Rolls-Royce is pouring extra resources into a fleet-wide Trent 1000 scheduled maintenance program after acknowledging the parts replacement initiative has been causing operational problems to Boeing 787 operators.
Up to 500 engines are involved in the effort which is a response to service issues caused by premature wear and corrosion, most of it in elements of the intermediate pressure (IP) compressor and turbine. The problems led to a series of engine shutdowns and replacements in 2016 and prompted a number of EASA and FAA airworthiness directives.
Specific issues related to fatigue cracks in the blades of the engine’s intermediate turbine caused by sulfidation, a chemical reaction which occurs at high temperatures between sulfur in fuel or the air, and oxides in the turbine blades. Although originally designed for a service lifetime equivalent to around five million miles, the issue prompted design revisions to the blade which are being introduced during the program. In addition, Rolls is also replacing elements of the IP compressor which has experienced cracking in the rotor seal.
Airworthiness directives have been issued for inspections of the IP compressor seal as well as the high pressure turbine blades. However it is not known if the turbine--which requires inspection for cracking at the tips, is part of the on-going maintenance program.
The issues have particularly impacted ANA, the largest Trent 1000-powered 787 operator which was forced to cancel 787 services and temporarily ground four aircraft late last year after at least three engine failures from February to August 2016. Other impacted operators include Thai Airways which as recently as July said a related engine parts shortage had caused it to ground four of its six 787s.
Commenting on the program in a recent second quarter earnings call, Rolls CEO Warren East says the issue is causing “problems for us and for our customers at the moment.” However the company is working to minimize disruption by improving its engine turnaround time, putting additional resources into its facilities in Derby and Singapore, and by increasing the number of engines available in the lease pool. Rolls has allocated a £59 million “technical provision” to cover costs on several programs of which just under half is currently associated with the Trent 1000 maintenance effort.
Part of the problems facing Rolls is that the refit program comes as the company dramatically ramps up production of the Trent XWB for the Airbus A350. At the same time it is also transitioning production to the Trent 1000 TEN for the 787 and is preparing to support flight tests of the closely related Trent 7000 engine on the A330neo. By mid-year just over 200 large engines had been delivered with a target of around 500 by the end of 2017. Industry sources describe the current situation as a “traffic jam of engines.”