In the second week of May, the crew of an Antonov An-124 operated by Russian cargo operator Volga-Dnepr got to work on the flightline at Victorville, California, loading a pallet measuring 3.96m (13ft) wide and 7.77m long into the cargo bay of the chartered widebody freighter for emergency shipment to Columbus, Ohio. The size of the payload and the route were dead give-aways: GE Aviation's first GE9X flight-test engine was coming home to Evendale, Ohio.
In early May, GE wrapped up the first phase of a two-stage flight-test effort on the 105,000lb-thrust (467kN) GE9X. Phase 1 included 18 flights on board the company's Victorville-based 747-400 flying testbed, GE9X programme manager Ted Ingling tells FlightGlobal.
GE is on a tight schedule. Boeing needs the GE9X ready to begin flight testing for certification on board the first 777-9 in 2019, allowing the aircraft to enter service in 2020, So the 105,000lb-thrust powerplant for the 777-9 needed to return to Evendale to prepare for phase 2, which is scheduled to begin in the third quarter. "It will be months of work to bring the engine down and back up again. The majority of the activities are around the instrumentation that we have on this vehicle. There's over 1,600 pieces of discrete information through sensors that get bundled onto this engine and routed into the aircraft," Ingling says.
"We want to preserve that instrumentation for the missions that follow. As a result, what would normally be a quick turn-around for incorporation of the hardware changes takes us a much longer time to bring the engine down and back up and make sure all the instrumentation is working," he adds.
GETTING STARTED
The first phase of flight-testing with the GE9X kicked off on 13 March, with the engine designated as No. 4 within the programme lifting off in Victorville. In nearly two months, the 747-400 flying testbed logged 110 flight hours overall during the 18 flights. "A portion [of the flight tests are reserved] for check-out of the aircraft and systems and the rest of it was dedicated to achieving the objectives of the flight test mission," Ingling says. Flight-test crews also explored the high-altitude envelope for the GE9X, evaluating how its cruise performance compared with ground test data.
GE Aviation
“We are very encouraged about the engine. All indications from fight test is that the engine is doing exactly what we want it to do and we're on track to meet our objectives on performance," Ingling says. "The engine is really performing well and we couldn't be happier with that."
The engine is installed on the inboard station of the left wing of the 747-400 flying testbed, which was itself an engineering challenge, he adds. "We put the engine on wing in record time and with little drama. Boeing designed the pylon for us… and how it attaches to the engine is really the same as how it would do on the 777X, so Boeing's been involved in our FTB since the beginning. The installation was really remarkably quiet and flawless. Engine and instrumentation systems came together perfectly."
The start of testing was delayed more than two months, after GE engineers made a late discovery. Inside the compressor of the GE9X are 11 stages of rotating blades, with stationary vanes located in between each set of spinning rotors. These stator vanes slow down the airflow, thereby raising its pressure as it moves upstream to the combustor. To optimise the pressure of the airflow in take-off and cruise conditions, the engine's computer-operated controls can adjust the position of the stator vanes relative to the airflow.
Lever arms mounted externally on the engine case set the pitch of the vanes, but GE discovered a problem last December. The mechanical design and materials used to build the lever arms are correct, but the device wears out faster than GE expected.
"We didn't alter the material of the lever arms or anything," Ingling says. "It was just the design was not as robust as we needed it to be. It didn't affect the engine from a [specific fuel consumption] standpoint."
It was too late to incorporate the new lever arm design in the first GE9X flight-test engine, so the first phase of flight tests began in March using the existing configuration. The redesigned lever arms for the variable stator vanes (VSVs) will be installed as part of the tear-down prior to the restart of flight tests in phase 2, Ingling says.
Meanwhile, ground testing is continuing at GE's test centre in Peebles, Ohio. GE delivered the first engine to test (FETT) for the GE9X programme in 2016. It features GE's most advanced engine core, with compression ratio of 27:1 versus 23:1 in the GE90-115B engine. The GE9X is loaded with new technology. Its $42 million list price makes a set of two engines on each 777X nearly equal to the advertised cost of a 737-700. For that price, GE has promised that the engine will burn 10% less fuel than the GE90 in flight and 5% less than a Rolls-Royce Trent XWB-97 on a test stand.
WRIGGLE ROOM
Driven by concerns about moving too quickly, GE afforded itself a 13-month window between delivering the FETT and the second engine to test (SETT) with certification-ready hardware. Since entering ground testing at Peebles 12 months ago, the SETT has been joined by four more test engines.
"We’ve made some fantastic progress on the certification program," Ingling says. "We’re through a little more than 25% of all required certification testing. Icing tests were completed in the first quarter. We completed all the crosswind testing, [as well as] inlet compatibility, aero-mechanics of the fan and booster, and aero-mechanics and thermal surveying of the high-pressure turbine."
The GE9X actually represents an entire family of engines. The 777-9 will be powered by the version designated GE9X-105B, with the numeral in the suffix representing the 105,000lb-thrust power rating. GE Aviation also plans to develop a 102,000lb-thrust version of the engine, along with a 93,000lb-thrust version, according to a regulatory document filed by the US Federal Aviation Administration in November 2017. The reduced ratings will likely power future variants of the 777X family, including the long-range 777-8 and a potential freighter version.
For now, however, GE is focused on getting the GE9X engine certificated.
"We’re in the middle of building the very first compliance engine in Durham, [North Carolina]. The long-lead hardware on production engines are coming in," Ingling says. "So, we're ramping the production process using the Durham facility. The development engines are built in Evendale. Compliance and production will be assembled in Durham and tested out of Peebles.
"We’re building the very first compliance engine and we're accumulating hardware up to the third engine, so more than 50% of hardware is accumulated depending on which engine you're looking at," he adds.
Source: Cirium Dashboard
