Airframes

[oldpax]

Looking at an airframe would it be any cheaper to build if you built without windows?After all except for those next to the windows theres not a lot to see after you reach cruising height!!With all the entertainment channels could not an external cam show what was going on,if anything.

[Mechta]

THe C5 Galaxy has a 75 seat passenger cabin without windows. Windows are expensive and heavy luxury the USAF decided its non-paying passengers could live without.

[Sidestick_n_Rudder]

The recent trend is actually opposite - newer airplanes, like the 787/350 tend to have larger windows than the older designs

[pattern_is_full]

I always get a window seat when in the back - get claustrophobic otherwise (plus I enjoy the scenery). Glad I never had the "opportunity" to experience the C5's "flying movie theater." Talk about "self-loading freight!" ;)

http://www.theaviationzone.com/images/other/personal/i-bin/mn_14.jpg

Build one without windows - and I'll fly with somebody else.

[WindSheer]

Take the windows out, and I don't want to fly!

Part of the journey is experiencing the magic of being 6 miles up.
Simple!

[MurphyWasRight]

Take the windows out, and I don't want to fly!

Totally agree, would be -very- breezy on the way up then a bit hard to breathe :)

This comes under the general category of consumer resistance, a related example is that having passengers face the rear would increase safety, whether train, airplane or automobile but simply will not happen.

[tonytales]

Many moons ago BOAC wet leased a Seaboard and Western L-1049D Connie for service to Bermuda from KIDL. Being a convertible cargo-pax aircraft the interior was Spartan. BOAC had not noticed there were only about five window to each side behind the curtains but the passengers did. To continue the lease BOAC required S&W to get an L-1049E-01 which they did from Cubana. It was converted in stages to an all coach configuration.
After a spell sitting atop a gasoline station for some years it has ended up at Dover AFB masquerading as a C-121 in their museum.
Windows do count.

[Intruder]

These days, everyone is so interested in the movies on their iPads, that they close the screens for 99% of the flight anyhow. Fewer/no windows would certainly make for a lighter & stronger fuselage. A series of OLED screens showing the view out the sides may be cheaper, lighter, and easy to implement.

OTOH, there would need to be SOME windows for the flight attendants to look for fire, etc during emergencies. Those in exit rows may be the ones privileged with windows...

[tdracer]

I've done a number of flight tests where I was sitting in the belly of a freighter with no windows (747-8F and 767-2C). It's horrible - especially takeoff and landing where you feel the motions but have no outside references.
I'd never pay to fly in something without windows.

[megan]

Twas back in the day when IFE consisted of one large screen for the entire cabin to watch movies. Had travelled half way round the world to find myself at thirty plus thousand feet on a gin clear day over the Grand Canyon when along comes a CC demanding the window shade be pulled down in order to show some B grade Hollywood trash. Was appalled that everyone seemed to prefer the trash to the magical vista to be seen outside. Why the heck didn't Boeing put a window at row seven, or there abouts, on the 738 LHS. Had it a few times and not a happy traveller.

[tdracer]

Why the heck didn't Boeing put a window at row seven, or there abouts, on the 738 LHS. Had it a few times and not a happy traveller.
Not sure about the 737, but I know that on the 767 there are a few rows without windows because that's where the ECS ducts move air to the overhead vents.

[megan]

Thanks td, just had a look and its the same on the 73.

[Homsap]

Two good reasons to have windows is from a safety point duriing an evacuation in daylight hours, in the even of no electrical power, as I think was the case in the A320 landing in the Hudson river, it is alot easier to evacuate and for the crew to check the aircraft, Secondly, it is easier for fire and rescue crew to locate fire and people, that is why the blinds are in the up poistion for take off and landing.

[Jet II]

The desire for windows is a bit overblown - if you sit in the middle in first class or business class on something like EK then you cant see the windows at all as the seat structure is built up around you with the express intent of giving you more privacy.

You could always replace the windows with lcd screens and show a picture of the world outside.... ;)

[triploss]

Two good reasons to have windows is from a safety point duriing an evacuation in daylight hours, in the even of no electrical power, as I think was the case in the A320 landing in the Hudson river, it is alot easier to evacuate and for the crew to check the aircraft, Secondly, it is easier for fire and rescue crew to locate fire and people, that is why the blinds are in the up poistion for take off and landing.

Blinds ain't got to be up for any reason in the good ole US of A.

The 787 is a horror when it comes to windows since the FA's can now lock the windows into "dark" mode, at least they usually don't do that until cruise though.

[Rick777]

I've spent plenty of time in the back of various KC 135, C 141, C130, and C5s. Never thought much about the lack of Windows, but I definitely prefer having them and leave the shades up.

[underfire]

I seem to remember that Airbus showed a design at the Paris Airshow with no windows, and had screens mounted where the windows would normally be. The screens showed the outside view from cameras mounted on the airframe.

https://i.amz.mshcdn.com/5BJmKcW9w93wQRjOWIkbDON-8dI=/fit-in/1200x9600/http%3A%2F%2Fmashable.com%2Fwp-content%2Fuploads%2F2014%2F10%2Foutside-flight-640x145.jpg

Without the weight of the windows, and the reinforcement required around the openings, I think it was about a 25% weight difference, and was actually much stronger.

[tdracer]

I think it was about a 25% weight difference
25% of what? Because I can guarantee it wasn't airframe weight, or even fuselage weight...
The problem with view screens is unless you give every passenger their own camera that they can pan/scan, it's not going to be even remotely the same - you'll be looking at the camera view, which probably won't be the view of interest.
It's not as important at night (although I've seen some pretty cool stuff at night as well) but some of the most spectacular scenery I've ever seen has been out the window of an aircraft (and I used to go backpacking in the Rocky Mountains - in large part for the views). If I'm paying for the ticket, I'm not willing to give that up...

[fizz57]

The problem with view screens is unless you give every passenger their own camera that they can pan/scan, it's not going to be even remotely the same - you'll be looking at the camera view, which probably won't be the view of interest.


Pan/scan isn't an issue with an all-round camera and some software - think Google Maps/Street View.


Come to think of it, with Google Maps you don't even need the camera!

[DaveReidUK]

25% of what? Because I can guarantee it wasn't airframe weight, or even fuselage weight...

In Jan Roskam's classic 1985 "Airplane Design" he quotes a formula, based on number of seats and max diff, for the weight difference between windows and windowless.

For a 150-seat aircraft, this comes out at around 200 kg.

Window sizes have grown since his book was written, so the weight penalty for newer aircraft will be a bit higher than that.

[ThreeThreeMike]

Twas back in the day when IFE consisted of one large screen for the entire cabin to watch movies. Had travelled half way round the world to find myself at thirty plus thousand feet on a gin clear day over the Grand Canyon when along comes a CC demanding the window shade be pulled down in order to show some B grade Hollywood trash. Was appalled that everyone seemed to prefer the trash to the magical vista to be seen outside. Why the heck didn't Boeing put a window at row seven, or there abouts, on the 738 LHS. Had it a few times and not a happy traveller.

When I have a window seat, the shade is up. There's a great big world out there with wonderful sights.

I almost always get annoyed stares from pax sitting next to me.

[DaveReidUK]

Why the heck didn't Boeing put a window at row seven, or there abouts, on the 738 LHS. Had it a few times and not a happy traveller.

https://i.pinimg.com/originals/ce/4f/1c/ce4f1caf21ffc3da7a35fea9c5166e62.jpg

[dixi188]

Same on trains in the UK.
I use "X country" trains from Bournemouth to the Midlands now and then, and the windows cover two rows of seats. I like to have a South side seat (with the sun) passing Southampton docks to see the shipping, and usually the other row sharing the window wants the blind down so they can see their screen.
Bloody annoying!

When flying as pax I also want to see the great outside.
Went to Florida with the kids a few years ago, and booked RH window seats for the outward journey to give the youngsters a geography lesson all the way down the East coast of North America.
How are you going to do that without windows?

[tdracer]

Pan/scan isn't an issue with an all-round camera and some software - think Google Maps/Street View.You really want to compare that fish-eye view with the view out a window? Because as someone who truly appreciates the beauty of our world, it's not even close...
Maybe if we gave all the passengers one of those F-35 helmets - of course so much for any cost/weight savings.

Window sizes have grown since his book was written, so the weight penalty for newer aircraft will be a bit higher than that. No first hand knowledge - it's well out of my area of expertise - but my understanding was they were able to go to the larger windows on the 787 because the composite construction minimized the weight impact of the windows.

[dixi188]

As I understand it then, the 787 has bigger windows to see the world through, but the cabin crew can turn the windows off so you can't see through them?

[underfire]

25% of what? Because I can guarantee it wasn't airframe weight, or even fuselage weight...
It was 25% of the weight of the structural elements of the fuselage. The structural sections could be optimally spaced, and smaller not having to reinforce around the windows. There is the weight of the window assembly, and associated flashing to consider.

The window assembly, associated reinforcement, and extra strength for each member, vs a thin layer of aluminum?

How can you guarantee it is not 25%? Did you read the Airbus information?

How are you going to do that without windows?

As shown by the Airbus patent and the article. There would be screens instead of windows, and cameras mounted on the outside of the aircraft would provide the same view.

Airbus also patented the pilot in the cargo holds, aviating by screens and cameras. Likely a much better view than the current windscreens, an probaly much more roomier flightdeck.
One uses screens in the sim, so what is the big deal?

[fizz57]

You really want to compare that fish-eye view with the view out a window? .


You're the one who said "The problem with view screens is unless you give every passenger their own camera ....."


I'm just pointing out that the technology exiats.


As for me, I think the idea is ghastly - I always take a window seat. But I don't think the beancounters (or Mr. O'Leary) will take that into account if it is ever offered as an option. Hell, they'll probably put it on pay-per view.

[Chu Chu]

The industry might want to think twice before it argues that seeing it on the screen is as good as being there . . .

[tdracer]

How can you guarantee it is not 25%? Did you read the Airbus information?
No, I didn't read the Airbus propaganda, but I do know this:
Boeing has been building jetliners for 60 years without windows (except for the flight deck and exit portals) - KC-135, 747F, 757F, 767F, 777F. Their fuselage structure is optimized for the lack of windows. Yes, it saves, weight, but the number is small single digits (the previous post quoting 200kg for 150 seater is ballpark). Once you add in a couple large view screens for each row, plus cameras, associated wiring and controls, it's probably close to a push.

[underfire]

Boeing has been building jetliners for 60 years without windows (except for the flight deck and exit portals) - KC-135, 747F, 757F, 767F, 777F

I understand that, but Boeing doesnt build a different structural frame for the F models do they?

Now going back, I did say saving 25% on the fuselage structure? Thinner elements, no bracing and no windows? Not to mention ease of construction...

[DaveReidUK]

This conference paper may be the origin of the 25% figure:

Aircraft Preliminary Design: a windowless concept (http://aerospace-europe.eu/media/books/CEAS2015_211.pdf)

[underfire]

Dave,

thanks for that link!

The formula and calculations they give amount to about a 28% weight savings in the fuselage structure, including the windows vs screens

https://i.imgur.com/0X9VkbV.jpg


As already cited, a mass reduction in any system of the airplane implies lower fuel consumption. Than the total weight is even lower and, for example, lighter landing gear could be sufficient to carry the plane weight. This process could improve weight savings of about 25%.

TD, now about your guarantee.....

[Chu Chu]

The only non-window-related weight considered in the formulas above is the weight of the skin itself. (In the paper, the formula for skin weight is the formula for the surface area of a cylinder times skin thickness times density.) So the paper is really saying that the weight of a skin without windows is 25% less than that of a skin with windows. It doesn't take into account frames, bulkheads, or anything else that makes up a fuselage.

There are probably some structural savings that the paper doesn't take into account. But the total savings can't be anything like 25% of the weight of the fuselage as a whole. I don't think TD's going to be called to make good on his guarantee.

[oldpax]

I recently travelled on an A-380 ,not a window seat.I may as well have been on a coach travelling through a long tunnel for 12 hours!So except for those next to a window the majority do not see a thing so get rid of them I say !If weight reduction and strength are improved then it has to be a good thing.I also flew many times facing the rear and it never bothered me!!

[tdracer]

TD, now about your guarantee.....


Still stands - 25% skin weight is no where near 25% fuselage weight.
Oh, and did you take a gander at their "small scale validation model"? Validating a structural design change with a 3d printed chunk of plastic?

[underfire]

Still stands - 25% skin weight is no where near 25% fuselage weight.

Did you look at the formula?

So the paper is really saying that the weight of a skin without windows is 25% less than that of a skin with windows. It doesn't take into account frames, bulkheads, or anything else that makes up a fuselage.

Did you look at the formula?

What exactly do you think Window metal frame and near hole reinforcement are? Structural elements perhaps?

Perhaps if you READ the article, you will comprehend where the 25% comes from, or you could continue to blindly argue your point when provided with facts to the contrary.

[tdracer]

What exactly do you think Window metal frame and near hole reinforcement are? Structural elements perhaps?They are structural elements of the windows. MOST of the weight of a fuselage isn't the skin and window surrounds - it's stringers, bulkheads, keel beam, floor and floor support. I've seen airframes going through D-check with all the skin and window surrounds removed - there is still a LOT there, which makes up the lions share of the strength and weight.
The formula you so proudly point at doesn't account for all that other stuff, except in a secondary manner (yes, lighter skin means some of the other structure gets lighter, but not by 25%). While the aircraft skin is a structural element - it's not the primary structure.

[msbbarratt]

Two good reasons to have windows is from a safety point duriing an evacuation in daylight hours, in the even of no electrical power, as I think was the case in the A320 landing in the Hudson river, it is alot easier to evacuate and for the crew to check the aircraft, Secondly, it is easier for fire and rescue crew to locate fire and people, that is why the blinds are in the up poistion for take off and landing.

Isn't another reason so that rescue crews can see in from the outside?

[underfire]

The formula you so proudly point at doesn't account for all that other stuff, except in a secondary manner (yes, lighter skin means some of the other structure gets lighter, but not by 25%)

What you are unable to comprehend is that those systems are static, and the removal of the windows and associated reinforcement is a difference..

Note: the weight of the windowless fuselage vs the weight of the fuselage without windows.

What is your experience in the structural design of an aircraft fuselage?

Have you designed the structural components of a wing? of a winglet?

keep trying to defend your postion, it is rather amusing watching you flail on the hot pavement.

Isn't another reason so that rescue crews can see in from the outside?

Actually, no. Windows are required in certain locations for cabin crew to look out and determine safe exit. Hence the Airbus design I posted previously.

[john_tullamarine]

Might we maintain our cool a bit, chaps ? Play the ball and not the player ?

Although I don't know him, I suspect that tdracer actually is very well placed to make the comments above ....

[Chu Chu]

Underfire,

I think the disagreement is about math, not engineering. No one's disputing that removing the windows makes the skin 25% lighter. And I think we agree that the weight of rest of the fuselage structure is static, or even decreases slightly without windows. But if the skin is 20%, or even 50%, of the fuselage weight, making the skin 25% lighter doesn't make the fuselage 25% lighter.

(I think you agree that even without the windows, a fuselage still has to have things like stringers and bulkheads. None of those go into the 1560 KG in the second formula.)

[tdracer]

Might we maintain our cool a bit, chaps ? Play the ball and not the player ?

Although I don't know him, I suspect that tdracer actually is very well placed to make the comments above ....

It's OK John, underfire just earned his way onto my ignore list. I guess 39+ years experience in aircraft and aircraft system engineering design just doesn't carry weight with some people.

[DaveReidUK]

OK, some actual numbers:

The paper is based on the centre section of an A320 fuselage. Assuming that corresponds to the production joins, it's 5.98 m in length. The O/D of the fuselage is 3.95 m. So, assuming a generous skin thickness of 1.6 mm, the total volume of material is approximately 0.118 cu m.

Assuming around 2,700 kg/cu m for aluminium alloy, that gives a total skin weight for the centre section of 320 kg. For the entire 36.6 m fuselage, skin weight would be around 2,000 kg (the figure in the paper is 2155.4 kg, so we won't argue with that).

So clearly the numbers quoted in the paper for "weight of windowless/traditional fuselage" are the skin weight.

[Owain Glyndwr]

It is pretty clear from the article being criticised that the weight gains quoted are their estimate of the savings in their estimate of the skin weight based on their understanding of the static design loads on a typical central section of an A320 fuselage.
It is pointless to talk of percentage gains in fuselage weight when the baseline used is just a fraction of the total fuselage structural weight. Typically, fuselage structural weights lie in the range 21 to 23% of the aircraft empty weight. For an A320, that is a lot more than the 2155 kg quoted, so to talk of a 25% reduction in fuselage weight is a nonsense.
More to the point is that almost none of a typical transport fuselage is designed by the static loads. Depending on what part of the fuselage you are discussing, manufacturing (minimum gauge) limits, fatigue, damage tolerance and crashworthiness considerations dominate. Any actual weight gain will be the difference between the windowed design and the windowless weight that meets these more severe criteria, not the theoretical weight that satisfies the static load condition.
Nobody is disputing that removing the windows would save weight, although I am with tdracer in doubting whether it would be anything like the number claimed, neither would one suggest there was any real technical risk, but the commercial risks would be very large.
I'm not holding my breath waiting for an announcement that the next design to surface will be windowless!

[EMIT]

As I understand it then, the 787 has bigger windows to see the world through, but the cabin crew can turn the windows off so you can't see through them?

No, the 787 windows, even when darkened to the max, still let light pass thru, allowing the pax to see the outside world in all its glory. Really a brilliant system.

[Concours77]

Fascinating discussion.

Perhaps more important is not the presence of Windows, but the shape of the hole they occupy? Especially the corners? Or the strength of the skin above? (deHavilland, Boeing).

Adios Comet, Aloha, Aloha.

[hans brinker]

Did you look at the formula?



Did you look at the formula?

What exactly do you think Window metal frame and near hole reinforcement are? Structural elements perhaps?

Perhaps if you READ the article, you will comprehend where the 25% comes from, or you could continue to blindly argue your point when provided with facts to the contrary.

Read the article, total weight savings 750kg. According to the formula total airframe weight with windows 3000kg.
Empty weight around 40.000kg. Very heavy wings, engines and landing gear........

[Concours77]

Removing Windows is a money saver, yep. But along with the glass and pertinent structure, a line could also remove all but perhaps twenty five seats; these for the remaining people who would purchase fares from this "lighter" line?

[megan]

Two days ago embarked on a 12.5 hour flight, midnight departure, about five minutes after take off CC came around asking for the shades to be closed, very politely, but with a measure of insistence. Asked why, it's so pax are not disturbed by the aircrafts external lighting, or raising/setting sun. Entirely new one on me.