“Two Air New Zealand flights forced into emergency landings had known engine problems, but were deemed safe to fly according to the manufacturer’s risk models.
In December 2017, an Air New Zealand Boeing 787 Dreamliner, bound for Tokyo, had to land suddenly after a failed engine caused the aircraft to shake violently with 282 people on board.
The following day another Dreamliner, this time bound for Buenos Aires, also had to turn back when similar problems arose after take off. Air New Zealand told Newsroom at the time that it was ‘extremely surprised by the two issues experienced’.
Two Air New Zealand’s Boeing 787 Dreamliner were grounded with failed engines in December 2017.
A subsequent inquiry by the New Zealand Transport Accident Investigation Commission (TAIC) found engine manufacturers Rolls-Royce knew of six in-flight incidents worldwide before the Air New Zealand incidents.
Damage to turbine blades on a Rolls Royce Trent 1000 engine shut down by pilots on an Air New Zealand Dreamliner just after takeoff from Auckland.
“The Commission’s continuing inquiries into these incidents suggest that the failures were consistent with a known problem with unmodified Trent 1000 engines,” said the Commission’s manager of air investigations, Peter Williams.
“Rolls-Royce has been replacing engine components with a new design, and managing the safe operating life of unmodified engines using a risk analysis model.
“After the December incidents Rolls-Royce reduced the number of flights Air New Zealand could make under its risk analysis model, but obviously it would have been preferable that the model had taken the engines out of service before the December incidents could occur.
The report confirms that all eight incidents occurred during the take-off or climb phases of flight when engines are subjected to the highest stress, and the blade separations have followed cracking in the blade shank that has been initiated by corrosion.
Rolls Royce told the TAIC it is likely a combination of environmental and operational factors are involved and that they may be operator specific.
Rolls-Royce has been replacing blades in the Trent 1000 single-stage intermediate pressure turbine modules with redesigned blades made from a different alloy and with an improved corrosion protective coating.
It had been using a risk analysis model to determine how many flights unmodified engines may make safely.
Air New Zealand has been approached for comment.
The aviation world has made a number of major advances (SMS, ASAP, VDRP, SASO, ASIAS, etc.) and one was done so with a fairly simple action, but significant potential to reduce risks. It is called Flight Operational Quality Assurance. Most safety experts regard this innovation to provide a tool of tremendous value.
Almost all airlines and almost all Civil Aviation Associations NOW collect massive amounts of operational data. Both sensors aboard the aircraft and important maintenance records are accumulated in a global data base. This meta file can now match the one or two seemingly insignificant incidents, for example, with Air New Zealand, with other small numbers elsewhere; now the risk can be raised for further assessment. That system assigns a probability and prioritizes it against other potential problems.
It would seem, from the general description of the above article, that the six known Trent 1000 problems would have identified this possible fault WITHTHOUT Rolls Royce’s warnings.
What makes this case more puzzling is that ANZ and the NZ CAA have been lauded as leaders in the SMS discipline.
“The Civil Aviation Authority defines an SMS as ‘a systematic approach to managing safety, including the necessary organisational structures, accountabilities, policies and procedures’. These case studies aim to demonstrate examples of this systematic approach. There are no confirmed Regulations requiring an SMS to be implemented as yet, however there is significant value in proactively doing so. These case studies highlight how proactive implementation is possible, and what the advantages are in doing so. It’s important to remember that the implementation of an SMS is a journey rather than a destination. Whilst aviation organisations should set objectives to measure success and progress, it also means every step taken along the way is valuable.
KEY FEATURES OF AIR NEW ZEALAND’S SMS:
- Integrating risk management philosophies, processes and practices into all parts of managing safety.
- Regularly implementing new ideas for capturing and using safety information.
- Making the most of training and education opportunities to connect with crew and staff.
- Recognising the need for improved formal, risk-based change management processes.
This is the first time a group-wide approach to reporting has been implemented; all staff and crew are using the same system for submitting safety reports. Reports are then collectively reviewed by the safety team, receive an operational risk classification, and actions are then tracked to completion via the same system. It’s also possible for the submitting staff/crew to see the progression of their own report through the database. Future enhancements are to include the integration of Health, Safety and Environment (HSE) reporting, and the inclusion of Bow Tie analysis modelling.”
It would seem as though this system should have captured these data, analyzed the risk and formulated a method to reduce the risk.
SMS, FOQA and the associated systems are still being developed and one of the cardinal principles of this discipline is the commitment to continuous improvement. Usually these introspective exercises are directed within an airline and even more micro perspectives.
This Air New Zealand case study and perhaps the Southwest Airlines CFM 56 accident should be catalysts for a Pan Industry Review of the SMS/FOQA data collection and analysis?
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