Pondering the Characteristics of Composites in the 787

We’ve all heard about how awesome the new 787 is going to be, but that doesn’t mean there aren’t still some risks to this program. Being the first composite-fuselage airliner means that there are some unknowns and we’re likely only to find all of those out once they become a problem, despite all of the testing that’s out there. At least we can check one thing off the list, as reported by the Seattle Times this past weekend.

If you’re like me, you look to Jon Ostrower for all things Boeing (and Airbus, for that matter). So when he put out a link to an article entitled “How will 787’s new materials fare in a crash landing?” and called it a must-read, I listened.

Comet and 787 Talk

In the article Dominic Gates explains a a huge problem that Boeing found in computer simulations back in 2005. In effect, an accident that might be survivable in a 777 would likely kill everyone on board the 787, as designed at the time.

There’s no question that composite materials act differently than metal. Instead of bending, they shatter. So while a 777 performing its best imitation of a belly flop would see its fuselage crumple, the passenger floor would stay intact. In addition, passengers would face 15g’s at the peak of the deceleration. Up to 20g’s is survivable.

The 787 as designed in 2005, however, would shatter and the floor would cave-in. In addition, people would face a deadly 25g’s of force. That ain’t good.

Of course, this is all just in a computer simulation, but the threat was real. Boeing has changed the design and addressed the issue to the point where they say it should be just as safe in the 787 as it is in the 777, but what else do we not know?

They’re obviously not going to go crashing a few airplanes to find out everything that could go wrong. That’s way to expensive, even if you could do it without people onboard. So they’ll keep doing computer simulations and hope that can accurately depict how composites will behave.

Sure, composites have been in use for a long time as fuselage, but primarily only in military aircraft which face much fewer cycles and different types of usage. It’s a different animal.

Maybe I’m just paranoid. You can call it “Comet-itis.” Back in the early days of pressurized travel, the de Havilland Comet came to the forefront as the first commercially viable jet. Unfortunately, soon after it went into service, planes started falling out of the sky. It took them awhile before they realized that the square windows were creating stress cracks in the skin, and each accident was caused by explosive depressurization and instant death.

Eventually, they switched to oval windows and strengthened the skin, but this all came about because they didn’t fully understand how the metal would react under constant pressurizing and unpressurizing.

There’s no question that the testing is more extensive for the 787 and the use of computers will help tremendously, but I always find myself wondering what we don’t know that we’ll only find out when the airplane goes into service. I’m not afraid, but I am keeping my fingers crossed.

[Original photos via Boeing and RushAS]

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