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,