What happened
On 19 April 2014, a Flydubai Boeing 737-800, registration A6-FEK, was descending toward Kiev Boryspil International Airport when an in-flight entertainment (IFE) unit at seat 9A began emitting smoke. Upon noticing the smoke, cabin crew immediately relocated the passengers from seats 9A, 9B, and 9C to different parts of the cabin.
The cabin supervisor deactivated the power to the IFE system and notified the flight deck. A crewmember equipped a smoke hood and used a fire extinguisher to suppress the smoke, which was accompanied by a crackling sound. As the smoke dissipated, the captain declared a "mayday" to Kiev Air Traffic Control as a proactive safety measure. The flight crew performed the required 'Smoke, Fire, Fumes' checklist from the Quick Reference Handbook. The aircraft subsequently landed at its destination without further incident, and no injuries were reported.
The investigation
The UAE Air Accident Investigation Sector (AAIS) conducted a technical examination of the Video Display Unit (VDU) and its components. The investigation included a teardown of the unit and a review of maintenance records, which showed no prior anomalies for this specific aircraft, though some screens in the fleet had previously required simple reboots. Investigators also examined the electrical characteristics of the fuse and the thermal properties of the printed circuit board (PCB).
Findings
Technical analysis determined that the smoke was caused by gases released from the PCB of the VDU backlight inverter board. The failure sequence began with a break in the secondary coil of the transformer, which led to increased current demand and subsequent failure of the primary side transistor components.
A critical factor was the failure of the fuse to interrupt the circuit quickly because its current rating was too high for the specific VDU application. Additionally, the investigation found that the fuse material may have facilitated heat transfer via conduction between the fuse and the PCB, contributing to the overheating of the inverter board.