Boeing first flew the 787-8 in December 2009, but the first run of the Rolls-Royce Trent 1000 engine came almost four years before in February 2006. Now more than a decade old, the engine competition between R-R and the GE Aviation GEnx-1B is as intense as ever, with still unpredictable twists and turns in operational service and in the development of new upgrades.

When they entered service in late 2011 and early 2012, both of the 787’s engines raised the state of the art of propulsion technology. Five years after entry into service and more than a decade after testing began, however, the Trent 1000 and GEnx-1B are still struggling to meet Boeing’s demands for fuel efficiency as the empty weight of the 787 climbed beyond initial expectations.

GE first raised the standard for fuel efficiency by introducing the performance improvement package (PIP) II version of the GEnx-1B, but even this fell short of Boeing’s original 787 fuel burn target.

R-R rolled out the Package C upgrade with a 1% improvement in fuel burn for the Trent 1000, but waited for the so-called “TEN” upgrade for a further bump of two percentage points. Developed to meet the higher thrust requirement of the 787-10, the Trent 1000-TEN would also restore R-R’s propulsion system to parity with the GEnx-1B PIP-2 standard.

The second major upgrade of the Trent 1000-TEN is fulfilling R-R’s expectations for fuel burn reduction in ground and flight testing, says Gary Moore, R-R’s Trent 1000 programme director: “It has been bang on the money as far as what we said.”

The TEN upgrade draws upon R-R’s investments in follow-on engine programmes, such as the Trent XWB and the Advance 3 technology demonstration. These upgrades include adapting the Trent XWB’s rising-line intermediate compressor and high-pressure compressor blisks. In only the second application of the technology industry wide, R-R is leveraging a modulated cooling air system developed for the Advance 3 in the Trent 1000-TEN. Siphoning air from the intermediate compressor to cool the high-pressure turbine blades is viewed as a necessary evil in modern turbofans, but modulating the airflow based on actual need helps limit the efficiency loss for cooling.

The Trent 1000-TEN development has been delayed by a year, however. Flight testing on R-R’s Boeing 747 testbed began in May, nearly six months late. Engine certification by the European Aviation Safety Agency is expected by late June or early July. Final certification on the 787-9 is now scheduled in 2017, or roughly a year behind schedule.

So far, the most critical elements in the package of new technologies developed for the Trent 1000-TEN are not driving the schedule delays. Last year, R-R discovered that a new, cost-saving material used to make the banded stators in the compressor was not ready for operational service, so the company redesigned the component with a conventional metal, Moore says.

“That was a cost reduction opportunity and on the basis of the test results it didn’t work out as we thought it would,” he says. “We took time to fix that. Certification is an important milestone but what you want is a robust product and something the customer can use as an everyday, reliable machine.”

Moreover, fatigue testing on the Trent 1000-TEN revealed cracking in the intercase about one-third of the way through the 3,000h-cycle, Moore says. In that case, a pedestal attaching a solenoid to the intercase cracked under the pressure. After tearing down the engine, R-R discovered that the out-of-balance testing conditions had exceeded the design parameters, so the components were being shaken harder than the engine was expected to experience in service. R-R’s engineers have slightly lowered the pedestal to prevent cracking and the redesigned component should re-enter testing by July, Moore says.

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Source: Cirium Dashboard