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Reducing weight of aircraft has become a priority as the aviation industry seeks greater fuel efficiency and commits to strict emissions targets. How much weight has been cut from single and twin aisle aircraft in last 10 yrs and where? How much further can OEM's and suppliers cut weight in the next 10 years and in what components/equipment/furnishings will the greatest savings be made? I am looking for some fun and relevant facts on this subject for an article I am writing.

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    $\begingroup$ Losing flight engineers saved about 300 kgs. 50 kgs for the seat, 50 kgs for the flight bag, the rest for the wetware talking ballast, coffee and meals ;) $\endgroup$ – Simon Oct 31 '16 at 15:59
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Perhaps the biggest weight reduction in aircraft across the board has been the use of composite materials over aluminum. This extends from small GA aircraft all the way up through airliners like Boeing Dreamliner. In the retro fit game, some older planes have been certified to take newer composite propellers. Even small savings matter according to this article

LED modules give on average a 40% weight saving over the incandescent modules they are replacing, which improves fuel economy

Glass cockpits and modern computerized avionics tend to weigh less and offer more than their earlier steam gauge counter parts. Even in the space shuttle.

The system also provides greater backup capability, weighs less and uses less power than the original design.

Another thing that has made a fair dent in take off weight is how fuel efficient engines have gotten. While there is a practical limit to this as engines have gotten more efficient the need to carry fuel has dropped or planes can go farther on the same fuel. In a similar vein as weather planning/predicting has gotten better fuel loads (while still in compliance with FAA reserve regulations) may be slightly lighter as they can now be more precisely calculated.

The one thing that has gotten heaver is the passengers...

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  • $\begingroup$ This, of course, only is feasible as manufacturers manage to wring the additional difficulties and added costs of manufacturing parts from composites (which have been VERY problematic in the industry - see the 787 and the ill-fated Lear 85). $\endgroup$ – Carlo Felicione Oct 31 '16 at 17:26
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Besides the use of composite materials, another weight reduction technique has come from creating lighter weight electrical wiring and cables used throughout the plane and by reducing the amount of wire needed overall.

This has been addressed in several different manners.

  1. Reduce the overall weight of wire and cable per foot by developing wire that uses light weight materials or that can withstand higher temperatures so that less insulator or conductor is needed. The Shrinking Size of the Cable
  2. Design electrical, flight, and data systems that require less wiring in the first place. By reducing the amount of wire needed, the overall weight can be reduced significantly. One example is Avionics Full-Duplex (AFDX), which is used to replace ARINC 429 data networks on large aircraft. AFDX requires less wiring than ARINC 429, thereby reducing the overall wire weight.
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I know what I'll say is not exactly what was asked, but I found very interesting in the same way :-)

If you look at GE jet engine's technology you will probably get impressed with its details. Especially the carbon fiber composite material is something that allows GE to make fan blades longer and thinner. Look at: http://www.gereports.com/the-art-of-engineering-the-worlds-largest-jet-engine-shows-off-composite-curves/

I've tried to extract some relevant content, and here it's:

Nick Kray works as a consulting engineer for composite design at GE Aviation. In the 1990s, he was part of a GE high-stakes gambit to make the front fan of its largest jet engine from epoxy and carbon fibers.

The blades from the material, called carbon-fiber composite, allowed GE’s aerospace engineers to design the GE90, still the world’s largest and most powerful jet engine. It’s also GE Aviation’s most profitable machine. “Our competitors make jet engine fans from titanium and steel and even some of our own people weren’t initially so hot about using composites,” Kray says. “Nobody had tried this before.”

The material allowed GE engineers to design blades that result in lighter and more efficient engines, allowing airlines to save fuel by shedding precious pounds.
Now Kray and his team are busy building the future. They are working on a fourth generation of the blade for the GE9X, GE’s largest engine yet, designed exclusively for Boeing’s next-generation wide-body jet, the 777X.

The blades will feature several new components, Kray says. They will use stiffer carbon fibers so GE can make them longer and thinner. Their trailing edge will be made from a special structural glass fiber composite that can better absorb impact energy.

Where the GE90 has 22 blades and the GEnx holds 18, the GE9X will have only 16, even though it is the largest of the three. Besides making the engine lighter, the fewer and thinner blades will also spin faster.

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  • $\begingroup$ GE is an OEM/supplier, so I think reducing weight in an engine applies. Assuming, of course, that the CF blades are lighter than traditional ones. $\endgroup$ – FreeMan Oct 31 '16 at 20:13
  • $\begingroup$ I think now it's better @J.Hougaard. What di $\endgroup$ – Ricardo Biehl Pasquali Oct 31 '16 at 22:56
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    $\begingroup$ * What do you think? $\endgroup$ – Ricardo Biehl Pasquali Oct 31 '16 at 22:57
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There are several measures that I can think of. I'm sure some of them only save weight as a side-effect, rather than that being the main driver for the change.

  • Switch to composite materials. This has definitely been driven by weight-saving. Building the wings and fuselage of lighter materials makes everything cheaper.
  • New seat designs. There are new slimmer seats, mostly in short-haul aircraft. The seats are much smaller, and quite a bit lighter. This is probably driven more by the ability to add more rows and still maintain decent pitch, but is also a weight saving measure.
  • Wireless and BYOD entertainment systems. Again, mostly short-haul. I've had aircraft with no entertainment at all, or with bring-your-own-device wifi systems. These save the weight of the devices, and especially of the wiring.
  • Toilet design. This is mostly for the weight of the systems themselves these days, though it also saves the weight of the water. I think a lot of the changes to these designs were actually safety and comfort related, though.

It is possible, that all of these changes are outdone by change in engine design and aerodynamics (winglets/sharklets), which reduce drag and save the weight of carrying more fuel on board, though I don't have data.

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The other answers to this question are all true, good and relevant. However, there are two important things that have not been mentioned so far.

One is that aircraft parts, especially critical parts such as wing spars, are less and less over-engineered than they used to be.

In the absence of more precise knowledge about the load-bearing, bending and other limits of important structures, aeronautical engineers would calculate for very large safety margins, making those structures much stronger and resilient (and heavier) than they would ever need to be.

Better understanding of the limits - knowing more about how and when structures will fail - has allowed those safety margins to be reduced safely, making the structures lighter.

Note that reducing safety margins doesn't necessarily mean making something less safe. A huge safety margin in wing design that allows a wing to withstand forces that would damage other critical parts or kill every person on board doesn't actually mean improved safety. Past a certain point, it just means increased weight.

And, reducing unnecessary weight allows more scope for improvements in other areas that in turn could improve safety.

Secondly, new computer-aided design techniques have begun to come up with and explore designs that no human could or would, based on mathematical modelling and simulations that produce unexpected results.

For example, some techniques have produced designs in which material is cut away (from, say, a cylinder or beam) in patterns that appear to be random. For the same strength/rigidity/resistance to failure, the part can be made very substantially lighter.

Both of these trends will doubtless continue, and because they can apply equally to well to structures like wings and tray-tables, they're going to have implications for all aspects of the design and engineering of aircraft.

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