What happened
On 22 March 2021, a Boeing 747-8F cargo aircraft, registration LX-VCD, operated by Cargolux Airlines, was en route from Al Maktoum International Airport to Luxembourg when the flight crew reported a technical malfunction. While cruising at flight level 280, the crew declared a PAN PAN due to electrical sparks and smoke emanating from the right-side windshield heating terminal block.
To manage the situation, the commander deactivated the electrical supply to the right window heater, which successfully stopped the sparking and allowed the smoke to dissipate. The crew subsequently requested to return to Al Maktoum International Airport and initiated fuel jettisoning to reach a safe landing weight. Despite the declaration of a full emergency by air traffic control, the aircraft landed safely without further incident.
The investigation
An investigation by the UAE Air Accident Investigation Sector (AAIS) involved a detailed teardown of the right flight deck window at a Boeing facility in Seattle. Using X-ray digital radiography and CT scans, investigators examined the terminal block assemblies. The examination focused on the pin/socket terminal design, which was intended to be more reliable than older screw/lug designs.
Technical analysis of the hardware revealed that the electrical arcing originated from the point where the integrated power braid wire was crimped to the connector base. The investigation also reviewed historical data, noting that a similar incident had occurred with another Cargolux Boeing 747-8F in January 2019.