Why No Curved Windshields On The A380?

747400sp · Wed Mar 07, 2012 1:12 am

A recent factory photo of the A350 XWB, reviled that it will have a curve wind shield, and the 787 has curve windshields, as a matter of fact, the 747-8, has a curve wind shields, so why Airbus waited until the A350 XWB, to start using curve wind shield, instead of putting them on the A380? The A380 would have looked a lot better, if Airbus design it to have curve wind shield. For one, a round wind shield, would have made that big ugly nose, look less pronounce, and it may have added to the reduction of drag in the design. So why Airbus stayed with the strait wind shields for the A380?

KELPkid · Wed Mar 07, 2012 2:04 am

Quoting 747400sp (Thread starter):
The A380 would have looked a lot better, if Airbus design it to have curve wind shield.

Always an aircraft designer's number one priority

It was probably cheaper to produce, and a cost/benefit analysis most likely proved that the benefits of making it curved had a minimal impact on drag, and creating the design with a curved windshield probably didn't outweigh the economic advantages of using a flat windshield. Since I don't work at Airbus, nothing I said is authoritative

tdscanuck · Wed Mar 07, 2012 5:21 am

Quoting 747400sp (Thread starter):
So why Airbus stayed with the strait wind shields for the A380?

It didn't pass the (very complicated) window trade study of cost, complexity, structural weight, drag, noise, etc.

Quoting KELPkid (Reply 1):
It was probably cheaper to produce

It was definitely cheaper to produce...there is a shocking price difference between flat and custom-curved glass.

Tom.

PITingres · Wed Mar 07, 2012 2:17 pm

Quoting tdscanuck (Reply 2):
there is a shocking price difference between flat and custom-curved glass.

Indeed; it's basically an entire separate production step. It's been a couple decades since I had anything to do with glass, but I believe we're still making flat glass by the float process (float the molten glass on top of a bed of molten tin). For curved glass, you start with a flat piece, cut it to shape, lay it on a form and run it through a multi-stage electric furnace. The furnace heats the glass just enough to let it sag down to the curved form shape, and then cools it slowly enough to avoid unwanted stresses.

I was involved for a while with the control software for an auto windshield glass line for an unusually large windshield; my recollection is that the electric furnace was an endless source of problems, plus being a power hog. The larger the curved piece, the larger and more expensive your (customized) electric furnace has to be.

Horstroad · Wed Mar 07, 2012 2:52 pm

I´d guess that on a 300million $ aircraft a couple thousands wouldn´t make that much of a difference.
I think there is another reason for the shape of the no. 1 windows. the shape of the fuselage and the no. 1 windows guides the airflow away from and around the next window to allow no. 2 window to be open for better view if no 1 windows are obstructed. http://youtu.be/NQZzTPd1HJw?t=2m18s
I think that´s the reason why aircraft that can open no 2 windows have a flat windshield and aircraft that have other cockpit emergency exits like the 747 or the CRJ can have curved windshields for better aerodynamics.

I have no idea how they do it on the plastic aircraft. maybe there is no open window operation

SlamClick · Wed Mar 07, 2012 4:23 pm

Quoting horstroad (Reply 4):
I´d guess that on a 300million $ aircraft a couple thousands wouldn´t make that much of a difference.

You might be right about that. But it is more like thousands per panel plus increased costs to create the "windows" in the structure into which the framed window panel will mount. This will be a plug-type opening like the doors.

Further, it is misleading to think of an aircraft windshield panel as "a pane of glass" when it is an elaborate construct of several layers of different types of glass, acrylic, gold, heating filaments and other things. I would not be surprised to hear that a curved panel was twenty times more costly than a flat one in the final installation.

Horstroad · Wed Mar 07, 2012 4:47 pm

Why then have so many small aircraft curved windshields? (ERJ, CRJ, Gulfstream etc)

//is this grammar correct? this looks odd, but google translate thought it´s correct

KELPkid · Wed Mar 07, 2012 6:46 pm

Quoting tdscanuck (Reply 2):
It was definitely cheaper to produce...there is a shocking price difference between flat and custom-curved glass.

Quoting SlamClick (Reply 5):
Further, it is misleading to think of an aircraft windshield panel as "a pane of glass" when it is an elaborate construct of several layers of different types of glass, acrylic, gold, heating filaments and other things. I would not be surprised to hear that a curved panel was twenty times more costly than a flat one in the final installation.

So, what is the construction of a typical airliner windshield? Does it have genuine glass in it? I'm much more familiar with GA planes, which usually have plexiglas windshields (sometimes, you get a small glass pane if you have a section of heated windshield on an ultra-high end plane, like a Bonanza). I know that there is electric heat in most of them, so I'm assuming that that means there might be some "real" glass in it

It just seems like glass would be a bad choice of material in an aircraft because of its relatively high weight. I also remember being told by a GM engineer once that modern automotive windsheilds were so strong that they were part of the structure of the vehicle...

my235 · Wed Mar 07, 2012 10:50 pm

Quoting KELPkid (Reply 1):
Always an aircraft designer's number one priority

If it looks good there's a good chance it will fly good. Of course not always but...

Starlionblue · Thu Mar 08, 2012 12:06 am

Quoting horstroad (Reply 6):

Why then have so many small aircraft curved windshields? (ERJ, CRJ, Gulfstream etc)

//is this grammar correct? this looks odd, but google translate thought it´s correct

Google Translate is typically a bit too literal, and the German sentence structure is showing through in this case. Anyway the sentence is grammatically correct, but stylistically not very elegant. A better sentence would be: "Why do so many small aircraft (e.g. ERJ, CRJ, Gulfstream) have curved windshields then?"

747400sp · Thu Mar 08, 2012 12:36 am

I understand, that curve winds shields cost more than strait one, but if you look at most of the worlds regional jets and the 787 and A350XWB, they have curve wind shields, even 747s and L1011s has curve winds shields.

tdscanuck · Thu Mar 08, 2012 5:08 am

Quoting horstroad (Reply 4):

I´d guess that on a 300million $ aircraft a couple thousands wouldn´t make that much of a difference.

If you've very lucky, you'd be talking at least tens of thousands of dollars *per pane*. Total cost differential for an entire aircraft would be well over hundreds of thousands of dollars. Aviation windows are not cheap.

Quoting KELPkid (Reply 7):
So, what is the construction of a typical airliner windshield?

Multiple layers of glass, conductive metal film, and acrylic.

Quoting KELPkid (Reply 7):
Does it have genuine glass in it?

Yes. If nothing else, the outer pane will usually be glass for erosion resistance.

Tom.

yeelep · Thu Mar 08, 2012 12:34 pm

Quoting KELPkid (Reply 7):
So, what is the construction of a typical airliner windshield? Does it have genuine glass in it? I'm much more familiar with GA planes, which usually have plexiglas windshields (sometimes, you get a small glass pane if you have a section of heated windshield on an ultra-high end plane, like a Bonanza). I know that there is electric heat in most of them, so I'm assuming that that means there might be some "real" glass in it It just seems like glass would be a bad choice of material in an aircraft because of its relatively high weight. I also remember being told by a GM engineer once that modern automotive windsheilds were so strong that they were part of the structure of the vehicle...

The construction of a 737 L1 or R1 windshield (forward facing) is from outboard to inboard. A non-structural outer glass pane with conductive heating film on the inboard side, non-structural urethane interlayer, structural vinyl interlayer, non-structural urethane interlayer and a structural inner glass pane. Its 1 inch thick and weighs 46lbs each, but feels like alot more when your'e installing one.

a380900 · Fri Mar 09, 2012 3:01 am

Quoting horstroad (Reply 6):
Why then have so many small aircraft curved windshields? (ERJ, CRJ, Gulfstream etc)

May I venture a guess? The larger the plane, the less disruptive flat winsdhields are to the overall aerodynamics. That could explain why much smaller business jet have curve windshield and the A380 does not as we know that it is not a technological issue for the A380. Now you may say that the 747 is big but the place where the cockpit is is much narrower than on an A380. Don't know about the L1011 though.

Anyway, the way things are going (787, A350), the flat "windscreen look" of the A380 will clearly be a sign of its age 20 or 30 years from now...

bristolflyer · Fri Mar 09, 2012 4:05 am

Quoting a380900 (Reply 13):
The larger the plane, the less disruptive flat winsdhields are to the overall aerodynamics.

Add to that the A380 has got a very large, rounded front end...the larger the diameter, the less the window would have to be rounded to make it follow the contours. If there's a negligibly small difference in a slight rounding compared to a flat, then why not have a flat?

MD11Engineer · Fri Mar 09, 2012 6:07 am

As for transport aircraft cockpit windows, they are 1 - 1c1/2 inches thick, made up out of several layers of mineral glass, acrylic, vinyl or polycarbonate plastic, gold etc. They rather resemble bulletproof glass as used for bank cashier´s booths and are VERY heavy. While two men can still install a (flat) B737 or A320 windshield, for the (curved) B747 window you´ll need a crane (or a proper dock).

Jan

musang · Fri Mar 09, 2012 6:17 pm

Quoting 747400sp (Reply 10):
even 747s and L1011s has curve winds shields.

Indeed. The 747 has curved windscreens and flat side panels (2 and 3), the DC-10 / MD-11 has flat windscreens and curved 2s and 3s, while on the TriStar all panels are curved.

Quoting a380900 (Reply 13):
The larger the plane, the less disruptive flat winsdhields are to the overall aerodynamics.

Imagine a Learjet if curved panels were not available to the designers!

Regards - musang

Starlionblue · Sat Mar 10, 2012 2:56 am

Quoting musang (Reply 16):
Quoting 747400sp (Reply 10):
even 747s and L1011s has curve winds shields.

Indeed. The 747 has curved windscreens and flat side panels (2 and 3), the DC-10 / MD-11 has flat windscreens and curved 2s and 3s, while on the TriStar all panels are curved.

The 747 cockpit is sitting in a very narrow part of the fuse, probably narrower than a 3-3 narrowbody. The 380 cockpit is sitting in a much fatter section.

747400sp · Sat Mar 10, 2012 3:00 am

Quoting a380900 (Reply 13):
Now you may say that the 747 is big but the place where the cockpit is is much narrower than on an A380. Don't know about the L1011 though.

When I was in High school, I used to go to LAX, and a lot of the time I would go to the DL terminal, and would see L1011s head on, and I can tell you, unlike DC-10s, they get narrower near the cockpit.

PS, I believe, that even though the L-500 was supposed to be a civilian version of the C-5, it was supposed to have a curve windshield. Knowing Lockheed, they would have likely done that.

MD-90 · Sat Mar 10, 2012 4:28 am

Quoting musang (Reply 16):
Imagine a Learjet if curved panels were not available to the designers!

It'd probably look like an early Dassault Falcon.

CM · Sat Mar 10, 2012 6:11 am

Quoting SlamClick (Reply 5):
This will be a plug-type opening like the doors.

It is true that many windows are plug type. This is not the case for the 787 flight deck windows, which are designed with a pinned tension joint. The window can float laterally on the pins, but pressure on the inside of the window is reacted into the window frame by fasteners through a retaining plate on the outside of the window. From available pictures, it appears the A350 will use this approach as well.

Quoting 747400sp (Reply 10):
if you look at most of the worlds regional jets

These windows are smaller than a typical commercial jet and significantly smaller than windows on the 787, making them easier to certify for birdstrike. They are also significantly thinner. Both of these things make them easier to manufacture as well.

An irony of the 787 and A350 going to curved windows is that curved windows are much harder than flat windows to optically match to the HUD, which both these aircraft offer. In fighter jets, the HUD combiner unit is often a matched pair with the canopy, ensuring the two are optically correct. If you replace one, you must replace the other. This is not practical for a commercial jet, so the optical quality controls on the curved glass is extraordinarily tight. If not, you may not be able to certify your HUD for takeoff and landing... at which point you have to ask yourself "what's the use?".

Quoting horstroad (Reply 4):
a couple thousands wouldn´t make that much of a difference

I'm afraid you would have to add some more zeros before you'd get the price right Wow!

Slcpilot · Sat Mar 10, 2012 1:20 pm

Funny, although I may have missed it, nobody seems to have mentioned the reason I assumed that the A-380 has flat window panes. Is it not the desire for a common, or derived type rating as well as commonality with the other Airbus products?

To be honest, it came as a surprise to me that the 787 shares a type rating with the 777, given the difference in the windows alone (not to mention the systems). If I'm not mistaken, transition from any FPW Airbus product to the A-380 is a relatively simple and painless procedure from a pilot perspective.

Cheers!

SLCPilot

Cheers!

CM · Sat Mar 10, 2012 5:24 pm

Quoting SLCPilot (Reply 21):
Is it not the desire for a common, or derived type rating as well as commonality with the other Airbus products?

This is partly true. Pilot vision must be validated to be largely the same between aircraft with a common type rating. In the case of the A380 and A350, pilot vision will be almost identical, despite the fact one has curved glass and the other flat. I think the larger reason for the A350 adapting the A380 cab architecture was to reduce certification risks. Certifying the structure in this area for birdstrike is one of the most difficult challenges of a new airplane design. It is why you see the 767 cab structure adapted onto the 777 as well.

Quoting SLCPilot (Reply 21):
To be honest, it came as a surprise to me that the 787 shares a type rating with the 777, given the difference in the windows alone (not to mention the systems).

What's far more important than window similarity is procedural commonality and handling properties between the types. In the case of the 787, pilot vision was improved relative to the 777, so no issues there. As for the systems; yes, they are quite different behind the curtain. in the flight deck, however, you will find the all the same controls in all the same locations. By memory procedures between the two aircraft are 100% identical, and checklist items are 90% the same. These things are the most difficult to achieve when trying to accomplish a common type rating between two aircraft. In the case of the 777 and 787, the two aircraft have common takeoff and landing currency, which means a pilot can truly move seamlessly between the types.

Viscount724 · Sat Mar 10, 2012 9:09 pm

Quoting musang (Reply 16):
Imagine a Learjet if curved panels were not available to the designers!

Or a CRJ/Challenger.

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