Delta Air Lines Flight 275
Boeing 747-451 · Incident: uncontained engine failure during initial climb
From Detroit Metropolitan Wayne County Airport (DTW) to Narita International Airport (NRT)
Event
- NTSB case
- ENG12IA003
- Event typeAccident: someone killed or seriously injured, or the aircraft substantially damaged (NTSB definition). Incident: an occurrence that affected or could have affected safety, short of that. Glossary
- Incident
- InvestigationHow far the investigation had got when the record was published: preliminary, ongoing, final or completed. Unknown where the source does not say. Glossary
- Completed
- API-reported fatalities
- 0 · all aircraft and ground
- Ground fatalities
- Unknown
- OperationWhat kind of flying it was, grouped by the rules it flew under: airline (US Part 121), air taxi and commuter (Part 135), general aviation (Part 91 and similar), military or government. Glossary
- Airline
- WeatherVisual meteorological conditions (VMC): good enough to fly by looking outside. Instrument conditions (IMC): cloud or low visibility, flying by instruments. Glossary
- Not recorded
Boeing 747-451
- Aircraft type
- Boeing 747
- Category
- Airplane
- RegistrationThe aircraft's tail number, such as N12345 or G-ABCD. Registrations are reissued, so the same one years apart can be a different aircraft. Glossary
- N661US
- Operator
- Delta Air Lines
- Onboard fatalities
- Unknown
- Route
- From Detroit Metropolitan Wayne County Airport (DTW), Detroit, MITo Narita International Airport (NRT), Narita, Tokyo
- Aircraft age
- Not recorded
- Flight rulesThe regulations the flight operated under: in the US, Part 91 (general aviation), Part 121 (airlines), Part 135 (air taxi and commuter) and others; for flights abroad, the NTSB's coarser commercial or non-commercial code. Glossary
- Part 121: Air Carrier
- Phase of flightThe stage of the flight when things started to go wrong: standing, taxi, takeoff, initial climb, en route, maneuvering, approach or landing. Glossary
- Initial climb
- Defining eventThe single coded event the NTSB judges best describes what happened (records from 2008 on). Older records name the first occurrence in the sequence instead. Glossary
- Uncontained engine failure
- DamageDestroyed: beyond practical repair. Substantial: damage that affects the structure, performance or handling and normally needs major repair. Minor: less than that. Glossary
- Minor
Cause areas
- Aircraft › Aircraft power plant
Approximate · Coordinates from the NTSB case API, which marks them as estimated or does not say; no uncertainty radius is established.
NTSB narrative
On October 23, 2011, 1600 eastern daylight time, a Boeing 747-451, registration number N661US, powered by four Pratt & Whitney PW4056 turbofan engines, experienced a left inboard engine (No. 2) low pressure turbine failure after takeoff from Detroit Metro Wayne Country International Airport (DTW), Detroit, Michigan. According to the flight crew statements, a large compressor stall and a muffled explosion were felt, followed by the No. 2 engine rollback and No. 2 engine fire warning indication. The flight crew performed an air turnback and made a successful three-engine landing at DTW. No injuries were reported.
Examination of the airplane revealed minor impact damage to the left wing, flaps, ailerons, and horizontal stabilizer. Initial examination of the engine revealed evidence of an undercowl fire, three burn-through holes on the No. 2 engine outboard core cowl, numerous exit hole penetrations in the rear turbine case, and a punctured No. 4 bearing compartment oil pressure supply line. Disassembly of the No. 2 engine revealed no damage upstream of the stage 3 low pressure turbine (LPT); one stage 3 LPT outer transition duct segment and two stage 3 LPT vane clusters were missing from their normally installed position, and extensive damage downstream of the stage 3 LPT vane clusters was found. The stage 3 LPT outer transition duct segments were approved but were an older configuration utilizing the riveted rear seal plate design that was prone to failure and had been superceded by a preferred design that incorporated an integral rear seal.
Comparing the airplane and engine damage to the requirements for engine debris containment and safety analysis at the time the engine was certificated revealed that the engine did not comply with the containment requirements set forth in Parts 33.19 and 33.75.
The undercowl fire was due to a failure of the rear riveted seal plates of the missing stage 3 outer transition duct segment that allowed hot gas path air under the duct segment, causing it to thermally distort and disengage from the rear turbine case. Once disengaged from the rear turbine case, the stage 3 outer transition duct segment released into the gaspath where it fractured all of the stage 3 LPT blades, which propelled blade fragments through the rear turbine case that punctured the No. 4 bearing oil pressure supply tube. The atomizing oil mist from the No. 4 bearing oil pressure supply tube ignited when it contacted the hot engine case, which created the undercowl fire.
Probable cause
The penetration of turbine blade fragments through the rear turbine case, which punctured the No. 4 bearing oil pressure supply tube, allowing misted oil to contact the hot engine case and ignite the undercowl fire.
Contributing to the incident was the installation of approved (but not preferred) stage 3 low pressure turbine outer transition duct segments with the riveted rear seal configuration and the failure of the engine design to comply with the engine debris containment requirements of 14 Code of Federal Regulations 33.13 and 33.75.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record ENG12IA003
- Event ID
- 20111024X74546
- Case number
- ENG12IA003
- Dataset
- full-current
- Source SHA-256
- 5cf380f0061817c0331a6b2d8cc7e0ee3a79bea469a1001dc5c10e56f35f5ab3
Source notes (4)
- Unreviewed is an editorial label, not an investigation status. API-sourced is not report-checked or human-reviewed. Explicit event totals are used without summing aircraft injury tables; onboard allocation is withheld. Unknown values remain unknown. The operation category is mapped from the NTSB-reported FAR part and has not been reviewed.
- Filled from the NTSB case API where the bulk record had no value: investigation status, coordinates. Values present in the bulk record are kept.
- The date is the local date, which is the same as the UTC date the NTSB stores.
- API snapshot SHA-256: 9fbb163340f48b26c5f450c6399634337a44131a63b88e6a428dd8a8d68665a0; retrieved 2026-09-15T16:52:53.738Z.