Strikemaster Inquest Update
The New South Wales Deputy State Coroner recently released findings into a 2006 fatal Strikemaster aircraft crash near Bathurst, NSW (Coroners Findings). Some of the findings relate to safety issues raised by the ATSB in its report released on 9 May 2008 (ATSB Report).
These issues cover:
- Inspection procedures for detecting cracking in the bore of a wing lug
- The transfer of an aircrafts systems of maintenance from the military to the civil environment.
Circumstances of the accident
On 6 October 2006 a BAC 167 Strikemaster broke up mid-flight with two people on board. The pilot was taking the passenger on an adventure flight which was intended to include high level aerobatics followed by a low-level simulated strike mission.
The majority of the available evidence was consistent with a break-up initiated by separation of the tail surfaces leading to the separation of a weakened right wing. The right wing had been weakened by fatigue cracking in the wings upper main spar attachment lug. Although the fatigue cracking was found not to have contributed to the initiation of the aircrafts break-up, the fact its presence was not picked up during maintenance checks underpinned the safety issues raised by the ATSB.
The Coroner reached the same finding as the ATSB as to how the aircraft broke up mid-flight. A number of the Coroners recommendations arose out of the safety issues identified by the ATSB.
Safety Issues
Inspection Procedures for Detecting Cracking in the Bore of a Wing Lug
The right-wing main spar upper attachment lug contained two pre-existing fatigue cracks that had not been detected.
Related to this finding the Coroner issued a recommendation to CASA that consideration be given to amending a servicing procedure instruction so that in preparation for non-destructive eddy current testing, the area for such testing is to have all coatings removed.
Transfer of an aircrafts systems of maintenance from the military to the civil environment
The Strikemaster aircraft involved in the accident was delivered new from the British Aircraft Corporation to the Republic of Singapore Air Force in 1970. It was retired from military operation in 1986. When it was brought out to Australia it was originally utilised for aerial and static displays at airshows before being used for adventure flights.
The ATSB raised a safety issue that the transfer of aircraft systems of maintenance from the military to the civil environment has the potential to reduce the level of safety, due to the probability of incomplete documentation and a lack of specialist aircraft type knowledge. In its report the ATSB noted that there is no certainty by which a civil owner of a military aircraft can obtain information from the military aircraft manufacturer or previous military owner.
Although there are currently no known Strikemaster aircraft flying in Australia, the safety issue was to be considered in relation to ex-military aircraft more generally.
Following the accident, CASA gave approval to the Australian Warbirds Association Limited (AWAL) to administer aircraft in the Limited Category. This was considered to be a positive action to advance safety. The aircraft must be operated and maintained in accordance with the AWAL manual or have a specific approval issued by CASA. In his findings the Coroner reviewed some of the progress with respect to implementing the administration arrangements involving AWAL.
The Coroner also addressed a concern that arose during the inquest about whether a penalty factor was supposed to be applied to the fatigue life of the aircraft. The ATSB raised this matter in its investigation report. After further inquiries made of the manufacturer during the inquest, the continuing lack of certainty led to CASA issuing Airworthiness Bulletin (AWB 02-041: issue 3), recommending registered operators and maintenance organisations review their aircrafts fatigue index records and determine if the penalty should be applied.
The Coroner has sought further action in relation to the issue of the availability of information from manufacturers of military aircraft to persons operating them in the civil environment. The Coroner made a recommendation that every year CASA contact manufacturers of military aircraft and other limited category aircraft seeking any new information that relates to the safe life and operation of the aircraft.
Other Recommendations of the Coroner
The ATSBs investigation focussed on factors leading to the occurrence of the accident. The Coronial inquest looked at these factors but also at matters affecting the search and rescue response which resulted in a number of findings and recommendations. These included recommendations with respect to the carriage of Emergency Locator Beacons and Emergency Position Indicating Radio Beacons. The Coroners report should be referred to for these to ensure that they are understood in the context of the evidence at the inquest.
ATSB Investigations and Coronial Inquiries
Inquests are separate to ATSB investigations. The Coroner formulated his findings and recommendations independently of the ATSB. The ATSB cannot speak for the Coroners findings. However, the ATSB supports the coronial process and in the interests of ensuring that safety information is made available to the broadest audience the ATSB is making this publication.
The NSW Coroners report can be obtained via the Coroners Court website. Queries regarding the Coroners findings should be directed to the Coroners Court of New South Wales.
The ATSB's report can be downloaded from the link at the top right of this page.