The fact that the pilot attempted to shut down the right engine (No. 2), which suffered significant damage while performing emergency procedures, but mistakenly turned off the comparatively good left engine (No. 1), was confirmed through black box records and a detailed engine investigation.
The Ministry of Land, Infrastructure and Transport's aviation and railway accident investigation committee (CRAIC) reached this conclusion regarding the Jeju Air passenger plane accident that occurred at Muan International Airport in South Jeolla Province last December. The CRAIC attempted to explain the engine investigation findings to the bereaved families on the 19th and announced them to the media, but the announcement was canceled due to opposition from the families.
According to comprehensive reporting on the CRAIC from the 23rd, the pilot of the Jeju Air passenger plane was performing emergency procedures on the damaged right engine (No. 2) due to a bird strike but actually stopped the operation of the left engine (No. 1).
The CRAIC explained that it derived this conclusion by synthesizing flight data recording device (FDR) data, cockpit voice recorder (CVR) data, switch positions in the cockpit, and results from the engine disassembly. The CRAIC is currently keeping data on the time of activation for left engine fuel shut-off and engine switches within the cockpit as evidence.
The CRAIC stated that while both engines were presumed to have stopped due to the bird strike during the early stages of the accident, the left engine was in comparatively good condition. A CRAIC official noted that precise analysis results showed that the right engine suffered damage severe enough to make normal operation difficult, whereas the left engine only sustained minor damage that would not significantly affect its output.
The CRAIC official noted, "After the bird strike, there was a 'surge' (a phenomenon where airflow inside the compressor is hindered due to damage and irregular combustion occurs), and flames were observed coming from the right engine," adding, "When we opened the engine, it was in better condition than expected on the left side. We thought it had been shut down due to the bird strike, but upon checking the FDR and CVR, that was not the case." The official concluded, "(The left engine) had no defects and only minor damage," saying, "The pilot was supposed to shut down the right engine but concluded that they shut down the left engine instead."
The CRAIC reported that at 8:58:11 a.m. on the day of the accident, the aircraft's pilot sent a message to the control tower saying, "There are migratory birds below the aircraft."
A few seconds later, the aircraft collided with birds, and it was confirmed that the pilot stopped the left engine while performing emergency procedures at 8:58:45 a.m. This occurred just 34 seconds after sending the bird strike warning message.
The CRAIC stated that this record of engine shutdown is retained in the CVR and FDR. The CVR reportedly recorded the pilots saying, "Let's turn off the (severely damaged) No. 2 engine (right engine)." However, contrary to what the pilots said, it was not the right engine that stopped operating, but the left engine. The CRAIC concluded that it appears to have been a mistake made by the pilots, resulting in incorrect input that caused the left engine to be shut down mistakenly.
Five seconds after the left engine shut down, at 8:58:50 a.m., FDR and CVR records were simultaneously halted. At 8:58:56, the pilot declared an emergency (mayday) to the control tower and attempted a belly landing while flying for four minutes over the left side of the runway without lowering the landing gear.
And after passing the runway at 9:02:57, it collided with the defense facility installed in front of the airport's outer wall.
To gain a more accurate understanding of the situation after the accident, additional FDR and CVR data are required; however, it has been reported that the black box operation was suspended starting at 8:58:50, making it difficult to find additional information.
It has also been revealed during the investigation that the aircraft's pilot did not activate landing-related devices, such as the landing gear, flaps, and speed brakes. The landing gear handle in the cockpit remained in the 'OFF' position, and there were no signs of operation for manual control devices and flap handles, according to the CRAIC official.
On the 19th, the CRAIC first explained these investigation results to the bereaved families before attempting to make them public, but the plan fell through. The reason for the families' opposition is that they believe, "The responsibility for the accident is only attributed to the pilot." They argue that there is a need to analyze other factors, such as the defense facility.
The CRAIC emphasizes that the results of this investigation are based on 'engine cause analysis.' In response to concerns that 'the collision with the concrete embankment installed at the end of the runway exacerbated the casualties,' a CRAIC official explained, 'An inspection of that structure is currently in progress, and the results are expected to be available by the end of August at the earliest.'
The CRAIC plans to decide whether to disclose the concrete embankment investigation results after consulting with the bereaved families. The final accident investigation report aims to be published by June next year.