German investigators have disclosed that both pilots of a Germanwings Airbus A319 were badly affected by fumes while approaching Cologne, but details about the seriousness of the event only emerged a year after it took place.
But the airline vehemently insists that it did not play down the event in its initial notification to German air accident authority BFU.
The aircraft, arriving from Vienna on 19 December 2010, had been preparing to conduct an instrument landing system approach to runway 14L.
But at about 3,000ft, while turning onto the base leg, the pilots began to detect an "unpleasant" electrical burning smell, says German accident investigation authority BFU.
As the A319 intercepted the localiser the first officer stated that he felt intensely nauseous and sought an oxygen mask. The captain, who was flying, felt a severe tingling in his hands and feet, along with strong sensations of dizziness, and his field of vision contracted. He also put on his mask.
While the captain's condition improved slightly, the first officer's deteriorated. The aircraft was 12nm from touchdown, but travelling too fast, and the captain disengaged the autopilot and took manual control.
Although the pilots managed to reconfigure the jet, the first officer struggled to focus on the situation and could not handle all the information, while the captain had "reached the limit of his performance", says the BFU, because he felt physically ill and was distracted by the sound of breathing in the masks during communication.
Despite the high airspeed the captain felt a go-around would be impossible to conduct, and that the crew had no option but to land immediately.
"Both pilots described their condition before landing as surreal, and as within a dream," says the BFU, adding that the couple of minutes' descent between 1,800ft and touchdown were "like an eternity" to the first officer. He was tired, unable to concentrate and "no longer in a position actively to influence the proceedings", says the BFU.
The aircraft landed safely but medical personnel who subsequently treated the pilots found their blood-oxygen content was "significantly lower" than 80%, compared with the normal healthy level of at least 95%.
Blood analysis on one of the pilots, the following day, showed "unusual" results for chemical make-up. The BFU says the pilots were unfit for service for more than six months after the incident.
Investigators initially received information stating that the A319, with 160 on board, had reported smoke in the cockpit and the pilots were suffering inhalation effects. But Germanwings, the next day, informed the BFU and civil aviation authority that the pilots had perceived an electrical burning smell, and had felt unwell, and that they were conducting the landing under oxygen. After preliminary indications that the smell had been due to de-icing fluid, and that the crew had not been poisoned, the BFU decided not to open an investigation.
But the BFU says that "more information" reached investigators a year after the approach, prompting it to open an inquiry.
Germanwings is adamant that its immediate notification did not mislead the BFU over the seriousness of the event, adding that all available data on the incident was handed over to investigators "immediately". It also points out that one of the pilots had filed the initial information details himself, and subsequently informed the carrier that he had been "always in control" despite his impairment.
"During the incidentthe pilots acted properly and accurately, according to their instructions," says the airline. Germanwings adds that the A319 underwent "extensive inspections" in Cologne but was put back into service after no clear reason for the odour was found.
Germanwings says a "similar" incident in May 2008, involving the same aircraft (D-AGWK), was investigated by Irish authorities after a cabin crew member appeared unwell and passengers fell asleep quickly after take-off from Dublin. No defect in the A319 was found and Germanwings stresses that the jet logged over 6,000 cycles, without problems, before the Cologne incident.