ATSB response to WA Coroner
On 29 September 2010, the Western Australia Deputy State Coroner, Ms Evelyn Vicker, handed down her findings in the inquest into two deaths arising from a Robinson R22 helicopter accident that occurred on 28 September 2003 near Derby in Western Australia. The ATSB had previously investigated this accident and published its finding on the ATSB website: ATSB investigation 200304074. The Coroner fully agreed with the ATSB's findings.
The ATSB's key findings in the helicopter accident were:
1. The failure of the A166 clutch shaft, involving torsional fatigue cracking, which was due to the inappropriate assembly of the shaft to the A907 yoke.
a. a non approved jointing compound was used during the assembly; and
b. the bearing blocks were installed over the painted yoke surface
2. A loss of main rotor drive which was most likely to have occurred at a combination of height and speed that was insufficient to enable the pilot to conduct a successful auto rotation.
Two recommendations from the Coroner affect the ATSB:
Recommendation 3
CASA [Civil Aviation Safety Authority] seek input from the ATSB as to the reasonableness of mandatory inspection of both yoke and clutch shaft attachments in helicopters operating at low height for evidence of fretting in view of the fact this seems to have been a factor in failure of the A166 component in an R22 in 1992, 2003 and 2005.
ATSB Response:
The ATSB wishes to draw attention to the safety actions on page 10 of the ATSB's accident investigation report. As a result of an ATSB recommendation on 6 November 2003, CASA issued Airworthiness Directive AD/R22/51 which mandated inspections of the A166 shaft to A907 yoke on all R22 helicopters operating in Australia.
CASA also issued AD/R44/019 on 28 November 2003, mandating the same inspection on those R44 helicopters that had the C166 shaft to C907 yoke disassembled since installation at the factory.
On 7 May 2009 the Airworthiness Directives were cancelled by CASA because the instructions contained in them with respect to mandatory inspections were introduced by Robinson Helicopters into the maintenance manuals for the R22 and R44 models.
The ATSB has been advised by CASA:
"In light of the fact that the relevant maintenance manuals were updated to adequately reflect the maintenance practices required by the ADs, it was considered that the ADs were no longer required and they were subsequently withdrawn.
The ADs were no longer considered necessary because person's performing maintenance on Australian Aircraft are required to do so in accordance with the instructions contained in the applicable approved maintenance data (which includes the manufacturer's maintenance manual) - see r.42V of the Civil Aviation Regulations 1988."
The review of the maintenance manuals for the R22 and R44 helicopters in light of this accident and the findings of the ATSB led CASA to the conclusion that there was a heightened risk of improper maintenance practices being employed in the assembly of the clutch shafts in these types of helicopter. CASA addressed this risk by promulgating the ADs which were later adopted by the Robinson Helicopter Company. CASA considers that this risk is now adequately addressed via the amendments which have now been made to the manufacturer's maintenance manuals for both helicopter types."
The ATSB notes that it is normally CASA that would make an assessment as to the reasonableness of the implementation of a specific recommendation after a safety issue has been identified. In this instance the ATSB issued the initial recommendation on 6 November 2003. The ATSB is satisfied with CASA's response that the inspection requirement to address improper maintenance practices is contained in the Robinson Maintenance Manuals and mandated through the application of regulation 42V of the Civil Aviation Regulations 1988.
Recommendation 5
ATSB continue to circulate relevant investigation findings to the industry to remind operators and maintenance engineers manufactures recommendations are made for sound technical reasons.
ATSB Response:
The ATSB wishes to draw attention to section 12AA of the Transport Safety Investigation Act 2003 (TSI Act) which outlines that the ATSB's function is to improve transport safety through means that include:
- Identifying factors that have contributed to transport safety matters;
- Identifying factors that might affect transport safety;
- Communicating those factors to relevant sectors of the transport industry and the public.
Through its investigation and research and analysis activities the ATSB is committed to fostering safety awareness, knowledge and action. During the course of an ATSB investigation or research project the ATSB works with the relevant sectors of the industry to encourage safety action as safety issues are identified. The final report is always published on the ATSB's website and hard copies made available as required. Further, the ATSB regularly issues media releases and alerts to provide notification of the Bureau's activities.
Education materials are also supported and issued by the ATSB.
Cooperation with Coroners
ATSB investigations are conducted with the objective of providing findings that can be used to improve transport safety in the future. Coronial Inquests are a separate process to the ATSB investigation and they are usually supported by their own investigation and brief of evidence. However, as Inquests also have the objective of seeking to prevent a death occurring again, the ATSB provides cooperation through the explanation of the ATSB's findings in its report. The ATSB appreciates the interest of Coroners in working with the ATSB in the interests of improving future safety.
Questions concerning the inquest findings should be directed to the Coroner's Court in Western Australia:
Western Australian Coroner's Court
Level 10
Central Law Courts
501 Hay Street
PERTH WA 6000