On 20 November 2013, an Airbus AIRBUS A-320 (PK-AXG) being operated by Indonesia AirAsia on a scheduled domestic passenger flight from Yogyakarta to Bali as AWQ 8411 partly entered the runway at Yogyakarta in normal ground visibility at the same time as a Boeing 737-900 (PK-LBH) being operated by Batik Air on a scheduled domestic passenger flight from Jakarta to Yogyakarta as ID 6360 was about to land in the opposite direction of the same runway and was not in contact with TWR. The 737 crew saw the A320 incursion as they touched down on the 2200 metre runway and were able to stop 100 metres before reaching the A320.
An Investigation was carried out by the Indonesian National Transportation Safety Committee. Data from the A320 FDR was successfully downloaded and available to assist the Investigation.
It was noted that the 60 year old Captain of the A320 with 20,000 flying hours including 500 on the A320 was accompanied by a 25 year old First Officer with 3100 flying hours, almost all on the A320.
The A320 was instructed by TWR to taxi to the Holding Point for Runway 27 via the N2 taxiway. The pilot advised the Investigation that he thought that the intended Holding Point was located near to the runway 27 threshold and that taxiing to the N3 taxiway was the best way to reach it without entering the runway. On request, TWR re-confirmed that the clearance was via taxiway N2 but the Commander appeared to have then assumed that this clearance included entry to the runway in order to backtrack to the Holding Point. However he then failed to clarify this assumption with TWR and since his aircraft was the only traffic to communicate with TWR during the taxi out, he "assumed that there was no aircraft on approach".
As he taxied across the N2 Holding Point, the Commander of the A320 saw an aircraft on final approach to Runway 09 and immediately stopped his aircraft as TWR simultaneously instructed him to hold position. FDR data from the A320 showed that the nose of the aircraft was 16 metres past the Holding Point.
The APP controller had previously informed the 737 that the runway was clear of traffic and issued a landing clearance subject to the runway being in sight. The 737 pilot reported runway in sight with 3.5 nm to go and the APP controller re-issued the landing clearance and instructed the pilot to contact TWR after landing.
After observing that the A320 had entered the runway and that the 737 was at about 600 feet on final approach, TWR requested APP to instruct the 737 to go around. However, the APP controller "perceived that a go around when an aircraft was on short final might jeopardise the safety of the flight" and did not do so. Realising that the 737 was continuing its approach, TWR instructed it to make a go around but there was no response. It was considered likely that the 737 was still monitoring the APP frequency given that they had been told to contact TWR only after landing.
The Landing Distance Required by the 737 was found to have been between 1467 metres and 2016 metres depending on braking action; the actual landing distance used was approximately 1650 metres. The Commander of the 737 subsequently reported that he had been able to see the runway from approximately 1500 feet and had also seen an aircraft taxi out to N2. Then, just after touching down, he reported having seen that the A320 was on taxiway N2 but that the nose of the aircraft was protruding onto the runway. He had then applied maximum manual braking and full thrust reverse and as a result, his aircraft stopped approximately 100 metres from the A320. TWR then instructed the A320 to return to the Apron via taxiway N3 and the 737 to proceed to the Apron via taxiway N2.
The actual taxiway layout at Yogyakarta at the time of the investigated event (reproduced from the Official Report)
Part of the Jeppesen Chart used by both the A320 and B739 crews (reproduced from the Official Report)
It was established that the confusion about taxi routes had occurred in the context of the failure to communicate changes to the taxiway system. It was found that 'new' Taxiways NP and N3 had been in use 'on trial' for over a year prior to the investigated incident but that, although this information had been included in a NOTAM, it had expired 6 days prior to the investigated event and had not been included in the AIP Indonesia. Both Operators were found to provide their crews with the Jeppesen Flight Guide which, like those of other commercial providers, relies on State AIPs for its content. The difference between the reality and the information available to pilots can be seen by comparing the two charts above.
In respect of ATC actions which had contributed to the potential for a runway collision, the Investigation found that:
- the failure of APP to transfer the arriving aircraft to TWR until after landing was contrary to the prevailing ATC SOP which stated that "the transfer of control for arriving aircraft shall be performed at 2500 feet". The fact that APP and TWR were not co-located meant this SOP was of particular importance.
- the failure of the APP controller to instruct the 737 to go around when asked was attributed to a lack of appreciation that the 737 can safely perform a go around "as long as the aircraft has not touched down".
It was also noted from the ATC recordings that there was evidence of "background conversations not pertinent to aircraft control".
A summary of the Safety Issues identified during the Investigation was formally documented as follows:
- Transfer of control and communication
- Taxi Clearance
- Controller coordination
- Go around from 600 feet
- The stopping distance of the landing aircraft
- Aeronautical Information Publication
Safety Action taken to improve risk awareness as a consequence of and during the Investigation by both Batik Air and Indonesia Air Asia was considered to have been a sufficient contribution to the prevention of similar occurrences.
The Investigation determined that the Contributing Factors to the accident were as follows:
- Misinterpretation between the pilots and the controller related to the position of the runway 27 holding point and the failure to clearly clarify the taxi clearance issued to the Indonesia Air Asia A320.
- The lack of a transfer of control and the ineffective communication between the APP and TWR controllers resulting in the initiative of the TWR controller to instruct the Batik 737 pilot to go around not being acknowledged by its pilots.
Seven Safety Recommendations were made as a result of the Investigation as follows. In respect of those made to ANSP AirNav Indonesia regarding Yogyakarta, the possibility of these particular issues extending to controllers at other airports was identified.
- that AirNav Indonesia Yogyakarta should emphasise to all controllers the importance of being consistent in the implementation of SOP, particularly on transfer of control and transfer of communication.
- that AirNav Indonesia Yogyakarta should ensure that controllers properly understand and implement standard radiotelephony phraseology.
- that AirNav Indonesia Yogyakarta should enrich the knowledge of controllers concerning to the aircraft performance and operation.
- that AirNav Indonesia Yogyakarta should ensure that the controller environment is free from any noise and non-pertinent conversation.
- that the Directorate of Civil Aviation (DGCA) should issue an amendment to the AIP for Yogyakarta Airport to include the taxiways NP and N3 on the airport charts.
- that the Directorate of Civil Aviation (DGCA) should review the existing AIP publication system to ensure the amendment of the AIP to the current condition in timely manner.
- that the Directorate of Civil Aviation (DGCA) should review the controller training program in order to enrich the knowledge of controllers concerning to the aircraft performance and operation.
The Final Report was released on 14 July 2014.