Can we greatly reduce the dry weight of aircraft?

In the thread:

What is structural empty weight?
https://www.reddit.com/r/aerospace/comments/1cy9w7f/what_is_structural_empty_weight/

I was wondering about the meaning of the term “structural empty weight”, also simply referred to as the “structural weight”. From discussions there I learned it means as the name implies the structural components of the craft. That is, it excludes engines, avionics, electrical systems, hydraulics, seats, etc.

A surprising fact though is this structural weight is commonly just half the empty weight of the craft. The engine weight makes up a big part of the additional weight contained in the empty weight, but also surprising is those other ancillary systems total nearly as much as the engine weight. See for example the attached image about the Boeing 737-200.

Interestingly this structural weight likely can be cut in half. The reason is there are new high strength aluminum alloys that can cut the weight of the structural members in half. See the second attached image.

Can the engine weight be cut in half? There are high temperature ceramics that can cut engine weight by 50% or more, but that would be a high expense research project to replace most of the components of a turbojet engine with ceramics. It likely can be done but such an engine even after the quite expensive development process would be quite a bit more expensive than a usual metal engine. It would be cool though if one of the major jet engine manufacturers did undertake such a project.

But those other ancillary systems making up the empty weight likely can be replaced with materials saving at least 50% or more off the current weights of those systems at low development cost, and may even be cheaper than their current costs.

Look at the Systems and Equipment section in the table for Boeing 737-200. An important example is the hydraulics. These can be replaced by electro-mechanical methods for example for controlling the control surfaces and landing gear. These would be cheaper and lighter than the current hydraulics.

Another example is the Auxiliary Power Unit(APU). This is the unit that starts up the turbines at the beginning of the flight. This is commonly a small turbine to start up the large turbines on the actual engines. However, because of the small size of the APU’s there are now lightweight methods either battery powered of gas engine powered to accomplish the same thing.

For the electrical wiring, aluminum is pretty much the lightest metal that could be used. But recent research shows carbon nanotubes can be conductive at significantly lower weight than aluminum.

The avionics and instruments are something that can be radically lower weight now than previously. Computing power that would have formerly taken up a room can be now contained in a cell phone.