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I see a lot of talk of the use of composite structures here. Composites have been used for years, and is a fairly mature technology. That they’re going to be 50% (by weight) of the 787 is a major step up, but Boeing sees it as an evolutionary step.

What isn’t being talked about much, but is revolutionary IMO, is the fact that the 787 is basically an “electric jet”. Traditionally, just about everything on an airliner is powered by engine bleed air—vast amounts of ~70 PSI 350 deg+ air pulled from whatever stage of the engine’s compressor. This air is directed all over the plane in what’s known as the pneumatic system. This air is not available to propel the aircraft.

The 787 is doing away with almost all that, and is switching to electrical powered devices. This is no small task, as evidenced by the 787 having over twice the electrical generating capacity of the much-larger A380. I saw some numbers in Aviation Week magazine and was astounded to read it takes several hundred horsepower to simply pressurize the aircraft at cruise. Boeing feels pneumatic technology (not very efficient and over 50 years old) has progressed as far as it will go, but electrical technology (motors, motor controllers, etc) have plenty of room to evolve in size, weight and efficiency.

While the B787 and the A350 will use the same engine cores and technology, the 350 will use traditional bleed air while the 787’s engines will have huge, 500+ KVA generators on them. Anyways, something to chew on.

"The 787 is doing away with almost all that, and is switching to electrical powered devices."

That's news to me.

I haven't run the numbers, but it would seem that using bleed air from the efficient compressor stage of an engine would be much lighter in weight, simpler and much more reliable than adding a several hundred horsepower electric air compressor that the ship has to lug around all its life. Mechanical work still has to be done, so it gets robbed from the engine in some way, no matter what particular system gets used.

The engine is already a very efficient air compressor, so why not use it, rather than increase the load on the spindle shaft and require more shaft energy from the engine to run a larger, heavier generator, to run a several hundred horsepower electric motor, (more added weight) to run another air compressor (still more added weight) for cabin pressurization?

Something tells me that good ol' Boeing may have bitten off more than it can chew with this new 787.