B767 No Winglets
Join Date: Sep 2002
Location: La Belle Province
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Let's say a design team is given the objective: design the best short-haul airliner you can. What is "best"? Most fuel efficient? fastest? Most pax? Fastest to turn around? Most reliable? Safest? Cheapest? How a given team balances all those competing criteria biases design choices. And there is no right answer to the question of balance - because there will be a customer who puts each individual item first.
Do you want an airliner that can do LCY? If I'm Southwest Airlines, no, of course not. If I'm BA, maybe it's my #1 priority?
The reason there are many different designs, is that there are many different design objectives. (Indeed even with identical design objectives, the exact same end result is unlikely. X-32 and X-35 were designed for the same contract, after all... )
To answer the specifics.
Why would the wing for the 787 and A350 not be exactly the same other than for size/scale differences ?
Why would the location and length of the pylons ( relative to the size of the wing ) not be exactly the same ?
Why wouldn't the airframe's ribs and spars and the profile/shape of the v/s be exactly the same, again allowing for size/scale ?
And why were some aircraft conceived, designed and built with underwing mounted engines and others with fuselage mounted engines and T-Tails ?
And others designed with high wing construction rather than conventional low wing construction ? Presumably one method or combination of the these alternatives produces the better aerodynamics compared to the other(s) ?
And others designed with high wing construction rather than conventional low wing construction ? Presumably one method or combination of the these alternatives produces the better aerodynamics compared to the other(s) ?
Join Date: Aug 1999
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Yes....See your point about horses for courses, etc.....and why a 777 looks a bit different from my old t/p's.....
Just that it's always struck me that given aerodynamic law is more or less inflexible, then aircraft have to be designed within these parameters - so if Boeing and Airbus are both designing / marketing / building generic aircraft for a certain market but not for specific customers or to customers' specific specification, then why wouldn't the 777 and A330 or the 787 and A350 ( more or less same range. size, possibly engines ) look and be more or less identical ?
In particular, I was thinking about wing profile / sweep / area / location ( which provides all the lift ) when depending on the various models, the airframes are more or less the same size, all are twins, all have more or less the same flight envelope/mach requirements, etc....
Still have a hunch that there's a little bit of ' design branding ' goes into the final product - think cars, motor yachts, etc, all fairly easily identifiable to specific manufacturers....
No big thing, as I said, it's just that I have always been curious....
And, back to the original post, maybe it's just that winglets were not en vogue when the 757/767 were originally designed, even if the technology was already known and available....
Just that it's always struck me that given aerodynamic law is more or less inflexible, then aircraft have to be designed within these parameters - so if Boeing and Airbus are both designing / marketing / building generic aircraft for a certain market but not for specific customers or to customers' specific specification, then why wouldn't the 777 and A330 or the 787 and A350 ( more or less same range. size, possibly engines ) look and be more or less identical ?
In particular, I was thinking about wing profile / sweep / area / location ( which provides all the lift ) when depending on the various models, the airframes are more or less the same size, all are twins, all have more or less the same flight envelope/mach requirements, etc....
Still have a hunch that there's a little bit of ' design branding ' goes into the final product - think cars, motor yachts, etc, all fairly easily identifiable to specific manufacturers....
No big thing, as I said, it's just that I have always been curious....
And, back to the original post, maybe it's just that winglets were not en vogue when the 757/767 were originally designed, even if the technology was already known and available....
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Now, there are corporate biases too - you don't vary from what you already know without good reason. So if company A has a track record with, say, sidesticks and FBW, and company B is more comfortable with control wheels and more traditional control design, then that's what you'll likely see in their next products. Because one of the design constraints isn't "what is the best design option?" but also "which design option can WE do best?"
