Jetrader - September/October 2010 - 9

Q&A
EMERGING TECHNOLOGIES

Dr. Alan H. Epstein
VP Technology & Environment Pratt & Whitney
Jetrader: Technological (generation) change has a huge impact on the aircraft ﬁnance and leasing community. Where do you see engine technology going over the next 20 years? Dr. Alan Epstein: We’ve been looking at engine technology over the next 30 years. In recent years, we’ve focused on the narrowbody market as opposed to widebodies. In some sense, there is a 25-year gap in narrowbody engine technology. New engines were introduced in the mid-’80s for narrowbodies and also for widebodies. Then in the ‘90s, yet another class of new engines was introduced for widebody aircraft, but not for narrowbody aircraft. And again in the 2000s, another generation of new widebody engines – A380, 787. Again, no new narrowbody engines were introduced. So, indeed there has been a 25-year gap in engine technology where the market didn’t demand stateof-the-art technology in narrowbody airplanes. And so that was a gap Pratt & Whitney saw and ﬁlled it with the geared turbofan (GTF) engine. You ask what are we going to be making in 10 years: it’s advanced geared turbofans; and in 20 years: more advanced geared turbofans; and in 30 years: even more advanced geared turbofans. The geared turbofan is such a good idea that I am convinced that our competitors will be making them in ﬁve to 10 years, as well. JT: Is the geared fan concept an interim solution bridging the gap to the open rotor? AE: No, we’re convinced there will be no open rotor. And I’ll explain why. The open rotor is a high-speed contra-rotating propeller. The original idea actually came out of our sister division, Hamilton Sundstrand, in the 1970s during the ﬁrst oil spike. Pratt & Whitney built an engine for a propeller airplane that could ﬂy at Mach 0.8. We called it a prop-fan, and we tested it on a DC-9, and we ﬂew it at Mach 0.8 in the late ‘80s/early ‘90s. The challenge was that at the high Mach number, the propellers are no more or even less efﬁcient, than turbofans. And it’s clear from studies we’ve been doing with airframers in the last three to ﬁve years, that you could build a high-speed turboprop, but it would be less fuel efﬁcient and much noisier than a turbofan airplane at current aircraft cruise Mach numbers. When people now talk about propeller airplanes, they talk about, really, slower airplanes—Mach 0.75 rather than Mach 0.8 and 0.85. Most of
the fuel-burn advantage is the fact that you made the airplane slower. Our studies show that the turbofans on that 0.75 Mach number airplane have just as low fuel burn as the propellers and are much, much quieter. Therefore, since we can build the geared turbofans with much less noise and the same fuel burn savings, for the same ﬂight speed, we don’t see that the open rotor will ever be real.

JT: Pratt and the other OEMs are focusing on more fuel efﬁcient engines. Do you see alternative fuels as a realistic and affordable way to reduce the environmental impact on air transport? AE: The simple answer to this question is yes. Not only is it realistic, but it is absolutely necessary because aviation is growing faster than technology can improve the engines and airframes. And so the only way to actually get to carbon-neutral growth, much less reduce the carbon, is to go to low-carbon fuels, for which biofuels are the most obvious candidate. And we’re working in several venues to make that real. We’re working to certify biofuels in several consortiums in the U.S., Europe, Canada, India, Australia and New Zealand, looking to develop new biofuels.

JT: When will biofuels exceed 10 percent of the total fuel
consumption in aviation and which feedstock offers the best perspective? AE: Which feedstock offers the best perspective? It doesn’t matter. The nice thing about the biofuels that have actually been developed and are in the process of being certiﬁed to date, is they’re agnostic to feedstock in terms of quality of the fuel. Last year we did a biofuel ﬂight test with Japan Airlines on a Boeing 747, and the feedstock was a combination of jatrophia, camelina and algae. That test proved that we can be agnostic to feedstock. There’s another reason why we used mixed feedstock—we couldn’t ﬁnd enough of any one thing to ﬁll a 747. So, right now, all these processes are in the experimental or demonstration phase. There is not now appreciable fuel available. I think the answer is region-of-the-world dependent. The fact that different feedstocks can work, means that the suppliers can just go on the market and buy whatever is cheapest at the moment and change J trad Jetra er Jetrader 9

Jetrader - September/October 2010

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