If you take a long international flight 10 years from now, there's a good chance the airliner carrying you will be made as much out of plastic as metal.
But not just any plastic. Tomorrow's airliners will make extensive use of advanced carbon-fiber composite materials, much stronger and lighter than the aluminum parts they replace.
The entire fuselage skin of Boeing's new 787 twin-engined widebody jet, due to enter service in 2008, will consist of composites. The skin and spars of the 787's wings are made of composite material too, though the ribs that shape and stiffen the wing from front to back are aluminum.
"We looked at how every part of the aircraft was [stress] loaded, and we chose the right part for every given application," said Tom Cogan, chief project engineer on the Boeing 787. For instance, Boeing used titanium for the large fittings joining the 787's wings to its fuselage, because "it's very light and it does very well in a highly loaded situation."
Today's airliners make use of composite materials, but not to the degree that the 787 and its future rival the Airbus A350 XWB will. Composite materials make up "roughly 50 percent" of the 787, said Cogan. The A350 XWB, which won't enter service until 2013, will be more than 60 percent composite.
Airbus was the first manufacturer to use composite materials for load-bearing parts and flight control surfaces in airliners, but Boeing chose to use composites for the 777's floor beams when designing the big twinjet in the 1990s.
Composite materials confer several major design advantages. Apart from being very light and very strong, they don't corrode and they aren't subject to metal fatigue.
The earliest-built 777s have recently undergone their first "heavy checks" — major structural inspections during which the aircraft essentially were taken apart, examined extremely thoroughly and rebuilt — and their floor beams were "pristine," said Cogan. "We haven't sold a single spare floor beam."
This is great news for airlines. In the course of normal operations their jets are subject to extremes of heat and cold and — particularly on transoceanic flights — fly for long periods in moist, salt-laden, corrosive air.
Employing composites to a greater degree will make airliners more reliable, letting airlines fly them more while keeping maintenance costs down. It will also make airliners lighter, reducing fuel costs and allowing them to carry more passengers and cargo — or fly longer distances — at their maximum takeoff weights.
Tomorrow's largely composite airliners also will improve the flying experience for passengers.
Making airliner fuselages out of composites banishes the fear of metal fatigue and corrosion that has constrained designers until now. Passenger-cabin air can be moister and kept at higher pressure, so passengers feel less dehydrated and don't find themselves gasping for breath.
Breathing in today's jets is like breathing at the top of an 8,500-foot mountain. But the 787 will have a 6,000-foot cabin altitude, making it much easier to breathe.
Passenger windows can be much larger, too. Each 787 window is some 30 percent bigger than today's cabin windows and window-height difference is particularly noticeable. The 787's windows will extend above seatback height, so passengers sitting between the aisles can look across and see outside.
"We like to say every seat is a window seat," said Cogan.
Building on these advantages, Boeing has adopted other technologies to make passengers feel comfortable on 787s.
It is using LED lighting to create a cabin lighting environment that can vary with the time of day from a restful pastel-colored glow at dawn and dusk to brighter daytime lighting and a subdued midnight-blue shade in late evening.
Additionally, not only does the 787 cabin environmental control system employ HEPA filters to keep the air free of particles as small as viruses, but Boeing also has incorporated a gaseous air purification system to scrub out even smaller molecules, to keep the air aroma-free.
"Actually, the air onboard will be cleaner than the outside air," said Cogan.
Since outside air at high altitude is very dry but people generate humidity, Boeing 787 pilots will tell the aircraft's computers how many people are on board and the computers will manage cabin humidity levels by drawing in greater or lesser amounts of air from outside. The 787 won't need cabin humidifiers.
Passengers won't notice all the advanced technologies used in the 787 and the A350 XWB. But one they will notice is the use of dynamic load alleviation to reduce gust forces.
Sensors in the aircraft's nose will sense lateral and vertical wind gusts as it begins to encounter them, allowing its flight computers instantly to move the aircraft's flight control surfaces to reduce the loads. This means the aircraft can have a lighter design structure — but more importantly for passengers, the flight will feel less bumpy.