GC, operated by Grand Canyon Airlines, experienced an uncontained engine failure in the left engine (No. 1) while flying at an altitude of 5,500 feet mean sea level (MSL), about 3 miles northeast of Grand Canyon West Airport (1G4). The pilot made a safe and uneventful landing at the Grand Canyon West Airport. All 17 persons on board including the crew were uninjured.
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.
Probable Cause: 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.
Accident investigation:
 |
|
Sources:
NTSB ENG11IA032
History of this aircraft
Other occurrences involving this aircraft
| 20 February 2015 | TI-AZD | Nature Air | 0 | Juan Santamaría Intl. San José, Costa Rica |  |
min |
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 02-Jun-2023 17:54 | ASN Update Bot | Added |
| 04-Jun-2023 05:40 | harro | Updated |
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