What happened
On 1 October 2020, a Boeing 787-9, registration G-ZBKF, was operating a commercial passenger flight from Miami to London Heathrow. Approximately 40 minutes before the scheduled arrival, a cabin crew member noticed a strong sulphur-like odour while tidying a passenger's seat. Upon investigation, the crew discovered a charging cable plugged into the seat socket, with the other end lost deep within the seat structure. Shortly after, a hissing sound was heard, followed by a plume of grey smoke and an orange glow emanating from the seat mechanism.
The crew immediately initiated firefighting procedures, using a BCF extinguisher to suppress the fire. The flight crew, having detected an acrid smell on the flight deck, performed smoke and fire checklists and evaluated diversion options. However, as the smoke dissipated, the crew identified a red mobile phone trapped and crushed within the seat mechanism. Because the aircraft was only 20 minutes from landing, the commander decided to continue to Heathrow, notifying air traffic control and requesting the fire service to meet the aircraft upon arrival. The aircraft landed without further incident and no injuries were reported among the 53 passengers or 10 crew members.
The investigation
The AAIB investigation established that the fire was caused by the physical deformation of a lithium battery. The device had fallen into the seat mechanism and was crushed when the seat was adjusted. The investigation also reviewed the operator's procedures, noting that while the crew managed the incident effectively, the crew member did not use water to douse the device due to concerns regarding potential damage to the seat's electrical components.
Further analysis revealed that the seat design, while intended to limit the entrapment of electronics, could not entirely eliminate the risk. The investigation noted a significant trend in the industry, with the CAA having recorded 166 instances of portable electronic devices (PEDs) becoming trapped in passenger seats over the preceding five years, 42 of which resulted in smoke or fire.
Findings
- A mobile phone became trapped in the seat mechanism and was crushed during seat adjustment.
- The damage to the lithium battery caused thermal runaway, resulting in flames, smoke, and fumes.
- There are currently no specific regulatory requirements from the CAA or EASA to design seats to prevent the crushing of electronic devices.
Safety action
- The AAIB has issued Safety Recommendation 2021-017, advising the CAA to require that passenger seats in commercial aircraft be designed to minimize the risk of portable electronic devices being crushed in mechanisms.
- The EASA has requested the SAE International Seat Committee to develop new design standards and recommended practices to address this known hazard.