What happened
On 27 July 2015, an Airbus A320-232, registration G-EUYE, was conducting a scheduled passenger flight from Paris Charles de Gaulle to London Heathrow. While cruising at 24,000 feet, the flight crew detected an unusual noise accompanied by the smell of electrical burning. The noise rapidly escalated into a high-pitched squeal and was accompanied by noticeable vibrations.
To protect themselves from potential fumes, the crew donned full-face oxygen masks using a 100% oxygen supply. The commander issued a MAYDAY call, and London Air Traffic Control provided clearance for an urgent descent. Following the smoke and fumes checklist, the crew set the avionics ventilation system blower fan to override. This action immediately silenced the noise.
While the cabin crew reported that the cabin remained largely unaffected, a brief smell of burning was noted in one area of the passenger compartment. During the descent, the aircraft's monitoring system issued alerts regarding a ventilation system blower fault and an extract fault. The aircraft landed safely at Heathrow, where the airport fire service performed an external inspection. There were no injuries to the 157 passengers or 6 crew members on board.
The investigation
Investigators examined the avionics blower fan, which is part of the cooling system located in the forward avionics compartment. While the fan appeared normal when stationary, it produced a rumbling noise and vibration through the cabin floor when activated. Upon removal and manual inspection, the fan emitted a burning odor, and the bearings were found to be worn and noisy.
The investigation confirmed that the fan in G-EUYE utilized ceramic bearings. At the time of the incident, the component had accumulated approximately 16,000 flying hours. The operator was in the process of updating maintenance protocols to overhaul such fans every 12,000 hours, and this specific unit was scheduled for overhaul during a maintenance check in September 20 15.
Findings
- The primary cause of the incident was worn bearings within the avionics blower fan.
- The fan had exceeded the recommended 12,000-hour interval between overhauls suggested by the manufacturer.
- The crew's effective use of oxygen masks and adherence to emergency checklists prevented exposure to fumes and ensured a safe landing.