What starts as a trickle can end up a torrent: when, in 2016, Rolls-Royce first announced a durability issue with blades in the Trent 1000's intermediate-pressure turbine (IPT), there was no indication that the modification programme would grow in scope and complexity, causing significant disruption for some Boeing 787 operators.
Airlines had to park Dreamliners as engines required unscheduled maintenance to replace IPT blades, and aircraft could not be returned to service amid a shortage of available spare Trent 1000s – some carriers had to lease additional capacity. Meanwhile, it became clear that on certain Trent 1000s the durability issues also extended to the high-pressure turbine (HPT) and intermediate-pressure compressor (IPC).
The costs are already mounting: R-R disclosed in March that in 2017 it incurred a charge of £227 million ($311 million) related to addressing technical issues on Trent 1000s and the Trent 900s powering Airbus A380s. And the UK engine maker said that this year, the upgrade programme's annual cash impact would "broadly double" from last year's £170 million, before dipping in 2019 as work drops off.
However, that was before the revelation in April of "additional disruption" – and higher costs – from further inspections required to address IPC blade durability issues on Trent 1000 Package C engines.
Of course, previous engine programmes – of both R-R and other manufacturers – have required updates to address premature part deterioration, particularly in the hot section. And R-R says it is "not uncommon for long-term engine programmes to experience technical issues during their life".
Teal Group vice-president analysis Richard Aboulafia, however, considers the Trent 1000 modification effort to be "somewhat worse than normal".
ENGINEERING RESOURCES
Aboulafia wonders whether R-R's issues with the Trent 1000 – and Pratt & Whitney's problems with its PW1000G geared turbofan – might be a result of having "greater ambitions than resources".
The technical challenges and required engineering effort to develop more efficient engines have hugely increased from previous generations of equipment. More broadly, Aboulafia thinks the Trent 1000 problems show that "we are on the very limits of squeezing performance improvement out of existing turbine architectures" and that highly engineered parts come with a "certain set of vulnerabilities".
Especially on Airbus and Boeing’s latest aircraft programmes – the A320neo, A330neo, 737 Max and 777X – fuel-efficiency gains have been mainly, if not entirely, achieved through new engine technology. As a result, the airframers have redistributed much of the research and development effort, and therefore risk, for new programmes to the engine manufacturers; at the same time, Airbus and Boeing have put engine suppliers under pricing pressure and driven production to record levels.
"The ability to add resources at the engine companies was constrained at exactly the moment when so much was expected of them," Aboulafia says.
Boeing 787 chief engineer Bob Whittington revealed in January that "all" operators of Trent 1000-powered Dreamliners were affected by "some of the wear-out issues in the Rolls-Royce engine", which entered service in 2011.
The initial IPT blade replacement programme for the Trent 1000 was disclosed after All Nippon Airways (ANA) had temporarily grounded some of its 787s in 2016 as a result of premature, corrosion-related part failures.
R-R redesigned the IPT blade and introduced it on the latest version of the Trent 1000, the 1000 TEN, and on the Trent 7000 derivative that powers the Airbus A330neo. The new part is being retrofitted to earlier Trent 1000s and, says R-R, should resolve the durability issue. But the modification programme nevertheless caused a wave of shop visits as some engines required urgent blade replacement.
OPERATIONAL DISRUPTION
There has been inevitable disruption for operators: Air New Zealand (ANZ) temporarily grounded several Dreamliners after experiencing in-flight failures on two of its 787-9s in December 2017. The carrier resorted to wet-leasing aircraft to support its schedule.
Virgin Atlantic in January disclosed plans to add four A330s to its fleet and return to service a stored A340-600 in a bid to improve "resilience" of its operation "in light of an industry-wide shortage of Trent 1000 engines".
The IPC blade issue was first disclosed after an engine failure aboard a Scoot 787-9 in late 2016. Singapore's Transport Safety Investigation Bureau determined that the failure was caused by an IPC blade having broken off – probably as a result of material fatigue – and linked two further shutdown events on Scoot 787-9s last year to the same issue.
R-R says the cracking problem applies to Trent 1000 with Package C configuration and that neither the TEN nor the Package B version is affected. The manufacturer is in the process of preparing redesigned blades for the IPC – and for the HPT where erosion is an issue on existing blades.
The new parts are scheduled to become available by year-end and will be retrofitted to affected engines. R-R believes that the modification effort can be completed during planned, rather than unscheduled shop visits.
Whether that retrofit programme will cover certain TEN engines is not entirely clear. R-R says Trent 1000 TEN compressors "are of different designs to the Package C", and that "a new standard" HPT blade is installed on the TEN.
However, the manufacturer does not rule out a retrofitting new IPC and the latest HPT blades to the TEN. "We will continue to positively confirm that none of the issues we are experiencing on the Trent 1000 Package C engines will apply to the Trent 1000 TEN," the manufacturer says.
And earlier this year, R-R said it was "possible that a population of early Trent 1000 TEN and Trent 7000 engines may benefit from proactive maintenance to embody parts in their first shop visit that weren't available at the point of production".
ETOPS LIMITATIONS
Regulatory pressure is compounding the disruption for operators.
Following the April disclosure relating to the IPC, the European Aviation Safety Agency mandated that operators conduct repetitive on-wing borescope inspections for all Package C engines, and introduced additional inspections for powerplants employed for extended twin-engine operations (ETOPS).
Meanwhile, the US Federal Aviation Administration more than halved the time that Trent 1000 Package C-powered 787s can fly under ETOPS regulations, to 140min, from a previous maximum of 330min.
The US regulator says that if an engine were to fail and the remaining powerplant already had cracked IPC blades, the "likelihood of the remaining engine failing will further increase before a diversion can be safely completed".
Bloomberg Intelligence warns that the ETOPS restriction could put R-R at a disadvantage on the 787 versus rival GE Aviation and its GEnx engine.
In a research note, Bloomberg senior aerospace analyst George Ferguson asserts that airlines will be required to "adjust operations to remain closer to diversion airports", and that this "reduces efficiency and range, especially for extreme long-haul operations, which are most appealing for 787 buyers".
He describes the FAA directive as a "blow" to R-R and operators of Trent 1000 Package-C-powered 787s, which will "probably hurt sales and value for the airplane".
ANZ subsequently disclosed that it needed to introduce refuelling stops on certain 787 flights as new weight restrictions apply to aircraft with affected engines. ANA and British Airways, meanwhile, say the ETOPS changes have had a minor effect on their operations.
Norwegian's chief executive Bjorn Kjos acknowledged in April that the increased inspection regime will affect operations, but says "it is too early to predict the scale of the issue".
R-R's effort to resolve the Trent 1000 problems and modify the in-service fleet "takes an awful lot of resources", which will likely have an impact on the company's ability to concentrate engineering staff on other projects like future engine development, Aboulafia suggests.
He says the development and implementation of modifications for issues on in-service engines is "fairly labour-intensive stuff", while the ramping-up of production for new engine programmes, such as the Trent XWB for the A350, is largely a matter of capital expenditure.
R-R says it had to redeploy "engineering resource" to tackle the Trent 1000 issues, but notes: "[We] expect this to be a temporary measure." The manufacturer says its developmental Advance and UltraFan engine programmes "continue to progress as expected".
LONG-TERM REPERCUSSIONS
Aboulafia does not believe that airlines and aircraft manufacturers have lost faith in R-R as a result of the Trent 1000 woes. Operators which have ordered Trent 1000-powered 787s have not yet switched to the GEnx. But he warns that the problems have not done R-R "any favours" either and that "a lot of it depends how quickly they can make it good".
R-R concedes: "Of course these issues must affect perception of the Trent 1000 by customers." But the engine maker says it is "confident" that the family's latest version and current production standard, the TEN, is a "great engine" for the 787.
"It is our job to show them [airline and airframe customers] they can continue to trust in us and the engine," R-R says. It foresees that solutions for the existing issues will be implemented throughout the fleet by 2022.
However, Aboulafia suggests the Trent 1000 problems could have an effect on future orders: "I think where it might hurt is where people are looking at A350-1000 XWB versus 777X and... A330neo versus 787." Both of the Airbus programmes are exclusively powered by R-R engines.
"The big issue here for Rolls-Royce is that the 787 is their only connection with Boeing right now," says Aboulafia.
GE, Pratt & Whitney and R-R have all submitted engine proposals for Boeing's projected New Mid-market Airplane (NMA), which could enter service around 2025. If Boeing were to launch the NMA programme without R-R on board, it would leave the UK manufacturer having almost the entirety of large engine business – all in-production models except the Trent 1000 – tied to Airbus.
That is already the case today, as the Trent 700, 900, 7000 and XWB are exclusively employed on Airbus long-haul aircraft. But Aboulafia thinks a further re-enforcement of that alliance in the long-haul segment is a "very risky concept" for R-R.
GE is, likewise, the sole engine supplier to Boeing's 777 and 747-8 programmes. But the US engine maker also has, via its CFM International joint venture with Safran, a strong position in the high-volume narrowbody market. Since it withdrew from the International Aero Engines consortium with P&W, Japanese Aero Engines and MTU, R-R has no active participation in the single-aisle segment.
R-R, for its part, argues that the prospect of a potential selection as NMA engine supplier is "unrelated" to the Trent 1000 problems: "We continue to invest in our future engine programmes irrespective of this [Trent 1000] challenge and will continue to evaluate any opportunities to have our engines selected as they come up."
Source: FlightGlobal.com
