On 18 April 2013, an Airbus A340-300 (9M-XAC) being operated by Air Asia on an international passenger flight from Tabriz to Medina for Saudi Arabian Airlines as SVA 2869 failed to complete an attempted 180° turn to align with the cleared take off direction in normal night visibility after backtracking the full length of the runway and the nose gear departed the side of the paved surface into soft ground and became stuck. The 295 passengers were disembarked and the aircraft subsequently recovered using ground equipment. On subsequent inspection by the Air Asia engineer accompanying the aircraft, it was found to be undamaged.
The nose gear stuck into soft ground outside the paved surface. [Reproduced from the Official Report]
An Investigation was carried out by the Aircraft Accident Investigation Department of the Iran Civil Aviation Organisation (CAO). CVR and QAR flight data, the latter with equivalent parameter recording to the FDR, were successfully downloaded and used to assist the Investigation. It was specifically noted that the downloaded data was consistent with the accounts given by the pilots.
It was noted that both pilots were Malaysian nationals. The 53 year-old Captain, who had been PF for the departure and had previously operated into Tabriz, most recently two weeks prior to the investigated excursion, had accumulated 19,178 total flying hours which included 675 hours on type. The 27 year-old First Officer had accumulated 3,612 total flying hours which included 203 hours on type and was on his first visit to Tabriz.
It was established that after leaving the apron, the aircraft had been cleared to taxi onto departure runway 30L via taxiway 'A' and then backtrack to the beginning of the 45 metre-wide runway in order to perform a full length (3,757 metre) take-off (see the illustration below). As the aircraft approached the end of the runway, the Captain began a clockwise 180° turn but when he detected skidding, judged that there was now insufficient room to safely complete the commenced turn and decided to change to an anti-clockwise turn. However, the turn in this new direction continued, the crew reported having become concerned that it may not be possible to complete it whilst maintaining sufficient clearance for the No 4 engine to pass safety over the jet blast barrier located just to the south east of taxiway 'C' on the north side of the runway and requested and obtained the assistance of a marshaller. Although the marshalling guidance was given to continue the turn, the crew were concerned at both the likely engine clearance over the jet blast barrier and the position of the nose landing gear in relation to the edge of the paved surface and the aircraft was stopped because of this concern rather than a marshaller signal. Once the aircraft had stopped, the Captain had asked the Company Engineer travelling with the aircraft to exit it via the avionics compartment access door to check the situation and once outside the aircraft he was able to see that the nose landing gear was already off the runway.
It was found that although the surface wind had been very light at the time of the excursion, it had been raining at the time and the asphalt surface of the runway had been wet. It was noted that the FCOM stated that the actual turn on a dry good condition runway for the aircraft involved "without margin" was exactly the same as the actual runway width. However, the prevailing wet runway surface would have meant that additional width for the turn would have been required despite the Captain's use of the full steering capability - a 72° angle - and his maintaining an appropriate ground speed whilst turning.
The aircraft track to the runway 30L threshold after entering via taxiway 'A' showing that little use was made of taxiway 'C' during the attempted turn near the threshold. [Reproduced from the Official Report]
QAR data confirmed that skidding had occurred during both the initially attempted (and SOP-recommended) clockwise turn and the subsequent anti-clockwise turn. In both cases, the Captain had used differential braking with ground speed 5 knots below the recommended minimum whilst significantly increasing engine thrust with the aim of tightening the turn "due to the low turning speed". Runway marks showed that in one of these episodes, the action had actually increased the turn radius by 0.3 metres. It was noted that the SOP for the turn detailed in the FCTM explicitly recommended not using differential braking and highlighted the importance of maintaining a minimum ground speed not less than 8 knots "so as to avoid the need to significantly increase thrust in order to continue moving". It was also noted that during the Captain's attempt at an anticlockwise turn, the aircraft had passed beyond the displaced runway threshold which had led directly to its closeness to the jet blast barrier and, having "not made much use of" the additional space provided by the presence of the very wide taxiway 'C' during the initial turn attempt, had resulted in this space being no longer available.
The Investigation also found that:
- Despite the fact that runway 12R/30L was, according to the Jeppesen Aerodrome Chart available to the crew, a "non-instrument runway" which was restricted to daylight use only, the departure was being made in the hours of darkness - as the earlier landing had been.
- No official aerodrome briefing for Tabriz had been available to the flight crew prior to their departure from Jeddah and it was found that "pilots’ knowledge and information related to operations at Tabriz were gathered from other pilots that had been there".
- The delayed departure from Jeddah and the short-notice roster changes associated with this meant that the pilots "did not have proper rest and the last minute duty change was not in accordance with Flight and Duty Time Limitations".
- The intended take-off was from runway 30L rather than the primary runway 30R because the latter was closed due to construction work and had been so notified by NOTAM. A full length take off was the only option because the flight crew did not have take-off performance for departure from the taxiway 'B' intersection.
- The Jeppesen Aerodrome Chart identified Hot Spots in respect of 180 turns made at both ends of the primary but closed runway 12L/30R, instructing pilots to begin such turns in the anti-clockwise direction at the 30R threshold and in the clockwise direction at the 12L threshold whereas there were no similar designations / instructions in respect of turns at the ends of runway 12R/30L. Both runways were of equal width and 180° turns would only be necessary for full length departures if the other runway was (as in this case) unavailable for use as a taxiway.
- The applicable A340-300 ACN was found to be 74 whereas the PCN promulgated in the State AIP for runway 30L/12R was only 60, meaning it was not suitable for use by an A340-300.
- Tabriz Airport did not have a suitable tow bar for an A340 although after the excursion and passenger disembarkation, one was used to get the A340 back onto the paved surface.
- Only one set of Jeppesen Charts was available on the flight deck of the aircraft involved and "they were not always up to date" with "most pilots resorting to using their own IPADs with Jeppesen applications installed, using an 'uncontrolled' chart database from the open market (P2P torrent download)".
- Neither of the Advanced Mission Display Systems (AMDS) - a fully integrated Class III EFB - installed on the aircraft to aid flight management were working.
The Conclusion of the Investigation was that the wet surface of a runway which was "unsuitable" for use by an A340 had resulted in the aircraft skidding during the attempted 180° turn despite the use of full nose wheel steering capability and use of a very low groundspeed.
A Contributory Factor was identified as the need to backtrack to the full length of the departure runway because the pilots did not have the necessary take-off performance data for a departure from taxiway 'B'.
Ten Safety Recommendations were made as follows:
- that the Saudi Arabia General Civil Aviation Agency should take immediate action to consider the implications of the findings of this investigation on Saudi Arabian Airline operation.
- that the Malaysian Civil Aviation Department should take immediate action to consider the implications of the findings of this investigation on Air Asia operations and perform effective supervision on its activities.
- that Air Asia should evaluate introduction of a Flight Data Analysis and Surveillance Program which would monitor crew behaviour associated with all aircraft fleets.
- that Air Asia should establish and implement an 'Action Plan for Prevention of a Similar incident' which achieves the following:
- Reinforces pilot education on behaviour in respect of SOP, FCOM, avoidance procedures and the careful use of airport information.
- Reviews flight crew procedures for efficient and immediate reaction against a similar situation.
- that Air Asia should ensure that its flight crew operate within applicable maximum FDP.
- that Air Asia should establish an annual CRM training for its pilots, evaluate its performance and send its conclusions to the Malaysian DCA.
- that Air Asia should ensure that DFDR parameters are recorded by reference to UTC.
- that Saudi Arabian Airlines should obtain all the limitations of their destination Iranian airports from the Iranian Airport Authority and then ensure that appropriate aircraft types are used to ensure adequate operational safety.
- that Saudi Arabian Airlines should take note of the content of the Operations Manuals of Chartered Airlines and ensure that flight planning takes place in accordance with it.
- that Airbus should insert a warning note in the A340 FCOM to the effect that additional runway width will be required for turns on wet and slippery runway surfaces.
The Final Report of the Investigation was "released" on 8 April 2013 and subsequently (2017) made available online.