On 16 April 2013, an Airbus A321 (HL7730) being operated by Asiana on a scheduled passenger flight from Harbin, China to Seoul Incheon as OZ 340 was damaged during a misjudged landing off a day Instrument Landing System (ILS) Category 1 approach at destination which was completed in Visual Meteorological Conditions (VMC). Three cabin attendants sustained minor injuries and ground impact caused substantial damage to the aircraft pressure bulkhead and stringers as well as superficial damage to the exterior skin of the rear fuselage.
An Investigation was carried out by the Korean Aviation and Railway Accident Investigation Board. Recorded data from the Flight Data Recorder (FDR) and Cockpit Voice Recorder (CVR) were successfully downloaded and recorded data from the ASDE showed when the aircraft crossed the landing runway (16) threshold and where and when the aircraft made its initial and second touchdowns and subsequently cleared the runway.
It was established that the 46 year old aircraft commander had accumulated 722 hours in command of the A321 after promotion to Captain just over a year earlier. The 32 year old First Officer had recently joined the airline and had 383 total flying hours including 33 hours accumulated since appointment as an A321 First Officer two weeks prior to the accident.
It was established that the commander had taken over as PF upon being informed by ATC that the cloudbase was 200 feet aal just over two minutes before touchdown. Prior to this, the First Officer had been flying the aircraft manually during descent to gain familiarity with the PFD. The A/T was disconnected about 3.5nm from touchdown passing 1200 feet aal but the PF made no callout. The aircraft was stabilised as required at the 1000 feet 'gate' and remained so until the aircraft descended below 100 feet aal when airspeed began to drop below the declared VApp and an excessive sink rate developed without any callout by the PM. The PF increased the thrust to compensate but the aircraft still touched down hard (almost 2g vertical acceleration was recorded) just 155 metres from the threshold of the 4000 metre runway. Touchdown pitch attitude was recorded as 6.7º and during the following 5 second bounce, it increased further to reach 9.8º before peaking at 10.9º at the second touchdown which occurred 491 metres from the threshold. The progress of the aircraft as depicted on and recorded by the ASDE is reproduced below.
Position and Time images recorded by ASDE (Reproduced from the Official Report) - click to enlarge
The A321 FCOM states that for an A321 with fully extended and compressed main landing gear, the pitch attitude limit is 9.7º - with the second touchdown occurring at 1.2º beyond this limit. The Investigation concluded that "the PF failed to think of pitch attitude limitations required for avoiding a tail strike when the aircraft pitch attitude was increasing during the bounce on the initial touchdown" and that, as a result, he had failed to maintain a pitch attitude which would ensure that the aircraft touched down at a pitch attitude below the limit.
It was noted that the PF, like all other Asiana pilots, had learned about bounce recovery techniques during a ground school course but had never been trained in the simulator to demonstrate proficiency in bounce recovery, which requires that pitch attitude should not be increased and thrust should be kept at idle.
After the accident, a simulator was used by the Investigation to see how an experienced Asiana Captain responded to a bounce and it was found that a tail strike occurred. It was considered that this indicated that "theoretical learning in the ground school course alone cannot allow the flight crew to make a safe touchdown after actual bouncing" and that such practical experience should be added to simulator training - with the ground impact recognition function disengaged.
The Investigation noted from the CVR recording that no approach briefing was given and that on a number of occasions throughout descent and approach, both pilots failed to make standard callouts and responses.
The formally documented determination of Causes of the investigated accident were as follows:
- The PF failed to maintain the proper approach speed until the flare just before touchdown, and the airplane bounced on touchdown because higher-than-normal vertical gravity was applied due to a high sink rate and increased thrust and speed just before touchdown.
- The aircraft made a second touchdown at the pitch attitude exceeding an A321 aircraft limitation and sustained a tail strike because the PF failed to keep thrust at idle and establish the proper pitch attitude during the bounce.
It was further determined that there were six Contributory Factors:
(1) the inadequacy of the pilot training program dealing with the recovery form the bounce;
(2) lack of pre-landing preparation due to a failure to conduct an approach briefing on pitch attitude;
(3) the failure of the PF to properly allocate his attention due to his delegation of flight control to the pilot monitoring (PM) who failed to meet flight control requirements;
(4) the inadequate advice and monitoring from the PM due to the failure of the PF to make standard callouts;
(5) the disconnection of the autothrottle and a failure to manually control thrust and speed;
(6) a failure to execute a go-around when stabilised approach criteria are not met.
Six Safety Recommendations were made a result of the Investigation:
- that Asiana Airlines should re-emphasise through their pilot training programs their (existing) policy that if a stabilised approach is not established, executing go-around is the safest choice for safe operation so that flight crew can be fully aware of it. [AAR1303-1]
- that Asiana Airlines should train its pilots in a simulator to ensure that they can operate the aeroplane in a stable manner after bouncing on touchdown and add this training to the ground training program. [AAR1303-2]
- that Asiana Airlines should train its pilots to comply with the Pilot Operating Manual requirements for flight control delegation to the First Officer, to put top priority on the performance of roles as the PF and the PM during flight and incorporate training outcomes into evaluation. [AAR1303-3]
- that Asiana Airlines should reinforce flight crew adherence to Pilot Operating Manual requirements for approach briefing and standard callout procedures on every flight through its training programs. [AAR1303-4]
- that the Ministry of Land, Infrastructure and Transport (Office of Civil Aviation) should, during line qualification check and aviation safety inspection, strictly check whether the pilots of all air carriers conduct an approach/landing briefing and comply fully with standard callout procedures and take complementary institutional measures. [AAR1303-5]
- that the Ministry of Land, Infrastructure and Transport (Office of Civil Aviation) should review measures to ensure that pilots of all Korean airlines can be given simulator training as part of ground training programs to attain proficiency that enables them to operate an aeroplane in a stable manner after bouncing during landing. [AAR1303-6]
The Final Report was completed in September 2014 and published in English translation on 22 January 2015.