Time Out
24th May 2005, 10:36
ANALYSIS
The KAflex® shaft had been fitted in accordance with the published requirements in the supplemental type certificate (STC) about 6 years, or 4,112.35 flying hours, prior to the occurrence. As far as could be determined, no certifications had been made that the shaft had been inspected in accordance with the STC inspection requirements during that period.
There was no flight manual supplement supplied as part of the STC, which would have alerted pilots to the specific inspection requirements and the significance of red dust production. As well as the daily inspection requirements for the shaft, the supplement did not include the warning not to disturb the bolts and to reject a shaft that showed evidence of turning of the fasteners.
The STC documents supplied with the shaft were not kept with the current helicopter logbook, although it was readily available. The retention of the STC documents in the archived logbook, instead of the current logbook, meant that the STC inspection requirements were overlooked and consequently not actioned by maintenance personnel. That resulted in the STC inspection requirements not being included as part of the routine or scheduled maintenance paperwork packages when they were assembled for release to service maintenance events.
The historical service record card for the shaft could not be located and had not been included in the helicopter records as required by the manufacturer in the STC accomplishment instructions. The minimal reference made to the card in the STC could easily have lead to the card being overlooked. When an example of the card was obtained, the appropriate location for the certification of maintenance activities was not readily apparent. The lack of a specific area on the card to certify completion of maintenance may have also contributed to the non-use of the card by maintenance personnel, including the 1500-hourly inspection certification in the airframe logbook. Also, inclusion of these inspection certifications in the airframe logbook could lead to the certification history for a driveshaft being lost if a driveshaft was subsequently moved from one helicopter to another. When overhaul became due, this service history would also have been unavailable to the manufacturer when the shaft and accompanying historical service card were returned to them.
The shaft failure had been initiated by fretting type movement at a flex frame bolted joint. This progressed until the joint failed, resulting in the gross overload failure of the remaining frames. That movement, in its early stages, should have been detectable by the presence of the red dust or loose bolted joints described in the STC inspection warnings. Had the maintenance and operating personnel been aware of the STC inspection schedules, they would have had a better understanding of the significance of the red dust and its ramifications.
Although the operator submitted that his personnel would have detected red dust had it been present around the flex frame joints, the wear pattern evident on the flex frame joint in Figure 1 was consistent with the flex frame fastener being loose for a period of time prior to the failure. The loose bolted joints were not detected. In this occurrence, the loss of bolted joint integrity may have progressed past the point where dust production may occur.
SAFETY ACTION
Civil Aviation Safety Authority safety action
Early in the investigation, consultative briefings were held between the Civil Aviation Safety Authority (CASA) and the ATSB. As a result of those briefings, CASA wrote to all Bell 206 operators on 11 August 2004, to raise awareness among those operators who had KAflex® driveshafts installed in their helicopters of the ongoing inspection and maintenance requirements, and the warnings listed in the STC. This was done to ensure that operators using KAflex® driveshafts incorporated the STC requirements into the appropriate periodic maintenance schedules and flight manuals for the affected helicopter on the Australian civil register.
Manufacturer safety action
Throughout the investigation, the manufacturer worked cooperatively with the ATSB to address the deficiencies identified. The manufacturer has advised that to date they have:
Changed the STC manual and included advice on the correct use of the historical service card. These changes, when approved, will be distributed as a revised Service Instruction to all operators using the STC
Reviewed the layout of the historical service card to determine if the format can be amended to include a section specifically for 1500-hourly helicopter inspections
Included warning notices in the flight manual supplement for the helicopter about red dust residue and turning fasteners
Advised that, although they intended the daily inspection of the KAflex® shaft to be a maintenance personnel action, the flight manual supplement would be produced for incorporation into the approved flight manual (AFM) for use by aircrew operating helicopters that have the STC incorporated.
Because the format of the historical service card, STC wording and AFM supplement are US Federal Aviation Administration approved, any changes made to these documents will be submitted to that regulator for final approval.
Operator safety action
The operator advised that the company had manufactured and was fitting a stainless steel placard to the engine firewall which would be in clear view when personnel opened the inspection panel. This placard would be adjacent to the KAflex® driveshaft and would read “KAflex Driveshaft – Daily Inspection” and list the STC warning and inspection requirements. This placard would be fitted to any helicopter operated by the company that is fitted with a KAflex® shaft or to any helicopter subsequently retrofitted with one.
The operator also advised that they would introduce and use a supplementary logbook for the driveshaft and that it would always accompany the aircraft logbooks. They would also instigate a program to highlight to company flight and maintenance personnel the differences between KAflex® and non-KAflex® equipped machines and the consequent maintenance and inspection requirements.
The Bureau will continue to monitor all proposed actions taken to prevent similar occurrences and subsequent evidence to address the deficiencies, when received, will be published on the ATSB website.
The full report is here (http://www.atsb.gov.au/aviation/occurs/occurs_detail.cfm?ID=639)
The KAflex® shaft had been fitted in accordance with the published requirements in the supplemental type certificate (STC) about 6 years, or 4,112.35 flying hours, prior to the occurrence. As far as could be determined, no certifications had been made that the shaft had been inspected in accordance with the STC inspection requirements during that period.
There was no flight manual supplement supplied as part of the STC, which would have alerted pilots to the specific inspection requirements and the significance of red dust production. As well as the daily inspection requirements for the shaft, the supplement did not include the warning not to disturb the bolts and to reject a shaft that showed evidence of turning of the fasteners.
The STC documents supplied with the shaft were not kept with the current helicopter logbook, although it was readily available. The retention of the STC documents in the archived logbook, instead of the current logbook, meant that the STC inspection requirements were overlooked and consequently not actioned by maintenance personnel. That resulted in the STC inspection requirements not being included as part of the routine or scheduled maintenance paperwork packages when they were assembled for release to service maintenance events.
The historical service record card for the shaft could not be located and had not been included in the helicopter records as required by the manufacturer in the STC accomplishment instructions. The minimal reference made to the card in the STC could easily have lead to the card being overlooked. When an example of the card was obtained, the appropriate location for the certification of maintenance activities was not readily apparent. The lack of a specific area on the card to certify completion of maintenance may have also contributed to the non-use of the card by maintenance personnel, including the 1500-hourly inspection certification in the airframe logbook. Also, inclusion of these inspection certifications in the airframe logbook could lead to the certification history for a driveshaft being lost if a driveshaft was subsequently moved from one helicopter to another. When overhaul became due, this service history would also have been unavailable to the manufacturer when the shaft and accompanying historical service card were returned to them.
The shaft failure had been initiated by fretting type movement at a flex frame bolted joint. This progressed until the joint failed, resulting in the gross overload failure of the remaining frames. That movement, in its early stages, should have been detectable by the presence of the red dust or loose bolted joints described in the STC inspection warnings. Had the maintenance and operating personnel been aware of the STC inspection schedules, they would have had a better understanding of the significance of the red dust and its ramifications.
Although the operator submitted that his personnel would have detected red dust had it been present around the flex frame joints, the wear pattern evident on the flex frame joint in Figure 1 was consistent with the flex frame fastener being loose for a period of time prior to the failure. The loose bolted joints were not detected. In this occurrence, the loss of bolted joint integrity may have progressed past the point where dust production may occur.
SAFETY ACTION
Civil Aviation Safety Authority safety action
Early in the investigation, consultative briefings were held between the Civil Aviation Safety Authority (CASA) and the ATSB. As a result of those briefings, CASA wrote to all Bell 206 operators on 11 August 2004, to raise awareness among those operators who had KAflex® driveshafts installed in their helicopters of the ongoing inspection and maintenance requirements, and the warnings listed in the STC. This was done to ensure that operators using KAflex® driveshafts incorporated the STC requirements into the appropriate periodic maintenance schedules and flight manuals for the affected helicopter on the Australian civil register.
Manufacturer safety action
Throughout the investigation, the manufacturer worked cooperatively with the ATSB to address the deficiencies identified. The manufacturer has advised that to date they have:
Changed the STC manual and included advice on the correct use of the historical service card. These changes, when approved, will be distributed as a revised Service Instruction to all operators using the STC
Reviewed the layout of the historical service card to determine if the format can be amended to include a section specifically for 1500-hourly helicopter inspections
Included warning notices in the flight manual supplement for the helicopter about red dust residue and turning fasteners
Advised that, although they intended the daily inspection of the KAflex® shaft to be a maintenance personnel action, the flight manual supplement would be produced for incorporation into the approved flight manual (AFM) for use by aircrew operating helicopters that have the STC incorporated.
Because the format of the historical service card, STC wording and AFM supplement are US Federal Aviation Administration approved, any changes made to these documents will be submitted to that regulator for final approval.
Operator safety action
The operator advised that the company had manufactured and was fitting a stainless steel placard to the engine firewall which would be in clear view when personnel opened the inspection panel. This placard would be adjacent to the KAflex® driveshaft and would read “KAflex Driveshaft – Daily Inspection” and list the STC warning and inspection requirements. This placard would be fitted to any helicopter operated by the company that is fitted with a KAflex® shaft or to any helicopter subsequently retrofitted with one.
The operator also advised that they would introduce and use a supplementary logbook for the driveshaft and that it would always accompany the aircraft logbooks. They would also instigate a program to highlight to company flight and maintenance personnel the differences between KAflex® and non-KAflex® equipped machines and the consequent maintenance and inspection requirements.
The Bureau will continue to monitor all proposed actions taken to prevent similar occurrences and subsequent evidence to address the deficiencies, when received, will be published on the ATSB website.
The full report is here (http://www.atsb.gov.au/aviation/occurs/occurs_detail.cfm?ID=639)