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b767
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737 Aerodynamics

Mon May 19, 2008 3:37 pm

When the 737ng series arrived,it had a new wing whitch was bang up to date.But the rather old fashion nose section was still there.Boeing problem I belive was that a new nose section would requere a new type sertificate.I been told that most of the drag come from the wings,but how much drag penalty does the old nose which is based on 707 create compared to newer designs?
 
SlamClick
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RE: 737 Aerodynamics

Mon May 19, 2008 3:42 pm

Can't answer your specific question but I believe they actually could have designed an entirely new nose that had the external shape they wanted but still fit the existing instrument panel, seat position, overhead panel etc, thus, no real training added. You can't see much of the exterior of the airplane from the pilot seats anyway.

Cost is the barrier. I'm sure it would cost a ton of money to design and tool up to manufacture this new nose, when they already have the patterns, jigs, dies, etc for the old nose. Do the airline customers want to pay for the changes to the airframe or a gallon per hour of fuel?
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miamiair
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RE: 737 Aerodynamics

Mon May 19, 2008 5:38 pm



Quoting B767 (Thread starter):
I belive was that a new nose section would requere a new type sertificate

Why would a new nose require a new type certificate? This is not the case. The MD-11 and the DC-10 share the same type certificate, but there are several structural difference.
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aeroweanie
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RE: 737 Aerodynamics

Mon May 19, 2008 6:09 pm

The Gulfstream II has a completely different nose OML (Outside Mold Line) than the later models (III, IV and V), but all the models share a common Type Certificate. The GII has flat windscreen panels and a stubby radome. The GIII and later models have curved windscreen panels and a longer radome. The curved glass necessitated changes to the skin panels.

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Other than vortices shed by the downwind corners of the flat windscreen panels, the 707/727/737 nose isn't that bad, dragwise.

Cost was a major factor in the 737NG development. Boeing had just finished developing the 777 and money was a big issue.
 
roseflyer
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RE: 737 Aerodynamics

Mon May 19, 2008 7:46 pm



Quoting SlamClick (Reply 1):
Cost is the barrier. I'm sure it would cost a ton of money to design and tool up to manufacture this new nose, when they already have the patterns, jigs, dies, etc for the old nose. Do the airline customers want to pay for the changes to the airframe or a gallon per hour of fuel?

You bring up a very good point. One thing though is that there just was and currently is a huge influx of money going into the 737 and being spent on Aerodynamics. It's coming from the Navy with the P8A Poseidon which is currently in production. There have been aerial improvements to improve aerodynamic efficiency. Such developments can work their way onto the production commercial airplane.

However one big difference is the mission of the planes. The navy will be flying their 737 submarine hunter at much lower altitudes at time so the weight versus aerodynamics equation changes.

In general, there are continuous improvements on the 737. With the 737 currently being at the highest production rate in the planes history and having the biggest backlog ever with over 2000 planes on order (more than all deliveries of the 757 and 767 combined), there is money available for economic improvements. If it would make a noticeable difference in fuel burn, then Boeing would change the nose. Yes it will take probably about 2 years to happen from concept, but it could. The people in product development have probably already looked at it. Since we haven't seen a change, it probably means that the 1950s design engineers did a pretty darn good job.
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474218
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RE: 737 Aerodynamics

Mon May 19, 2008 10:32 pm



Quoting B767 (Thread starter):
When the 737ng series arrived,it had a new wing whitch was bang up to date.But the rather old fashion nose section was still there.Boeing problem I belive was that a new nose section would requere a new type sertificate.I been told that most of the drag come from the wings,but how much drag penalty does the old nose which is based on 707 create compared to newer designs?

The 737 is the single most successful commerical jet airliner in history. It doesn't matter how it looks, it has been and will continue to make money for the airlines that fly it. That "old fashion nose section" has been on more airliners than any other nose and changing it is not in the cards.
 
b767
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RE: 737 Aerodynamics

Mon May 19, 2008 10:46 pm

But what about the hearing problems some 737 drivers got when they had flown the NG series for a while?It was as a resoult of aerodynamic turbulence around the sharp edge cockpit windows.It wasn.t a problem with the classic,but the NG had a significant higher cruise speed.
If the old nose did the job so good,how come boeing designed a new nose for the 757? When the NG arrived ,the range and average time in cruisealtitude increased.As a resault aerodynamics become more importent.Winglets for example was not an issue with the earlier versions.Could the continuing increase in fuel prices force Boeing to do some future re-design?
 
KELPkid
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RE: 737 Aerodynamics

Mon May 19, 2008 10:53 pm



Quoting B767 (Reply 6):
If the old nose did the job so good,how come boeing designed a new nose for the 757?

Because, to maintain the common 757/767 type rating, the pilot's perspective had to be *IDENTICAL* between both aircraft. If you notice, you step up to enter the 767 cockpit and down to enter the 757's cockpit...  Wink
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seabosdca
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RE: 737 Aerodynamics

Tue May 20, 2008 1:37 am



Quoting B767 (Reply 6):
If the old nose did the job so good,how come boeing designed a new nose for the 757

So that a 767 flight deck would fit inside.

I have read on this forum (so no guarantees this is accurate) that Boeing considered, and rejected, the idea of using the 757 nose on the 737NG. Apparently, it would have saved fuel, but is so different in shape that retaining a flight deck with significant 737 Classic commonality would have been impossible. Therefore WN didn't like the idea, and the rest is history.

A shame. A 73G with a 757 nose would be quite the looker.
 
rsbj
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RE: 737 Aerodynamics

Thu Jun 26, 2008 3:56 pm

We were told Boeing considered putting a 757 nose on the 737NG. I think the fuselage of the two are identical, so I would think that would be feasable. But....when Boeing told Southwest, Herb said he wanted all of his planes to look the same.
Urban legend?
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2H4
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RE: 737 Aerodynamics

Thu Jun 26, 2008 5:01 pm



Quoting 474218 (Reply 5):
That "old fashion nose section" has been on more airliners than any other nose and changing it is not in the cards.

I just wish they had held on to the B-377 nose section....  Wink

Quoting SeaBosDca (Reply 8):
A shame. A 73G with a 757 nose would be quite the looker.

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KELPkid
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RE: 737 Aerodynamics

Thu Jun 26, 2008 5:49 pm

Quoting RSBJ (Reply 9):
We were told Boeing considered putting a 757 nose on the 737NG. I think the fuselage of the two are identical, so I would think that would be feasable. But....when Boeing told Southwest, Herb said he wanted all of his planes to look the same.
Urban legend?

I think this is a myth...as I recall from previous threads on this subject, there are two lower fuselage diameters for the Boeing narrowbody aircraft families. The 737's have a smaller fuselage diameter below the floor deck than the 707's, 727's, and 757's of the world  , so Section 41 (the pointy end of the bird), may look similar, but is in fact *NOT* identical between all members of the Boeing narrowbody family.

EDIT: disclaimer-I am going by memory alone here.

[Edited 2008-06-26 10:50:02]
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Starlionblue
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RE: 737 Aerodynamics

Fri Jun 27, 2008 12:40 am



Quoting KELPkid (Reply 11):
The 737's have a smaller fuselage diameter below the floor deck than the 707's, 727's, and 757's of the world , so Section 41 (the pointy end of the bird), may look similar, but is in fact *NOT* identical between all members of the Boeing narrowbody family.

Indeed. The fuses are the same width at the widest point, but the cross sections are different below the waist.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
tdscanuck
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RE: 737 Aerodynamics

Fri Jun 27, 2008 2:02 am



Quoting RSBJ (Reply 9):
We were told Boeing considered putting a 757 nose on the 737NG. I think the fuselage of the two are identical, so I would think that would be feasable. But....when Boeing told Southwest, Herb said he wanted all of his planes to look the same.

Also, a 757 nose has a different pilot view than a 737. That makes common type rating (a *huge* deal for Southwest) harder to obtain.

Tom.
 
Blackbird
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RE: 737 Aerodynamics

Fri Jun 27, 2008 2:44 am

To the best of my knowledge, the B-727 type nose (same on the 737) is better aerodynamically than the B-757's nose.

The nose was designed to allow the 767's cockpit to basically fit inside the contours of it.


Andrea Kent
 
aeroweanie
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RE: 737 Aerodynamics

Fri Jun 27, 2008 3:44 am



Quoting Blackbird (Reply 14):
To the best of my knowledge, the B-727 type nose (same on the 737) is better aerodynamically than the B-757's nose.



Quoting Blackbird (Reply 14):
To the best of my knowledge, the B-727 type nose (same on the 737) is better aerodynamically than the B-757's nose.

The 707/727/737 nose has aero problems with the sharp break in the contour at the bottom of the glass and the sharp corners at the edges of the front flats. The 757 nose with the curved glass solves both of these aero problems.
 
AA737-823
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RE: 737 Aerodynamics

Fri Jun 27, 2008 11:31 am



Quoting Blackbird (Reply 14):
To the best of my knowledge, the B-727 type nose (same on the 737) is better aerodynamically than the B-757's nose

I'm afraid that's not correct. The 707-style nose is quite ugly, if you look closely, you can see many edges that jut out and are clearly unaerodynamic.

Notice that the 787 has a nose profile very much reminiscent of the 757 aircraft- a low point, good sweep, etc.

The reason the -NG didn't get a new nose, B767 from Norway, was the same reason that it didn't get a lot of other current updates: customers said 'no.'
I just went through six weeks of Boeing (Alteon) Gen/Fam for the 737NG, and having just come off of working 747-400s, I was surprised at how many things went missing on the -NG... and the -NG is ten years newer than the -400. The explanation? Boeing's willing to do it, but the big 737 customers (cough cough... Southwest) asked them to keep costs down. In fact, they wanted costs even lower than what they had with the 'classics', and so Boeing redesigned the trailing edge flaps down from tripple-slotted to double-slotted. Are they as marvellous as the old ones were? No, they're not. Are they as complex? Nope, they're not that, either.

I would have loved to see a Central Maintenance Computer on the -NG. Didn't happen.

So yeah, cost cutting at the request of airlines.
 
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SEPilot
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RE: 737 Aerodynamics

Fri Jun 27, 2008 4:17 pm

If the 737 has sharp corners around the windshields that cause aerodynamic problems I would think that they could be fixed without a complete redesign. Why was this not done?
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
aeroweanie
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RE: 737 Aerodynamics

Fri Jun 27, 2008 5:27 pm



Quoting SEPilot (Reply 17):
If the 737 has sharp corners around the windshields that cause aerodynamic problems I would think that they could be fixed without a complete redesign. Why was this not done?

The VGs kit that Boeing offers helps improve the situation, but beyond this, its a hard problem to fix.

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SEPilot
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RE: 737 Aerodynamics

Fri Jun 27, 2008 5:58 pm



Quoting AeroWeanie (Reply 18):

The VGs kit that Boeing offers helps improve the situation, but beyond this, its a hard problem to fix

Why couldn't they have fitted curved windows into the same overall contours when they did the NG? It is not a trivial exercise, but they could have done it without changing the cockpit configuration or the visibility and gotten away from the problems.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
SlamClick
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RE: 737 Aerodynamics

Fri Jun 27, 2008 6:54 pm



Quoting SEPilot (Reply 19):
Why couldn't they have fitted curved windows into the same overall contours

Can you make a curved piece of glass lie on a flat surface and be in contact all the way around?

If the windows are flat, the window frames are flat on the surfaces against which the glass rests. That dictates that the sheet metal that supports the window frames must be shaped to accomodate a basically flat structure.

Aircraft sheet metal design presents interesting problems. You have to design an interior structure that will have some strength and rigidity but not too much weight, that will support and anchor an exterior skin that conforms to a very specific exerior shape. On all modern airplanes that includes compound curves. So you have to do all this "inside-out" so to speak. The Boeing cockpit, nose area would have to be substantially redesigned to make the changes.
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SEPilot
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RE: 737 Aerodynamics

Fri Jun 27, 2008 7:24 pm



Quoting SlamClick (Reply 20):
Aircraft sheet metal design presents interesting problems. You have to design an interior structure that will have some strength and rigidity but not too much weight, that will support and anchor an exterior skin that conforms to a very specific exerior shape. On all modern airplanes that includes compound curves. So you have to do all this "inside-out" so to speak. The Boeing cockpit, nose area would have to be substantially redesigned to make the changes.

I acknowledge all of this. I thought newer planes (A330, A380) had curved windshields, but on examining photos closely I guess that is not the case. But it seems that they do not have the problems that the 737 has, so it seems that the windows could have been tweaked to eliminate the problem areas without a complete redesign. But I am aware (from first hand experience) that some minor changes end up having major ramifications, and things do have a great tendency to snowball once you start changing things.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
SlamClick
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RE: 737 Aerodynamics

Fri Jun 27, 2008 7:53 pm



Quoting SEPilot (Reply 21):

Believe me, I'm not arguing against modernizing the 737 nose. I think it would be striking with a 757-esque nose. I don't think it would be a simple cosmetic change, though, but a complete redesign of section ___ of the plane. (can't remember my Boeing structures numbers)

In light of the fact that it has known such success and that it remains conceptually very different from its main competitor Airbus, I think some profit from continued sales might go to the project. Who knows, with that one fix the benefits may add another twenty years to the production run. I'd like that.
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474218
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RE: 737 Aerodynamics

Fri Jun 27, 2008 8:20 pm



Quoting SlamClick (Reply 20):
Aircraft sheet metal design presents interesting problems. You have to design an interior structure that will have some strength and rigidity but not too much weight, that will support and anchor an exterior skin that conforms to a very specific exerior shape.

I am a little confused about your statement of interior structure conforming to the exterior shape and that it anchors to and supports the exterior? Aircraft interiors are made from molded fiberglass and plastic, carry no loads and may or may not conform the the exterior shape. Example: most cabin ceilings do not conform to the shape of the exterior.
 
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PITingres
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RE: 737 Aerodynamics

Sat Jun 28, 2008 3:01 am



Quoting SEPilot (Reply 19):
Why couldn't they have fitted curved windows into the same overall contours



Quoting SlamClick (Reply 20):
Can you make a curved piece of glass lie on a flat surface and be in contact all the way around?

I'm don't follow this, can you elaborate? You can make glass fit any curve you like, it's just a matter of heat-sagging. (I've dealt with auto glass in my past, and you can make it fit any reasonable shape you care to imagine.) I'm unclear on where the "flat surface" is relevant, or am I just being late-evening stupid....???
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tdscanuck
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RE: 737 Aerodynamics

Sat Jun 28, 2008 3:57 am



Quoting SlamClick (Reply 22):
but a complete redesign of section ___ of the plane. (can't remember my Boeing structures numbers)

41

Quoting 474218 (Reply 23):
I am a little confused about your statement of interior structure conforming to the exterior shape and that it anchors to and supports the exterior? Aircraft interiors are made from molded fiberglass and plastic, carry no loads and may or may not conform the the exterior shape.

SlamClick is talking about the structure under the skin, not the aircraft interior (which isn't structural). If you peel the skin off of the nose section, you'll find a very complex mess of stringers, frames, bulkheads, and intercostals that are holding the skin in the right contour and providing most of the strength.

Quoting PITIngres (Reply 24):
Quoting SlamClick (Reply 20):
Can you make a curved piece of glass lie on a flat surface and be in contact all the way around?

I'm don't follow this, can you elaborate? You can make glass fit any curve you like, it's just a matter of heat-sagging. (I've dealt with auto glass in my past, and you can make it fit any reasonable shape you care to imagine.) I'm unclear on where the "flat surface" is relevant, or am I just being late-evening stupid....???

I think PITIngres is talking about that fact that the existing window frame is planar. You can't fit a curved window into the existing frames without making it planar at the edges (which negates any aerodynamic advantage). If you want to actually go curved, you need to alter the structure that's holding the window frame up, which is not trivial.

Tom.
 
474218
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RE: 737 Aerodynamics

Sat Jun 28, 2008 3:15 pm



Quoting Tdscanuck (Reply 25):
SlamClick is talking about the structure under the skin, not the aircraft interior (which isn't structural). If you peel the skin off of the nose section, you'll find a very complex mess of stringers, frames, bulkheads, and intercostals that are holding the skin in the right contour and providing most of the strength.

I sure didn't get that out of what he wrote.

Additionally, modern aircraft structure is called a semi-monocoque construction where the skin, frames, stringers, ribs, etc. share the load equally.
 
SlamClick
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RE: 737 Aerodynamics

Sat Jun 28, 2008 4:24 pm



Quoting PITIngres (Reply 24):
I'm unclear on where the "flat surface" is relevant, or am I just being late-evening stupid....???

The existing area of the 737 where the windshield is mounted is shaped to accomodate a windshield composed of flat panels. You cannot install curved panels without completely redesigning the entire area around the windshield frames. (Nor can you take a compound-curved piece of glass at room temperature and lay it on a flat surface and have it be in full contact with that flat surface all the way around. Don't overthink that picture, lay something curved on a table and see if it is in full contact or just resting in a couple of places.)
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tdscanuck
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RE: 737 Aerodynamics

Sat Jun 28, 2008 4:57 pm



Quoting 474218 (Reply 26):
Additionally, modern aircraft structure is called a semi-monocoque construction where the skin, frames, stringers, ribs, etc. share the load equally.

"Semi-monocoque" just means it shared, not that it's shared equally. However, this technique applies a lot more to the main fuselage sections than the nose. Due to impact and geometry constraints, the nose is held together a lot more by the underlying structure. A nose without skin is still a reasonably effective structure. A fuselage without skin is essentially useless.

Tom.
 
b767
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RE: 737 Aerodynamics

Tue Jul 08, 2008 11:28 pm

But what if you let the side cockpit windows stay as they are,but re designed the two front windows,and made them more swept back in both directions.You also would have to do a little redesigning over the front cockpit windows,but when the chinese built their arj 21 that was excactly what they did with the old DC9 nose.I guess if Boeing did that the cocpit window design would be very A320 like and better than today,and cost a hell of a lot less than a complete re design.
 
tdscanuck
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RE: 737 Aerodynamics

Thu Jul 10, 2008 6:23 am



Quoting B767 (Reply 29):
But what if you let the side cockpit windows stay as they are,but re designed the two front windows,and made them more swept back in both directions.You also would have to do a little redesigning over the front cockpit windows,but when the chinese built their arj 21 that was excactly what they did with the old DC9 nose.I guess if Boeing did that the cocpit window design would be very A320 like and better than today,and cost a hell of a lot less than a complete re design.

If you sweep the windows in both directions, you've changed the flight deck sightlines and changed the loads on most of the nose structure. At that point, you might as well do a complete redesign.

Tom.

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