Powering the Dream: Atypical paths to Boeing 787 EIS

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An early Christmas occurred at Rolls-Royce on 28 September. That was the day that All Nippon Airways (ANA), the launch customer for the Boeing 787-8 Dreamliner, took delivery of its first aircraft. Under the wings of the mostly composite 264-seat twinjet were two Rolls-Royce Trent 1000 turbofans.

"My firm belief is that once the aircraft is delivered, the whole field within the industry will change," says Simon Carlisle, Trent 1000 programme manager for Rolls-Royce. "It's like being a child waiting for Christmas - it's magical."

As a result of the protracted 787 development programme, Carlisle, who took his position two weeks after the 787 first flight just before Christmas 2009, is actually in charge of three Trent 1000 development programmes simultaneously - Package A, the launch engine; Package B, a higher-thrust, more efficient engine that will power all 787-8 aircraft as of next year; and the 74,000lb-thrust (330kN-thrust) Package C engine destined for the 787-9, a stretched, higher-capacity version of the aircraft slated for entry into service (EIS) in 2013.

Over at rival engine provider GE, Bill Fitzgerald, the vice-president and general manager of the GEnx product line, was not yet on the job when first flight occurred - he started just one year ago. However, he too is essentially running three programmes at once - a Block 4 engine, the first to be certified; the recently approved PIP (performance improvement package) 1 engine that gets to within 1% of Boeing fuel efficiency targets, and a more powerful PIP 2 engine for the 787-9.

 787 engines

 Copyright: Boeing

Simultaneous engine upgrade efforts were not originally part of the plan when Boeing launched the 787 in April 2004 with the two engine choices. The turbofans are 15% more fuel efficient than the engines they will replace, helping to produce an overall fuel burn reduction of 20% compared with the Boeing 767, the aircraft the 787 replaces.

"Nothing about this engine programme is typical," says Rolls-Royce's Carlisle. Given Boeing's original plan to get the 787 certificated and flying in time for the 2008 Olympics in Beijing, Rolls-Royce developed and worked to a compatible schedule. "From our perspective, we followed our normal design new product introduction process and in 2007, certified the engine with full expectation it would go into a flight test programme and be delivered."

However, Boeing only achieved US Federal Aviation Administration (FAA) certification on 26 August 2011, three years after the initial target. The long string of delays certainly was not optimal from the engine manufacturers' perspective. "None of us thought it would be quite this long," Carlisle says.

"If in 2008, Boeing would have said 'It is going to be the end of 2011 [for certification]', it would have been relatively easy to cope with," says Carlisle. "We would have relooked at the programme. But to some degree, the way the programme slipped - six months every six months - all of the supply chain had to maintain readiness to flight test, which took away from improving the product."

"We took advantage of the delay to get the engine as current as it could possibly be," Carlisle adds. "We did a ton of flight testing that has given us a lot of confidence in the maturity of the product. It will be the most mature product we have ever put into service."

For GE, the chief challenge with the ever-expanding schedule was making sure the company remained "focused on the execution of PIPs while finishing industrialisation of the production engines", says Fitzgerald. GE has the added pressure (and privilege) of being the sole source supplier of the similar GEnx-2B engines for the Boeing 747-8 programme, which has meant a dual ramp-up for the new line of turbofans. "We delivered 44 GEnx-1B and -2B engines in 2010, and we'll triple that number in 2011," Fitzgerald said in mid-August. Boeing plans to certificate the GE-powered 787 in the fourth quarter this year, with the first delivery going to Japan Airlines.

The more-electric turbofans created for the 787, no matter how delayed, will be worth the wait.

GE's offering is similar in architecture to the high-bypass, composite fan, two-spool GE90 for the Boeing 777, but takes the next step with a composite fan case (saves 181kg or 400lb per engine), titanium aluminide turbine blades (saves 91kg per engine) and a low-emission twin annular pre-swirl (TAPS) combustor. The 6,126kg engine has a 282cm (111in) fan diameter, three-stage low pressure compressor (LPC), a 10-stage high pressure compressor (HPC), a two-stage high pressure turbine (HPT) and a six-stage low pressure turbine (LPT). The overall bypass ratio is 9.6:1.

Like the Rolls-Royce offering, the GEnx-1b is a bleedless engine (except for hot bleed air for engine inlet anti-ice protection) that drives twin 250kW starter generators on each engine, pumping 1MW of power into the 787. The more-electric design required GE to build power storage banks in the ground testing area to dump all that power, and drove changes to the company's Boeing 747 flying testbed to handle the excess electricity.

Along with production demands, GE has been deploying a worldwide infrastructure to support the engine in service, five years ahead of the first expected overhaul in 2016. "When the GE90-115B entered service, we had one [GE] certified maintenance facility," says Fitzgerald. "We have two certified sites for the GEnx from the start, five times the number of GEnx on-wing support sites, 10 times the number of field support engineers and four times the quick-turn capability." GE has two certificated overhaul facilities in place. "You have one chance to make a great first impression," says Fitzgerald.

The most significant lesson learned, technically, came from trying to squeeze too much performance out of the LPT. "In our design, we took a very aggressive approach on the LPT and reduced the blade count by 30% [compared with the GE90]," says Fitzgerald. The resulting Block 4 engine missed Boeing's specific fuel consumption (SFC) targets by several percent, an issue that will be addressed incrementally with the PIP 1 enhancement soon after EIS and the PIP 2 upgrade in 2012. While GE obtained PIP 1 certification from the FAA in August, thrust was limited to 70,000lb due an HPT nozzle problem discovered during a ground test at 35% above red line temperature. Fitzgerald says a modified nozzle that will allow for 75,000lb thrust should be certificated by January or February for the PIP 1 variant.

While SFC is currently higher than specification, the engine is meeting targets for exhaust gas temperature (EGT) degradation. Using the GE90 engine as a baseline, engineers had designed the GEnx for a 6-8°C reduction in EGT per 1,000 cycles, down from 10°C per 1,000 cycles for the GE90. "We're seeing all of that," says Fitzgerald. Delaying EGT degradation prolongs engine life.

Rolls-Royce used its trademark three-spool architecture as a starting point for the Trent 1000. Behind a 284.5cm (112in) titanium fan is an eight-stage intermediate pressure compressor (IPC), a six-stage HPC, a single-stage HPT, a single-stage intermediate pressure turbine (IPT) and a six-stage LPT. The overall bypass ratio for the 5,936kg engine is 10:1.

Key design features include an intermediate shaft electrical power offtake that Rolls-Royce says helps reduce fuel consumption with the engine running at idle. Overall, the company says its three-shaft architecture has better deterioration characteristics than GE's two-shaft design.

Package B upgrades include a modified LPT design, high-aspect-ratio blades, relocation of the IPC compressor bleed offtake ports and improved aerodynamics for the fan outlet guide vanes. The Package B engine is also said to incorporate hardware changes put into place after an August 2010 uncontained failure of a Package A engine on the Rolls-Royce test stand at Derby in the UK.

Carlisle says Rolls-Royce has approvals to perform repair and overhaul work on the engines at its Derby facility, with "all engines brought there for overhaul". He says ANA will have "some capability" for engine testing and light maintenance in house at EIS, but adds that, "as the fleet grows, we will look to have more capability through the established maintenance network in partnership with our leading customers".

Lessons learned by the companies are not all technical. "There are leading indicators [on programme delays]," says Carlisle. "We've started to look more at that. We're not second guessing our customers, but will be more robust in our challenging of timeframes. Boeing encourages that."

Although they agree on the product improvement roadmap, the two companies are as competitive as ever when it comes to the sales job. As of late August, GE had sold 830 engines, giving it an edge over Rolls-Royce in the number of engines sold given that 821 aircraft have been purchased, but buyers have not yet declared their engine choice for roughly 250 aircraft. Boeing plans to build 10 aircraft each month by the end of 2013.

"I would hope that everyone would celebrate the delivery of the [Dreamliner], says Rolls-Royce's Carlisle. "It will be a fantastic product - even better for those who have selected the Trent engine."