Boeing's 787 flies today!

2,786
13
Anyone remember this brilliant idea?

http://flyingelectrons.com/page7/page18/files/page18_2.jpg [Broken]

Boeing decided it would be a good idea to cruise right at the edge of ma 1, i.e where drag is the absolute highest. I talked with a former Boeing engineer who told me the entire airplane was a marketing gimmick they had no intentions of making.

transonic-drag.jpg


Hmmmm, lets make an airplane cruise at that peak.....brilliant idea.
 
Last edited by a moderator:

Ivan Seeking

Staff Emeritus
Science Advisor
Gold Member
6,734
172
The answer from Cyrus is "I don't know"?
 

Ivan Seeking

Staff Emeritus
Science Advisor
Gold Member
6,734
172
It is pretty tough to fake 20% better mileage.

Of course I'm sure none of the buyers have anyone who knows what they're doing. God knows that none would have a newby college grad to keep them straight.
 
343
0
Anyone remember this brilliant idea?

http://flyingelectrons.com/page7/page18/files/page18_2.jpg [Broken]

Boeing decided it would be a good idea to cruise right at the edge of ma 1, i.e where drag is the absolute highest. I talked with a former Boeing engineer who told me the entire airplane was a marketing gimmick they had no intentions of making.

transonic-drag.jpg


Hmmmm, lets make an airplane cruise at that peak.....brilliant idea.
Well there are a lot of factors consider when talking about the drag caused by mach divergence... I'm not saying that it didn't impact the particular air liner your talking about but I'm sure boeing would probably have looked into technologies to further reduce the effect than the modern supercritical airfoil does.
 
Last edited by a moderator:
2,786
13
The answer from Cyrus is "I don't know"?
What "answer from cyrus"? I didn't answer any specific question.
 
2,786
13
It is pretty tough to fake 20% better mileage.

Of course I'm sure none of the buyers have anyone who knows what they're doing. God knows that none would have a newby college grad to keep them straight.
Yeah, because its not like a leading aerodynamicist wrote the book I scanned for you. Or that I gave you something I was told by an aerodynamicist at boeing. Perhaps we should do more reading on this subject?
 
2,786
13
What is specific productivity?
It is defined as:

[tex] SP = \frac{(\mbox{Max Payload})x\mbox{(Transport speed)}}{\mbox{Max T/o Weight}}[/tex]
 
343
0
It is defined as:

[tex] SP = \frac{(\mbox{Max Payload})x\mbox{(Transport speed)}}{\mbox{Max T/o Weight}}[/tex]
I figured it was something like this, I've only ever seen the term used in biology to do with cells. So I wasn't exactly sure how it applied here. However is this diagram based on the 'low-end' models of the planes or the 'high-end' because the gap in specific productivity between even the 3 models of 787 is quite large... or does it maybe average it out or something?
 

turbo

Gold Member
2,758
44
It is pretty tough to fake 20% better mileage.

Of course I'm sure none of the buyers have anyone who knows what they're doing. God knows that none would have a newby college grad to keep them straight.
Prime motivation for sales. Fill the seats on popular longer runs and save a pile of money on fuel. And yes, that kind of efficiency is impossible to fake. A higher-capacity plane can also help relieve congestion in the skies and on the ground. If I were operating an airline and a manufacturer offered me a new plane that could cut fuel costs by 20% on runs like NY to LA, NY to LV, LA to Honolulu, etc, I'd sure have some orders in place. You're still going to have fees to pay at airports, catering costs, etc, but if you can make fewer flights, spreading the costs over the same number of passengers (or more passengers, perhaps) AND save 20% on fuel, that's a game-changer. I hope that Boeing gets the plane certified soon and starts cranking them out - a little bright spot in the economic gloom.
 
4,360
55
Yeah!

Observation: The chase plane wasn't exactly in the safest location, wingtip vortex-wise! Would have been tragic to get off the ground only to loose a wingtip...
Well wing tip vortices are always below the flightpath and I never say the chase that low.
 

FredGarvin

Science Advisor
5,016
6
Hooray for substandard improvements in technology!!!!! Hey, at least it has a fancy paint job...
Come back to us when you have had a nonosecond of experience getting an aircraft FAA certified. If you had any, you would know that because of a lot of reasons you don't see huge advancements in a single aircraft and still stay in business. There is way more than simple design calculations to look at. For example, before you even begin the process of building and testing a new aircraft, the FAA has to sign off on the aspects that go into it, basically saying that whatever problems you run into they will not require breaking the laws of physics, etc...In other words, the FAA knows of all of the issues up front and they think you have a reliable approach to solving. That kind of system does not lend to massive or earth shattering advancements in one aircraft. Slow, gradual advancements are the way to go, especially if you are embarking on a program that will cost you tens of billions of dollars. Even in your chart, look at the one data point that showed "huge jump in technology!" The Concorde. While a cool aircraft, it made 0 money and cost huge sums and was, for all intents a business failure.

I'm not defending the marketing morons. I hate them too. However, this is just a bit more complicated than that.
 
Last edited:
2,786
13
Come back to us when you have had a nonosecond of experience getting an aircraft FAA certified. If you had any, you would know that because of a lot of reasons you don't see huge advancements in a single aircraft and still stay in business. There is way more than simple design calculations to look at. For example, before you even begin the process of building and testing a new aircraft, the FAA has to sign off on the aspects that go into it, basically saying that whatever problems you run into they will not require breaking the laws of physics, etc...In other words, the FAA knows of all of the issues up front and they think you have a reliable approach to solving. That kind of system does not lend to massive or earth shattering advancements in one aircraft. Slow, gradual advancements are the way to go, especially if you are embarking on a program that will cost you tens of billions of dollars.
<shrug> and then you build the same airplane for 40 years. You need to read the book I linked to, which explains the current problem with industry. The 787 is a perfect example of small changes due to unambitious thinking. Wow.....5% better performance in 40 years. AMAZING. It's time for something that is 50% better. Helicopters suffer greatly from this very problem. There are almost no new ones built in the last 20 years, and the V-22 is a piece of heavy, expensive, junk.

I'm not being a smartass, read this book, you'll love it being a helicopter guy Fred.
 

FredGarvin

Science Advisor
5,016
6
You have to live with the business realities before you get a job doing it. Period. To get something that is "50% better" (better in what?) there needs to be a business case and a way to fund it. Boeing and Airbus bet the farm with every new aircraft that comes out.
 

Borek

Mentor
27,875
2,449
[tex] SP = \frac{(\mbox{Max Payload})x\mbox{(Transport speed)}}{\mbox{Max T/o Weight}}[/tex]
Thanks. But if it is defined this way nothing strange there is not much that can be done, perhaps that just means we are close to the physical limits for this type of the plane. I suppose if you could plot cost of kg mile (or passenger mile), or MTBF (or some other parameter of similar meaning) against time, plot would be not that flat.
 

FredGarvin

Science Advisor
5,016
6
I don't agree with that metric being the lone one to compare to. How about "does the manufacturer make money and continue to do business" metric? Or in the case of the Concorde, which had very few routes to fly, how useful is the aircraft for which it was designed. I can think of a hundred more parameters to judge a design against that the Concorde would fail miserably in.
 

Borek

Mentor
27,875
2,449
It's time for something that is 50% better.
Somehow I doubt such solutions exist. After almost 100 years of polishing and optimizing every single detail in the planes I am ready to assume every reasonable approach has been tried - and those that were better were already selected. Assuming it is still possible to jump higher by 50% just by doing it differently is getting us dangerously close to those crackpots that tell us now and again that car industry hides miracle solutions for water fuelled cars.

I would love to be wrong.
 

minger

Science Advisor
1,496
1
Right now I would say things are limited by materials. Better materials will let us run higher temperatures, which will raise efficiencies. Will you see a 50% raise? I don't think so, the thermal efficiencies of those engines are already fairly high, and Cd values are of magnitude ~0.01.

I just don't see from even a macroscopic view you can expect to get an additional 50% from.

Fred: Those are the people that I was speaking of in fact. My graduate adviser split time between the university and Glenn.
 
4,360
55
Well if you want to improve 50%, Cruise altitude and speeds are optimized, if there was anything in the design to improve, it would have been already. Also, there is not a lot more efficiency to be gained from burning liquid hydrocarbons. What kind of fuel would we be thinking off in the first place?
 
2,786
13
I don't agree with that metric being the lone one to compare to. How about "does the manufacturer make money and continue to do business" metric? Or in the case of the Concorde, which had very few routes to fly, how useful is the aircraft for which it was designed. I can think of a hundred more parameters to judge a design against that the Concorde would fail miserably in.
I'm not arguing that is the only metric to compare to, nor does the book. It simply illustrates a point I was making. The book also explains why the Concorde appears to be an outliner, and taken with caution on the next page (which I didn't scan).
 
2,786
13
Somehow I doubt such solutions exist. After almost 100 years of polishing and optimizing every single detail in the planes I am ready to assume every reasonable approach has been tried - and those that were better were already selected. Assuming it is still possible to jump higher by 50% just by doing it differently is getting us dangerously close to those crackpots that tell us now and again that car industry hides miracle solutions for water fuelled cars.

I would love to be wrong.
You'll never find a new solution building the same old airplanes. That is the point. The point of thinking is flawed in industry in terms of innovation. They only make small baby steps.
 

minger

Science Advisor
1,496
1
There are efficiencies to be gained, but not that amount. Aside from better materials letting us burn hotter, one thing I've also heard of it....smart "shapes" or...hell I can't think of what it's called.

Either way, the idea is to have the engine change its shape during the operating range to maintain efficiency, particularly during take-off, climb. How to accomplish this though....whew, no idea.
 
2,786
13
Right now I would say things are limited by materials. Better materials will let us run higher temperatures, which will raise efficiencies. Will you see a 50% raise? I don't think so, the thermal efficiencies of those engines are already fairly high, and Cd values are of magnitude ~0.01.

I just don't see from even a macroscopic view you can expect to get an additional 50% from.

Fred: Those are the people that I was speaking of in fact. My graduate adviser split time between the university and Glenn.

I hope I did not give you the impression that I meant 50% improvement in the engines. I meant 50% improvement in the airframe aerodynamics.
 
2,786
13
Note: It is quite interesting how many of you throw in the towel so quickly when presented the facts of the current state in industry.

"Cant be done"....."They would have found it by now"......etc, etc......... not a good sign. There is a good example of a car factor that made a stamped part. It took 3 mins to make each part. Someone said he wanted it redone in under a minute. Everyone said he was crazy, impossible. They got it. Then he said, now I want it in under 30 seconds. Again, impossible. After much work, they got each part in under 10 seconds. Don't be those engineers who give up so easily.

Is the 787 a new airplane with composite materials: yes. Does that make me happy: sure. Is it the hottest thing since sliced bread? No.
 

Borek

Mentor
27,875
2,449
I'm not arguing that is the only metric to compare to, nor does the book.
Trick is, selecting metric that suits you you can prove whatever you want. Weight of the EOS camera I am using now is almost identical to weight of the mechanical camera I used 30 years ago, yet it has a zoom lens, works at ISO 100-1600 instead of the one of the film that is loaded, takes 400 pictures and not 36 before "cartridge" has to be changed, allows me to check the picture immediately and so on. Judging from the weight alone there was no progress in the meantime :smile:
 

Want to reply to this thread?

"Boeing's 787 flies today!" You must log in or register to reply here.

Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving

Top Threads

Top