Thread: Air mail
12-28-2006, 04:58 AM #1
- Join Date
- Dec 2006
Over recent months I've noticed that a lot of the comments we get are not only comments, but also pose some thought-provoking questions and raise some interesting issues.
So as I've done occasionally in the past, I'd like to try to address some of these questions here in the blog.
C.W. from California recently asked about composite "skins" on commercial airplanes, as in, why not make all of our existing models composite airframes?
Given that a 747 or 777 is built around an aluminum frame, how difficult would it be and how much weight would be saved by "re-skinning" with the same material that is being used for the 787? It would seem to be relatively easier to make pre-molded sheets vs. an entire fuselage .. would this be at all practical?
Well, the answer is, it's not really practical. To get the full advantage of composites we really have to create the airplane design from the beginning with the composite "material set" in mind. The cost of re-doing an aluminum fuselage design that is already complete, using another material set makes it pretty much prohibitive. I should add, though, that we are already making significant use of composite materials in some of our airplanes. 9% of the 777's structural weight, for example, is composite - primarily floor grids and the empennage section.
From Boulder, Colorado, Walter brings up a topic we frequently get questioned about: the "blended wing" concept. Earlier this year an image of a blended wing "797" made the rounds of the Internet, and got speculation swirling that Boeing has this in the works.
Is there any truth to the emails showing a blended wing 1,000-passenger concept that is dubbed a Boeing 797? Makes sense that the airline industry would head this direction some day, but it just sounds too good to be true!
Yes, too good to be true, indeed, Walter. Someone was having a bit of fun with PhotoShop perhaps. Boeing is not planning to build a 1,000 passenger commercial airplane dubbed the "797," based on the blended wing body (BWB) concept or any other futuristic concept. It's certainly not in our commercial market forecast, which goes out for 20 years. We think the commercial airplane market favors point-to-point routes, and we're developing the 787 as the perfect match to help meet that demand.
Glen, from Warrington, Pennsylvania brings up the same subject:
Is there a blended wing in the works? Are there floor plans of it?
No, not for a commercial airplane. But having said that, I should point out that Boeing Phantom Works, the company's advanced research and development group, tells me it is conducting research on the BWB concept with NASA and the U.S. Air Force. They're working to better understand what they describe as the BWB's "fundamental edge-of-the-envelope flight dynamics" and structural characteristics. The Air Force is interested in the BWB concept for its potential as a flexible, long-range, high-capacity military aircraft.
As part of the research, Phantom Works has built a scale model for wind-tunnel testing of the concept's low-speed flying characteristics. There also are plans to flight-test the scale model next year. You can read a little more about this project here.
The Dreamliner has a sleek design. But is it stealthy? Not really.
One commenter from Houston asked a 787 question I don't think I've ever heard before.
Since the 787 Dreamliner will have a full-composite fuselage and wings (or mostly so), won't its radar signature be smaller than a more metallic plane? To me, that is a good selling point.
Maybe. If you were designing a stealth aircraft. But actually, you want commercial jetliners to show up on radar for good air traffic control. Also, the ability of military jets to escape radar detection is only partially due to materials. So, in short - no, the radar signature will not be significantly different for the Dreamliner.
Then, we got a comment from Sam, who sounded a bit worried that the new A350 could potentially nip at the heels of Boeing's product line.
As threatening (or not threatening) as this new A350X is, wouldn't it be in Boeing's best interests to look into further improving the 787 .. just to keep on top of things?
Well, we always look at improvements for all of our airplanes. Short answer: not to worry, Sam. We're on top of it.
From Long Beach, California, Anton wants to suggest a novel way to make painting an airplane obsolete.
Is there a means to infuse an airlines' color scheme directly into the composite without weakening the carbon fiber structure? Wouldn't this save a lot of additional weight of not having to paint the plane?
Sometimes I'm amazed at the thoughtful ideas that come through this blog. And this one sounds fascinating. Unfortunately, our carbon fiber structure is black and would not be infusible.
Here's a comment from "G" about Boeing's strategy for twin-aisles, and plans to configure the 747-8 Intercontinental at the same length as the 747-8 Freighter.
This can be a good idea especially if Boeing considers building a bigger, better and lighter 777-8 and 777-9. Boeing's wide-body-long-range (WBLR) aircraft family will have a uniform capacity separation of 20% from 230 seats to 475 seats. It will be very difficult to position an aircraft between two Boeing WBLRs.
This statement about 20% capacity difference is correct. That's why we have four model sizes of long-range widebody airplanes to cover the 200-400 seat market - 787-8, 787-9, 777-200ER/777-200LR, and 777-300ER. Their capacity steps are approximately 20%. And then, the 747-8 is approximately 20% bigger than the 777-300ER, with about 20% less capacity than the A380-800. So yes, we think this is a good strategy.
We get lots of questions about the 747-8 Freighter and the 747-8 Intercontinental.
From New York, Ed keeps the conversation focused on the 747 with this question:
I know that the answer to this is quite simple, but why does the passenger version of the 747 have nearly twice the range as the freighter? Is it because the TOW is that much heavier; does it fly at a lower altitude? Assuming both jets land with an "empty tank" and a full load of passengers vs. a full load of cargo, the passenger jet would be a continent ahead of its freight twin. Why?
Ed, the simple answer is that the freighter is carrying a lot more weight in cargo. That means it is burning more fuel and that reduces its range. The freighter carries a full cargo payload of 295,400 pounds. The passenger version only carries 94,500 pounds with a full load of passengers and their baggage. If we reduced the payload of the freighter to that of the passenger airplane, it would actually go a little farther than the passenger version.
And then we had this note from Ivan in Ontario, Canada about our comparisons of the 747-8 Freighter and the A380F.
Re: Weight a minute. What about actual productivity measured in ton-miles? The A380F range is almost as far as the 747-8F. How would the calculations look then? Total fuel + landing fees + pilot additional labour cost.
Well, by looking solely at productivity, you may not a get a full picture of the economics of an airplane. It's equivalent to comparing a 30-passenger bus and a 15-passenger van. Granted, the bus may be more "productive," but if the van is more efficient, it would be more cost effective to have 2 vans.
With commercial airplanes we usually use a measure called cost-per ton-mile. This measures how much it costs to move a ton - one nautical mile. Using this we calculate that the 747-8F has a 23% advantage over the A380F. Anyway, I hope that somewhat answers your question, Ivan.
And now that I've gotten that all off my shoulders, it feels pretty good. For those of you who asked the questions, I hope it was worth the "weight."
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