What happened
On the morning of 3 October 2015, an Airbus A320-214, registration EI-DVJ, departed Dublin Airport for a scheduled flight to Munich. Shortly after takeoff, the flight crew noticed an unusual odor in the cockpit. This was quickly followed by reports from the cabin crew regarding a strong, smoky smell and visible fumes within the passenger cabin.
In response to the deteriorating air quality, the flight crew declared a PAN (state of urgency) to Air Traffic Control and donned their oxygen masks. The aircraft returned to Dublin, performing a normal landing. Upon arrival at the stand, the cabin crew requested the immediate opening of doors to provide fresh air, as the fumes were significant enough that some passengers used clothing to cover their faces during disembarkation. No injuries were reported to the 148 passengers or the 6 crew members on board.
The investigation
The AAIU examined the maintenance activities performed the previous night. It was discovered that a scheduled engine compressor wash had been conducted on both engines. During this process, maintenance personnel mistakenly added a significant amount of corrosion inhibitor into the water tanks of the engine wash rig instead of the aircraft's engine oil tanks.
Investigators also looked into the aircraft's pneumatic and air conditioning systems. They determined that the chemical contamination had entered the intermediate pressure (IP) bleed ducts. This allowed the inhibitor to be distributed through the air conditioning system, contaminating the air supplied to both the cockpit and the passenger cabin.
Findings
- The primary cause of the incident was the presence of corrosion inhibitor in the engine bleed ducts, which contaminated the aircraft's air conditioning system.
- This contamination was caused by an error during the engine wash procedure, where corrosion inhibitor was erroneously added to the wash rig's water tanks.
- The maintenance engineers involved had not yet received specific training for the engine wash task at the time of the occurrence.
- An alternative post-wash test performed after the wash only tested engines at idle power and failed to detect the presence of the contaminant.
- There was a delay in the positioning of the air bridge, which prevented the immediate opening of cabin doors for ventilation upon arrival at the stand.