5 ms·

If it really saves 50% of the aircraft weight, it's crazy that long haul airplanes today are even allowed to have windows.

degenerate 8y ago
That is the biggest 'wow' in the article, and I'd really love to see a source on that... but they don't provide a source and I cannot find this info when googling. Anyone can back up that claim?
- deleted 8y ago
  [deleted]
cecilpl2 8y ago
I can't believe that's possible. I really want to know where that number came from. Maybe you could reduce the weight of just the frame of the fuselage by 50%, but I bet you'd save at most 2-3% of the total takeoff weight, once you include fuel, wings, tail, engines, gear, cabin, baggage, people, cockpit, etc. Edited: I looked into this more deeply and found the following: https://aerospace-europe.eu/media/books/CEAS2015_211.pdf https://aerospace-europe.eu/media/books/CEAS2015_211.pdf It claims a total possible weight reduction on an A320 from 2155kg to 1560kg, or 600kg off the fuselage (plus an additional 150kg elsewhere for a total savings of 750kg). An A320 weighs 42,000kg empty and 78,000kg at takeoff. 2155kg is probably the weight of the fuselage frame sections containing the windows - makes sense that you could save 50% off that piece. That's a reduction of 1% or so off the takeoff weight. Also, note that cargo planes are already windowless. I couldn't find a good example of a plane that has both freight and passenger versions that are otherwise identical.
- ethagknight 8y ago
  Not to mention that their projection system will bring some weight and use energy, surly offsetting gains, so that whole sentence should be stricken from the article.
- kolinko 8y ago
  Well, it's not just the added weight of windows, but, I imagine, additional reinforcements for the structure that are needed when you have windows? (IANAPE - I'm not a plane expert :) )
  - WalterBright 8y ago
    You are correct. There's a forged doubler that goes around the window opening to reinforce it. The DeHaviland Comet lost several airplanes due to cracks starting from the windows; Boeing was having none of that.
    - tikhonj 8y ago
      Which is a real shame because that plane looked gorgeous, especially with square windows. It's always sad when physics gets in the way of aesthetics...
    - manigandham 8y ago
      A fantastic video about the De Havilland Comet from one of my favorite channels: https://www.youtube.com/watch?v=v0Cg2ZeYa5E https://www.youtube.com/watch?v=v0Cg2ZeYa5E
    - jacquesm 8y ago
      That was more due to the shape of the windows then due to the fact that it had windows. Square holes are not a good idea in aluminum that's under tensile stress. For the same reason you end a straight cut into metal in a round hole, otherwise you'll surely end up with a stress fracture.
      - WalterBright 8y ago
        The square corners were indeed a problem, but round windows wasn't enough. The doubler was added.
- dmurray 8y ago
  > It claims a total possible weight reduction on an A320 from 2155kg to 1560kg...An A320 weighs 42,000kg empty Does this seem odd? The fuselage only accounts for 5% of the empty weight of the plane. I checked your sources and that's what I see too, but it still sounds low. Where does the rest of the weight go? The engines weigh about 4600 kg total. Seats weigh 35 kg x 200 or about 7000 kg. That leaves 28,000 kg. Wings? Landing gear?
  - deleted 8y ago
    [deleted]
  - innocenat 8y ago
    Wings can easily take up 20-30% of total plane weight. Then there's a whole flight electronics and hydraulics, other interior (like ceiling, A/C), APU, tail, landing gears, etc.
    - dmurray 8y ago
      So wings could be as much as 14,000 kg (7 times the weight of the fuselage) and all those other bits total 14,000 together? I'm on a plane now and it's still hard to believe that each wing (without the engine) could be 3 times the weight of the body of the plane. But I guess it must be true. Thanks for the colour.
  - manigandham 8y ago
    That is the Operating Empty Weight: https://en.wikipedia.org/wiki/Operating_empty_weight https://en.wikipedia.org/wiki/Operating_empty_weight The operating empty weight (OEW) is the sum of the manufacturer's empty weight (MEW), standard items (SI), and operator items (OI). Basically the whole plane, interior outfit and crew needed for full operations, excluding the actual fuel and payload.
  - forapurpose 8y ago
    Fuel (all numbers approximate): An A320 carries around 25,000 L of fuel.[0] Jet fuel weighs ~0.81 kg/L (it varies by temperature).[1][2] 25,000 L * 0.81 kg/L = 20,250 kg = 44,550 lbs. [0] https://en.wikipedia.org/wiki/Airbus_A320_family https://en.wikipedia.org/wiki/Airbus_A320_family [1] https://en.wikipedia.org/wiki/Jet_fuel https://en.wikipedia.org/wiki/Jet_fuel [2] https://aviation.stackexchange.com/questions/48785/how-is-fuel-weight-calculated https://aviation.stackexchange.com/questions/48785/how-is-fu...
chejazi 8y ago
I imagine that's for the empty plane, and that passengers and luggage and fuel offset that % a fair amount.
- wavefunction 8y ago
  Any chance to reduce fuel consumption is a win.
  - leesalminen 8y ago
    Not necessarily. Another commenter on this subthread found that the weight savings equate to 1-3% of total take off weight (fuselage, engines, fuel, people, cargo). There is a safety benefit to having windows (inspecting in-flight damage to aircraft). Is 1% weight savings enough to remove a safety feature? I don’t know the answer, but it certainly isn’t a clear-cut win.
ravitation 8y ago
To be perfectly honest, this number sounds speculative at best (utter nonsense at worst). The fuselage is generally about 20-40% of the entire dry, empty weight of an aircraft (speaking strictly about large transport aircraft). So clearly seeing that kind of reduction in weight isn't really possible strictly from structurally modifying the fuselage (and even major modifications of the entire airframe). If we look at comparing planes with windows (like those operated by passenger airlines) to those without (like those operated by cargo airlines), loose estimates are less than 1% to around 1% weight savings from removing windows alone. Even if you assume massively increased returns on weight savings because of massive changes in airframe design it's probably no where near 50%... Keep in mind, even incredibly small weight reductions mean huge savings over the lifetime of an aircraft (especially if they are also carried out over an entire fleet).
mikec3010 8y ago
It's probably done using Hollywood accounting: 50% lighter for the specific oval region where there used to be glass. Probably only a 7% gain for the total fuselage. Also Windows play a role in emergencies: "that sides on fire, let's open the other escape door"
- paulcole 8y ago
  > Also Windows play a role in emergencies: "that sides on fire, let's open the other escape door" That seems extremely hypothetical and optimistic. If your large passenger plane is on fire you're probably already dead.
  - Declanomous 8y ago
    Windows actually are used for visual inspection in flight in a number of cases. You can actually see markings above certain rows where a pilot or a flight attendant could look out and inspect something. I think the types of things they would be looking for are flap deployment, icing, damage to the wing, gear deployment (though there is usually a window in the floor for this), etc. There's a great YouTube channel called Mentour Pilot that covers a lot of stuff like this, but I can't find his video that discusses visual inspections. https://www.youtube.com/channel/UCwpHKudUkP5tNgmMdexB3ow/featured https://www.youtube.com/channel/UCwpHKudUkP5tNgmMdexB3ow/fea...
  - matt4077 8y ago
    The emergency door exit instructions specifically mention checking for fire outside as one of the steps. It's also one of the requirements for starts and landings, along with "make sure your seat back and folding trays are in their full upright position".
    - paulcole 8y ago
      Yeah, I'm sure Emirates forget about this before considering a windowless plane. Or maybe there are other ways to check for fire?
- 8y ago

degenerate 8y ago

That is the biggest 'wow' in the article, and I'd really love to see a source on that... but they don't provide a source and I cannot find this info when googling. Anyone can back up that claim?

deleted 8y ago
[deleted]

cecilpl2 8y ago

I can't believe that's possible. I really want to know where that number came from. Maybe you could reduce the weight of just the frame of the fuselage by 50%, but I bet you'd save at most 2-3% of the total takeoff weight, once you include fuel, wings, tail, engines, gear, cabin, baggage, people, cockpit, etc. Edited: I looked into this more deeply and found the following: https://aerospace-europe.eu/media/books/CEAS2015_211.pdf https://aerospace-europe.eu/media/books/CEAS2015_211.pdf It claims a total possible weight reduction on an A320 from 2155kg to 1560kg, or 600kg off the fuselage (plus an additional 150kg elsewhere for a total savings of 750kg). An A320 weighs 42,000kg empty and 78,000kg at takeoff. 2155kg is probably the weight of the fuselage frame sections containing the windows - makes sense that you could save 50% off that piece. That's a reduction of 1% or so off the takeoff weight. Also, note that cargo planes are already windowless. I couldn't find a good example of a plane that has both freight and passenger versions that are otherwise identical.

ethagknight 8y ago
Not to mention that their projection system will bring some weight and use energy, surly offsetting gains, so that whole sentence should be stricken from the article.
kolinko 8y ago
Well, it's not just the added weight of windows, but, I imagine, additional reinforcements for the structure that are needed when you have windows? (IANAPE - I'm not a plane expert :) )
- WalterBright 8y ago
  You are correct. There's a forged doubler that goes around the window opening to reinforce it. The DeHaviland Comet lost several airplanes due to cracks starting from the windows; Boeing was having none of that.
  - tikhonj 8y ago
    Which is a real shame because that plane looked gorgeous, especially with square windows. It's always sad when physics gets in the way of aesthetics...
  - manigandham 8y ago
    A fantastic video about the De Havilland Comet from one of my favorite channels: https://www.youtube.com/watch?v=v0Cg2ZeYa5E https://www.youtube.com/watch?v=v0Cg2ZeYa5E
  - jacquesm 8y ago
    That was more due to the shape of the windows then due to the fact that it had windows. Square holes are not a good idea in aluminum that's under tensile stress. For the same reason you end a straight cut into metal in a round hole, otherwise you'll surely end up with a stress fracture.
    - WalterBright 8y ago
      The square corners were indeed a problem, but round windows wasn't enough. The doubler was added.
dmurray 8y ago
> It claims a total possible weight reduction on an A320 from 2155kg to 1560kg...An A320 weighs 42,000kg empty Does this seem odd? The fuselage only accounts for 5% of the empty weight of the plane. I checked your sources and that's what I see too, but it still sounds low. Where does the rest of the weight go? The engines weigh about 4600 kg total. Seats weigh 35 kg x 200 or about 7000 kg. That leaves 28,000 kg. Wings? Landing gear?
- deleted 8y ago
  [deleted]
- innocenat 8y ago
  Wings can easily take up 20-30% of total plane weight. Then there's a whole flight electronics and hydraulics, other interior (like ceiling, A/C), APU, tail, landing gears, etc.
  - dmurray 8y ago
    So wings could be as much as 14,000 kg (7 times the weight of the fuselage) and all those other bits total 14,000 together? I'm on a plane now and it's still hard to believe that each wing (without the engine) could be 3 times the weight of the body of the plane. But I guess it must be true. Thanks for the colour.
- manigandham 8y ago
  That is the Operating Empty Weight: https://en.wikipedia.org/wiki/Operating_empty_weight https://en.wikipedia.org/wiki/Operating_empty_weight The operating empty weight (OEW) is the sum of the manufacturer's empty weight (MEW), standard items (SI), and operator items (OI). Basically the whole plane, interior outfit and crew needed for full operations, excluding the actual fuel and payload.
- forapurpose 8y ago
  Fuel (all numbers approximate): An A320 carries around 25,000 L of fuel.[0] Jet fuel weighs ~0.81 kg/L (it varies by temperature).[1][2] 25,000 L * 0.81 kg/L = 20,250 kg = 44,550 lbs. [0] https://en.wikipedia.org/wiki/Airbus_A320_family https://en.wikipedia.org/wiki/Airbus_A320_family [1] https://en.wikipedia.org/wiki/Jet_fuel https://en.wikipedia.org/wiki/Jet_fuel [2] https://aviation.stackexchange.com/questions/48785/how-is-fuel-weight-calculated https://aviation.stackexchange.com/questions/48785/how-is-fu...

chejazi 8y ago

I imagine that's for the empty plane, and that passengers and luggage and fuel offset that % a fair amount.

wavefunction 8y ago
Any chance to reduce fuel consumption is a win.
- leesalminen 8y ago
  Not necessarily. Another commenter on this subthread found that the weight savings equate to 1-3% of total take off weight (fuselage, engines, fuel, people, cargo). There is a safety benefit to having windows (inspecting in-flight damage to aircraft). Is 1% weight savings enough to remove a safety feature? I don’t know the answer, but it certainly isn’t a clear-cut win.

ravitation 8y ago

To be perfectly honest, this number sounds speculative at best (utter nonsense at worst). The fuselage is generally about 20-40% of the entire dry, empty weight of an aircraft (speaking strictly about large transport aircraft). So clearly seeing that kind of reduction in weight isn't really possible strictly from structurally modifying the fuselage (and even major modifications of the entire airframe). If we look at comparing planes with windows (like those operated by passenger airlines) to those without (like those operated by cargo airlines), loose estimates are less than 1% to around 1% weight savings from removing windows alone. Even if you assume massively increased returns on weight savings because of massive changes in airframe design it's probably no where near 50%... Keep in mind, even incredibly small weight reductions mean huge savings over the lifetime of an aircraft (especially if they are also carried out over an entire fleet).

mikec3010 8y ago

It's probably done using Hollywood accounting: 50% lighter for the specific oval region where there used to be glass. Probably only a 7% gain for the total fuselage. Also Windows play a role in emergencies: "that sides on fire, let's open the other escape door"

paulcole 8y ago
> Also Windows play a role in emergencies: "that sides on fire, let's open the other escape door" That seems extremely hypothetical and optimistic. If your large passenger plane is on fire you're probably already dead.
- Declanomous 8y ago
  Windows actually are used for visual inspection in flight in a number of cases. You can actually see markings above certain rows where a pilot or a flight attendant could look out and inspect something. I think the types of things they would be looking for are flap deployment, icing, damage to the wing, gear deployment (though there is usually a window in the floor for this), etc. There's a great YouTube channel called Mentour Pilot that covers a lot of stuff like this, but I can't find his video that discusses visual inspections. https://www.youtube.com/channel/UCwpHKudUkP5tNgmMdexB3ow/featured https://www.youtube.com/channel/UCwpHKudUkP5tNgmMdexB3ow/fea...
- matt4077 8y ago
  The emergency door exit instructions specifically mention checking for fire outside as one of the steps. It's also one of the requirements for starts and landings, along with "make sure your seat back and folding trays are in their full upright position".
  - paulcole 8y ago
    Yeah, I'm sure Emirates forget about this before considering a windowless plane. Or maybe there are other ways to check for fire?
8y ago