Story ID: 
Engine makers consider clean-sheet designs
By: Thierry Dubois
Caption: Engine manufacturers are here at EBACE providing a glimpse at where powerplant technology is going for business aviation with several clean-sheet designs o
Word Count: 2143
Engine manufacturers are here at EBACE providing a glimpse at where powerplant technology is going for business aviation with several clean-sheet designs or derivatives under development. Honeywell and Rolls-Royce each are working on two programs for business jets, while Pratt & Whitney Canada is involved in one. New players in the field–GE Honda and Snecma–each have a brand-new turbofan to promote, but the latter has yet to find an application. 
In December, the 7,445-pound-thrust Honeywell HTF7250G made its first flight on the Gulfstream G250 and had flown 60 hours as of the first quarter. “We have logged several thousand hours in HTF7250G development on our test benches, this includes four dedicated engines, among others,” senior technical sales manager for propulsion Mike Bevans told AIN. Certification is pegged for late this year, so Bevans sees most of Honeywell’s test effort as being complete by now. 
Honeywell’s 7,000-pound-class HTF500E, for the Embraer Legacy 450 and 500, is in the early development phase. “Our technology focus here is weight and emission reduction, as well as fuel efficiency,” Bevans said. The program passed a critical design review in December.
The first HTF500E is being put together in time for a first run in the next few weeks. “We will have eight engines and one core in development,” Bevans explained. Honeywell (Booth No. 7041) is planning on 15,000 hours of testing. “We have computers and simulation software but we feel comfortable with actually running the engine,” Bevans added, pointing out this is the best way to ensure reliability at entry into service, especially when the engine is used in intensive fractional ownership operations from the beginning.
Certification of the HTF500E is pegged for late 2011. Both the Legacy 450 and the larger Legacy 500 will be powered by the same engine. “We may make modest changes to the Fadec [full-authority digital engine control],” Bevans said.
Meanwhile, Honeywell’s Saber 1 low-emission combustor is slated for certification in the third quarter of this year. Production engines will be fitted with the new combustor early next year. “We’ll easily beat CAEP 8 standards for emissions and this is just the first generation of Saber,” Bevans said. 
The International Civil Aviation Organization’s CAEP 8 will be applicable to new aircraft certified from Jan. 1, 2014.
Honeywell is studying new alloys and coatings for high-pressure (HP) turbines with the Tech 7000 demonstrator. The coatings use nano technologies for low thermal conductivity. Bevans acknowledged that this technology will still not be able to eliminate today’s complex air-cooling systems inside turbine blades. “I wish it could, but we build on top of cooling,” he said.
This approach means that design engineers can increase turbine temperatures to boost the power density of the engine. “That’s more thrust from the same core size,” Bevans said. The new Tech 7000 coatings are almost ready for the manufacturing stage.
Bevans also explained that the company is expending a lot of effort on noise reduction. Honeywell also is working closely with UOP, a sister company that specializes in biofuels. “We are endeavoring to emulate jet-A; in other words, we adapt the fuel to the engine, rather than adapting the engine to the fuel,” Bevans said.
Rolls-Royce Takes Off with G650Rolls-Royce (Booth No. 539) now has its 16,100-pound-thrust BR725 in flight tests on the Gulfstream G650. Eight BR725 flight test powerplants are dedicated to the development program for the new large-cabin business jet–six installed on three aircraft and two spares. The engine was certified by both European and U.S. authorities last year and this involved testing at simulated altitude. Nevertheless, those tests– including relight, crosswind, reverse thrust during a rejected takeoff and cold weather trials– are being performed again with the engine actually installed on the new aircraft. 
Meanwhile, maturation testing is under way for the BR725. One engine has been running in service-representative cycles. This unit, which includes the nacelle and thrust reverser, has so far accumulated 1,200 cycles, on top of the 3,500 cycles run in the certification program. In addition, every engine accessory has its own maturation program in a rig environment, explained Norbert Arndt, managing director for engineering at Rolls-Royce Deutschland and BR725 program director.
Rolls-Royce Deutschland, the division of the UK-based engine group which is the company branch in charge of the BR725, has delivered eight flight test engines, including two spares. The first two production engines have been handed over, too. “Now we are producing the next two,” Arndt said. A total of eight units will be manufactured this year.
The BR725 features a 50-inch fan, two inches larger than its predecessor BR710, which powers the G550. This, along with swept blades, allows for more flow and higher efficiency in the fan, Rolls-Royce claims. Five of the 10 stages in the HP compressor are blisks (blade-integrated disks), which reduces weight. The entire HP compressor has benefited from three-dimensional aerodynamics to create greater efficiency.
The combustor draws from that of the BR715 turbofan, which powers the Boeing 717 airliner (now out of production). Rolls-Royce claims it yields longer life and lower emissions. Relative to CAEP 6 limits, emissions are 80 percent lower in terms of smoke and unburned hydrocarbons and 35 percent better in terms of nitrous oxide (NOx) emissions.
In the two-stage HP turbine, improving the aerodynamics in three dimensions helps reduce the cooling air flow. The HP turbine also features active blade tip clearance control, which makes it more efficient. The low-pressure (LP) turbine now has three stages instead of two, the mixer having been improved with 3-D aerodynamics. Weight-reduction efforts and increased power have delivered a 3.38 thrust-to-weight ratio at takeoff. Specific fuel consumption is 0.657 lb/lbf/h (at FL450, Mach 0.85).
The dual-channel Fadec borrows some technology from the much larger Trent 1000 engine, and time between overhaul jumps from 7,000 to 10,000 hours. In terms of noise performance, the BR725 is 4- to 12-cumulative EPNdBs below ICAO’s latest Stage 4 limits.
The other engine that Rolls-Royce design engineers are developing, in Indianapolis this time, is the 9,000-pound-class AE3007A2. It powers the Embraer Legacy 650, currently in flight tests, and promises 6 to 12 percent higher altitude takeoff and climb thrust than its AE3007 predecessor. “We are on track for engine certification in the second half of this year,” said Barb Stratton, senior vice president for AE series corporate and regional aircraft engine programs.
Compared to the current AE 3007, the A2 has a new fan module, but the diameter is still 38.5 inches. Not only are the wide-chord blades new, but the vanes, case, spinner and disk also are new. This results in greater air flow, which in turn increases efficiency that is further helped by updated software. “We have optimized the engine for long-range fuel burn,” Stratton told AIN.
Engine testing is complete, as far as certification ground tests are concerned. Rolls-Royce has delivered four prototype engines to Embraer for Legacy 650 flight testing. As of the end of first quarter, manufacturing of production engines had started at the component level, which should allow Rolls-Royce to deliver production engines this year.
GE Honda Begins TestingThe GE Honda Aero Engines HF120, rated at 2,095 pounds of thrust, first ran last fall. Since then it has completed comprehensive testing across the flight envelope in GE’s altitude test facility in Evendale, Ohio. The new turbofan has been developed jointly by General Electric and Japanese automaker Honda to power the HondaJet and the Spectrum S40 Freedom.
So far, performance mapping for the new engine has been tested from sea level to 46,000 feet. Engine starting performance has been mapped throughout the flight envelope. In addition, transient operability testing has been conducted and endurance testing on key engine components continues. “All test results illustrate the engine is performing as expected,” a GE Honda spokesman told AIN.GE Honda’s plan for the March to May period is to run seven engines as part of the process leading to U.S. Federal Aviation Administration certification. The plan includes testing for hail and bird ingestion, endurance and module aeromechanics. Type certification, earlier planned for late this year, is now expected in the first quarter of 2011.
The HF120 features a wide-chord, compound-swept front fan and a two-stage booster. The single-stage compressor is made of a high-temperature titanium impeller “for maximum engine pressure ratio and stall-free performance,” according to GE Honda. The combustor is in a reverse-flow configuration, with single-stage air-blast fuel nozzles. The HP turbine has one stage, while the LP turbine has two. The HP and LP spools are counter rotating.
Bypass ratio is 2.9, the thrust-to-weight ratio is “over 5” and specific fuel consumption at cruise is “less than 0.7 lb/lbf/h.” The engine weighs “less than 400 pounds.” As for maintenance, the company is pledging a 5,000-hour time between overhaul.
By the time it enters service, the HF120 should have logged 15,000 cycles. GE Honda (Booth No. 158) is targeting the 1,000- to 3,500-pound-thrust bracket and so the HF120 may just be the first member of a family. 
Pratt Preps for Learjet 85Pratt & Whitney Canada (Booth No. 328) is developing the 6,100-pound PW307B for the Learjet 85, whose service entry is pegged for 2013. The engine features Pratt’s Talon advanced combustor technology, which is claimed to outperform ICAO standards by more than 30 percent for NOx emissions. The engine also will meet additional “Zurich 5” requirements needed to avoid the special noise surcharges at Switzerland’s Zurich Airport. 
The PW307B is in the detailed design phase and is due to make its first run in the fourth quarter of this year. Engine certification should occur in the fourth quarter of 2012.
The PW307B is built on the same turbomachinery as other PW307 turbofans, but with some software and external changes. The existing PW307A engine powers the latest Dassault Falcon 7X trijet, while the PW307C powers the Falcon 2000DX twinjet.
Although the PW810 program ceased shortly after the Cessna Citation Columbus program was terminated last year, Pratt & Whitney Canada is still keeping an eye on the possible market for the PW800 family. It would use the same core engine as the PW1000G geared turbofan, which will power next-generation regional jets and would be aimed at the large and ultra-long-range business jets, supplying 10,000 to 20,000 pounds of thrust.
The development of this new core requires more than 1,200 measurements and is being tested in an upgraded test facility until the second quarter. So far, trials have included operability, structural, cold start, emission and aerodynamic testing. Moreover, the compressor’s operation has also been mapped.
Pratt & Whitney Canada is using advanced measurement techniques such as noncontact stress measurement systems. The core test facility can simulate the engine systems and bleed off-takes. Dedicated cooling systems simulate all secondary air flows.
Silvercrest Bides Its TimeSnecma (Booth No. 639) is still looking for a large or long-range business jet on which to hang its new Silvercrest. Designed to provide 9,500 to 12,000 pounds of thrust, the Silvercrest could be ready to power an aircraft entering service between 2013 and 2015.
The French engine maker claims that its first business aviation design will bring a 15-percent fuel burn improvement. NOx emissions are expected to be 50 percent below CAEP 6 requirements and noise levels are projected to be 20 dB below Stage 4. The Silvercrest’s core engine completed an 80-hour test campaign in 2008.    

Microturbo Has New APU
Safran group company Microturbo (Booth No. 639) is promoting its new “e-APU” electronic auxiliary power unit (APU) designed for new-generation business aircraft, which are expected to need more electric power. Performance tests are complete and endurance trials are about to begin.
The French company will not reveal the name of the first application, but a spokeswoman told AIN that ground testing on the aircraft in question is to start later this year, followed by flight testing early in 2011.
Microturbo claims the e-APU will have 20-percent lower maintenance costs, compared to its Honeywell competitor. The new APU should also be more environmentally friendly, promising a reduced fuel burn, lower emissions and quieter operation (below 70 dB).
For business aircraft, including helicopters, weighing more than five metric tons (11,000 pounds) the e-APU will offer an electric power output of 15 to 90 kWe (kilowatt electric)–enough to start the aircraft’s engines electrically. The e-APU will be able to start at altitudes up to 41,000 feet, operating at up to 51,000 feet. The e-APU’s turbomachinery is made of a single-stage centrifugal compressor and a two-stage turbine.
Certification and first customer deliveries are pegged for early 2012. Microturbo is forecasting that the e-APU’s production rate will reach “several hundreds” per year, by 2020.