The Pratt & Whitney Geared Turbofan™ (GTF) has been selected for use on five of the seven new narrow-body programs under development, including Bombardier’s CSeries, Airbus A320neo, Mitsubishi Regional Jet, IRKUT MS-21, and Embraer E2Jets. We spoke with Bob Saia, Vice President of the Next Generation Product Family at Pratt and Whitney, to gain perspective on where the program stands today, and to discuss P&W’s plans for future GTF development.
CURRENT STATUS
The current status of the GTF program is that there are three different versions of the engine in testing today, and that P&W is solidly focused on execution — as they have five aircraft on which the engine will be certified in the next five years, a significant undertaking.
The CSeries engine, the PurePower PW1500G, that was certified last February is currently flying on two flight test aircraft at Bombardier, and P&W has built 12 production engines for the flight test program, with #13 and #14 in assembly. P&W is in the process of finalizing all of the supply chain and production requirements to get ready for production ramp-up and meet Bombardier’s delivery stream. P&W has also indicated that they will meet all of the fuel burn and maintenance targets agreed with Bombardier at program launch.
Bob indicated that the GTF testing has been going extremely well, with initial experimental engine test results for all three PurePower models being close to the customer guarantees established at program launch. Engine testing with the final production designs has confirmed that the PurePower models will meet all fuel burn guarantees at entry into service. In addition, Bob said engine maintenance cost, noise, and emissions are all on target.
To date, P&W has completed 7,000 hours to total testing on the PurePower engine family, which includes more than 750 hours of in-flight testing on P&W’s 747 experimental airplanes. P&W has completed three flight test programs on the 1500G for the CSeries, one flight test program on the 1200G for the MRJ, and two flight test programs for the 1100G for the A320neo (and subsequently MS-21). A third flight test program for the 1100G-JM engine is scheduled for next month. Engine certification for the PW1100G-JM is expected in the Fall.
WHAT’S NEXT
Although the GTF has not entered service yet, P&W is already working on next generation GTF configurations. The GTF engine for Bombardier and Airbus has a bypass ratio of 12:1 with a pressure ratio just under 50 to 1. The first generation GTF has capitalized on the inherent design efficiencies of a larger and slower fan to increase bypass ratio and gain additional propulsive efficiency from the fan.
P&W will increase the bypass ratio for the next generation GTF, approaching 15:1 and increase compressor pressure ratio to the low 60’s, two elements that will drive further performance improvements. With a planned change in the gear ratio increasing from 3 to 4, slower fan speeds will more fully optimize propulsive efficiency from bypass air, increasing fuel efficiency. P&W is also focusing on a higher performance core to improve thermal efficiency that will enable the engine to generate the same level of power with lower fuel consumption.
P&W’s technology plan includes the development of advanced aerodynamic features, lightweight materials, along with advanced hot section materials and cooling techniques. P&W’s technology maturation program is very active even though they are targeting product readiness well into the next decade. P&W’s current programs have EIS dates through 2020, and the company has chosen to focus on the next differentiated architecture for EIS in the first half of the next decade, rather than the current architecture, for another aircraft application.
How good will this advanced GTF be? With a 25% increase in bypass ratio and a 20% higher compressor pressure ratio, AirInsight estimates the potential for at least 5%, and as much as a 10% improvement in fuel burn for the next generation GTF.
BOTTOM LINE
P&W’s breakthrough with the GTF architecture has enabled it to regain market share in the narrow-body market. Should P&W be able to achieve AirInsight’s projected 10% improvement for a next generation GTF, which would bring its savings relative to today’s engines into the 25% range. This would be economically competitive with open-rotor concepts, but without the inherent problems of additional noise, large rotor size, lack of rotor failure protection, and lower aircraft operating speeds that present challenges for open rotor designs. As a result, the GTF appears to have a bright future well into the next decade and beyond.
P&W has the tight design an will have no problem competing with the open rotors or unducted fans. Unducted fans will not provide the power for fast climbs that are needed in today’s air traffic environment.
Once in a while, a manufacturer creates a great design, which eclipses others by far… in the engine arena, such designs were the CF6 core, the Trent core, and certainly the PWC 100 Series and the PT6 (both Turboprops)… it may well be that the GTF turns out to be a respected member of this distinguished list.
I think it was clear from the start PW focused on the gearbox and GE/CFM on materials, pressures, temperatures. It was also clear PW could/would put those Leap technologies on their engines. But GE could not GTF their Leap.. It made Embraer and BBD switch IMO. IMO Boeing has issue too. Saying a 69 inch LEAP is as good as a 79 inch GTF.. maybe stockholders take that but not airline engineers / fleetmanagers.
Fitting a 79 inch engine under the 737-MAX would require much additional weight in lengthening the landing gear and positioning it further out on the wing. This may even require moving the engine further out on the wing beyond the landing gear.
The 737 is a mini narrow body – low to the ground. It has evolved from the original 707 in 1957. Boeing expects the 737-MAX to remain more fuel efficient than the Airbus A320 despite its faster engine.
The next generation of GTF will be exciting when they get the bypass air subsonic with a 4:1 gear.
P&W has learned many lessons from the past. They are as quiet about their next generation GTF as the current generation GTF’s are in the air. Their revolutionary forward thinking, creativeness and second to none R&D process is years ahead of the competition. Perhaps we may see a 2 stage GTF with ultra high bypass ratio, one for ratio for climb/decent, then switch to a higher bypass ratio at cruse/altitude speeds for ultra fuel savings. We are only limited by our thinking and of course R&D money and that ROI accounting thing.
True, but with the advent of NextGen ATC, those fast climbs may well become a thing of the past.