History of the Flight
On 22 March 2021, at 0122 UTC, a Boeing 747-8F aircraft registered LX-VCD, operated by Cargolux Airlines, departed from Al Maktoum International Airport (OMDW) for Luxembourg International Airport (ELLX). On board were six people: two flight crewmembers and four deadhead crew (two pilots and two aircraft maintenance engineers). The commander was the pilot monitoring and the copilot was the pilot flying.
The aircraft began its takeoff roll from runway 30 at 0122:12 and lifted off after 36 seconds. At 0147:15, after leveling off at flight level 280, the flight crew contacted Bahrain ATC, declared a PAN PAN due to a technical malfunction of the window heating system, and requested to return to OMDW. The controller confirmed and provided instructions.
At 0148:00, the crew informed the controller of their intention to initiate fuel jettisoning. The controller vectored the flight toward Dubai and asked for more details. The crew reported electrical sparks followed by smoke from the right windshield heating terminal block. The commander, as pilot monitoring, switched off the right window heater, which stopped the sparks and dissipated the smoke. The controller asked if assistance was needed, and the crew replied that the sparks had stopped and smoke had dissipated, requiring no further assistance.
At 0150:00, the aircraft began descent. At 0152:52, fuel jettisoning was approved and conducted. The aircraft landed at OMDW at 0242:52 uneventfully. The commander informed the tower that no assistance was needed, but the tower had already declared a full emergency before landing. After landing, the runway and taxiway were inspected for debris; none were found. The emergency was canceled at 0252:00.
Aircraft Information
The Boeing 747-8F was manufactured in October 2011 and received its first certificate of airworthiness on 13 October 2011. The last renewal was on 30 September 2021, valid until 13 October 2022. The time since the last C-check was 2,789 flight hours and 490 cycles. The last A-check was accomplished in February 2021. Maximum takeoff, landing, and zero fuel weights were 447,695 kg, 346,090 kg, and 329,761 kg, respectively.
Technical records showed no defects prior to the incident. No pending maintenance messages or fault messages were reported post-flight.
The aircraft was equipped with an L-3 Communications flight data recorder and cockpit voice recorder. The CVR was found to be overwritten by maintenance personnel conversations during post-flight inspection.
Personnel Information
The commander held an air transport pilot license issued by the Directorate of Civil Aviation of Luxembourg, valid until 30 November 2021, with a medical certificate valid until 5 October 2021. The copilot also held an ATPL issued by the same authority, valid until 30 October 2021, with a medical certificate valid until 15 February 2022. Both crewmembers were current in training and stated they were well-rested and fit for the flight.
Meteorological Information
Weather conditions were normal.
Communications
ATC recordings from Bahrain ATC were available and clear. They confirmed that the flight crew declared a PAN PAN and reported a technical malfunction on the right window electrical terminal.
Tests and Research
The right (R1) flight deck windshield was removed and shipped to Boeing's Equipment Quality Analysis Laboratory in Seattle. The windshield had Boeing part number 141U4800-24, supplied by GKN Aerospace Transparency Systems (supplier part number 13933, serial number G9025).
X-ray examinations and electrical resistance checks were performed. Physical examination of the windshield anti-ice terminals (A) and (J) revealed no defects on terminal (J). However, evidence of heat damage was noted adjacent to terminal (A), with deposited material on the transparency. Discoloration due to heat was observed on the wire and case of terminal (A). A hole was found on the side of terminal (A) with evidence of heat damage.
Digital radiography and computed tomography scans were performed. The scans of terminal (A) showed the power braid wire, connector pin, ship side wire, and socket. No defects were noted on the sense elements and connections.
Damage to Aircraft and Property
There was no damage to the aircraft or property.
Probable Cause
The investigation did not state a probable cause.