Begun on December 10 and completed on May 7, the second and final phase of GE9X certification flight-testing involved three times more flight hours than did the first, which was conducted in the spring of 2018.

Ted Ingling, GE Aviation’s GE9X program manager, told AIN that the second certification flight-testing phase involved “north of 300 hours of flight time” in an unspecified number of flights. The first phase, which began on March 13, 2018 and ended less than two months later, accumulated 105 flight hours in 18 flights.

One reason the second phase of GE9X flight-testing lasted much longer than the first and involved so many more flight hours is that “we repeated some work,” said Ingling. “We continued to map out the entire environment [of operation] and we tried to back info for opportunities that might present themselves later. We put in some additional parts for that kind of work…for possible future opportunities on this program, for improvements to the product as we go forward. We like to re-baseline [each engine performance measurement] when we do hardware changes.”

During the testing, GE Aviation (Chalet 144) ensured that “we did the normal software, performance, and thrust-management assessments—all of the statutory campaigns,” said Ingling. “Everything we were shooting to understand about the engine and the [test] process was completed. We’re excited about the performance we’re seeing on these engines; they perform to expectations on the ground and we have demonstrated [the design performance] at altitude as well.”

According to Ingling, “The culmination of the whole campaign” was to fine-tune in phase two the fuel-burn performance the GE9X demonstrated in phase one, which will be a major contributor to the 20 percent fuel-efficiency improvement Boeing has designed the 777X to offer over the 777-300ER. “We feel good about the engine’s contribution to that goal. We [still] have to fly the engine on the 777X, but we feel comfortable” with the performance it is achieving, he said. So comfortable is GE Aviation with the way the GE9X is performing that it has brought one of the eight development examples—the First Engine To Test—to the Paris Air Show to show the engine publicly for the first time.

Ingling revealed that, during the latter stages of the second flight-test phase, several Boeing test pilots flew GE’s 747-400 flying testbed, which had the certification flight-test GE9X mounted on the number-two engine position. “When the software was completed, the Boeing pilots would fly the engine on the testbed as if it was on the 777X, to get comfortable flying the engine and understand it [by] putting it through their [own Boeing] test card.”

The GE9X was fitted with the production nacelle Boeing designed for the GE9X on the 777X. The Boeing pilot-participation flights “culminated with a Boeing pilot demo-testing” the GE9X in the full compliance-engine configuration in which the GE9X will be flight-tested on the 777-9, said Ingling. “They wanted to fly the software and the engine [configuration] that is going to be on the first aircraft.”

Overall, the number of flight hours the GE9X certification flight-test program involved was “perhaps a little on the high side, [but] we don’t think it was typically out of the ordinary” for a type-certification program for a completely new powerplant incorporating “a handful of new technologies” that have never before featured in a commercial jet engine, said Ingling. In particular, “We’ve done some fantastic things with scaling up our PMC [polymer matrix composite] technology from the fan blades to the fan case, guide vanes, and platforms,” to make the GE9X fan module enormously strong but very low-weight, he said.

While GE Aviation began the second phase of GE9X flight testing a little later than it had envisaged upon completing the first phase, Ingling said GE still expects to achieve type certification of the massive powerplant—the largest jet engine ever built—in 2019. Although the flight-test program was completed, several of the eight development engines GE built are still involved in certification ground-testing.

“From a certification standpoint, we’re between 85 and 90 percent through testing,” Ingling said in late May. “We have closed some major testing,” including tests of the engine’s ability to withstand fan-blade separation; all ingestion tests (birds, water, hailstones, and rainstorms); all icing tests; testing for the aeromechanical properties of every module of the engine; and all testing of emissions levels, except the emissions test actually required for type certification. “We feel good about setting up the engine” for final type-certification tests, he said. Additionally, “our certification reports are in the same kind of benchmark—we’ve got a lot of approved reports done and a lot [of others] submitted.”

While “there is still a lot of testing to do,” including non-certification endurance testing of two engines, which will be performed in the latter half of this year, Ingling said GE Aviation is “very much” satisfied with the reliability and durability the GE9X has demonstrated throughout all ground and flight-testing to date. The 777X will “play into the same operations as the 777-300ER” and so GE wants the GE9X to be highly reliable and dependable in service right from the outset. “We want to come down the learning curve to get to that [high in-service reliability] faster” than GE did with previous engine families. “We laid that out in the early days [of GE9X design] and added some thoughts to that process, and that list made it into the trades and technical objectives,” he said.

Preparation for Service Entry

To help ensure the GE9X will prove highly reliable from the moment it enters service, in the early stages of the GE9X design process GE “got together with our customers and learned the big issues in customers’ fleets” of GE90s, GEnxs, and other engine types, said Ingling. This customer input gave GE a list of more than 300 unwanted issues customers had with their existing engine fleets. “These made it onto our program list that we made sure the GE9X addressed,” he said. Now, “we’re in the middle of validating the final third of the changes we made [to the GE9X design] to eliminate those customer concerns. This is not part of certification—it’s part of [ensuring] reliability, durability, and maintenance-free operation. It’s part of the evolution of our process in the design phase to tackle [reliability] differently and more completely than in the past.”

One GE9X performance measure of which GE is fully confident is the engine’s ability to provide its maximum rated thrust. Ingling revealed that, during ground runs on very cold days in which the fan was run up to rotation speeds well within its design envelope and with all temperatures and pressures “margined” within production-engine performance parameters, the high air density led to the development engine producing thrust levels far beyond the GE9X’s 105,000-pound design rated maximum thrust level. Those tests showed that the GE9X “is not airflow-limited,” he said. “The flow at the inlet and through the nacelle is sufficient and the fan can pump it” through the engine at the rate required to achieve rated maximum takeoff thrust.

The GE9X cold-day tests even produced thrust levels well beyond the 115,000-pound maximum thrust rating of the GE90-115B, today the most powerful jet engine in the world, Ingling revealed. While he won’t confirm the actual thrust levels the engine achieved until GE validates the results, it appears possible that on some of those cold-day runs the GE9X achieved a thrust level beyond even the 127,900-pound maximum the GE90-115B achieved during cold-day testing. Today that level remains the highest thrust level ever officially produced by a jet engine, but “for sure there will be a new record in the books soon,” Ingling told AIN.

By late May GE had supplied the first two sets of compliance engines to Boeing for 777-9 flight-testing and they had been installed on the first two flight-test aircraft. The third set was undergoing validation testing at GE’s Peebles test facility in Ohio. The fourth set was also at Peebles, while the first of two spare compliance engines for Boeing was completed and assembly of the second was underway. All five sets of compliance engines are of common configuration and certification-configured. Additionally, “We’re starting to put together the first production engines in terms of kitting and accumulation of hardware,” said Ingling.