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lvhgel
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Posts: 118
Joined: Sat Apr 14, 2007 5:30 am

Do All Modern Airliners Look Alike?

Thu May 10, 2007 3:20 am

Reading some discussions regarding airplane design, if they are beautiful, economically viable, so on and so forth, got me thinking on today’s designs, and from my own perspective if you line up all the Airbus, Boeing, EMBRAER, etc. being built today, there is a pattern, a long tube (longer or shorter) with under the fuselage wings, engines under the wing, vertical stabilizers at the end of the fuselage, an horizontal stabilizer at the back formed like a tetrahedron that wants to become a triangle rectangle, well, you get the picture.
The bottom line is that it seems that airplane design has become like American car design of the late 80s, functional but not revolutionary and if you are not a knowledgeable person, you weren’t able to tell one model apart from the other. (I am not talking about construction material or about avionics or engine technologies, I am talking about the design that can be seen in plain view).
I think that a plateau has been reached, unless a radical concept as the passenger flying wing is developed further, telling apart one airframe from another without going into the small details, is becoming more difficult. May be because of its’ function, the design development has reached its’ optimum point where the Form function and the Functionality function intersect.

The next questions might seem trivial, I am not an Aeronautical Engineer, but being more than casual observer I post them here:

1) Why not the wing over the fuselage a la AN-124 for bigger PAX planes.
2) Why not invert the angle of the engines pylons, instead of protruding from the attack edge of the wing, push the engines completely to the back, so the nacelle is under the wing, so that instead of “pulling” they “push”. similar to the Honda Jet but under the wing.
3) Why not go back again to multiple Vertical Stabilizers "a la" Connie?

I am fully aware that these concepts are not exactly elegant or feasible, but, for the sake of discussion

What other design changes if any would you propose?
What's next in airliner design?
 
FriendlySkies
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RE: Do All Modern Airliners Look Alike?

Thu May 10, 2007 3:38 am

Quoting LVHGEL (Thread starter):
1) Why not the wing over the fuselage a la AN-124 for bigger PAX planes.
2) Why not invert the angle of the engines pylons, instead of protruding from the attack edge of the wing, push the engines completely to the back, so the nacelle is under the wing, so that instead of “pulling” they “push”. similar to the Honda Jet but under the wing.
3) Why not go back again to multiple Vertical Stabilizers "a la" Connie?

Easy. Modern engineering has determined that these ideas are either not feasible, or not as efficient or aerodynamic as modern designs. Everything today looks similar because we've been designing airplanes for quite some time, and there's only so much you can do with a tube, a pair of wings, and some engines.
 
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solnabo
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RE: Do All Modern Airliners Look Alike?

Thu May 10, 2007 3:47 am

My guess is the BWB (Blended Wing Body), a huge flying wing with circa 1000 pax.

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davidkunzVIE
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RE: Do All Modern Airliners Look Alike?

Thu May 10, 2007 3:54 am


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No.




But seriously, I get your point.
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grandtheftaero
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RE: Do All Modern Airliners Look Alike?

Thu May 10, 2007 4:00 am

Quoting LVHGEL (Thread starter):
1) Why not the wing over the fuselage a la AN-124 for bigger PAX planes.

Because there is a structural advantage to having the fuselage sit on the wing rather than hanging under it. I'm sure there are other reason but that's the one that stand out in my mind.

Quoting LVHGEL (Thread starter):
2) Why not invert the angle of the engines pylons, instead of protruding from the attack edge of the wing, push the engines completely to the back, so the nacelle is under the wing, so that instead of “pulling” they “push”. similar to the Honda Jet but under the wing.

Pulling vs pushing? Ever draw a free body diagram? As long as you're sucking from the big end of the engine and blowing out of the small end, it really doesn't make a difference whether you're pushing or pulling. By hanging the engines in front of the leading edge you're avoiding the wake producd by the wings which would be detrimental if ingested by the engines. The only benefit I could think to putting the engines at the trailing edge would be to counteract the moment produced by downwash off the wings. But this obviously isn't a big enough deal to have changed wing/engine integration philosphy for the last 50 years.

Quoting LVHGEL (Thread starter):
3) Why not go back again to multiple Vertical Stabilizers "a la" Connie?

For the same reason I don't go out and put a big-ass spoiler on my car like in The Fast and the Furious. If one vertical stab will work then why add more? More "stuff" means more weight and more drag.


And to just add my two cents... one of the more elegant aspects of aerospace engineering is that airplanes, as beautiful as they may be, are design by numbers and physics. There is no artist and designer than comes in after the fact who messes with the mold lines of an airframe or fan blade or exhaust nozzle just so it will look different from Brand X's design.

In your example you say cars can be differenated by factors other than technology or engine performance. That's only because a designer has had a MAJOR say in what the vehicle should look like. This does not happen in aerospace. Anything that doesn't make it safer, faster, lighter, cheaper, or more comfortable is not put into the design. I think all us airplane nerds should be thankful that physics and aerodynamics alone have given us such graceful shapes to admire.

[Edited 2007-05-09 21:11:51]
 
lvhgel
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RE: Do All Modern Airliners Look Alike?

Thu May 10, 2007 4:37 am

Quoting DavidkunzVIE (Reply 3):
No

 Silly , Yup you might have a point there...  Silly
 
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SEPilot
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RE: Do All Modern Airliners Look Alike?

Thu May 10, 2007 5:05 am

Quoting LVHGEL (Thread starter):
1) Why not the wing over the fuselage a la AN-124 for bigger PAX planes.

Would require longer, heavier, and more expensive landing gear. Advantage; slightly less drag because dihedral would not be required for stability. But the landing gear is the biggest reason for keeping the wing low.

Quoting LVHGEL (Thread starter):
2) Why not invert the angle of the engines pylons, instead of protruding from the attack edge of the wing, push the engines completely to the back, so the nacelle is under the wing, so that instead of “pulling” they “push”. similar to the Honda Jet but under the wing.

The aerodynamics of the engine nacelles is very carefully worked out; as GrandTheftAero stated keeping the engines in front keeps the airflow "clean" and the wing doesn't disturb it. Boeing did a great deal of research on the best way to mount jet engines on wings when they were designing the B-47; nobody has really improved on it.

Quoting FriendlySkies (Reply 1):
3) Why not go back again to multiple Vertical Stabilizers "a la" Connie?

Weight and complexity; the horizontal stabilizer has to be beefed up and the controls are much more complicated. The Connie's tail came about as a fix for a mistake; IIRC it started out with a single tail; that proved inadequate so they went to a double tail (on the ends of the horizontal stabilizer.) That was still inadequate, so they put the original tail back on, and that proved to be sufficient. A very inelegant way to get to a very beautiful plane; but it would have been more efficient just to put a large enough tail on it. There may have been a factor that Howard Hughes wanted it to fit into his existing hangars; I have a vague recollection of something like that being an issue.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
flydreamliner
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RE: Do All Modern Airliners Look Alike?

Thu May 10, 2007 5:45 am

Quoting Solnabo (Reply 2):
My guess is the BWB (Blended Wing Body), a huge flying wing with circa 1000 pax.

Boeing was looking into this back in the Sonic Cruise days, they built a large tester which simulated the very wide seating area such an aircraft would have (easily a few dozen seats across, if not more) and simulated how far the seats furthest from the center would pitch up and down during normal maneuvering, which was about 10 feet. When they put people in those seats and simulated the aircraft maneuvering, the test subjects reports were incredible negative, the extreme pitching apparently makes people nauseous, haha.

Quoting LVHGEL (Thread starter):
1) Why not the wing over the fuselage a la AN-124 for bigger PAX planes.

Then you'd need additional bulges and cargo space taken away for landing gear which could easily fold into the wings. Also it is far easier, and thus cheaper, to inspect and service engines, flaps, alerons (and all of the hydraulic/electric components there) on a low wing aircraft, as opposed to needing to use large equipment to get up to the wing.

Quoting LVHGEL (Thread starter):
2) Why not invert the angle of the engines pylons, instead of protruding from the attack edge of the wing, push the engines completely to the back, so the nacelle is under the wing, so that instead of “pulling” they “push”. similar to the Honda Jet but under the wing.

Placing them back would interfere with the flaps. Additionally it would cause undesirable airflow disruptions, and the air intake being placed under the wing would create the possibility for causing severe disturbance to air entering the engines during extreme maneuvering. With honda - and engines above the wing, you don't have this problems nearly as much - and notice how far above the wings the engines are. Structurally it's much easier too if you balance the engine under the structure of the wing, rather than having a majority of it behind the load-bearing elements of the wing.

Quoting LVHGEL (Thread starter):
3) Why not go back again to multiple Vertical Stabilizers "a la" Connie?

What would the point be? It'd be heavier with no apparent advantage to outweigh it.

I'd love to see some form of delta wing appear on a commercial jet, but it'd never happen because of the inferior low speed handling characteristics of delta vs conventional airfoils.
"Let the world change you, and you can change the world"
 
AADC10
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RE: Do All Modern Airliners Look Alike?

Thu May 10, 2007 6:11 am

I do not know about the design concepts that the OP mentioned but aircraft have certainly become more homogenized. It used to be that planes with more engines were larger and for longer flights. Engines have become more powerful and reliable so two are enough for most applications.

There was some controversy about the layout of the 737, which of course is now the basic layout of most airliners. Boeing was playing catch up at the time and used the 707/727 fuselage and many other components from the 727. Originally it was to look like a two engined 727 but apparently the wide and short fuselage caused problems with the rear engine aerodynamics so they mounted the engines below the wing. This was a problem because many airports in those days did not have jetways and airlines like planes to be lower to the ground.

With the development of high-bypass turbofans, placing the engines below the wing became more of an advantage because it could accommodate larger diameter fans. I suspect that engines are placed at the leading edge of the wing so they get a clear airflow and they are below fuselage to reduce cabin noise.

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