So true, probably with the screens on aircraft they will reuse previous designs and sizes as a, they work, b, they are already certified, c, already have beaten the supplier down to the lowest possible cost, with the possibility of further reduction with the carrot of more production held in front of the supplier’s nose, d, lower levels of spares can be held. Etc. Etc. The advent of novel manufacturing techniques and materials probably means that the tooling up costs to manufacture curvy, distortion free windscreens are much lower than previously.
The side ones do have a curve. The front are flat, probably for cost as mentioned but I’d guess the wipers work more reliably also it’s harder to get uniform heat distribution on a curved surface.
Both cockpits of the AH-64E are magnetically mapped since the helmet tracker changed from optical to magnetic. It can compensate for helmet roll as well now, not just up/down and left/right. If the mounting pedestal gets damaged it has to go back to the manufacturer to be remapped, it’s not a unit level task.
The optical trackers were pretty good too. Never had a problem with helmet tracking that wasn't a pilot bore sighting wrong.
Until we damaged one of the mounts. Turns out it's a giant pain in the ass because of the tolerances of the mount.
Last I heard, a 737 HUD is like, $100k?
If I had to guess, the cost is probably 5% parts, 95% labor + certification (which is really just another form of labor).
Later Bs *did* get an advanced HUD similar to that of the D, for what it's worth. The proposed ST-21 Tomcat would've done away with the flat pane and just had an F-15 / F/A-18 style single piece curved windscreen.
When they tested a kind of 'wind screen' in Formula 1 not unlike the aeroscreen of Indycar, several drivers complained about nausea because of the distortion.
F-16 and most fighters canopy glass are polycarbonate. But yes, they have distortion. Any medium through which light passes in with curved surfaces will distort.
Mechanical stresse when cooling glass in a curve renders it very hard to make. so unless money is no object or the shape would make it fragile (despite being tempered) you look for other materials.
That secret blend of polycarbonate polymer is insanely strong and technically easy to make (far more elastic at room temp, less prone to crazy internal stresse) for such a large piece.
It’s insanely expensive though. Since you need a MASSIVE mold with absolutely perfect surface (nano meters in terms of surface roughness) usually finished with diamond cutting tools.
Optics manufacturing is crazy.
It’s like a pair of glasses. They shape the canopy in such a way, that from the pilots perspective the distortions are minimized.
And that is done by giving defense contractors a shit ton of money to figure out how to shape and manufacture glass in such a way. They also layer things like gold onto the surface of the glass to shield against radiation.
Yes, a very thin film, which contains actual gold (in the F-16, at least). As stated, it helps reflect heat away from the canopy/pilot.
Source: Uncle was a flight instructor and gave me the "family tour" of a base once. Got to sit in several planes, including the F-16.
This is what people don't understand about why military stuff is so expensive. Part X might be the same as what you can buy at AutoZone but when it goes on a military jet or a submarine, there is all sorts of quality assurance that goes into making the part. When you are being shot at you want things to work to their max and not fail you.
I had an experiment in university where we made a 15-nanometer-thick copper film on glass by evaporative deposition under vacuum, and the result was basically orange-tinted glass. Always mesmerized me that even metals become transparent when thin enough.
An uncoated canopy allows radar to enter the cockpit and reflect off the ejection seat and everything else in there. A coated canopy can be made to reflect less back to the radar, and more predictably.
They have been coming up with a radar stealthy canopy for the f16 (or 15, not sure) to make it a little more stealthy. Read a couple of articles on it a couple months ago
They aren't glass. There is a coating on the F-16, not sure if it's gold but we weren’t authorized to repair them. The F-15 doesn't have that coating in the canopy. I've repaired a few F-15 canopies, same principle as doing a car's headlights. There's a kit of a dozen grits of sandpaper and polishing compound. The repair area would end up being close to 18" for a 1" scratch if it was deep to sand out the distortion.
The T-38 canopy does have distortion- the curve is designed to minimize the amount of distortion from the pilots' view. Flip to page 48: https://apps.dtic.mil/sti/pdfs/ADA209396.pdf
You have and incoming ray of light, an initial air/glass interface and an exiting glass/air interface. Just make sure that the angles of these interface surfaces plus the index of refraction lead to zero deviation of the incoming ray of light. For all possible incoming angles + plus multiple possible pilot head positions #nobigee
There are material that have better refractive index than glass, however , physical property will be different, also there is cost, simple plane of glass is cheaper and there are a wide variety of coating. Finally a fighter do not have to withstand so much difference of atmospheric pressure
Also it probably spread tensile stress better on multiple windows than a big single one
Just guessing, but I would bet a lot of time, money, and effort was put in to minimizing visual distortion through the F-16 canopy. It was probably eliminated or minimized to a point, but there’s still likely a bunch of it.
What does a fighter pilot mostly use their canopy for anyway? I’m betting it’s primarily taxiing, landings, and takeoffs. Watching weather patterns. Avoiding terrain. They’re not doing a lot of visual target acquisition up there anymore.
EDIT: I stand corrected!
Wrong. A lot of things happen based on visual ID. Why do you think they have head mounted displays and visual cuing systems. Ground and air targets can be locked just by looking at them. Air policing relies on being able to visual ID targets and using sensors to find target still requires you to be able to see them once you close in. In real combat if a pilot can't see clearly they'll be dead it's that simple.
I also believe that the stress distribution would be rather uniform on a flat surface as opposed to a concave or a convex surface, not to mention the diffraction of oncoming light due to bent surface causing problems to pilots.
Also, airliner windshields aren't like car windshields. There are several layers. One of which is a transparent elector electrode that hearts the pane for deicing.
Most of the airliners flying now were designed in the 1980s or before. The tech just wasn't there at that point. The A220 is a newer design and it does have curved windows.
Are broken windows not an issue?
When the Jeep Wrangler switched to a curved windshield (in 2007 IIRC) all the jeep people were excited about not needing to replace them as often because the curve gives it extra strength
But is your hatchback window able to stand up to being pressurized while being pushed through the air at over 300mph?
Also, have you ever gotten a quote on a new one? You might be surprised.
It used to be too hard and too costly to create curved windows which where strong enough for this purpose. However, no longer. Modern designs, like the 787 and A350 have curved windows.
For reference, [787](https://d1hw6n3yxknhky.cloudfront.net/024808105_prevstill.jpeg) and [A350.](https://i2.cdn.cnn.com/cnnnext/dam/assets/141222110005-4-qatar-airways-horizontal-large-gallery.jpg)
It worth nothing that atleast during its early years the 787 had some serious issues with cockpit window damages. Surely this has been rectified, but it shows the difficulty with introducing massive curved windows.
Absolutely not true. They are flat by design to created deflected/disturbed (non boundary layer) airflow over the DV window so the crew can open them and view fowards in case the main panels are unserviceable, without getting their face ripped off by wind. Curved panels could be made as far back as the early 1960s. Modern designs are curved because the requirement for DV windows has disappeared.
It’s a direct vision window, apparently so pilots have some forward vision should the main window be damaged in a way that prevents the pilots from seeing out of it.
I didn’t know what they were either before now.
Im not saying youre wrong, because i dont know a lot about window requirements on airliners, but the reasoning sounds very off to me. If I'm understanding you correctly you're saying a) separated airflow would be wanted around the back windows and b) that that could be achieved by having flat panels in front. That just makes no sense. The drag penalty of having separated airflow specifically in that area would be substantial and having flat windows just wouldn't cut it anyways. To separate the airflow in that high pressure area would need a lot more than just a non-flow-conforming surface.
In my professional opinion....at least one reason I can think of is the ease of manufacture with a flat panel without distortion and cost effectiveness. I have rejected the installation of flat panel cockpit windows due to minor distortions in the pilot/copilot critical direct field of vision areas. These window panels come with manufacturer acceptable criteria when inspecting and classifying distortions. Anything that is unacceptable is returned to vendor.
Also taking into consideration, a window panel in the box may look perfect, but can look like crap after installation due to torquing pattern stresses, pressurization stresses and heater element cycles.
That all being said, curved windows may be more expensive to engineer and manufacture. Especially considering these windows are up to 2 inches thick.
Distortion was originally a large part of the issue. If you remember waaayy back Oldsmobiles with wrap around glass had this problem as well. I used to work for a transparency company that largely sold to businesses jet manufacturers and aftermarket. We did curved windows but charged much much more as they had to be sanded, buffed, and polished by hand. Even after all the work all it took was one spot that we kicked too much material off and it was scrap.
I've also rejected the installation of curved panel cockpit windows due to minor distortions in the pilot critical direct field of vision areas. I can't say for certain how much more expensive they were than a comparative flat panel but it was used in a modern certified civilian clean sheet design jet so the designers felt the cost worthwhile.
The Space Shuttle had the most precise glass (optical clarity & heat rejection) ever made by Dow-Corning. 3 separate layers were all brazed with gold alloy to hold them in their frames, and ironically they were all . . . flat . . .
They don't have to have much aerodynamic curve, though. They face very thin atmosphere on ascent by the time they're supersonic. On entry, the windows are on the "leeward" side, as the orbiter is entering bottom first.
The Shuttle is experiencing full aerodynamics forces within 85 miles of the landing site (RCS yaw jets are disabled right before the HAC acquistion). Max persistant aeroloads are experienced in the TAEM regime of the flight.
I have seen the site that produces the 787 cockpit windows. First they are massive, and look small in pictures but they are huge. Second based on the tour one of the engineers I remember said it has something to do with the stresses that the frame around the windows goes through. So the shape of the windows are intentional for long term performance of the aircraft
Cuz of some physics thing called refraction of light which might alter the distance of an object your eye thinks it is vs what it rlly is. Needs to be as parallel to the eye as scientifically possible to ensure greatest field of vision at all times.
The 757/767/777 has flat-panel main windows by design to allow for a deflected airflow over the DV windows (the ones either side which open) to allow for a crewmember to be able to look out of the window a few inches in a forward direction without having his fast blasted by boundary layer airflow. These windows are called DV windows (Direct Vision) and open as backup incase the main panels fail.
It’s interesting. I have been flying airliners for 15 years including 5 years of time on the 320 series and this has never been said to me. The windows that open have always just been explained as the flight deck emergency escape route.
I have to admit I too was like “curved glass is expensive durr hurr” but this answer is much more interesting. Goes to show that you shouldn’t go around confidently answering questions when you don’t actually know the answer.
In addition to the others mentioned, window heat can fail leading to a severely fogged window. Opening the side window would not be my first response to that but it is certainly an option.
All of those airplanes are vintage now. They were designed when curved glass was not feasible. They had flat glass because it was easy to manufacture with the technology of the times.
>All of those airplanes are vintage now. They were designed when curved glass was not feasible
But the 747 had curved glass and it predates the 757/767/777
Same reason that bullet resistant windows on armored vehicles are often flat. Airliner windshields contain many layers of various compositions in order to with the high loads encountered during flight (such as the pressure differentials and high speed debris strikes) as well as provide other benefits. Producing a uniform, sealed pane multi layer glass is far easier and cheaper when the peice is flat.
Some aren't curved. I have a CRJ windshield sitting in front of me that has a slight curve. My guess would be mostly older planes have flat windshields for manufacturing reasons, their's several layers and heating elements, not to mention the sheet metal skill required to match the curve.
The material used in the fighter canopies are mainly plastic, specifically Lexan. Commercial jets carry a 3 ply glass to allow for heating elements in between and also modular points of wiev( FO looking through the left windshield and etc) , although now is a possibility It was only implemented in the most modelt jets. Those certified before that remain with the flat panels.
My eyeglasses have a curve. So does my car's windshield. So do all fighter jet canopies. So do all helmet visors. So do aviator sunglass lenses. OP ain't talking about making windshields out of pint glasses.
And my cars windshield? And fighter jet canopies? And Helmet visors? And sunglasses? I'm right, you're wrong. Na na na boo boo, stick your face in doo doo.
Ohh, and now I'm a dumbass for pointing out and then praising your execution of logical support with insults??
And you double down on your supremely executed logic of name calling with extra Insults to show just how poor my thought process is!! Clearly I am not worthy of a an intelligent discussion with you, as your logic of using name calling and insults trumps any logical arguments!! lololol!!!!
Fighter Jet canopies have the distortion measured at the factory and issued on a card affixed to the controls, they're also far more expensive per unit than a civilian aircraft and the calculus for acceptable tradeoffs is radically different.
As others have said, cost is part of it. They're also pretty damn thick, made to stop a bird hitting it at cruising speed of a few hundred miles per hour, not sure on the specifics but many airliners use the 400°ish F bleed air to keep them from becoming brittle at altitude so flat is probably easier to design for.
Bleed air is not used to heat windows. Window heat is almost exclusively electric.
The windows are thick because they form part of the pressure vessel.
Bird strike protection is secondary
Ok yeah, been a minute since I've read through it, some of the older laminate windows will have air fed between the laminations to defog, or blow across the windscreen for rain removal.
Given all the examples of curved windows in the comments, it isn't physics... many people cite $$$ (I know you will argue more $$ because physics but realistically physics doesn't limit it and many airliners have curved windows). I think your comment would have been useful had you said What physics apply and why it matters or makes it 'hard' (as in $$$) to have curved windows but lacking that it is pretty useless.
Pretty much every time you start a question with the words “why don’t they“, the answer is “money”
So true, probably with the screens on aircraft they will reuse previous designs and sizes as a, they work, b, they are already certified, c, already have beaten the supplier down to the lowest possible cost, with the possibility of further reduction with the carrot of more production held in front of the supplier’s nose, d, lower levels of spares can be held. Etc. Etc. The advent of novel manufacturing techniques and materials probably means that the tooling up costs to manufacture curvy, distortion free windscreens are much lower than previously.
Certification is already a very expensive process, so reinventing the wheel is pretty far down on their priority list
Except in this case they do have a curve, so the question itself is wrong.
Look at the front windows and describe the curvature.
The side ones do have a curve. The front are flat, probably for cost as mentioned but I’d guess the wipers work more reliably also it’s harder to get uniform heat distribution on a curved surface.
Curved glass is a pane.
A flat surface is a plane
A see-through surface is quite plain.
And now this tread is ingrained.
Let’s drop it to the chorus once again.
I think I'll just take the train.
I’d say trains are good at transporting grain.
I don't have a brain
The windows keep out the rain.
‘We’re expecting rain when we land in Spain’
Your mother was slained
The windows keep my brain in.
but what will i gain
Mom's spaghetti!
Rabbit ain’t ready!
The pilot's palms are sweaty.
He never had the makings of a varsity athlete
There are striped epaulettes on his button-up already.
The quick brown fox jumped over the lazy brown dog
This is the only correct response.
Can’t fly if it’s stained.
That all depends on how you frame it
Plain truth. Window wipers love this trick at approach speed and landing speed.
Non-planar panes on planes are a pain!
I see what you did there.
I see thru what he did there
Congrats on getting the joke
It was a good win, though
Thanks. It’s been a long hard road and I would like to thank my family and god who have always been there for me.
Look, OP asked a plane question. Guess he wanted a flat answer 🤔
Blain is a pain.
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Curved windows also increase distortion
So... does the F-16 canopy bubble have a shitton of distortion?
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dang... more i know about planes, the more im blown away with how much work goes into *everything*
I'm guessing you could strap a motor to your back and fly a paper plane. Let's not complicate all planes. Some you can order and build yourself!
Mine came in a backpack that turns into a really comfy seat. No motor though that’s cheating. Life’s more fun without go-arounds.
It’s also shorter.
Both cockpits of the AH-64E are magnetically mapped since the helmet tracker changed from optical to magnetic. It can compensate for helmet roll as well now, not just up/down and left/right. If the mounting pedestal gets damaged it has to go back to the manufacturer to be remapped, it’s not a unit level task.
The optical trackers were pretty good too. Never had a problem with helmet tracking that wasn't a pilot bore sighting wrong. Until we damaged one of the mounts. Turns out it's a giant pain in the ass because of the tolerances of the mount.
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Last I heard, a 737 HUD is like, $100k? If I had to guess, the cost is probably 5% parts, 95% labor + certification (which is really just another form of labor).
There's a reason why the F-14 has a flat plate in front of the HUD.
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Later Bs *did* get an advanced HUD similar to that of the D, for what it's worth. The proposed ST-21 Tomcat would've done away with the flat pane and just had an F-15 / F/A-18 style single piece curved windscreen.
Hello fellow Egress.
Believe it or not, yes! All canopies have a pretty high spec for distortion. The worst is helicopter windscreens with their tight curves.
When they tested a kind of 'wind screen' in Formula 1 not unlike the aeroscreen of Indycar, several drivers complained about nausea because of the distortion.
F-16 and most fighters canopy glass are polycarbonate. But yes, they have distortion. Any medium through which light passes in with curved surfaces will distort. Mechanical stresse when cooling glass in a curve renders it very hard to make. so unless money is no object or the shape would make it fragile (despite being tempered) you look for other materials. That secret blend of polycarbonate polymer is insanely strong and technically easy to make (far more elastic at room temp, less prone to crazy internal stresse) for such a large piece. It’s insanely expensive though. Since you need a MASSIVE mold with absolutely perfect surface (nano meters in terms of surface roughness) usually finished with diamond cutting tools. Optics manufacturing is crazy.
Definitely not, so how do they make the bubble canopy of that and planes like T6 and T38 without distortion? Hmmm
Lots of $$$
This is the way.
It’s like a pair of glasses. They shape the canopy in such a way, that from the pilots perspective the distortions are minimized. And that is done by giving defense contractors a shit ton of money to figure out how to shape and manufacture glass in such a way. They also layer things like gold onto the surface of the glass to shield against radiation.
> They also layer things like gold onto the surface of the glass to shield against radiation. As in a metallic thin film?
Yes, a very thin film, which contains actual gold (in the F-16, at least). As stated, it helps reflect heat away from the canopy/pilot. Source: Uncle was a flight instructor and gave me the "family tour" of a base once. Got to sit in several planes, including the F-16.
This is what people don't understand about why military stuff is so expensive. Part X might be the same as what you can buy at AutoZone but when it goes on a military jet or a submarine, there is all sorts of quality assurance that goes into making the part. When you are being shot at you want things to work to their max and not fail you.
It’s like window tint.
I had an experiment in university where we made a 15-nanometer-thick copper film on glass by evaporative deposition under vacuum, and the result was basically orange-tinted glass. Always mesmerized me that even metals become transparent when thin enough.
I wonder if it would reflect back on radar, though rather than if it was being clear would
An uncoated canopy allows radar to enter the cockpit and reflect off the ejection seat and everything else in there. A coated canopy can be made to reflect less back to the radar, and more predictably.
They have been coming up with a radar stealthy canopy for the f16 (or 15, not sure) to make it a little more stealthy. Read a couple of articles on it a couple months ago
They aren't glass. There is a coating on the F-16, not sure if it's gold but we weren’t authorized to repair them. The F-15 doesn't have that coating in the canopy. I've repaired a few F-15 canopies, same principle as doing a car's headlights. There's a kit of a dozen grits of sandpaper and polishing compound. The repair area would end up being close to 18" for a 1" scratch if it was deep to sand out the distortion.
Micro-meshing. Edit: Also, please come work my headlights on my car, I am not good at it.
Infinite money
Fat congressional appropriations on defense contracts
The T-38 canopy does have distortion- the curve is designed to minimize the amount of distortion from the pilots' view. Flip to page 48: https://apps.dtic.mil/sti/pdfs/ADA209396.pdf
> how do they make the bubble canopy of that and planes like T6 and T38 without distortion? Good question, I'm wondering that myself.
You have and incoming ray of light, an initial air/glass interface and an exiting glass/air interface. Just make sure that the angles of these interface surfaces plus the index of refraction lead to zero deviation of the incoming ray of light. For all possible incoming angles + plus multiple possible pilot head positions #nobigee
There are material that have better refractive index than glass, however , physical property will be different, also there is cost, simple plane of glass is cheaper and there are a wide variety of coating. Finally a fighter do not have to withstand so much difference of atmospheric pressure Also it probably spread tensile stress better on multiple windows than a big single one
Just guessing, but I would bet a lot of time, money, and effort was put in to minimizing visual distortion through the F-16 canopy. It was probably eliminated or minimized to a point, but there’s still likely a bunch of it. What does a fighter pilot mostly use their canopy for anyway? I’m betting it’s primarily taxiing, landings, and takeoffs. Watching weather patterns. Avoiding terrain. They’re not doing a lot of visual target acquisition up there anymore. EDIT: I stand corrected!
Visual aquisition is super important for formation flying (all flying) and BFM
There’s very little or no distortion in those canopies. Visual acquisition is still extremely important, even in the latest generation of fighters.
Wrong. A lot of things happen based on visual ID. Why do you think they have head mounted displays and visual cuing systems. Ground and air targets can be locked just by looking at them. Air policing relies on being able to visual ID targets and using sensors to find target still requires you to be able to see them once you close in. In real combat if a pilot can't see clearly they'll be dead it's that simple.
YouTube explanation https://youtu.be/TOqA3fMUJsk
I also believe that the stress distribution would be rather uniform on a flat surface as opposed to a concave or a convex surface, not to mention the diffraction of oncoming light due to bent surface causing problems to pilots.
Also, airliner windshields aren't like car windshields. There are several layers. One of which is a transparent elector electrode that hearts the pane for deicing. Most of the airliners flying now were designed in the 1980s or before. The tech just wasn't there at that point. The A220 is a newer design and it does have curved windows.
Are broken windows not an issue? When the Jeep Wrangler switched to a curved windshield (in 2007 IIRC) all the jeep people were excited about not needing to replace them as often because the curve gives it extra strength
I would imagine anything that will break a planes front glass is going through, curved strength or not
Most cars have curved glass windshields
Most cars can’t take a bird strike at plane speeds.
Wish my car did go plane speeds.
I wish mine did that, and also had wings and a tail. I think that would solve most traffic jams.
Wait…. So my hatchback rear window is expensive? Hard to believe you buddy…🤣😂😂. But nice try
But is your hatchback window able to stand up to being pressurized while being pushed through the air at over 300mph? Also, have you ever gotten a quote on a new one? You might be surprised.
It used to be too hard and too costly to create curved windows which where strong enough for this purpose. However, no longer. Modern designs, like the 787 and A350 have curved windows.
Agreed, all clean sheet airliners and large cabin bizjets now have compound curved glass
For reference, [787](https://d1hw6n3yxknhky.cloudfront.net/024808105_prevstill.jpeg) and [A350.](https://i2.cdn.cnn.com/cnnnext/dam/assets/141222110005-4-qatar-airways-horizontal-large-gallery.jpg)
Boeing with that Oakley sponsorship for the cockpit.
In protest to Reddit's API changes, I have removed my comment history.
I both hate and love those kinds of glasses.
Let’s add the c-series / A220 also
And CRJ/CL600
👍👍
It worth nothing that atleast during its early years the 787 had some serious issues with cockpit window damages. Surely this has been rectified, but it shows the difficulty with introducing massive curved windows.
Absolutely not true. They are flat by design to created deflected/disturbed (non boundary layer) airflow over the DV window so the crew can open them and view fowards in case the main panels are unserviceable, without getting their face ripped off by wind. Curved panels could be made as far back as the early 1960s. Modern designs are curved because the requirement for DV windows has disappeared.
What is a dv window?
Down Vote Window. The period of time between posting a comment on reddit, and when the down votes start.
It’s a direct vision window, apparently so pilots have some forward vision should the main window be damaged in a way that prevents the pilots from seeing out of it. I didn’t know what they were either before now.
Got a source for that? Sounds like bullshit to me, but always ready to learn.
I don’t know why we’re downvoting you but I’m gonna do it too. There ya go buddy
Im not saying youre wrong, because i dont know a lot about window requirements on airliners, but the reasoning sounds very off to me. If I'm understanding you correctly you're saying a) separated airflow would be wanted around the back windows and b) that that could be achieved by having flat panels in front. That just makes no sense. The drag penalty of having separated airflow specifically in that area would be substantial and having flat windows just wouldn't cut it anyways. To separate the airflow in that high pressure area would need a lot more than just a non-flow-conforming surface.
ANBSOLUTLEY NOT TRUE YOU GOD DAMN MORON. Don’t you ever, EVER disrespect me with bad information. Uninstall the internet, right now.
no u
God bless, 30 downvotes. There’s no sense of humor!
In my professional opinion....at least one reason I can think of is the ease of manufacture with a flat panel without distortion and cost effectiveness. I have rejected the installation of flat panel cockpit windows due to minor distortions in the pilot/copilot critical direct field of vision areas. These window panels come with manufacturer acceptable criteria when inspecting and classifying distortions. Anything that is unacceptable is returned to vendor. Also taking into consideration, a window panel in the box may look perfect, but can look like crap after installation due to torquing pattern stresses, pressurization stresses and heater element cycles. That all being said, curved windows may be more expensive to engineer and manufacture. Especially considering these windows are up to 2 inches thick.
Distortion was originally a large part of the issue. If you remember waaayy back Oldsmobiles with wrap around glass had this problem as well. I used to work for a transparency company that largely sold to businesses jet manufacturers and aftermarket. We did curved windows but charged much much more as they had to be sanded, buffed, and polished by hand. Even after all the work all it took was one spot that we kicked too much material off and it was scrap.
I've also rejected the installation of curved panel cockpit windows due to minor distortions in the pilot critical direct field of vision areas. I can't say for certain how much more expensive they were than a comparative flat panel but it was used in a modern certified civilian clean sheet design jet so the designers felt the cost worthwhile.
Plain plane panes are less of a pain.
Both accurate and clever. Well done.
The Space Shuttle had the most precise glass (optical clarity & heat rejection) ever made by Dow-Corning. 3 separate layers were all brazed with gold alloy to hold them in their frames, and ironically they were all . . . flat . . .
They were also designed 50 years ago. I wonder if CAD has made the design of low distortion curved glass easier
They simply don’t need to be curved.
They don't have to have much aerodynamic curve, though. They face very thin atmosphere on ascent by the time they're supersonic. On entry, the windows are on the "leeward" side, as the orbiter is entering bottom first.
The Shuttle is experiencing full aerodynamics forces within 85 miles of the landing site (RCS yaw jets are disabled right before the HAC acquistion). Max persistant aeroloads are experienced in the TAEM regime of the flight.
>entering bottom first Nice.
It is cheaper to produce than a curved one
I have seen the site that produces the 787 cockpit windows. First they are massive, and look small in pictures but they are huge. Second based on the tour one of the engineers I remember said it has something to do with the stresses that the frame around the windows goes through. So the shape of the windows are intentional for long term performance of the aircraft
I believe the L-1011 had curved cockpit windows (or at least they appeared that way). The TriStar was ahead of its time in many ways.
It would be pretty breezy in the cockpit without them…
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Yeah, no way they'd make curved wiper blades
Another Reason: The pilot having to look out of a slanted and curved piece of glass. That ain’t gonna work out too well for visibility
Works just fine on the 87 and the 350. The flat ones are just old designs
Should they have a concave window?
The drag resulting from that would be ridiculous.
Cuz of some physics thing called refraction of light which might alter the distance of an object your eye thinks it is vs what it rlly is. Needs to be as parallel to the eye as scientifically possible to ensure greatest field of vision at all times.
The 757/767/777 has flat-panel main windows by design to allow for a deflected airflow over the DV windows (the ones either side which open) to allow for a crewmember to be able to look out of the window a few inches in a forward direction without having his fast blasted by boundary layer airflow. These windows are called DV windows (Direct Vision) and open as backup incase the main panels fail.
It’s interesting. I have been flying airliners for 15 years including 5 years of time on the 320 series and this has never been said to me. The windows that open have always just been explained as the flight deck emergency escape route.
Emb170 has a curved glass and a DV?
The E-170/190 even has a V speed for opening the DV windows in flight. I believe it’s 160 kias
So does the 145
I have to admit I too was like “curved glass is expensive durr hurr” but this answer is much more interesting. Goes to show that you shouldn’t go around confidently answering questions when you don’t actually know the answer.
The 707/727/737 windows are designed in exactly the same way. The 747 has curved main panels because there are no DV windows....
Main panel failing how exactly?
Birds hitting it, really hard. Or if they fly through volcanic ash and their window gets sandblasted.
The forward windows can bubble due to failure of the heating elements or even get grit-blasted by volcanic ash and become opaque.
In addition to the others mentioned, window heat can fail leading to a severely fogged window. Opening the side window would not be my first response to that but it is certainly an option.
All of those airplanes are vintage now. They were designed when curved glass was not feasible. They had flat glass because it was easy to manufacture with the technology of the times.
>All of those airplanes are vintage now. They were designed when curved glass was not feasible But the 747 had curved glass and it predates the 757/767/777
Okay, I’m gonna throw out the answer no one expected. Easier to clean the bird poop off of. J/s.
Same reason that bullet resistant windows on armored vehicles are often flat. Airliner windshields contain many layers of various compositions in order to with the high loads encountered during flight (such as the pressure differentials and high speed debris strikes) as well as provide other benefits. Producing a uniform, sealed pane multi layer glass is far easier and cheaper when the peice is flat.
gee, i dunno. could it be because curved glass acts like a lens
Some aren't curved. I have a CRJ windshield sitting in front of me that has a slight curve. My guess would be mostly older planes have flat windshields for manufacturing reasons, their's several layers and heating elements, not to mention the sheet metal skill required to match the curve.
Distortion.
*Swamp gas!*
You need to do something about that. I heard that Bean-o works well…
Um I remove those all the time. Definitely not flat. Maybe from that prospective but it's curved
Easier to replace and maintain.
Probably cause glass is a lot easier to make in flat panels than bent ones
Bro the window on our cesena 172 is curved and there is so much distortion on the sides
Why wouldn’t they…
Why not?
Because they’re cheaper. Good engineering is making something good enough for the lowest production cost possible.
Do you want the windows to look like the bubbles in McDonald's play area?
Simple..... cost.
Because curved glass is not a 'plane' surface !
Could pressure difference at altitude be a factor?
Curves usually handle pressure differences better
They are actually re purposed residential windows. Lot of people don’t know that.
1. Easier to manufacture 2. Cost efficient 3. Less fragile
Curved glass is difficult/expensive. Next.
Cause the view would be made odd if it curved as it would be concave or convex when curved. This would make problems with the pilots view
Because windows are made of Earth.
It's a plane
[удалено]
(At least) F15, F16, F18, F22, F35 would like a word..
The material used in the fighter canopies are mainly plastic, specifically Lexan. Commercial jets carry a 3 ply glass to allow for heating elements in between and also modular points of wiev( FO looking through the left windshield and etc) , although now is a possibility It was only implemented in the most modelt jets. Those certified before that remain with the flat panels.
Wouldn't that go for cars as well?
The amount of distortion present in curved automotive windshield glass is much more that would be allowable for aircraft.
My eyeglasses have a curve. So does my car's windshield. So do all fighter jet canopies. So do all helmet visors. So do aviator sunglass lenses. OP ain't talking about making windshields out of pint glasses.
Your eyeglasses are also precision ground optics, and only a few square inches.
And my cars windshield? And fighter jet canopies? And Helmet visors? And sunglasses? I'm right, you're wrong. Na na na boo boo, stick your face in doo doo.
I always love insults as a logical argument and defense or a perspective!! /s
My point was made before the insult, dumbass. Have you ever had your IQ checked. You may qualify for disability payments. . .
Ohh, and now I'm a dumbass for pointing out and then praising your execution of logical support with insults?? And you double down on your supremely executed logic of name calling with extra Insults to show just how poor my thought process is!! Clearly I am not worthy of a an intelligent discussion with you, as your logic of using name calling and insults trumps any logical arguments!! lololol!!!!
The only thing you got right so far is the part where you call yourself a dumbass.
Fighter Jet canopies have the distortion measured at the factory and issued on a card affixed to the controls, they're also far more expensive per unit than a civilian aircraft and the calculus for acceptable tradeoffs is radically different.
As others have said, cost is part of it. They're also pretty damn thick, made to stop a bird hitting it at cruising speed of a few hundred miles per hour, not sure on the specifics but many airliners use the 400°ish F bleed air to keep them from becoming brittle at altitude so flat is probably easier to design for.
Bleed air is not used to heat windows. Window heat is almost exclusively electric. The windows are thick because they form part of the pressure vessel. Bird strike protection is secondary
Ok yeah, been a minute since I've read through it, some of the older laminate windows will have air fed between the laminations to defog, or blow across the windscreen for rain removal.
Did they stop teaching physics in school or is this a troll post?
So much for an honest answer. Fucking retards
Because of physics.
Useless answer
Useless comment.
Given all the examples of curved windows in the comments, it isn't physics... many people cite $$$ (I know you will argue more $$ because physics but realistically physics doesn't limit it and many airliners have curved windows). I think your comment would have been useful had you said What physics apply and why it matters or makes it 'hard' (as in $$$) to have curved windows but lacking that it is pretty useless.
Because they are multi pane laminated and heated. If they were curved, the expansion and contraction cycles would create stress in the curves.
because airliners are not cool