Dehavilland DHC-6-300 incident near Peach Springs, Arizona, May 21, 2011
On May 21, 2011 at about 11:00 pm local time, a Dehavilland DHC-6-300, registered N178GC, was involved in an incident during enroute (cruise) near Peach Springs, Arizona (Boulder City Muni airport). It was flown under charter and air-taxi rules (Part 135). No one was hurt; 17 people were on board or involved. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
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.
Source: NTSB aviation accident database, copy made November 2, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- May 21, 2011 · about 11:00 pm local time · cases in 2011
- Place
- Peach Springs, Arizona · Boulder City Muni · cases near this airport · map
- Type
- Incident
- Injuries
- No one was hurt; 17 people were on board or involved.
- Weather
- visual conditions (good weather)
- Aircraft
- Dehavilland DHC-6-300 · all DHC-6-300s on the register
- Registration
- N178GC · registry record · serial 697
- Damage
- Not recorded
- Flight
- Flight · charter and air-taxi rules (Part 135)
The NTSB's narrative final · quoted from the NTSB record
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.
The complete narrative as the NTSB published it. The NTSB's docket holds the report as a PDF and any photographs, statements and other documents from the investigation.
The factual record from the NTSB's investigation tables, in plain English
What happened, in order
- Uncontained engine failure during enroute (cruise) defining event
The NTSB's findings
- cause Aircraft › Aircraft power plant › Engine (turbine/turboprop) › Reduction gear and shaft › Failure other cases naming the engine
- cause Organizational issues › Development › Manufacture/production › Equipment manufacture › Manufacturer
The aircraft
- Seats: 22
- Landing gear: fixed
- Engine 1: Pratt and Whitney Canada PT6A-27 (turboprop); 0 hours total
- Engine 2: (turboprop); 0 hours total
- Operator: Cortez Fisher LLC
The flight
- Departed from: IGM Peach Springs AZ
- Destination: IGM Peach Springs AZ
- Flight plan: not recorded
Weather at the time
- Light: daylight
- Temperature: 0°F (-18°C), dew point 0°F (-18°C)
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Flight crew | 2 | |||
| Passengers | 15 |
Documents from the investigation the NTSB's docket: the evidence folder behind the report
5 documents, released by the NTSB on October 9, 2020. View them here, or download them; the NTSB redacts some personal details before release, and this site shows the NTSB's own titles rather than its file names.
| # | Document | What it is | |
|---|---|---|---|
| 1 | Powerplants Factual Report | PDF, 31 pages | View Download |
| 2 | Materials Laboratory Factual Report 12-100 | PDF, 14 pages | View Download |
| 3 | Materials Laboratory Factual Report 12-101 | PDF, 5 pages | View Download |
| 4 | Materials Laboratory Factual Report 12-102 | PDF, 4 pages | View Download |
| 5 | Materials Laboratory Factual Report 12-103 | PDF, 5 pages | View Download |
The same docket at the NTSB · documents without a copy here are fetched from the NTSB when you open them.
Connections how this case links to the rest of the register
- N178GC on the register today · the tail number may have moved to another aircraft since
- Dehavilland DHC-6 114 registered today · the model family and its accident history
- Dehavilland 861 aircraft on the register
- Engine: Pratt and Whitney Canada PT6A-27 31 aircraft carry this series today · as the NTSB recorded it
- Engine: · as the NTSB recorded it
- Boulder City Municipal · nearest airport
- Kingman Airport · departed from
- Accidents and incidents in Arizona 2,985 since 1982 · 467 in the last ten years
- Arizona 8,436 aircraft registered
The whole map of how records connect · these connections as data: /graph/accident/ENG11IA032.json.
The bigger picture in Aviation Analytics: accidents over time since 1982, by model, by phase of flight and conditions, by place and on the map.
Everything on this page comes from the NTSB's public records. The narrative, probable cause and findings are the NTSB's own words; the coded tables behind the report are written out in plain English, with pilots' ages, home towns and medical details left out. The documents and photographs are the NTSB's docket, shown as the NTSB released them. This site's own text does not name anyone involved, its policy at this time. A preliminary report can change; the final report usually follows one to two years later, and the page is refreshed when it does.