"Mayday" shortly after take-off Swiss flight ended abruptly - Sust report shows lack of maintenance
In September 2024, a Swiss Airbus had to return to Zurich shortly after take-off due to problems with the cabin pressure. The incident was triggered by a maintenance oversight, as the final report shows.
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- On a Swiss flight from Zurich to Newark in September 2024, the cabin pressure system failed shortly after take-off and the crew made the Mayday emergency call.
- The cause was a defective valve, which Airbus had already recommended replacing in 2016 - the maintenance recommendation was not implemented on the aircraft.
- In its final report, Sust criticized the omission and ordered stricter maintenance and control measures.
They had only just taken off when the pilots made an emergency call: In September 2024, a Swiss flight from Zurich to Newark, USA had to turn back shortly after take-off. There were problems with the cabin pressure. The final report (PDF) of the Swiss Transportation Safety Investigation Board (Sust) is now available on the serious incident.
What happened?
Flight LX18 took off from Zurich on September 13, 2024. There were two pilots, ten crew members and 205 passengers on board the Airbus A330. During the climb, the pilots noticed a malfunction in the cabin pressure system. They put on their oxygen masks, triggered the oxygen masks for passengers and crew in the cabin and sent an emergency message ("Pan-Pan").
20 seconds later, the crew then transmitted the emergency call "Mayday" and announced an emergency descent. The plane returned to Zurich, where passengers and crew were able to leave the aircraft unharmed and by normal means.
What was the cause?
In its final report, which has now been published, Sust writes that the cabin pressure system was not able to build up sufficient cabin differential pressure. This was despite the fact that both outlet valves were indicated as fully closed.
According to Sust, the serious incident is due to a defective checkvalve (skin check valve). The manufacturer Airbus had already recommended replacing the component as soon as possible in 2016. However, this was "not carried out on the Swiss Airbus, which was the cause of the serious incident", Sust clarified.
What measures were taken?
This omission was incomprehensible from a safety point of view, "since failure to carry out this service bulletin can also affect flight safety and the skin check valve had to be removed and reinstalled for inspection every 24 months anyway, i.e. at least three times on [the affected aircraft]."
In response to the incident, Sust has supplemented the maintenance instructions and ordered additional work steps to check the affected components. In addition, part of the Swiss A330 fleet was specifically inspected. The responsible persons were also informed of the critical aspects and potential safety risks in a separate mailing.
