What happened
On July 4, 2005, a Kalitta Air Boeing 747-200B, registration N714CK, departed New Chitose Airport for Anchorage International Airport. Shortly after takeoff, while the aircraft was climbing through approximately 1,300 feet, the crew received a fire warning for the No. 3 engine, accompanied by an audible alarm and a high temperature reading on the nacelle temperature indicator.
In response to the emergency, the pilot in command shut down the No. 3 engine and activated the fire extinguishing system. To manage the aircraft's weight for an emergency landing, the crew jettisoned approximately 140,000 lbs of fuel over the sea. The aircraft returned to New Chitose Airport and landed safely at 12:09 JST. There were no injuries among the six persons on board.
The investigation
The investigation focused on the No. 3 engine, where physical damage was identified on the right cowling, including broken hinge fittings and deformed areas. Investigators found sooting on the engine exterior, extending from the high-pressure compressor to the high-lag turbine, and a 75 cm long hole in the turbine sleeve.
Technical examinations of the fuel delivery system revealed that the primary fuel tube, which connects the No. 2 and No. 3 nozzles, was deformed. Specifically, the tube exhibited dents and a bend in the inner tube axis. A fit check confirmed a significant misalignment and a 9 mm gap between the No. 3 fuel nozzle and the primary fuel tube end. Furthermore, while a burnt O-ring was found on the secondary tube, the O-ring at the No. 3 nozzle interface was missing, with only heat-affected residue remaining.
Findings
- The fire warning was triggered by a flame within the engine's fire suppression zone.
- Fuel leaked from the interface between the No. 3 fuel nozzle and the primary fuel tube.
- The leakage was caused by a misalignment and a 9 mm gap between the fuel tube and the nozzle.
- It is believed that a deformed fuel tube was likely used during previous maintenance work, which prevented proper sealing and allowed fuel to escape into the engine nacelle, where it ignited upon contact with hot engine components.