Detailed information regarding maintenance and upgrade
of Boeing 787 Aircraft Engines
ANA has learned of a possible issue with a component in the Rolls-Royce engines on a limited number of Boeing 787 aircraft. As safety is our top priority, we have decided to take extra steps to ensure the safe operation of our aircraft and as a result, several domestic flights have been cancelled. We would like to express our regret for any concern or inconvenience caused.
Earlier this year, we had experienced two cases in which aircraft had to return to their departure airports due to engine-related irregularities. These flights were:
- ANA Flight 816 from Kuala Lumpur to Narita (February 22, 2016)
- ANA Flight 858 from Hanoi to Haneda (March 3, 2016)
As outlined below, we have been working with Rolls-Royce, the designer and manufacturer of the engines in question, to implement permanent technical solutions to this issue.
Cause of irregularity
According to analysis by Rolls-Royce, the issue was determined to be fatigue cracks in the blades of the engine’s intermediate pressure turbine (refer to the diagram below). Such cracks are the result of sulfidation corrosion caused by chemical components in the atmosphere, and the propagation of these cracks correlates with the number of flight cycles that an engine has been used for.
Solutions Implemented to Date
1) Aircraft Used for International Flights
Aircraft operating on international routes fly through airspace which have higher atmospheric concentrations of the chemical components in question and their engines also produce higher temperature exhaust gases due to greater power output. These factors were determined to be more likely to generate fatigue cracks. Therefore, we implemented a program to determine the number of flight cycles at which intermediate pressure turbine blade cracks could occur based on analysis of each engine’s flight environment and flight cycle count, and engines have been systematically replaced before that number of flight cycles is reached.
2) Aircraft Used for Domestic Flights
Compared with aircraft operating on international routes, those which operate on domestic routes within Japan fly through airspace with lower atmospheric concentrations of the chemical components in question and their engines also have a lower power output. Therefore, it was determined that fatigue cracks due to sulfidation corrosion is less likely to occur in such an operating environment and these engines will not be subject to systematic replacement.
Although the above measures were in place, the same issue occurred on ANA Flight 609, a domestic flight from Haneda to Miyazaki, on August 20. Therefore, based on our own initiative, we have decided to replace the engines on aircraft used for domestic operations earlier than what was designated by Rolls-Royce. This has led to a temporary reduction in available aircraft, which in turn has led to some flight cancellations.
Going forward, we will be replacing the engines with new ones which are equipped with improved, corrosion-resistant turbine blades as a permanent solution. As a measure to prevent the occurrence of cracks until this solution is fully implemented, engines which have been removed from aircraft will be fitted with brand new or minimally-used turbine blades of the type that is currently in use. We would like to emphasize that this current type of turbine blade does not pose any safety concerns when in brand new or minimally-used condition.
This engine-related issue is unrelated to the battery-related issue which caused the aircraft’s grounding in January 2013.
We will continue to give top priority to safe flight operations, thoroughly implement recurrence prevention measures, and make every possible effort to ensure safety.
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