The supplementary ATSB investigation report into the Whyalla Airlines fatal accident tabled in the Senate today confirms the likelihood of the ATSB's accident scenario in its December 2001 report in contrast to the findings of the SA State Coroner in July 2003.
In November last year the ATSB formally re-opened its investigation into the VH-MZK accident after possible significant new evidence about a potential manufacturing defect in the left engine crankshaft steel became available from the US engine manufacturer:
- ATSB re-testing of the crankshaft, including using independently witnessed destructive testing and the input of external laboratories, found no problems with the steel that could have led to it fracturing under normal operating conditions
- in contrast to the Coroner's findings, this confirmed the ATSB's earlier conclusions
- the Coroner's solicitor has advised the ATSB that the Coroner did not receive expert advice on the ATSB 50-page test report before concluding it took the matter no further.
The ATSB does not agree with the SA Coroner that the pilot of VH-MZK would have allowed, ahead of any stressful flight situation, his right engine to overheat to the point of melting a hole in the number 6 piston eight minutes into the cruise phase of the flight, especially when the temperature monitoring probe is on top of the number 6 cylinder:
- the SA Coroner conceded that 'it is difficult to form definite conclusions on this issue'
- the ATSB's latest report confirms the much greater likelihood that the left engine failed first and then the right engine overheated when power was boosted in response
- as the ATSB told media when releasing its report on 19 December 2001, it is not appropriate to blame the young pilot in this scenario and the ATSB did not do so.
As in December 2001, the ATSB's report does not criticise Whyalla Airlines for its fuel leaning settings in climb that were in accordance with aircraft manufacturer guidelines:
- the ATSB continues (since October 2000) to urge industry to use conservative (rich) fuel climb settings in Piper Chieftains to minimise the possibility of engine damage
- the Bureau report also reinforces other areas of safety action accepted by the Coroner.
It is most unfortunate that damages proceedings in the US cast a long shadow over the inquest and exacerbated problems in gaining access to the scant available evidence.
In light of the detailed material in the ATSB's 170-page supplementary report strongly supportive of its December 2001 report, the ATSB finds the sharp criticism of its investigation by the South Australian State Coroner last July to be deeply regrettable.
The ATSB will be prepared to further explain and, if necessary, defend its conclusions in Senate Legislation Committee public hearings next week.
For the future, the ATSB will continue to seek to work cooperatively with state and territory coroners around Australia because of the public interest in transport safety.