On 2 March 2009, an Airbus A320-200 being operated by Wizz Air Hungary on a scheduled passenger flight from Stockholm Vasteras to Poznan was in the cruise at night when the flight crew detected an unfamiliar smell on the flight deck and decided to guard against possible incapacitation by donning their oxygen masks from time to time for the remainder of the flight. There was some evidence of the same effect in the passenger cabin. The flight was completed without further consequences and none of the 85 occupants was affected except temporarily.
An Investigation was carried out by the Swedish AIB following their notification of the event 17 days after the occurrence.
The Investigation noted that two members of the cabin crew and one passenger had been afflicted by a slight breathing difficulty and felt irritation in their eyes during the same period that the flight crew intermittently used their oxygen masks. In order to alleviate the breathing difficulty, the cabin crew reported that oxygen from the portable therapeutic oxygen bottles carried on the aircraft was used.
During the aircraft turn round at Vasteras prior to departure, there was heavy snowfall and it was de-iced with hot water then treated with de/anti icing fluid. The treatment was found to have begun before the ground staff had received actual clearance from the flight crew to commence but when they believed that it had. The misunderstanding which occurred involved the use of language which was easily mis-heard. Once the de/anti icing operation commenced, it proceeded without awareness of no-spray areas specific to the aircraft type. As a result of both the aircraft systems status and the mis-application of fluid, some fluid entered the APU and the air conditioning system then distributed the contamination. When the flight crew detected the air conditioning contamination, they called for de-icing to stop and the aircraft doors were opened to enable ventilation and the air conditioning system was run at a high temperature for about 20 minutes. The aircraft de/anti icing operation was then repeated.
It was concluded that during the subsequent flight, residual de/anti icing fluid in the air conditioning system again evaporated and mixed with air supplied to the aircraft cabin.
The Investigation disclosed that there were deficiencies in the education and training of the personnel who performed the ground de/anti-icing and deficiencies in the aircraft operator’s training and checks on the supplier of this service at the airport.
The health risks arising from the inhalation of glycol-water evaporation fumes were considered by the Investigation. It noted that Monopropylene Glycol had been used for anti icing and that, “according to the Swedish Arbetsmiljöverket (Working Environment Agency) this glycol is only mildly toxic and hygienic limit values for the working environment have not been established. Nor are there indications that inhaling the fumes has any harmful effect on humans. If the liquid enters the eyes, however, they can sting.” The Investigation therefore concluded that no health risks arose due to the incident.
Causes of the Incident
It was concluded that: “The cause of the incident was a deficiency in the use of standard phraseology in the communication between the ground staff and the commander. Contributory were deficiencies in the airline’s follow-up and checking - by means of an agreement and audits - of the negotiated service’s quality and implementation.”
One Safety Recommendation was made as a result of the Investigation: “It is recommended that the Transport Agency, in connection with operational checks of airports, confirms that there is an agreement between the purchaser and supplier of de-icing services in the case of operators who conduct their operations in accordance with EU-OPS 1. “ (RL 2009:R1)
The Final Report of the Investigation was published on 15 December 2009 and is available at SKYbrary bookshelf: Report RL 2009:19e