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May 29, 2024
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Rolls-Royce has been working through a series of durability issues with some of the Trent family of engines. The Trent 1000, which powers early Boeing 787s, and the Trent 900, which powers the Airbus A380 have experienced issues. Other members of the Trent family, including the Trent XWB that powers the Airbus A350, and the Trent 1000 TEN, which powers more recently built 787s, have not been impacted by reliability issues and remain in full production and service. Trent 7000 deliveries for the new Airbus 330neo have experienced some delays due to industrial ramp-up issues.

The Trent 1000 Issues

Since early 2016, problems emerged with the Rolls-Royce Trent 1000 series engines for the Boeing 787. While those problems have been traced to their cause, and a solution developed, it will take until 2021-2022 to fully retrofit the Trent 1000 fleet and return to normal flying conditions. In the interim, several aircraft have been grounded for inspections and part replacements, reaching a peak of nearly 50 aircraft in late summer 2018. As parts are replaced and engines returned to service, the number of grounded aircraft will be reduced, but these problems have been disruptive to airlines operating the Trent 1000 powered Boeing 787.

In early 2016, corrosion-related fatigue cracking was found in Intermediate Pressure Turbine blades in the Trent 1000 fleet. Blades showing extensive corrosion were replaced by a more corrosion resistant blade. In the financial year for 2017, Rolls-Royce took a £148m charge for technical costs that included certain costs relating to the Trent 1000 and Trent 900 in-service issues and incurred a total cash cost in the year for in-service issues on the Trent 1000 of £119m and £51m on the Trent 900. In April 2018, the inspection interval for 380 Trent 1000 Package C engines was reduced from every 300 flights to every 80 flights to address Intermediate Pressure Compressor durability problems, and ETOPS operations were reduced from 330 to 140 minutes for higher-life engines, negatively impacting trans-Pacific flights.

An Airworthiness Directive was issued on 19 April 2018 for the Package C engines after Intermediate Pressure Compressor Rotor 1 and Rotor 2 blades were found cracked, which, if not corrected, could lead to an in-flight blade release. On 26 April 2018, the FAA limited ETOPS for Package C engines, operated by airlines such as Air Europa, Air New Zealand, Avianca, British Airways, Ethiopian, LATAM, LOT Polish, Norwegian, Royal Brunei, Scoot, Thai Airways, and Virgin Atlantic.  Inspections were mandated to be completed by 9 June 2018 and resulted in a number of aircraft being grounded as nearly 30% of the engines failed inspection.

Rolls-Royce assigned hundreds of people to address the situation, and installed a revised IPC blade for testing, with production parts available in late 2018 to solve the issue. Rolls-Royce budgeted £450 million to solve Trent 1000 and Trent 900 issues in 2018, with £450m in 2019 and £350m in 2020 against a 2018 free cash flow of $643 million, providing insight into the magnitude of the problem. The number of grounded aircraft peaked just below 50 aircraft in mid-2018. Rolls-Royce responded with increased MRO capacity and parts supply, with turbine blade capacity increasing by more than 50% since the start of 2018.

The Cause and its Mitigation

The IP turbine blade problem appears to result from the coating eroding prematurely due to “hot corrosion” from high atmospheric sulfur linked to polluting industries near major cities with airports in Asia.

The initial fix entails both a more corrosion-resistant base material and a coating system and has so far been installed in 62% of the affected fleet at the time of writing. Laboratory testing of the new blades has been positive, and in-service inspections should demonstrate that the problem has been mitigated.

The IP compressor blade failure mechanism was not clearly understood when the issue was first discovered. A vibration survey indicated that a fan wake was impacting the compressor blade, with a 100Hz frequency difference between the IP and LP spools resulting in an eigenmode synchronized vibration in the first two IP compressor rotors. This caused wear and tear leading to micro-cracks, which would grow into larger cracks after about 1,000 cycles. To resolve this issue, Rolls-Royce has designed a new blade that shifts the mass toward the periphery of the blade to avoid eigenmodes, with testing showing no damaging vibration.  New IPC blade production has begun in anticipation of regulatory approvals.

Further blade testing has taken place on the Rolls-Royce 747 testbed to further understand the issue and to obtain regulatory restoration of ETOPS limitations.

Trent 900 Issues

Issues with the Trent 900 engine for the Airbus A380 are linked to thermal erosion in high-pressure turbine blades, for which a new design was introduced in early 2017.  In addition, a further re-design has been scheduled for 2020 that should fully solve durability issues and return those engines to originally specified inspection limits. As a result, some A380 operators are experiencing higher than anticipated inspections and maintenance costs.

Trent 7000 Delays

The Trent 7000 is a new engine model designed for the A330neo and is just entering service.  In October Rolls-Royce confirmed it would deliver fewer Trent 7000 engines in Q4 than originally planned, reflecting early stage production ramp-up challenges, such as testbed and supplier issues as well as general teething issues in ramping up the production of a new engine.

While there have been no issues with the engines in testing, production difficulties have will likely result in delayed deliveries at Airbus.

Ramp-up delays have also impacted other manufacturers new technology engine, including Pratt & Whitney for its GTF, and CFM with the LEAP. However, the unfortunate timing of those delays, occurring at the same time as reliability issues with the Trent 1000 and Trent 900, placed Rolls-Royce in a more difficult financial situation. Nonetheless, Rolls-Royce expects to be back on schedule for the A330neo in Q1 2019.

The Bottom Line:

While Rolls-Royce has identified and is developing solutions for the problems with the Trent 1000 and Trent 900 engines, it will take time to bring the entire fleet into compliance, which is not expected to occur until mid-2020.  The operational impacts on airlines will result in a financial drain for Rolls-Royce that has already been stated to the market and is also impacting its relationship with its key customer, Airbus, with whom it has exclusive positions on the A330neo and A350XWB aircraft families.  2018 through 2020 may be tough years for Rolls-Royce shareholders, but an opportunity for potential investors who can determine when share prices will bottom out.  In this case, what goes down will come back up.

author avatar
Ernest Arvai
President AirInsight Group LLC

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