Fallout from '10K' engine battle pushes market in new direction
While economic woes continue to emasculate the lower- and mid-tiers of the business aircraft market, engine makers are focusing on new development efforts in the apparently recession-proof larger jet segment.
Dominated for decades by, the big business jet power market is under attack from , , Pratt & Whitney Canada (PWC) and , all of which are expected to update their progress at EBACE, the European Business Aviation Convention & Exhibition being held in Geneva May 14-16.
Each company is evolving new engines from designs that emerged from the “10k” (10,000-lb.)-thrust contest from the last decade. Although the rush to develop the 10k engines themselves proved premature—projects were either being canceled, deferred or delayed—the contest spawned a flurry of higher-thrust developments that continue to this day.
Eager to penetrate the market sector, PWC has selected the core of the commercialgeared turbofan, in development for the , as the basis for its next-generation PW810 business engine demonstrator. The move picks up from development work on the original PW810, which was put on ice following the demise of the large-cabin Columbus project in 2009. Although that concept was shelved, it served as a bellwether for market change. “It used to be a 50:50 split between large and everything else, now it is 70% large,” says PWC President John Saabas.
“The real reason we are embarked on this program is the core exists, and the very reason the core exists is a huge step forward for us,” says Saabas, who adds that the use of the baseline engine variants on theand the CSeries will demonstrate and validate the technology before it moves into business aviation. “So the job is to do a demonstrator of a PW800 engine. We are talking to a couple of OEMs about a range of thrust from 10,000 to 16,000-17,000 pounds, and we're looking at all of them.”
PWC plans to run the demonstrator this year using a conventional low-pressure system better optimized for the rapid-climb performance requirements of business jets. “The technology is really in the fan,” says Saabas, who adds that design know-how from the larger commercial engines—in particular the Engine Alliance GP7200 and PW1500G CSeries—will be incorporated. No specific application has been tied to the engine, although the PW800 has been strongly linked to Gulfstream's secretive P42 next-generation G450 replacement project.
Another manufacturer looking to break into the sector is Snecma, whose focus remains on development of the 9,500-12,000-lb.-thrust Silvercrest engine. The super-midsize and large business jet engine project emerged initially from studies into a 50-seat regional jet engine, and is now aimed at programs such as's SMS twinjet. Although Rolls-Royce's RB282-3 was originally selected for the SMS in 2007, the engine contest was reopened in 2009 with the Silvercrest tipped as the front-runner. Snecma is widely expected to officially confirm at EBACE its position on the Dassault aircraft, which is targeted at certification in 2016.
Silvercrest incorporates a centrifugal compressor in combination with four axial stages—a first for Snecma. The compressor configuration enables the number of stages to be reduced to around 10, compared with more than double that for some competing current designs. It was developed in conjunction with Snecma sister companyand in early tests demonstrated a better-than-expected stall margin. Silvercrest also features counterrotating core and power shafts and builds on experience gained from the program with GE. Although Snecma has become increasingly tight-lipped about the program in recent years, the overall performance targets are still thought to include a decrease in fuel burn by up to 15% and an increase in climb and cruise thrust by around 25%, relative to similarly rated state-of-the-art engines.
Honeywell is exploring a raft of new aerodynamic, material and design technologies for a possible “next-gen” TFE731 family, as well as for growth versions of its HTF7000 series, the latter of which “maybe could go up to 9,000- or 10,000-pound thrust,” says Jim Kroeger, director of engineering for propulsion. “10 K is an area we are paying a lot of attention to, even though there aren't any competitions,” he adds.
Honeywell's original HTF10000 concept was shelved because “the platforms we were targeting seemed to grow away from 10,000 pounds and it was tough for us to change it without a radically different architecture,” says Kroeger. Since then, the market has continued to evolve, and concepts in the 10K arena are once again in the offing. “There seems to be a gap in the market there with long-range platforms, bigger cabins and high speed. The original equipment makers see all that market growth in the Asia-Pacific region, but what will come in below that? What sort of engine will that be? That's where our attention is focused.”
The company is studying more-efficient, forward-swept, blisked rotor fans which “would apply frankly to the whole range” as a possible means of developing that next-gen TFE731 or HTF7000-series engine, says Kroeger. Also known as integrally bladed rotors (IBR), the blisk concept could be used to boost existing architectures to higher bypass ratios of 6:1-plus without any increase in overall fan diameter. “This is important for business jets, which like to direct climb to 43,000 ft. and cruise at Mach 0.8 for one to two hours. Engine frontal area becomes part of the total equation,” says Kroeger, who adds that “a number of blisk fans are under test.” The fans are sized for the TFE731-60 Falcon 900EX engine. “Next will be an HTF7000,” he says.
Along with fan changes, Honeywell is also working a series of technology programs to improve compressor efficiency. “As we push power density we will see centrifugal compressor engines go up to higher thrust levels.” Together with weight-reduction efforts through increased use of composites and other non-metallics, Honeywell also continues to test new thermal-barrier coatings for higher temperatures as well as innovative turbine-cooling approaches. Further developments of its Saber (singular annular combustor for emissions reduction) combustor technology are also under way to reduce nitrous oxide emissions beyond the reductions provided by the initial Saber 1 standard in the HTF7250G for the Gulfstream G280 and the Saber 2 in the HTF7500E-poweredLegacy 450 and 500. Saber 1 can also be retrofitted into HTF7000 engines on the Bombardier Challenger 300.
General Electric's aggressive plan to enter the high-thrust bizjet arena remains on track with the freezing of the design of its new Passport business jet engine following a “toll gate 6” program review on April 27. Rated at 16,500-lb.-thrust, the initial Passport 20 variant is in development for Bombardier Global 7000 and 8000 ultra-long-range, large-cabin business aircraft.
Previously called TechX, Passport is a parallel development to GE's NG34 regional jetsuccessor program. Both leverage high-pressure compressor and turbine technology now being developed and tested in the eCore 2—an advanced gas generator technology program that also forms the basis for CFM's Leap engine for the , MAX and aircraft. Two eCore 2s have accumulated 150 test hours and a third demonstrator is set to run near year-end.
Hardware for the first of seven test engines will arrive in October with assembly set to begin by year-end. Actual testing is set for second-quarter 2013. First flight on a flying testbed is targeted for 2014 with engine certification due in 2015. Recent validation tests include blade out, bird ingestion and aeromechanical verification of the solid titanium, 52-in.-dia. blisk fan using two test units.
Another fan blisk will be tested in 2013, according to GE. The engine maker has also conducted booster icing work and testing of a new full authority digital engine control unit. The powerplant is designed to have at least 8% lower specific fuel consumption than current business jet engines in the 10,000-20,000-lb.-thrust class, double-digit margins to CAEP/6 regulations on all emissions and air transport-like standards of reliability.