Summary

The final report of the accident involving Qantas B747-400 VH-OJH at Bangkok, Thailand on 23 September 1999 concluded our most important investigation of an accident involving an Australian registered jet aircraft.

The investigation was one of the most comprehensive and exhaustive ever conducted by the ATSB (or its predecessor the BASI).

Investigator In Charge, Mike Cavanagh, reports on the investigation itself.

The Australian Transport Safety Bureau released its report on the Qantas B747-400 runway overrun accident at Bangkok International Airport on 23 September 1999 on 25 April 2001.

The accident occurred when the B747-400 landed well beyond the normal touchdown zone and then aquaplaned on a runway that was affected by water following very heavy rain. The crew omitted to use either full or idle reverse thrust during the landing. The aircraft was still moving at 88 kts (163 km/h) at the end of the runway and stopped 220 m later in soft turf with its nose on the airport perimeter road. A precautionary evacuation was made using emergency escape slides about 20 minutes later.

Although the flight crew and cabin crew made a number of errors, many of these were linked to deficiencies in the Qantas operational procedures, training and management processes. CASAs regulations covering contaminated runways and emergency procedures were also found to be deficient, as was its surveillance of airline flight operations. Qantas and CASA either have made, or are in the process of making, significant changes in the areas where deficiencies were identified including the development by CASA of a systems-based surveillance audit approach.

The on-site phase

As the accident occurred in Thailand, responsibility for conducting the investigation fell to Thailand in accordance with Annex 13 to the International Civil Aviation Convention. As the State of registry, Australia had the right to appoint an Accredited Representative to the investigation. On the day following the accident, a team of four ATSB investigators travelled to Bangkok with the Qantas incident response team. Thai agreement to the Australian nominated Accredited Represent-ative was received en route.

A series of meetings was held with the Aircraft Accident Investigation Committee of Thailand over the next few days. The Committee took possession of the cockpit voice and flight data recorders, examined the aircraft, and interviewed the flight crew.

Runway 21L was closed because of the position of the aircraft in the overrun area. It was necessary to reopen the runway as soon as possible so that normal operations could resume. To facilitate this, the Committee handed custody of the aircraft back to Qantas so that recovery of the aircraft could begin. By that time, aircraft recovery experts from Boeing had arrived.

The first step in the recovery involved stabilising the aircraft to prevent further movement in the very wet, muddy soil. The landing gear was removed and a gravel road sloping down from the end of the stopway to below ground level beneath the aircraft was then constructed. New landing gear was fitted and the aircraft lowered on to the road. It was then towed backwards on to the runway. The recovery process took about seven days to complete.

In the meantime, the Committee delegated investigation of the cabin safety aspects of the occurrence to the ATSB. That enabled the ATSB investigators to conduct a detailed examination of the aircraft cabin and to speak to local sources regarding post-accident events.

The Committee retained control of other aspects of the investigation and asked the ATSB to conduct readouts of the flight recorders under the Committees supervision. Four Thai investigators attended the ATSBs Canberra facility in October 1999 and supervised the readouts. On 18 November 1999, the Committee delegated the complete investigation to the ATSB. The ATSB accepted the delegation and agreed to provide the draft report to the Committee for review in accordance with Annex 13 clause 6.9 before public release.

The investigation process

In common with widely accepted international practice, the ATSB formed an investigation team consisting of a number of groups aircraft operations, flight recorders, engineering, cabin safety, and organisational issues each under the control of an ATSB investigator reporting to the Accredited Representative who acted as investigator in charge.

The function of the groups was to collect all factual information that was relevant to the groups area of investigation. As standard practice, organisations with a direct interest in the investigation (such as Qantas, Boeing, CASA, and the flight and cabin crew industrial organisations) were invited to nominate relevant experts to the groups. In some cases, the expertise and resources available within the ATSB were not sufficient for the level and volume of information required. This meant that assistance from outside organisations was requested both as participation in a group or providing specific information to the group.

Qantas provided a very high level of cooperation and substantial expert assistance and advice regarding all facets of the investigation, especially in the areas of aircraft operations, engineering and cabin safety. This level of assistance made a major contribution to the safety benefits achieved by the investigation.

From an initial assessment of the accident and post accident events, a logical approach to the investigation seemed to be to break the task into two segments and these were:

1. The accident flight (ie. the approach and landing) to determine the issues relating to the flight itself that led to the overrun. Aspects to be examined included:

- weather
- air traffic control
- aerodrome/runway
- crew performance
- aircraft systems
- aircraft performance in the air and on the runway
- crew procedures and training.

2. Post accident events (ie. from the time the aircraft touched down until the precautionary disembarkation was complete) to determine any passenger or crew safety issues. Aspects to be examined included:

- cabin damage
- aircraft emergency escape and communications systems
- flight and cabin crew performance
- flight and cabin crew procedures and training
- airport emergency response
- the evacuation process.

As these tasks progressed and the picture of events emerged, it was possible to identify areas where deficiencies might have existed. These areas then became the subject of closer and more detailed examination. Eventually, this enabled conclusions to be drawn regarding the active failures that occurred.

The next step was to look at the systems behind the active failures to see if any deficiencies existed that might have set the scene, for the active failures to have occurred. The sorts of things to be examined here included how various procedures and training programs were developed and how possible hazards were identified and risks assessed. This examination centred on Qantas and CASA.

It should be noted that the investigation groups were not involved in collecting and assessing all of the factual information. Certain types of information, such as the cockpit voice recorder, had restricted access. The organisational factors group was composed only of ATSB personnel. The analysis of the factual information was undertaken solely by ATSB investigators.

By July 2000, more than 45 files (each containing 200 documents), more than 500 photographs, and over 1100 emails of information had been collected. The next step was to draft the investigation report.

Since September 1999, three ATSB investigators had been working full-time on the investigation. A number of other investigators assisted at various stages. In total, the investigation involved six ATSB investigators.

The report and review process

Writing the report was a challenging and difficult task. It was important for the document to be reader friendly, but at the same time contain enough information to justify the conclusions of the investigation. It was felt that the recommended ICAO format for accident reports was not appropriate because of the many issues involved and their complexity. The structure settled upon involved diiding the report into a number of parts, each part covering a particular aspect and, in effect, being a report within a report.

By mid-October 2000, the draft had been completed. An extensive interested party review took place to ensure factual accuracy and natural justice. A final draft was sent to the Accident Investigation Committee of Thailand on 12 February 2001.

On April 2001 the Chairman of the Committee, Air Chief Marshal Kongsak Variana, advised ATSBs Executive director that the Committee had considered the draft report and agreed without amendment. It concluded one of the most detailed world-wide investigations of a non-fatal large passenger aircraft accident.

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