Boeing 747-451 incident near Detroit, Michigan, October 23, 2011
On October 23, 2011 at about 8:00 pm local time, a Boeing 747-451, registered N661US, suffered minor damage in an incident during initial climb near Detroit, Michigan (Detroit International Airport). It was flown under scheduled airline rules (Part 121). No one was hurt; 394 people were on board or involved.
The NTSB's probable cause their words, unchanged
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.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- October 23, 2011 · about 8:00 pm local time
- Place
- Detroit, Michigan · Detroit International Airport · map
- Type
- Incident
- Injuries
- No one was hurt; 394 people were on board or involved.
- Weather
- not recorded
- Aircraft
- Boeing 747-451 · all 747-451s on the register
- Registration
- N661US · registry record · serial 23719
- Damage
- Minor damage
- Flight
- Flight · scheduled airline rules (Part 121)
The NTSB's narrative final · quoted from the NTSB record
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.
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 initial climb defining event
The NTSB's findings
- Aircraft › Aircraft power plant › Power plant › Engine cowling system › Damaged/degraded
- Aircraft › Aircraft power plant › Power plant › Engine cowling system › Capability exceeded
- cause Aircraft › Aircraft power plant › Engine (turbine/turboprop) › Turbine section › Failure
- cause Aircraft › Aircraft power plant › Engine (turbine/turboprop) › Turbine section › Fatigue/wear/corrosion
- factor Aircraft › Aircraft power plant › Engine (turbine/turboprop) › Turbine section › Related maintenance info
- factor Aircraft › Aircraft power plant › Engine (turbine/turboprop) › Turbine section › Design
The aircraft
- Seats: 450
- Landing gear: fixed
- Engine 1: P&W PW4056 (turbojet); 0 hours total
- Engine 2: P&W PW4000 SER (turbojet); 0 hours total
- Engine 3: P&W PW4000 SER (turbojet); 0 hours total
- Engine 4: P&W PW4000 SER (turbojet); 0 hours total
- Operator: Delta Air Lines INC
The flight
- Departed from: DTW Detroit MI
- Destination: NRT Narita, Tokyo
- Flight plan: VFR
- A second pilot was aboard
Weather at the time
- Temperature: 0°F (-18°C), dew point 0°F (-18°C)
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Flight crew | 21 | |||
| Passengers | 373 |
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.
Other NTSB records under N661US the same tail number, which may have belonged to a different aircraft at the time
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.