Incident Summary
On 3 March 2015 at approximately 01:00 local time, a Boeing 747-400, registration HS-TGW, operated by Thai Airways International Public Company Limited as flight TG910 from Suvarnabhumi Airport (Thailand) to London Heathrow Airport (United Kingdom), experienced an electrical arcing incident. The aircraft carried 4 pilots, 18 cabin crew, and 249 passengers, totaling 271 occupants.
Sequence of Events
While climbing to flight level 340 (34,000 feet), a passenger reported to a flight attendant that arcing was observed above the passenger seats at positions 32-33 H, J, and K. The flight attendant inspected the area but found no abnormality and informed the Air Purser (AP) and Inflight Manager (IM). The IM and AP also inspected without finding any issue. Approximately 10–15 minutes later, the passenger again reported arcing in the same area. The IM instructed the flight attendant to prepare fire extinguishers and monitor the situation.
In the cockpit, the Engine-Indicating and Crew-Alerting System (EICAS) displayed the warning message "ELEC UTIL BUS R." The pilot followed the Malfunction Checklist, and the message ceased. When the aircraft reached FL340 near the BETNO reporting point (approximately 150 nautical miles, 297 degrees from Suvarnabhumi Airport), the co-pilot left the cockpit to inspect the reported area. While discussing the event with the IM, arcing appeared again. The co-pilot directed the flight attendant to prepare fire extinguishers and monitor the area, then returned to inform the pilot-in-command. The pilot-in-command decided to request air traffic control from the Union of Myanmar to return to Suvarnabhumi Airport.
Landing and Inspection
The aircraft landed at Suvarnabhumi Airport without further incident. There were no injuries or fatalities to crew or passengers. After parking, a licensed aircraft engineer inspected the area above seats 32-33 H, J, and K and discovered wiring chafing where the Galley Feeder Line contacted a water pipe from the Water Shutoff Valve Galley 8. The aircraft sustained no damage.
Investigation
The Aircraft Accident and Incident Investigation Commission Thailand conducted the investigation, with the United States (as the state of design and manufacture) appointing accredited representatives. The final report was publicly released on 24 December 2025. The report noted that the aircraft had been manufactured on 28 April 1997 and had accumulated 83,650 hours since new. The last C-check was completed on 3 December 2014, and the last A-06 check on 21 January 2015.
Conclusion
The cause of the serious incident was not explicitly stated in the provided source. The investigation identified wiring chafing between the Galley Feeder Line and a water pipe as the physical evidence of arcing.