Engines special report: GE

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When Bombardier’s Global 7000 undergoes certification some time in 2016, the aircraft’s launch engine will be GE’s new Passport engine. This is also currently under development, but is expected to certify in 2015, comfortably ahead of the arrival of the Global 7000.

With 16,500lb of thrust per engine, the Passport will help the Global 7000 to achieve a range of 7,300 nautical miles at a speed of Mach 0.85. However, GE is not just focusing on the top end of the business aviation market. It is just as interested in taking on Pratt & Whitney’s legendary PT6 turboprop engine at the other end of the scale. GE’s re-engineering of the stalwart and “ruggedly efficient” Walter M601 engine into the GE H80, H75 and H85 family, is finding an expanding circle of customers in the turboprop world.

The pick of these is undoubtedly Ken Ricci’s Nextant Aerospace, which specialises in “re-imagining” and re-engineering older aircraft, namely the Beechcraft 400, re-launched as the Nextant 400XT, and most recently, the Beechcraft C90 turboprop, to be relaunched by Nextant as the G90XT.

According to Brad Mottier, vice president and general manager of GE’s Business & General Aviation and Integrated Systems Organisation, the key to success in both instances has been GE’s ability to draw on its lead in innovative technology, particularly the use of composites.

Mottier points out that the Passport engine was GE’s first application of Ceramic Matrix Composite (CMC), where it was used in 15 different parts in a number of major sub assemblies, including the centre body of the exhaust. “The Passport was our first non-military application of this technology in a GE engine,” he notes.

At a push the Passport could be considered a scaled down version of GE’s LEAP engine, which it is producing in partnership with Snecma. Mottier points out that Passport uses much the same technology as LEAP in its compressor section, its eCore technology. “In addition to the core we have introduced a number of new technologies, including a fan blisk. The fan has 18 blades and is one single piece of titanium,” Mottier explains.

The beauty of a blisk fan is that it maintains its balance whereas a conventional fan with slot in blades inevitably has balance issues. The conventional design relies on the centrifugal force of the rotating fan to keep the blades in position. This gives it a different balance at the start of its revolution to when it is going at speed. “With the blisk, we can machine the balance into the blisk and it stays that way forever,” Mottier observes. From the point of view of the owner of a business jet powered by the Passport, what this equates to is noticeably less vibration and less noise, creating a quieter cabin. “On a long range business jet, that is a very important value for the customer,” Mottier adds.

According to Mottier the Passport is moving smoothly through its testing program. “We built four test engines and we have so far accumulated about 400 hours running time, including 100 cycles, and the engine is meeting or exceeding the expectations,” he comments. GE has also finished the altitude tests on the Passport. “We took it up to 51,000 feet in our altitude test facility that we use for our military engines and we ran it through the full operational spectrum of the engine. This means that when we mount the engine to one of our two Boeing 747 test planes, we expect everything will run smoothly,” Mottier notes. Icing tests have already been completed in Winnipeg, Canada, with no problem. Engineering cross wind tests and fan “blade out” rigs have been completed, with formal certification tests later this year. Other remaining hurdles include bird strike test, hailstorm and water ingestion tests. “Fuel and emission performances are coming in right on spec. Comparing Passport to today’s long range business jet engines, we will be 8% better on fuel burn and we meet the Stage 4 noise regulations and the emissions restrictions with margin to spare,” Mottier adds.

He reckons that other airframe OEMs are already expressing considerable interest in Passport. “We are talking to a number of people. The performance of this engine is really phenomenal, and when it enters service it will obsolete everything already out there,” he comments.