Introduction
On 17 April 2023, at approximately 0507 UTC, a Singapore Airlines Boeing 747-412F freighter, registration 9V-SFO, was involved in a serious incident during take-off from Jomo Kenyatta International Airport (HKJK) in Nairobi County, Kenya. The aircraft was operating a scheduled cargo flight to Amsterdam International Airport, Netherlands. There were four crew members on board and no injuries were reported.
Flight History
The aircraft commenced its take-off roll on runway 06. During the take-off phase, the crew heard a loud bang and experienced significant vibration. They promptly rejected the take-off (RTO) and brought the aircraft to a stop on the runway. The crew declared an emergency and were assisted by airport emergency services. The aircraft was disabled on the runway, requiring the deflation of 13 tires and the offloading of cargo before it could be towed away.
Damage to Aircraft
Initial inspection revealed minor damage to the aircraft, primarily confined to Engine No. 4. Borescope inspection showed a section of the high-pressure compressor (HPC) stage 5 disk and blades were damaged. The engine subsequently was removed for detailed examination.
Investigation Findings
The Aircraft Accident Investigation Department (AAID) of Kenya conducted the investigation. The engine failure was traced to the HPC 5th stage compressor disk. Metallurgical examination revealed that the disk had failed due to fatigue cracking that originated from the cooling holes in the disk. The cracks propagated over time, leading to the eventual failure during take-off.
Probable Cause
The investigation determined that the probable cause of the incident was the failure of the HPC 5th stage compressor disk due to fatigue cracking emanating from the cooling holes. A contributing factor was the failure of the Approved Maintenance Organization (AMO) to detect the cracks during previous maintenance inspections.
Safety Recommendations
The AAID issued several safety recommendations aimed at improving inspection procedures and compliance with airworthiness directives to prevent similar occurrences.