The interim report describes that the incident on board escalated into a critical situation within minutes. About 21 minutes passed between the first signs of trouble and the landing, as stated in the document published by the Austrian Federal Safety Investigation Authority (SUB).

Swiss Emergency Landing in Graz: Loud Bang and Smoke in the Cockpit

During the flight on December 23 of the previous year, everything went according to plan until 4:30 PM. The aircraft, an Airbus A220, was cruising at an altitude of 40,000 feet, approximately 12,200 meters. At 4:32 PM, a first error message suddenly appeared in the cockpit of the two pilots: It was "L ENGINE FAULT" along with the additional note "79 L ENGINE FAULT- OIL DEBRIS ABOVE LIMIT". Translated, a failure of the left engine and problems with the oil system of this turbine were indicated, explained the Austrian aviation magazine "Austrian Wings". About a minute and a half later, the "Master Caution" was triggered in the cockpit, accompanied by the message "ENG VIBRATION", which was supposed to alert the crew to strong engine vibrations. At the same time, there was a loud bang, which was unmistakably perceived by passengers and flight attendants. There was another "Master Caution" along with the message "L ENG OPER DEGRADED". Less than 30 seconds later, the pilots also noticed smoke in the cockpit and donned their oxygen masks, which should be done immediately by the pilots in any kind of smoke situation, explained "Austrian Wings".

"Mayday Call" from the Captain of the Swiss Flight

Immediately afterwards, at 4:34 PM, the "Master Warning" sounded. This warning has a higher priority than the "Master Caution". The trigger was a smoke detector in one of the toilets that went off. The warning "LAV SMOKE" (for Lavatory Smoke) appeared in the cockpit, followed by the four-time acoustic smoke alert from the computer voice: "Smoke, smoke, smoke, smoke!" Immediately afterwards, "Master Warning" was triggered again. A new message indicated low oil pressure in the left engine: "L ENG OIL PRESS". Subsequently, the captain declared an emergency over the radio by issuing a "Mayday Call", reported smoke in the cockpit, and initiated a descent. At 4:35 PM, the captain instructed the cabin crew to take their seats and prepare for a possible emergency landing. At this time, the aircraft's position was about 23 nautical miles northeast of Graz. At 4:36 PM, about two minutes after declaring an emergency, the pilots requested an immediate landing at Graz-Thalerhof Airport from air traffic control. The masks for the passengers were not deployed, as they are unsuitable in the event of smoke on board and would have worsened the situation, stated "Austrian Wings" in its article. The three flight attendants donned their "Smokehoods" intended for such cases.

Swiss Emergency Landing in Graz: Two of Six Doors Not Opened During Evacuation

At 16:37, the pilots shut down the left engine according to the checklist. The flight continued with only one engine. At 16:40, eight minutes after the first problems occurred and four minutes after declaring an emergency, the passengers were informed about the situation by the captain. At 16:53, the aircraft landed on runway 34C in Graz, and the pilots quickly braked the jet. About 30 seconds after landing, the captain made an announcement in English to the cabin crew to prepare for a possible evacuation. At 16:54, the pilots also shut down the remaining right engine. Immediately afterwards, at 16:55, the captain ordered the evacuation of the aircraft via the emergency slides over the loudspeaker. For safety reasons, he waited until the remaining right engine was shut down. In total, four of the six doors of the aircraft were opened for the evacuation. The doors at the front and rear right were not used during the evacuation, according to the interim report: "The investigation of the unused doors is not yet complete." It is still unclear whether the doors were not opened or if they were jammed.

Further Investigations Needed for Swiss Emergency Landing in Graz

During the accident investigation, the left engine was dismantled and technically examined before being shipped to the manufacturer Pratt & Whitney in the USA for further investigations. The current investigation results show damage to the front drive system as well as to bearings number two and number four. Further metallurgical tests and component analyses are part of the investigation, which is being conducted both in Austria and in the USA. The engines were apparently maintained according to the applicable procedures. The "smoke hoods" of the crew are also still being examined. It should be clarified whether there was a defect in one of the "escape hoods" or whether a handling error possibly led to the death of the young flight attendant. The cause of the engine problems is still unclear.

Swiss stated on Tuesday in response to an APA inquiry that the death of the colleague still deeply concerns them: "We want to know what happened, which is why we welcome any new insight and any measure that helps to find answers. However, the interim report does not bring any new insights for us. Our own internal investigations are ongoing. We will not rest until we have the answers that we, our colleagues, and the relatives are urgently seeking. We are also continuing to work closely with the SUB and still support them unconditionally."

The Swiss Airbus A220 was on its way from Bucharest to Zurich on December 23 with 74 passengers and five crew members when the jet had to make an emergency landing in Graz due to engine problems and smoke in the cabin. Several people, including crew members, were seriously injured. A 23-year-old flight attendant later died in the hospital. This is the most consequential incident in the history of Swiss to date.

(APA/Red)

This article has been automatically translated, read the original article here.