It’s mid-February, the night sky above the center of Naples is spectacular: so clear you can vividly see the stars twinkling, a light breeze and mild temperatures heralding the arrival of spring. A distant rumble bursts onto the scene; for certain it’s an airplane taking off from Capodichino and gaining altitude, with the force of its two turbofan engines which ingest air and gradually take the aircraft higher and higher. I think as I watch: they’ll be GE or CFM engines, and I can distinctly hear the air flow passing through the fan as it’s sucked in to produce a thrust after combustion. The rumbling sound isn’t constant and changes slightly from one moment to the next, as the quantity of air being channeled inside by the fan is variable.
At this point, my thoughts move to the Avio Aero plant in Pomigliano, just a few kilometers to the northeast of where I watch the plane turn, and where just a few hours before I saw and touched with my own hands parts of the low-pressure turbine of the new GE9X engine. It's the largest commercial engine ever built, with a 3.40m-diameter fan, and will power the Boeing 777X. I make the connection between the new GE9X and the take-off I’ve just admired and the after-effects of the rumble that are still spreading shortly after the aircraft exited from my view: for sure it’ll be bigger than the engine I’ve just heard and maybe just as loud, or possibly quieter. “In January 2016, we sent the first complete turbine to GE Aviation in Evendale. To think that since then we’ve sent seven of them,” said Roberto Marrone, Manufacturing manager for the GE9X turbine module at the Pomigliano site.
The GE9X is a large piece of technology: for instance, its low-pressure turbine – the module which Avio Aero is primarily responsible for – has TiAl (titanium aluminum) 5th and 6th stage rotor blades, 3D printed at the Cameri facility and finished in Pomigliano. I held them when I met Giacomo Veneruso, Manufacturing Specialist at the Airfoils center of excellence, and they were very light but at the same time extremely solid. They weighed more or less the same as a packet of spaghetti!
“Within few time, will be ready to complete all the processes here at Pomigliano: the unfinished blades come from Cameri (3D-printed by EBM machines), which we grind, mill and polish, then perform non-destructive tests and X-rays, and finally plasma spray treatment,” Giacomo explained. “At the moment we can manage everything with one cell. But according to the plans, the volume will increase toward 2020, and, on the basis of this forecast, we’re working on and investing in four new cells for the GE9X.”
Apart from main components coming from France, Germany and Japan (from Safran, MTU and IHI respectively) for the GE9X turbine, practically all the Avio Aero facilities are involved with the other modules. Rivalta supplies the largest turbine disc, the 6th stage disc, with other parts for the assembly of the turbine, and is responsible for the design and production of the entire accessory gearbox module. Avio Aero Polska produces and designs the stator blades of the low pressure turbine in Bielsko Biala, and then there’s Brindisi, which produces the enormous structures that house the turbine.
Widening the view beyond our own borders, the GE9X is an excellent example of intercontinental collaboration. IHI Corporation, for example, is a cornerstone of Japanese industry, a company which has been active since 1853; a symbol of modernization and Japanese manufacturing excellence, it has built every part imaginable for the aviation industry. In Pomigliano, inside the area where the GE9X low pressure turbine is assembled, I saw a team of IHI engineers from Tokyo: they visit the site quite often and work in close contact with Avio Aero staff. So much so that I had the chance to meet Tomotake Ogawa in Rivalta, the IHI GE9X Engineering Representative who acts as the liaison between the two teams in Italy and Japan. “I follow every aspect,” he explained to me, “together with the Italian engineers: from design, to production and assembly of the turbine. In fact, I work between Pomigliano and Rivalta, where I use an office right next to the engineering area: it’s effective, because we can deal with, discuss and analyze every technical aspect, problem or advancement in constant harmony.” IHI is responsible for the first three rotor stages and the first five discs of the low-pressure turbine, as well as other components and the main engine shaft of the GE9X.
Reflecting again on the mass of air that enters the engine, I think about how the low-pressure turbine performs a delicate task: this is the part of the engine in which the air, which has become thermal energy in the combustion chamber and the high pressure turbine, converts to kinetic energy, feeding the engine shaft, which moves the front fan as well as producing the thrust. Gilberto Bonfigli is the GE9X LPT Design Module Engineering Leader in Avio Aero, and works together with the whole in-house team and naturally with the external team. He knows Tomotake very well, for example. “It took us a record time to design this turbine, only a couple of years: materials and aerodynamics are at the core of innovation, making the most of the drawn air that generates the thrust. The current development phase is central for us, involving the analysis and verification of performance translated into efficiency. This can be seen first of all from the size of a project (especially that of the team), without forgetting all the suppliers coming from various parts of the world, or the GE Aviation team of engineers in India that supports the design analysis for our turbine.”
Ciro Esposito and Michele Coppola are GE9X Design & Material Senior Engineers at Pomigliano, working with Gilberto. They were the ones who helped me understand the innovative impact of the TiAl blades printed using Arcam machines in Cameri and installed on the low-pressure turbine. “Designing these blades and producing them using 3D printing doesn’t just bring notable benefits in terms of the overall weight of the whole engine and fuel consumption. In fact, the freedom of the design allows you to perfect the typical leaf shape in the last two stages of the turbine (fifth and sixth, ed.): the blades in the last two stages, all with the same shape, rotate in the same direction. The airfoil shape is optimized to make the conversion into kinetic energy as effective as possible.” I can see that the titanium aluminide alloy that the blades are made of fits perfect with the thermal and physical regime of the last two stages of the low-pressure turbine.
All the work on the new GE9X is coordinated and managed by GE Aviation; teams from different units are working on this impressive development stage, with the direct involvement in the field of the Supply Chain and, of course, Engineering. Fernando Ceccopieri is a renowned professional at Avio Aero. He graduated from the Polytechnic University of Turin, and he took his first steps as an Aerodynamics Design Engineer at FiatAvio in the 1980s. In 1985, he moved to Cincinnati (Ohio) with his family; he, like other professionals at GE Aviation, is proof of how Avio Aero was in a certain sense destined to become part of the GE family. “Avio engineers have always worked closely with GE, in the field and following every activity from technological conception, working well with the US teams,” he told me, and this is partly what happened to him. He is now the Principal Engineer Systems - LPT Leader for the GE9X, based at the GE Aviation headquarters.
He also underlines the importance of this development stage, “FAA and EASA certifications, which we have already completed around a thousand hours on so far, are the goal of the tests on the complete engine and will come before it enters into service. There are around 20 different types of test in total. At the moment there are seven engines, two undergoing the assembly and reconfiguration stage; in fact, often the configurations can change from one test to another.” Talking about testing activities with Fernando highlights the huge variety of tests, which are worthy of a standalone story, and some of which are particularly impressive. “There’s the icing test, conducted in Winnipeg (Canada), where polar temperatures are reached, simulating tremendous ice storms, during which the engines must guarantee full functionality. Or at the other end of the scale, it is expected that the engine will guarantee functionality well beyond thermal limits, or there’s the potential number of revolutions of the turbine. In one of the fundamental tests for the low-pressure turbine, the engine is stressed under a condition in which it is kept running for 5 minutes at more than 75° Fahrenheit (23° C) above the maximum tolerated temperature.”
Talking to Fernando makes you think about how distances are becoming shorter. Especially because of the ease with which many professionals carry out such a delicate, complex and demanding job, moving from one continent to another. That’s what the next Boeing 777X powered by the GE9X will do, transport up to 425 passengers across continents.
The very first GE9X engine lifted off on March 13 under wing of GE Aviation’s 747 flying testbed in Victorville, California: it's turbine certainly came from Pomigliano. Maybe we’ll see a 777X take off over the forest of Capodimonte, and who knows what it’ll be like to see that from the heart of the city.Author: Yari Bovalino