What happened
On the night of September 8, 2022, a Boeing 747-400 operated by Air Atlanta Icelandic was performing a cargo flight from Liège Airport (EBLG) to Malta. During the initial climb phase, while the aircraft was executing a requested deviation from its standard instrument departure to avoid weather, a large piece of the engine structure became detached. Specifically, the left-hand core cowl of engine number four was torn away from the aircraft.
The detached component fell into a residential area in Waremme, Belgium, striking the roof of a garage before landing in a garden. While the impact caused damage to the garage structure, there were no injuries to persons on the ground. The aircraft crew, unaware of the loss during the flight, only discovered the missing part upon arrival at their destination in Malta.
The investigation
AAIU(Be) investigators examined the aircraft's maintenance history and the conditions surrounding the flight. Prior to departure, maintenance technicians had performed work on engine number four, which included replacing a fan air modulating valve. This procedure required opening and closing the engine cowls. Although the maintenance tasks were documented and the job cards were signed off, the investigation focused on the integrity of the cowl closure.
The investigation also reviewed the pre-flight walk-around inspection performed by the captain. This inspection took place at night under rainy conditions with limited lighting. While the technical log noted the recent maintenance work, it did not explicitly state that the engine cowls had been opened.
Findings
Technical analysis of the remaining engine components revealed that the right-hand core cowl remained on the aircraft but was deformed, while the left-hand cowl had been completely torn from its hinge assembly. Crucially, the investigation found that the four independent latches on the cowls were not securely fastened prior to takeoff.
Several contributing factors were identified:
- The engine cowls were not properly latched following the recent maintenance work.
- The pre-flight inspection failed to detect the unsecured latches, partly due to the darkness and rainy weather during the walk-around.
- The maintenance documentation did not specifically highlight that the cowls had been opened for the valve replacement, which could have alerted the crew to check them more closely.
Safety action
Following the incident, the operator implemented human factors training for maintenance personnel to increase vigilance regarding the securing of all latches and panels.
AAIU(Be) issued two safety recommendations:
- The operator should implement a procedure requiring maintenance staff to explicitly note in the technical log whenever engine cowls have been opened and closed during maintenance.
- The operator should remind flight crews of the necessity of a thorough pre-flight inspection and ensure that effective lighting, such as a bright torch, is used during night operations.