Dubai Air Show

GE Working Hard to Meet GEnx Fuel-Burn Targets

 - November 12, 2011, 3:37 AM
GE expects the performance improvement package for the GEnx-2B to go to test in February or March next year and fly on its test bed during next year’s third quarter.

When Boeing 747-8F launch customer Cargolux postponed delivery of its first two airplanes in September, pundits almost immediately began tossing about theories that Qatar Airways boss and Cargolux director Akbar al Baker was behind the sudden move for various ulterior motives. After all, Boeing and Cargolux had already reached terms on an agreement in July–before Qatar Airways bought 35 percent of the Luxembourg-based freight carrier–over fuel-burn deficiencies in the early airplanes that would affect their range and payload capability. Al Baker, the theory went, was angling for more leverage in his negotiations over compensation for late delivery of Qatar’s Boeing 787s.

While only Al Baker can truly know his own motives, no doubt remains that the airplane’s General Electric GEnx-2B engines did not meet their promised fuel-burn performance, and the new Cargolux director did not find acceptable the compensation originally negotiated over the summer. It took about three weeks, but Cargolux, Boeing and GE eventually settled the issue, and Cargolux took delivery of its first two airplanes on October 12 and 13.

Meanwhile, GE continues to work on a performance improvement packages (PIP) for both the GEnx-2B–the sole powerplant for the 747-8–and the Boeing 787’s GEnx-1B, which exhibited slightly more than a 3-percent shortfall in fuel-burn performance before GE Aircraft Engines completed the first of two PIPs on that model.  

Bill Fitzgerald, GE Aircraft Engines’s vice president and general manager of the GEnx program, explained to AIN last month that PIP 1–a program launched in early 2009 and certified this past August–has already improved the -1B’s fuel-burn efficiency by at least 1.6 percent.

Designed to deliver 15 percent better efficiency than GE’s CF6-80C2 base, 20 percent more durability than the GE90, 30 percent less noise than other engines in its class and 50 percent less nitrous oxide (NOx) than regulatory limits, the GEnx failed to meet efficiency goals early in the program, when the company designed the low-pressure turbine to use 30 percent fewer airfoils than the LP turbine in the GE90. “We went too far with the technology,” conceded Fitzgerald.

“The first thing that we did is modify the low-pressure turbine and some elements of the compressor, and that got us 1.6 percent better fuel efficiency and it also increased the thrust level to 75,000 pounds from 70,000 pounds,” said Fitzgerald, who replaced former program head Tom Brisken roughly a year ago. Of course, Boeing’s nautical air miles survey (NAMS) test, scheduled to run between this month and next, will ultimately prove the fuel efficiency gain. Nevertheless, said the GEnx boss, “our production engines are demonstrating north of the 1.6 percent improvement we designed in.”

Now the current production configuration, the PIP 1 engine will gain certification for 75,000 pounds of thrust in the first quarter, and plans call for the first PIP 1-equipped 787 to roll out “early next year.”

A second performance improvement package for the -1B, known as PIP 2, will recover at least another 1.1 percent of the 3-percent shortfall and raise thrust limits to 78,000 pounds, said Fitzgerald. Although Boeing hasn’t asked for the extra 3,000 pounds of thrust, the increase will help prepare GE for potential applications on the 787-9 and, eventually, the 787-10. “Boeing has told us they don’t need it,” Fitzgerald added. “We have designed it just in case. All other programs have always wanted a little more thrust.” GE expects to gain certification for 78,000 pounds of thrust by next June.

PIP 2 involved adding a booster stage, an “optimization” of the 3-D aeromechanics and some materials within the compressor, an adjustment to some elements of the design in the high-pressure turbine and combustor and some modifications to the fan, specifically lengthier fan blades and some “adjustments” to the outlet guide vanes.

Now demonstrating two PIP 2-equipped engines at its Peebles, Ohio test cell, GE plans to run the design on its flying test bed some time next month and perform durability testing during next year’s first quarter and into April. The company expects to certify the engine under FAR Part 33 in June of next year, by which time it fully expects to close the 3-percent efficiency gap with still further improvements gleaned through a combination of PIP 1 and PIP 2 “and a few things we learned along the way,” said Fitzgerald, who added that certification under FAR Part 25 of the PIP 2-equipped airplane would happen during the fourth quarter of next year.

Although PIP 2 for now represents the ostensible limits of the improvements, as GE assesses and settles on the new technology for the next-generation GE90 for the Boeing 777 and continues to make progress with the new CFM LEAP technology with Snecma, it will quite likely transfer what it learns into the GEnx design, according to Fitzgerald.

“I like to say that we have a secret GEnx fuel-efficiency program that is hiding in plain sight, and it’s got a super-secret codename called LEAP,” he joked. “But all kidding aside, that’s absolutely one of our technology demonstrator programs that, as it makes sense and the technology will make a difference, we’ll probably fold it in probably mid-next decade.”

In the much more immediate future, GE still has work to do on the version of the GEnx known as the -2B, which, of course, raised a point of contention with Cargolux. Designed to produce 67,000 pounds of thrust, it, like the -1B, burned more fuel than expected. Fitzgerald estimated the fuel-burn deficiency falls “in the mid-2-percent range,” prompting GE to insert some of the same modifications used in the -1B into the -2B through its Tollgate 6 design confirmation process.

GE has begun manufacturing the hardware meant to demonstrate the -2B’s single PIP, expected to go to test in February or March next year and fly on the company’s Boeing 747 test bed during the third quarter. GE expects FAR Part 33 certification in April 2013 and FAR Part 25 approval in October 2013.  

GE expects the -2B’s PIP to result in a 1.7- to 2-percent gain in fuel-burn efficiency. “We’re still in the process of nailing that down,” said Fitzgerald, “and it may be better than [2 percent]. We’re getting a lot of learning, and we’re applying it wherever it makes sense.”

Improvements featured in the -2B’s PIP will, in many ways, replicate those in the -1B, including similar modifications to the low-pressure turbine, some adjustments in the compressor materials and 3-D aeromechanics and changes to the combustors and the high-pressure turbine. “We did not modify the booster because it doesn’t need additional thrust, and the fan is the same,” said Fitzgerald.

While engineers continue to work on improvements to both the -1B and -2B, GEnx production continues to accelerate, from 45 engines last year to some 140 this year, to a planned “200-plus” next year. Now holding 62 percent of the market for the 787, GE believes it will have to satisfy at least that proportion of demand for the Dreamliner into the foreseeable future as Boeing raises production from its current rate of 2.5 per month to a planned 10 per month by the end of 2013.

“Our supply chain is ready to support that,” said Fitzgerald. “Our piece of that, should that come to fruition, needs to be in the 300- to 400-engine-per-year range. We’re facilitating for that, [and] we’re delighted with our industrialization process. We’re producing five engines a week right now from our assembly and test sites and doing it with plenty of capacity to spare. So we are well positioned.”

Of course, GE will also have to meet 100 percent of the propulsion demand for the four-engine 747-8, the production rate for which Boeing plans to increase from 1.5 per month to two per month by the middle of next year.

GE has assembled a team of employees dedicated to examining capacity availability and secondary source alternatives specifically to ensure it can meet Boeing’s demands. Fitzgerald said he sees no bottlenecks in GE’s supply chain that remotely threaten its commitments to the airframer. Asked if he felt happy with the GEnx supplier base, Fitzgerald hedged a bit. “I would say happy is a relative term,” he said. “We operate in the trust and verify mode, and we’re doing both.”