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]

18 Responses to Pondering the Characteristics of Composites in the 787

  1. DGS says:

    The 787 will be a smashing success, one way or another…

  2. Didn’t they make some models of both type materials and drop them off the roof of a building to see what happens?

    I await the day the first A380 crashes to see what happens to the 300 people on the main deck when 300 other people come crashing down on their heads.

    • Oliver says:

      Well, what happens to the people in the front part of a 747 when it crashes?

      (I guess another reason why I love flying on the upper deck)

    • james says:

      David SF I’d be more concerned with the grand piano in the lounge and the balls and pins in the bowling alley becoming deadly projectiles.

      I read that all 380s have those. And hot tubs.

  3. Brett, military aircraft may have fewer cycles. But I’d bet they endure harder landings much more routinely and go through flights with much more stressful maneuvering. Surely there’s something to be learned there. And Boeing realizes that a catastrophic failure of a 787 or three due to its manufacturing processes could at best send the company’s stock plummeting, not to mention a whole slew of lawsuits. Could some of this not be a repeat of the usual hand-wringing that accompanies something innovative?

    • True about military aircraft being used more/rougher/etc, but they are really compacted and every inch of space is used. The 787 is still a hollow tube with big areas of no support so maybe that could make a difference.

    • CF says:

      I think that any time you do something new, there’s always a risk. That doesn’t mean you shouldn’t take it. It just means it’s there.

  4. A says:

    Cranky I think you’re being a little hard on Boeing here. We’ll never progress anywhere without taking some risks. Imagine the first ever manned space flights, or first apollo or shuttle flight. Some things are worth the risks of using untested equipment, materials, etc. Even if a 787 is lost early on it can still go on to prove itself as a very safe and reliable aircraft. Just look at DC-10 history.

    • You mention the DC-10 history and yes they had issues in the beginning, but my only DC10 trip (r/t LAX-HNL-LAX on AA) in the mid-1990′s I still didn’t like the idea of being on a DC10. Even the years I worked for TWA people would ask “you don’t fly DC10′s do you”. So a problem early on could effect how people feel about the plane even years latter. So they need to get it right in the beginning.

    • CF says:

      I don’t see how I’m being harsh on Boeing here. I’m not suggesting they’re doing anything wrong at all. I’m just saying there’s a risk when you do something new. That doesn’t mean they shouldn’t do it. It just means there’s a risk. I love what Boeing is doing with this airplane.

  5. matt weber says:

    While it is true we don’t have the century of experience in composite airframes that we have with aluminium, I am compelled to point out that there are some very signficant difference between the military aircraft utilizing composite materials and the 787. In addition we now have about 25 years experienced with composite parts on some airframes (like the A300/A310/A320 composite fin). There aren’t a lot of airplanes that operate in commercial service for more than 25 years.

    What makes the 787 a lot different is that there are strain gauges actually embeded in the composite structures. What that means is that structural loads that exceed the design specifications are likely to be detected long before they result in failure.

    Brett is correct however in pointing out that composites generally don’t fail gracefully. It usually takes a lot more force to damage them, but they don’t simply deform, they do indeed tend to shatter. In fact that is probably one of the reasons the 787 wing tests were not take to the point of failure. Nobody wanted to have to deal with the mess…

  6. Ed Casper says:

    There are risks to every new aircraft, but I, along with you, believe we can anticipate these risks better than ever before through the experience gained over the years, advanced technologies and virtual testing. The Comets had to fall out of the sky. At least now, fewer aircraft have to do so because we have the capability to better anticipate problems. DC-10 incidents taught the aviation world about metal fatigue, a phenomenon unknown before those accidents occurred. We are now aware of metal fatigue and the behavior of materials under stress in ways unknown to us only a few years ago. While there are inevitable risks, they are probably far fewer now than they were at the dawn of the jet age 45+ years ago (that I vividly remember, by the way). Even so, we must never stop being prudent and cautious.

  7. amicus says:

    If you read the attached PDF attachments to the Seattle Times in depth,(most of which we written by me), the key issues for myself are rupturing, opening and compromising of the fuselage as usually happens in survivable crashes and the flammability of epoxies as used on 787 and as proved in the B-2A Guam crash in 2008 and the resulting FST ingress into the cabin impeding and preventing passenger egress.

  8. Doug says:

    I used to work for both Pacific Southwest Airlines and Delta Airlines. I was a flight attendant and in flight operations respectively. One thing I used to hear repeatedly from Pilots and mechanics was; ” If it’s not Boeing I’m not going “.

  9. I’ve been comparing the 787 to the Comet for a while now over at the PCDU Commentaries blog (http://blog.planecrazydownunder.com/2010/05/18/boeing-787-vs-de-haviland-comet-will-history-repeat/). I have some serious concerns about Boeing’s reliance on simulations to show that all is well, given their track record of not finding all the problems (wing box problem, tail problem, etc).

    As Ben Sandilands has pointed out on the Plane Talking blog (http://blogs.crikey.com.au/planetalking/2010/07/23/787-short-cuts-dont-add-up-for-jetstar/), Boeing are using simulations to show that the 787 can meet evacuation standards.

    Boeing’s apparent over-reliance on simulation is leading to concerns that the 787 may not live up to its reputation, on both commercial and safety fronts. I want to see evacuation standards proven by live demonstrations (with the maximum number of people that customer airlines will squeeze into it). I want to see demonstrated crash survivability as this is a set of major new technologies in a commercial environment.

    The aviation world has managed to carry more people in far greater safety than ever before thanks to a cautious approach to new technology. Certainly it should be embraced and used where possible, but lets also do all we can to verify we’re not creating another Comet. After all, most commercial airliners are used for far more than 25 years (707s, DC8s, etc).

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