Incident Overview
On September 21, 2008, at 12:29 Japan Standard Time, Air India Flight 307, a Boeing 747-337 (registration VT-EPW), departed from Narita International Airport bound for Indira Gandhi International Airport in India. Approximately nine minutes after takeoff, while climbing through 15,700 feet about 10 kilometers south of Narita, a loud clunking noise was heard from the No. 3 engine. Concurrently, the N1 rotational speed indicator for that engine dropped sharply to 79.0 percent, indicating an abnormality.
Crew Actions and Return
The flight crew—comprising a Pilot in Command (PIC), a First Officer, and a Flight Engineer—responded by reducing the No. 3 engine thrust lever to idle. After leveling off at FL200, they attempted to advance the thrust lever again, but the N1 remained between 60 and 70 percent. The engine was subsequently shut down. The PIC decided to return to Narita due to the engine problem. At 12:57:58, the No. 3 engine was shut down, as recorded by the digital flight data recorder.
Fuel jettisoning was performed to reduce landing weight. The aircraft coordinated with air traffic control for radar guidance to a designated fuel jettisoning area. At 13:24:16, the crew reported completion of fuel jettisoning and began an approach. The aircraft landed normally on Runway 16R at 13:50. The crew did not declare an emergency, stating that the aircraft could land safely with three engines.
Occupants and Damage
The aircraft carried 182 people: the PIC, 13 other crewmembers, and 168 passengers. No injuries were reported. The incident resulted in extensive damage to the internal components of the No. 3 engine, as later determined during examination.
Investigation
The Japan Transport Safety Board (JTSB) initiated an investigation on September 22, 2008. Accredited representatives from the United States (as the state of design and manufacture) and India (as the state of registry and operator) participated. The investigation included interviews, examination of the aircraft and engine, analysis of flight data recorder and cockpit voice recorder records, and a teardown inspection of the engine. The Japan Aerospace Exploration Agency (JAXA) assisted with fracture surface analysis of the low-pressure turbine section. The investigation did not assign a probable cause in the report text beyond the classification as a serious incident under Japanese regulations.