| Executive Summary: | During a previous flight on 19 December 1996 and whilst in the cruise, acrid smoke and fumes affected the flight deck causing the crew to transmit a 'Pan' call before making a precautionary descent and diversion into Bristol Airport. The smoke drill was actioned by the crew and, during the descent, the fumes dissipated and the aircraft landed safely. Subsequent engineering inspection of the air conditioning system failed to find any evidence of oil ingress, burning or smoke damage. Since level 2 anti-icing had been in use at the time of the incident, the engines were ground run at 80% torque for some 2 minutes. However, no signs of overheating or smoke were observed and the aircraft was therefore released back to service, with no attendant recurrence of the fault.
However, on 16 February 1997 the aircraft was returning from Dublin to London Gatwick when traces of smoke, accompanied by pungent fumes, again appeared on the flight deck. At about this time,the cabin staff reported that there was smoke in the centre area of the cabin, around seat row 6, and that the cabin walls in this area were 'hot'. The commander declared an emergency and diverted into Liverpool. After subsequent inspection the aircraft was cleared for a flight to Gatwick Airport where more detailed engineering checks could be carried out. Following arrival at Gatwick a problem was identified with the No 1 air conditioning recirculation fan/control circuit where a relay, positioned beneath row 6 in the passenger cabin, was found to show evidence of electrical arcing and overheating. Overheating damage was also evident on the cabin air recirculation fan motor. This unit was removed from the aircraft and sent to the manufacturer for inspection and rectification, and a report has been requested by the AAIB. Any significant findings will be reported in a future issue of the AAIB Bulletin. |
