SQ12 - Report: Singapore B773 near Los Angeles on Mar 27th 2023

A Singapore Airlines Boeing 777-300, registration 9V-SWQ performing flight SQ-12 from Tokyo Narita (Japan) to Los Angeles,CA (USA) with 234 people on board, was descending towards Los Angeles when a passenger reported smoke was emanating from an inflight entertainment panel. Cabin crew observed smoke and sparks from the USB port of the passenger's seat, the power for the seat row was turned off, two fire extinguishers were discharged, then the situation appeared to be under control. The aircraft continued for a safe landing on Los Angeles' runway 24R. Upon touchdown smoke and flames were again observed from the passenger's seat. Cabin crew turned off the IFE Master switch and discharged a third fire extinguisher. The aircraft rolled out and taxied to the apron.

On Mar 22nd 2024 Singapore's TSIB released their final report concluding the probable causes of the incident were:

The IFE smoke was the result of an overvoltage condition and heating within the IFE unit which originated from a combined fault of damaged cable harness and liquid intrusion.

The TSIB analysed:

A previously undetected wire damage on the folding arm-type IFE display panel at seat 41H resulted in a shorting condition where 28V high voltage main power was presented to all other seats’ IFE units within the cabin column concerned via the chassis ground wiring system.

In addition to this latent exposure to the high voltage coming from the chassis ground, a secondary exposure to liquid ingression on the MPJ panel established a connection between this high voltage chassis ground and the digital ground within the MPJ panel. This resulted in an overvoltage condition and heating within the IFE unit that led to smoke and sparks forming.

Despite the cabin crew having turned off the SPM maintenance switch under Seat 47H to cut off the IFE power supply to that seat row, Seat 47’s MPJ panel was still exposed to high voltage coming through the chassis ground from Seat 41H due to the damaged cable harness. As a result of this continued heat stress to the MPJ USB port, a second occurrence of smoke and electrical sparks resulted. It was only after the IFM had turned off the IFE Master Power switch, which cut off the electrical power to the entire IFE system in the cabin, was the high voltage coming through the chassis ground shut off.

The TSIB also mentioned: "According to this passenger, he had attempted to charge his laptop using the right USB port before the aircraft took off from Narita Airport, but as his laptop was not charging, he disconnected the laptop from the USB port and did not use any of the USB ports for the remainder of the flight."
Related Flight: SQ12, Singapore Airlines News