What happened
On 27 March 2023, during the descent to Los Angeles International Airport, a passenger on a Singapore Airlines Boeing 777-300ER, registration 9V-SWQ, noticed smoke emitting from the in-flight entertainment (IFE) panel at the back of seat 47K. Cabin crew responded by deactivating the seat power module for that specific row and using two fire extinguishers to suppress the smoke and visible sparks.
Despite these efforts, the situation escalated upon touchdown. As the aircraft landed, the crew observed renewed smoke, electrical sparks, and a visible flame within the IFE panel. A crew member used a third fire extinguisher to address the flare-up, and the In-Flight Manager deactivated the IFE Master Power switch to cut electricity to the entire cabin system. There were no injuries during the incident, and the aircraft taxied to the gate without further trouble.
The investigation
Investigators examined the electrical architecture of the IFE system and the aircraft's maintenance history. They discovered that the aircraft had experienced a similar smoke incident involving a different seat just four days prior.
An inspection of the electrical wiring revealed previously undetected damage to the cable insulation on a folding arm-type IFE display panel at seat 41H. This damage had left bare wires exposed, allowing 28V power to leak into the chassis ground wiring system. Furthermore, the manufacturer found evidence of liquid ingression on the MPJ panel of the affected seat, which created a bridge between the high-voltage chassis ground and the digital ground.
Findings
- The primary cause of the smoke was an overvoltage condition and subsequent heating within the IFE unit.
- This was triggered by a combination of a damaged cable harness at seat 41H and liquid entering the MPJ panel.
- Deactivating the row-specific maintenance switch was insufficient to stop the heat stress because the high voltage was being supplied through the shared chassis ground.
- The hardware involved had not yet been updated with the manufacturer's latest design improvements (MOD 3 and MOD 4) intended to isolate the digital ground.
Safety action
Following the investigation, the IFE manufacturer suggested periodic inspections of seat armrest cable harnesses every five to seven years to prevent similar routing or clamping damage. Additionally, a safety recommendation was issued for the aircraft operator to replace the MPJ units across the Boeing 777 fleet with updated versions incorporating the MOD 3 and MOD 4 design improvements.