Part I of DN Editor-in-Chief John Dodge's interview with 787 Dreamliner Chief Project Engineer Tom Cogan zeroes in on the myriad technologies in Boeing's newest airplane.
DN: Our materials expert Doug Smock says the composites are the biggest innovation in this airplane. Would you agree with that and if not, which ones are?
Cogan: I would have a hard time saying any one is the single biggest innovation. In an airplane like this to be successful, it is a collection of those. It’s all of them as a system together that make the difference. Certainly, composites are easy for people to get their mind around and something you can see. For a passenger, they won’t know what airplane is made of. For the airlines, it’s a huge benefit, making for lighter weight to reduce fuel burn and environmental improvements.
DN: Can you give any metrics on the plane’s reduced weight?
Cogan: Theoretically, composites are on the order of 30 percent lighter for a given strength (than aluminum). It’s a little bit dangerous putting a number to it because it depends on whether you’re talking about tensile strength or compressive strength, but a number around 25 to 30 percent lighter is reasonable. Composites have different characteristics than aluminum because when you apply it to production, you lose a little of the benefit. You may have to add some weight in some areas – for example (how) electromagnetics affects protection. Maybe (you need) a current return network or something that very efficiently ties the airplane together. It’s 20 or 30 percent lighter (by way of comparison, maximum takeoff weight for the biggest 787 is 540,000 lb versus 774,600 lb for the biggest 777). Making the plane more fuel efficient has allowed us to do some things on the airplane that we could not have done if we built it with aluminum. For the interior we have made the windows tall enough so you see across the seat backs and see out. Using composites allowed us to put in those windows without adding a lot of weight. We have a lower cabin altitude than in an aluminum airplane because the composites allow us to have a higher pressure in the cabin without fatiguing the materials on the airplane. That’s less maintenance. This plane is on the order of 30 percent lower maintenance than a seven six seven. A lot of it comes from advanced systems, but a lot of it is the composites. The airlines won’t have to do as much maintenance because you will not have the fatigue and corrosion issues that you have on a metal airplane. That’s one that gets talked about a lot.
DN: What else?
Cogan: This is a more electric airplane. It is more efficient to take electrical power off generators and run the air conditioning system with electrical compressors than to take air off the engine like we do today with a 777. One of the nice things about a more electric airplane is not relying on pneumatics. That not only reduces maintenance costs, but has made the airplane more fuel efficient.
DN: That raises the question of scarce jet fuel. Could a commercial jetliner ever get off the ground without kerosene?
Cogan: Our expectation is that fossil fuels will be around for some time. As the world’s population grows and nations become more industrialized, obviously alternate power sources are going to be required. When the fuel cell technology becomes evolved, we can replace the jet engine in the back (APU) producing electricity with a fuel cell. That should not be in the too distant future. The 787 was targeted to be 20 percent more fuel efficient than anything out there flying today. The whole reason for the program was recognizing we needed to reduce fuel burn.
DN: What about aerodynamics? The wing tips look so slender and curved up, the wings look like their going to start flapping.
Cogan: Aerodynamics was a very evolved technology before the 787. One of the things that allowed us to make improvements in aerodynamics was composites.Aerodynamic efficiency comes from high aspect ratio of wings. Making a wing out of carbon fiber, we’ve been able to go to a higher aspect ratio wing. Our ability to model the airplane in three dimensions has allowed us to optimize the aerodynamics in ways we never have been able to do before. The wing tips are purposely designed so they not only sweep back but have a slight upward curvature. That’s part of the aerodynamics, (but) the overall curvature of the wing is not a lot different from today’s airplanes. As we were doing the wing design, we looked at the wing tips to give the airplane a distinctive look. Next time you fly in a 747 and the plane is heavily loaded with fuel, look out the window as you take off, you’ll see that the wings curve up. When a plane is sitting on the ground and the weight is on the wheels, the fuel is pulling the wings down and they sag. Once you’re airborne, they flex up dramatically.
DN: What other innovations are there?
Cogan: If I start listing them off the top of my head, I’ll miss some and feel bad.
DN: Go ahead and try.
Cogan: If you’re a propulsion engineer from GE or Rolls, you would say the engines, which are extremely quiet, fuel efficient (and clean). If you’re a structures engineer, you would argue for the composites and the architecture. If you are systems’ engineers, you would argue for the electrical or hydraulics systems. The flight control system on this airplane is another example of how we are using technology and fly-by-wire. This will be the most sophisticated flight control system on any commercial jet, allowing us to do vertical gust suppression and maneuver load alleviation.
Vertical gust suppression is using flight controls to dampen turbulence. You can’t eliminate it completely, but as the airplane senses vertical or lateral excursions from the flight path, the flight control surfaces can move quick enough to be able to reduce that and make it a more enjoyable ride. Maneuver load alleviation is using the same technique when you’re loading the wings a little bit heavier (while turning, for example). It reduces those loads.
DN: What will jump out most to a pilot?
Cogan: We’ve spent a lot of time making the flight deck a very pleasant environment. The first thing we do is around basic safety to make sure this is better than anything we’ve done before, providing better situational awareness for pilots. We design that into the pilot machine interface. The flight deck is dramatic and modern-looking with very large displays so the pilots have access to more and better information. I think pilots will find it a real joy to fly.
DN: Similarly, what will passengers, who typically don’t know the difference between a 727 and 747, notice most?
Cogan: When they walk on to the airplane, they will know they are on a different airplane. The Triple Seven has a very distinctive and pleasing interior. After 10 years of operation, surveys give it high marks for a very comfortable interior. We have taken that a step further on the 787. You mentioned new lighting and bigger windows. One of the things I get anxious about as the last one to get on the airplane is a place to put my carry-on luggage. This airplane is going to have very large bins so that every passenger has ample room to put their carry on, but we’ve designed them in such a way they don’t look big or are obtrusive. The interior is harmonized, comfortable and welcoming.
There’s things during a flight that passengers won’t know about, but they’ll feel better when they get off the airplane. With the lower cabin altitude, they won’t feel the effects of altitude as they would on today’s airplanes. We have a gaseous air purification system which makes the air on the inside purer than on the outside. The lighting and the humidity levels will make passengers feel better when they get off the 787 and they won’t know why. They’ll know that it was a really good flight, especially if they experience a lot of different airplanes. It did not just happen. This is something we put a lot time, effort and research into to get it right.
DN: What’s new on the 787 that will make it safer from terrorism?
Cogan: I really can’t comment on that. Certainly we work with the regulatory authorities on the things we can do to ensure safety in our industry. There’s a lot of different aspects to it and it’s a system, I can’t comment on it.
DN: Boeing has obviously learned much from building this airplane. What would you do differently knowing what you know now?
Cogan: That’s a really difficult question because the business model and relationships are a bit different from what we’ve done in the past.There’s always some detail things that you might do differently, but overall it’s worked amazingly well. When the airplane gets into service, that will bear itself out.
DN: What comes after the 787?
Cogan: Another new airplane, probably (laughter). We’ll listen to the market and respond with the right product.
DN: With Airbus having delays with the A380 and the 787 the most successful new plane in history with over 500 orders, how do you feel?
Cogan: Certainly there’s a quiet confidence on our part that we can deliver what we’ve promised. Airbus is a world-class manufacturer of commercial jets and they are having their struggles just as we have had our challenges in the past. It’s the nature of the business and the products we design. They’ll be in this with us for many years, but we stay focused on our products and let them worry about theirs.
DN: Can you give a dollar spent on the development of the 787?
Cogan: I can’t do that.
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|Sections 41 (nose) and 47 and 48 (aft fuselage) arrive at Boeing's plant in Everett, Wash. on May 11.