Crew lacked knowledge of cabin pressure system in serious Jeju Air incident
The flight crew conducted preflight checks before the aircraft started but failed to notice that the engine bleed switch which supplies air to the aircraft cabin, was off.
On the 23rd December 2015 Boeing 737-8AS (WL) took off from Gimpo Airport at around 18:42.
While carrying out the climb check at 10,000ft, the crew again failed to verify the position of the bleed air switch.
At 18:46:37, flight 101 continued to climb, reaching an altitude of 13,317 ft, when the cabin pressure altitude warning came on.
The aircraft reached 14,163 ft before a descent to FL100 was initiated.
The captain found that the two engine bleed switches were off and turned on the engine bleed switch at 18:47:01.
At 18:49:15, HL8049 reached 10,000 ft and the first officer instructed the captain to carry out the Cabin ALT warning emergency procedure and set the pressure control mode to the Manual position and the outflow valve to the Closed position.
At 18:50:38 HL8049's cabin altitude warning light turned off and the crew stopped the emergency procedures.
But the cabin pressure control mode was still set to the manual position and the outflow valve was kept closed.
At 18:55:16 The first officer asked the cabin crew about the situation in the passenger cabin and it was reported that everything was fine.
At around 18:57:35 the flight crew commenced a climb to FL220.
At 19:01:09, at 18,966ft, the captain was informed that the passengers were complaining of earpain.
The flight crew did not recognize the cause of this and again carried out the emergency procedure in accordance with the quick reference handbook (QRH), while initiating a descent.
The flight crew donned their oxygen masks and confirmed that the outflow valve was closed.
At 19:05:39, the aircraft had reached FL100, but the passengers continued to suffer from earaches.
The oxygen masks were deployed and the flight requested permission to descend to 8,000ft, which was granted.
At 19:14:52, the crew declared an emergency and requested an expedited landing at Jeju.
At 19:21 the flight crew contacted a company maintenance engineer at Jeju Airport, stating that the cabin pressure was at an altitude of 25,000ft, even though they had descended to 8,000 feet.
The inside and outside differential pressure of the aircraft exceeded the limit of 8.9 psi The mechanic stated that the outflow valve should be fully open and advised the crew to slowly open the valve.
A safe landing was carried out at 19:36 and three minutes later the pressure had cabin altitude both had dropped to zero. Cause: "The Air and Railway Accident Investigation Committee confirmed that the engine bleed switch was set to "off" before the flight, but that the flight crew carried out three pre-flight checks and that flight crews failed notice the cabin pressure setting due to a lack of understanding of the cabin pressure system.
As a contributing factor, it is decided that there is a lack of theoretical training and practical training on the cabin pressure system of the flight crew." ■