Description

On 5 March 2011, an Airbus A320-200 being operated by Finnair on a scheduled passenger flight from Helsinki to London Heathrow was en route in Swedish airspace in the cruise at FL360 in day Visual Meteorological Conditions (VMC) when the no 2 bleed air system failed. Because the aircraft was operating under release to service with No 1 bleed air system inoperative and both air conditioning packs were being supplied by No 2 system, an emergency descent became necessary. It was subsequently possible to restart the failed bleed air system and the planned flight was continued to destination at a lower altitude.

Investigation

An Investigation was carried out by the Finland Safety Investigation Authority. Flight Data Recorder (FDR) and Cockpit Voice Recorder (CVR) data were successfully downloaded but as the two hour CVR had not been stopped until after the flight landed, data from the time of the incident had been overwritten.

It was noted that the release to service with No 1 bleed air system inoperative was allowed under MEL procedures for up to 10 days. The incident flight was the eighth day of this ten day period and all flights since the beginning of this period had been uneventful. During the period, attempts to rectify the fault had been made but without success. It was also noted that raising an ADD for the fault did not place any operational restrictions on the conduct of flights, although the MEL did provide the flight crew with some instructions for precautionary action prior to the flight as well as actions to take during the flight.