What happened
On 11 July 2009, during the engine start-up sequence of a pushback at Phoenix Sky Harbour Airport, a Boeing 747-436, registration G-CIVB, experienced an influx of smoke and fumes within the cabin. The incident began while the aircraft was being positioned; as the engines were being started, the additional pilot noted an acrid burning smell.
As the aircraft moved, the situation in the cabin deteriorated, particularly toward the rear. The intensity of the fumes increased to the point that flight crew members donned oxygen masks. During the confusion, a passenger opened an aircraft door, and the cabin crew utilized a fire extinguisher to combat what appeared to be smoke coming from the sidewall under the seats.
Due to the worsening conditions, the commander decided to return the aircraft to the stand. However, a delay occurred while the tug was reconnected. During this period, the fumes intensified, leading the commander to initiate an emergency evacuation. The evacuation was directed toward the right side of the aircraft due to the proximity of the airbridge. While most slides deployed successfully, one upper deck door was opened in error, causing a slide to deploy onto the airbridge.
The investigation
The investigation examined the sequence of events, the aircraft's mechanical state, and the preservation of flight data. Investigators noted that the Cockpit Voice Recorder (CVR) did not provide full audio insight because the recording continued during subsequent maintenance activities, resulting in the loss of relevant event data.
An engineering investigation was conducted by the operator and the manufacturer. This included an examination of the aircraft for any evidence of heat sources or fire damage. Additionally, the investigation looked into the effectiveness of the crew's communication and the management of passenger behavior during the high-stress event.
Findings
- The investigation could not identify a specific source for the smoke or fumes.
- There was no evidence of actual fire or heat damage found on the aircraft.
- The intensity of the fumes in the flight deck was initially low, but the physical distance between the flight deck and the lower deck made it difficult for the commander to assess the cabin situation accurately.
- Passenger distress and the incorrect call of a "fire" contributed to the difficulty in maintaining cabin control.
- The loss of CVR data was attributed to the failure to electrically isolate the recorder following the incident.
Safety action
Following the investigation, the AAIB issued two safety recommendations:
- It is recommended that British Airways plc review procedures and training for flight and maintenance crews to ensure the timely preservation of CVR recordings by tripping the circuit breaker.
- It is recommended that the Civil Aviation Authority review procedures for UK operators to ensure the timely preservation of CVR recordings in accordance with international standards.