Now that the first engine developed by the GE Honda Aero Engines joint venture is powering dozens of in-service HondaJets, the new turbine engine manufacturer is looking to the future, not only for the HF120, but new engines that could grow into a family of powerplants.
Two other companies had announced plans to use the HF120, but neither program has advanced very far. Spectrum Aeronautical was the first to formally announce an agreement with GE Honda Aero for an airplane powered by the HF120–prior to the HondaJet–but the company’s S.40 Freedom never made it into production. Earlier this year, there were rumors about restarting the Freedom program, but so far nothing has transpired. “There’s a glimmer of hope in [Spectrum founder] Linden Blue’s eyes,” said GE Honda Aero president Steven Shaknaitis. “He’s talking to the Mexican government about potentially building in Mexico. We had committed to doing the engine on the S.40 if it ever restarts.”
The other program was the Sierra Industries Sapphire, a re-engining of the original CitationJet, CJ1 or CJ1+ with the HF120.“We did some integration work, and we have a hope of someday powering CitationJets,” he said. The HF120 has already flown on a CitationJet testbed during engine testing, but according to Sierra’s new owner Innova Aerospace, the Sapphire program will now use a different engine.
The HF120 grew out of the HF118 that Honda designed and built and that powered the first proof-of-concept HondaJet. After the establishment of the 50-50 joint venture company, engineers from GE and Honda developed the more powerful 2,095-pound-thrust HF120, which has a 5,000-hour TBO and no hot-section inspection event.
“The state of the joint venture is very healthy,” Shaknaitis said. “One of the key things we see is that the engine was designed by people who put commercial engines in the air. It might have been over-designed, but it’s a hell of a reliable engine with a high life limit.” As of early October, GE Honda Aero had delivered 120 engines.
There are some key attributes that give the HondaJet its outstanding performance (max cruise speed of more than 420 knots), and one that is significant is the HF120’s higher thrust at altitude. This is due to the wide-chord blisk-type fan with 3-D compound swept blades that enable a higher fan pressure ratio, according to the company.
The HF120 also features a high-pressure-ratio core, which is facilitated by the design of the compressor and its titanium alloy construction. This “enables the engine to minimize thrust loss during climb,” thus helping the HondaJet climb quicker and cruise faster at the mid-30s flight levels.
The HF120’s specific fuel consumption is relatively low, and this is because of the laser-drilled multi-hole combustor design, which “provides low pressure drop across the combustor and efficiently transfers compressor energy to the turbine,” and air-blast fuel nozzles providing better fuel atomization, which yields better fuel-to-air combustion, according to the company.
The unique over-the-wing-engine-mount scheme on the HondaJet does reduce vibration and noise in the cabin, but aspects of the engine design also help with those parameters. “A lot is due to our engine design,” said Daniel Harris, director of marketing and programs for GE Honda Aero. “We put a lot of effort into core and fan vibration, and we’ve got stringent standards that we agreed to with Honda Aircraft.” Some initial production engines didn’t meet the vibration standard due to the way the fan blisk was made, but that was fixed. “We had to craft assembly processes so the engines stay within the vibration limits for delivery,” he said. “You simply don’t hear and feel the engines.”
These low noise and vibration characteristics, said Shaknaitis, “will translate to fuselage-mounted engine too.”
With its airliner engines, GE is famous for on-condition maintenance programs where engines stay on the wing for tens of thousands of hours. While that isn’t likely for a business jet, which doesn’t fly nearly as much as an airliner, the HF120’s long 5,000-hour, no-hot-section TBO also contributes to lower operating costs. Design features that make the TBO so long include using super alloys to manufacture turbine blades so they can run hotter and last longer. Comprehensive engine monitoring is also an important factor.
“We are getting to an on-condition kind of [situation],” Shaknaitis said. “We’re looking at data to help the industry understand how you can get there. Taking an engine off when you hit 4,999 hours, that’s not [efficient]. There’s so much data, so many sensors…can you capture that and do something with it that will benefit the owner?”
At its Burlington, N.C., factory, he said, “We’ve got a really good team, a state-of-the-art facility, and we’ve made tremendous gains coming up the learning curve. We’re ready to double down with this joint venture. We have a solid business, support infrastructure, spare engines, distribution centers, and everything you need we have put in place. Now we’re ready for the next step.”
That step could include new engines developed by the joint venture company. “We want to do another engine or two to serve other sectors in this business jet arena,” Shaknaitis said. “We believe the sweet spot is a 3,000- to 4,000-pound thrust engine. We are studying it, but we also need to have a home for it. We’re talking to people and trying to collect market intelligence. The Phenom 300 is the best-selling business jet now, and that’s the area we think is the place to play. We’re looking at key characteristics and requirements for the next engine, but we will not walk away from the best performance, quality and 5,000-hour TBO without a hot-section inspection. That’s where we’re not going to compromise.”