Boeing 777 incident near Ugolny Airport, Ru, July 2, 2013
On July 2, 2013 at about 10:26 am local time, a Boeing 777, registered HL8275, was involved in an incident during enroute (cruise) near Ugolny Airport. It was flown under foreign airline rules (Part 129). The NTSB record does not give the injuries. The weather was conditions the NTSB did not record.
The NTSB's probable cause their words, unchanged
The failure of the transfer gearbox resulting from the fracture and separation of the radial gearshaft from fatigue cracking as a result of a combination of high residual tensile stresses produced by local decarburization during the manufacturing process coupled with the normal operating stresses.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- July 2, 2013 · about 10:26 am local time
- Place
- Ugolny Airport, Russia · map
- Type
- Incident
- Injuries
- The NTSB record does not give the injuries.
- Weather
- conditions the NTSB did not record
- Aircraft
- Boeing 777 300ER · all 777s on the register
- Registration
- HL8275 · no longer on the register · serial 37651
- Damage
- Not recorded
- Flight
- Flight · foreign airline rules (Part 129)
The NTSB's narrative final · quoted from the NTSB record
On July 2, 2013, a Korean Air Lines (KAL) Boeing 777-300ER, registration number HL8275, powered by two General Electric (GE) GE90-115B turbofan engines, experienced a No. 1 engine (left) in-flight shutdown (IFSD) while crossing the Bering Sea. The pilots diverted the airplane to Ugolny Airport (DYR), in Siberia, Russia where an uneventful single engine landing was made. The Korean ARAIB requested delegation of the investigation and the NTSB accepted responsibility for investigating this incident. Post landing examination of the No. 1 engine revealed that the radial gearshaft within the transfer gearbox housing was fractured. Metallurgical examination of the radial gearshaft found an 0.049-inch axial crack with striation features indicative of fatigue propagation and a morphology consistent with initial fatigue initiation occurring under a torsional and/or biaxial stress condition. This axial crack was considered the primary crack and the fracture origin area. Microhardness tests near the fracture origin revealed a reduction in near surface hardness (lower hardness values than required). GE concluded that the near surface low hardness was attributable to decarburization due to marginal (thin or detached) copper plating existing on the gearshaft surface during the hardening process. Through computer modeling and testing of the radial gearshaft, GE concluded that the initiation of the axial crack was likely the result of a combination of high residual tensile stresses produced by local decarburization coupled with the operating stresses experienced at the outer diameter surface. To address the manufacturing process deficiency, GE issued seven service bulletins to remove, inspect, and repair the suspect radial gearshafts. To expedite the removal of the suspect radial gearshafts, the Federal Aviation Administration issued three separate Airworthiness Directives (AD). According to GE, all affected radial gearshafts addressed by the various FAA ADs have been removed from service.
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
- Loss of engine power (total) during enroute (cruise) defining event
- Engine shutdown during enroute (cruise)
- Powerplant sys/comp malf/fail during enroute (cruise)
The NTSB's findings
- cause Aircraft › Aircraft power plant › Engine (turbine/turboprop) › Accessory drives › Failure
- factor Aircraft › Aircraft power plant › Engine (turbine/turboprop) › Accessory drives › Design
The aircraft
- Landing gear: fixed
- Engine: General Electric GE90-115B (turbofan); 0 hours total
- Operator: Korean Air Lines Company LTD
The flight
- Departed from: ORD Chicago IL
- Destination: ICN Seoul
- Flight plan: IFR
- A second pilot was aboard
Weather at the time
- Light: not reported
- Temperature: 0°F (-18°C), dew point 0°F (-18°C)
Documents from the investigation the NTSB's docket: the evidence folder behind the report
The docket, the folder of records gathered during an investigation (maintenance records, photographs, witness statements, examinations), has not been read from the NTSB for this case yet; the list appears here once it has. Open the docket at the NTSB.
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 never names anyone involved. A preliminary report can change; the final report usually follows one to two years later, and the page is refreshed when it does.