Less than three months ago, on March 24, General Electric’s newest engine, the GEnx-2B, took to the air on the company’s Boeing 747 flying test bed, marking another milestone in the development of its latest and most advanced civil powerplant.

The GEnx program is now busier than ever as the two applications for the engine–the Boeing 787, powered by the GEnx-1B and Boeing 747-8, powered by the -2B–have each suffered delays that have drawn their respective timescales closer together. Service entry for the Boeing 787 was originally set for late 2008, more than a year ahead of the 747-8. Now the two aircraft are expected to start earning money within a couple of months of each other, in mid-to-late 2010.

The flight test program will involve around 35 flights on GE’s ex-Pan Am 747, the 16th off the original production line, which entered service in 1972. As with the flight-test program of the 787 engine, the GEnx-2B will be flown to a 40,000-foot altitude in 5,000-foot increments, in the process being put through FAR25 icing trials, verification of control logic, altitude relighting trials and so on.

Fortunately GE (Hall 2 Stand C137) has been able to take advantage of the commonality between the two variants to simplify the test program for the GEnx-2B. Both engines share the same core and have 80-percent commonality between their line-replaceable units. The main differences are the smaller, 105-inch-diameter fan of the 747-8 engine, compared with 111 inches for the -1B, and reduced stages on the low-pressure section. The -2B also is not “all-electric,” using a traditional bleed-air pneumatic system for starting.

As a result, only five development engines have been necessary for the 747-8 program compared to nine for the 787. “We confirmed the aeromechanical integrity of the GEnx core during the -1B program,” said GEnx program manager Tom Brisken. He told AIN that another major synergy was that the fan blade containment test did not need repeating because the integrity and design of the all-composite fan and fan case had been proven in the July 2007 test of the -1B engine. “This saved us from destroying a $15 million engine,” he said. The -2B fan system completed a full-scale rig test in April at the ITP Engines test facility in Rugby, England.

Tweaking the Design
The only major modification to come out of the test program has been to the all-new, low-emissions TAPS double-annular combustor, which has been running on CFM International’s Tech56 development engine [GE is a partner in CFM with France’s Snecma]. “We ran into a few dynamic and durability issues during tests on the GEnx,” said Brisken. “The Boeing 787 engine runs at higher temperatures and pressures, and we found we had to make a few modifications. Now it’s running really well and has demonstrated full operability in the FAA block test.”

Otherwise, durability of the GEnx has been, Brisken claimed, “excellent.” He explained that the all-electric 787 engine, which has a unique Hamilton Sundstrand starter-generator, was put through a rigorous program of 1,600 restarts with no problems.

Certification of the GEnx-2B is set for later this year, with first flight of the Boeing 747-8 due in late September. GE has already shipped one engine to Boeing, which has mounted it on a 747-8 engine pylon for ground vibration tests. The remaining three engines will follow by early summer.

Aircraft certification should come in the mid-2010, with delivery to launch customer Cargolux shortly after. All 747-8 deliveries in the first year of production are for the freighter variant, for which there are 78 orders. A further 20 have been ordered by sole airline customer Lufthansa, with the remaining eight aircraft of the current 106-aircraft order tally being for VIP customers.

Decisions To Be Made
“That’s more than 400 engines already, which makes this a pretty big program,” said Brisken. Bill Brown, marketing manager for widebody engines, added, however, that he had thought the freighter program “would be ahead of this by now.” He blamed the global economic crisis and said he is “optimistic” that the planned ramp-up in production of the 747-8 will coincide with a recovery.

GE Aviation claims 60 percent of the Boeing 787 market over Rolls-Royce’s Trent 1000. Brown remarked that around 300 of the aircraft ordered to date still await an engine choice, “so we’re expecting a lot of decisions in the next two or three years.”

Brown also revealed that GE is “still in dialogue” with Airbus over a possible GEnx-powered A350XWB. The U.S. company has always said the engine is available to power the two smaller versions of the European widebody, but not the longest range A350XWB-1000 variant, which would compete directly with the Boeing 777-300ER powered exclusively by the GE90. “Realistically we’ll want to see the installed performance of the GEnx on the 787 first,” added Brown. “Then we’ll see if we can reach the very high target Airbus has set.”

Meanwhile, the first four 787 flight test aircraft will be equipped with Rolls-Royce engines, the fifth and sixth with the GEnx. Such are the continuing uncertainties with the 787 timescale, however, that Brisken could not give a firm date for the engine’s 787 debut. He remained enthusiastic about the program, however. “We support Boeing; we’ve delivered the first two engines and we’re ready to go into production,” he added. “We’re anxious to get up there.”