What happened
On 20 January 2017, an Airbus A320-214, registration G-EZTK, was performing a scheduled passenger flight from Paphos to London Gatwick. While cruising at 34,000 feet, the flight crew noticed a sudden vibrating noise and a "whirring" sound coming from the area beneath the cockpit and the forward galley. Shortly after, a distinct smell of electrical burning became apparent in the cockpit, a fact confirmed by the senior cabin crew member.
In response to the developing situation, the commander and co-pilot donned oxygen masks and declared a PAN alert. The crew initiated a descent and diverted the aircraft to Athens. During the descent, the crew followed the smoke and fumes checklist from the Quick Reference Handbook. Despite the presence of the smell, no ECAM cautions or other system indications prompted the crew to switch to an emergency electrical configuration. The aircraft landed safely in Athens with no injuries to the 169 passengers or 6 crew members, although the aircraft landed approximately 1.5 tonnes above its maximum weight.
The investigation
Technical examinations of the aircraft identified the source of the noise and smell as the avionics bay cooling extractor fan. The investigation established that the fan had seized due to a bearing failure. This type of failure in the cooling system's extractor or blower fans typically causes friction between the rotor, stator, and body, resulting in the characteristic rumbling, vibration, and burning odor experienced by the crew.
While the aircraft was equipped with more reliable ceramic bearings, these components remain the primary failure mode in the fan assembly. The investigation noted that the specific extractor fan on G-EZTK had accumulated 25,181 hours since new. Because the paired blower fan had been recently replaced in 2016, this particular unit had not been flagged as a high priority for overhaul under the operator's existing mitigation programme.