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#11
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Boeing Launches 7E7
"Olivers" wrote in message ... Nik muttered.... Now my point is that if the 7E7 is to be 15-20% more efficient than the 767/A300 then this size of the plane might be the optimal. When you start stretching it to get into the A330 market it will be relatively less efficient and hence will represent even less of a direct competitor. As your logic doesn't work with ocean going vessels (where extending waterline length actually increases hull speed), it doesn't necessarily work with a/c either. The MD80s, long stretches of the original DC-9 fuselage had a substantially lower passeenger mile operating cost, more seats and about equal fuel consumption (except on takeoff), and IIRC an actual few knots increase in economical cruise speed. Many "stretch" a/c actually outperform their original versions. TMO Isn't dynamic drag to a large extent dependent on weight? (To my knowledge, this issue doesn't really apply to ocean going vessels). Nik Nik |
#12
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Boeing Launches 7E7
In article ,
"Nik" wrote: No the 7E7's efficiency gain possibly comes from being able to replace a second generation aircraft with a third generation FBW composite build one. I strongly doubt that the improvements in design techniques and knowledge about aerodynamic on its own would allow for a 20 percent efficiency gain One factor is the wing tip which is similar to what is found on some 737NGs. The Aviation Partners design works well enough that airlines are starting to retrofit it to their a/c (i.e., it's worth the investment). Have a look at how much better climb rate, range, payload are increased and fuel consumption and noise decreased. Continental is launching design to retrofit 757s. |
#13
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Boeing Launches 7E7
"Not the Karl Orff" wrote in message ... In article , "Nik" wrote: No the 7E7's efficiency gain possibly comes from being able to replace a second generation aircraft with a third generation FBW composite build one. I strongly doubt that the improvements in design techniques and knowledge about aerodynamic on its own would allow for a 20 percent efficiency gain One factor is the wing tip which is similar to what is found on some 737NGs. The Aviation Partners design works well enough that airlines are starting to retrofit it to their a/c (i.e., it's worth the investment). Have a look at how much better climb rate, range, payload are increased and fuel consumption and noise decreased. Continental is launching design to retrofit 757s. Well - the A330 also have wing tips... I'm not saying that the A330 cannot be improved. What I say is that to get a significant improvement you'll likely have to introduce some kind of concept. Therefore the 20 percent is most likely over the 767 and the A300. Nik. Nik |
#14
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Boeing Launches 7E7
Nik extrapolated from data available...
"Olivers" wrote in message ... Nik muttered.... Now my point is that if the 7E7 is to be 15-20% more efficient than the 767/A300 then this size of the plane might be the optimal. When you start stretching it to get into the A330 market it will be relatively less efficient and hence will represent even less of a direct competitor. As your logic doesn't work with ocean going vessels (where extending waterline length actually increases hull speed), it doesn't necessarily work with a/c either. The MD80s, long stretches of the original DC-9 fuselage had a substantially lower passeenger mile operating cost, more seats and about equal fuel consumption (except on takeoff), and IIRC an actual few knots increase in economical cruise speed. Many "stretch" a/c actually outperform their original versions. TMO Isn't dynamic drag to a large extent dependent on weight? (To my knowledge, this issue doesn't really apply to ocean going vessels). Obviously, there's an penalty, and greater takeoff weight requires more fuel to climb and to cruuise, but the derived result in some stretches, starting with the "Stretch 8" offset some of the potential. Of course, in modern a/c, the vast advances in engine economy make comparisons difficult, but certainly the 757 was an attempt to profit from a longer fuselage and reduced cross section. As for ships, the "weight" problem is expressed a different way...Stretch it (without changing beam or hull lines), and the volume of the extension and weight of the new materials cause an increase in "displacement", the volume of water displaced by the ship. The increased displacement is in almost every case of which I'm aware, offset by the increased "hullspeed" available from a longer waterline. The "Cut off" square transom sterns which are popular are an artificial method by which the hull "acts" longer. I suspect the short fat 747, was it the SP?, were a venture in another direction, reduced structural weight, lower pax/cargo weight, allowing longer range from the same size tanks. TMO |
#15
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Boeing Launches 7E7
In article ,
"Nik" wrote: n to retrofit 757s. Well - the A330 also have wing tips... And so do others but the question is whether they work as well as those ones used on some of the the 737NGs I'm not saying that the A330 cannot be improved. What I say is that to get a significant improvement you'll likely have to introduce some kind of concept. Therefore the 20 percent is most likely over the 767 and the A300. I think that's not disputed. At any rate it is Wweight. |
#16
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Boeing Launches 7E7
"Not the Karl Orff" wrote in message ... In article , "Nik" wrote: n to retrofit 757s. Well - the A330 also have wing tips... And so do others but the question is whether they work as well as those ones used on some of the the 737NGs That is right. However, I do believe that wing tips is a part of an aircraft's structure that might be the easiest to modify if the need should occur. Nik |
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