Raytheon Plans Carbon-Fiber Commercial Plane

dlkf writes: "CNN has an article that talks about Raytheon Aircraft's plans for a new business jet. They intend to make the fuselage out of molded carbon-fiber instead of aluminum. Thats the same stuff used in tennis racquets, golf clubs and some military aircraft. This should make the fuselage 30% lighter, reduce the cost of the plane by 25% and use less than half the parts of its traditional aluminum counterparts."

Comments

Re:Invisble to radar?

[Zachary Kessin]

Very few, for 1 thing it will have a transponder, which is what ATC really cares about. When a plane is painted by ATC the transponder sends back a code which ATC gave you and your alititude. That way they know who you are and where you are going (Assuming you are IFR or working with ATC) and can keep you away from other aircraft.

Ofcourse the other thing is that it was not desinged for stealth.

Carbon fiber unproven?

[PD]

Raytheon's competitors say they are sticking with metal airframes because carbon fiber is unproven. Excuse me? Carbon fiber has properties that are well known. It's superior in many ways to metal airframes. I'm making a guess here, but perhaps the business jet market is a wee bit too conservative for their own good. Perhaps it was the highly visible market failure of the Beechcraft Starship. But saying that carbon fiber is unproven implies that the technology is unproven, which is untrue. The problem seems to lie with the marketers and salesman who are afraid of change.

Re:Carbon fiber unproven?

[RareHeintz]

I'm making a guess here, but perhaps the business jet market is a wee bit too conservative for their own good.

Well, given that on any normal flight you're transporting between 10 and 400 human lives, yeah, I can see where they'd be conservative. Between that and related regulatory issues, this is one field where conservatism pays more than technofetishist neophilism. I doubt that it's just the marketers and salesmen who are afraid of change - I'm willing to bet that the engineers are of a conservative bent as well.

And truthfully, I don't mind that a bit - I like having some assurance that I'll leave an airplane alive. OTOH, your point about the technology being proven is well-taken. The fact that the military uses carbon fiber plane parts regularly - the military being a pretty conservative technology consumer who puts a high value on durability and zero failure - ought to provide commerical aircraft manufacturers with some encouragement.

OK,
- B
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Re:also used as...

[scheme]

Actually I think the really nice bikes are titanium like the litespeed bikes or scandium for ultrahighedn

Re:Invisble to radar?

[MrNixon]

As I understand it, civilian radar systems don't rely on active radar as much as military systems do. Most of it is accomplished through passive radar systems (like recieving a transponder transmission from the planes...). In addition, the airframes in civilian aircraft aren't designed with minimizing radar profile in mind - so there shouldn't be too much of a problem.

bye bye faraday cage

[panZ]

This should make the fuselage 30% lighter, reduce the cost of the plane by 25% and use less than half the parts of its traditional aluminum counterparts."

...and make lightning strikes 95% more dangerous to the aircraft. W/O a conductive cage holding the meat puppets and electronics inside, an electrical storm would rip right through one of these instead of traveling around the outside leaving a big smoldering hole and a bunch of disappointed commercial passengers. Lets hope they have the good sence to use a hybrid matrix of conductive metals and carbon fibers.

Re:bye bye faraday cage

[selectspec]

They thought of that. The material contains a layer of fabric woven from metal filaments to provide lightning protection.

From an engineering standpoint

[arete]

There's enough info out there for them to work with, so if they do their jobs right, it'll be no problem. But they have harder jobs than just repeating what's been done before.

In a novel building design, you usually see a factor of safety of 2 or 3 - sometimes more for parts with particularly bad failure modes. That means if everything was up to spec you could at least double or triple the loading. Sometimes this number is more like 5. For code-based building, like in a normal frame house, it's even higher, because they basically assume that a lot of the joints will be poorly made.

For aircraft it's often 1.2 or 1.3. Scary, huh?

But it gets worse - because even the metals (which start out tough, instead of brittle, so a crack doesn't propagate quickly) usually embrittle before long. Oh, and the average aircraft is held together with 1 ton of glue.

just more info :)

Failure modes and also not as gentle as metals

[Totally_Lost]

stress this stuff and it is almost certain to come apart. Many aircraft metals handle over stressing much more gracefully.

Re:Failure modes and also not as gentle as metals

[morcheeba]

Oh, you mean like when you bend a paperclip too many times?

No, just kidding. You're right-- they design them so that no parts become dislodged (safety wires hold most/all nuts) and the screws elongate rather than crack off.

Invisble to radar?

[Pembers]

I notice the article says that carbon fibre is what makes "stealth" aircraft invisible (or at least, less visible) to radar. What implications would it have for air traffic control if commercial aircraft were like this? Would the bottom of the plane have to be made of metal, just so the radar would have something to reflect from?

Re:Invisble to radar?

[morcheeba]

As I understand it, the transponders do most of the actual identification-- they return the plane's ID and altitude, and without a transponder, the radar's range is limited.

The solution that some hang glider pilots use (and, for that matter, many boaters), is use a radar corner reflector -- pretty effective. And, since the radar is relatively high frequency, the reflector doesn't have to be that big.

Re:Invisble to radar?

[mangopaw]

I suspect the answer is very little, given that most commercial aircraft radiate a signal informing air traffic control who they are (identify friend foe(?) - iff in military jargon).

Re:Invisble to radar?

[BigBir3d]

Remember, radar works on the principle of detecting a moving body, or "bubble" of air, basically. The cfc body in of itself does not reduce the radar cross section drastically. That is dependant on the internal design of the airframe and wings. checck this out for some basic info.

Planes, Pillows, and things that aren't pillows.

[Kibo]

Carbon fiber is not magic. It is carbon fiber, embeded in a matrix of well basically plastic. As such it has certain advantages over aluminum, and certain severe disadvantages. Strength was mentioned specifically. But there are many other variables in consideration: Specific strength, toughness, corrosion resistance (coffee, water, salt water, fretting, microbial, hydralic fluids, different materials mated to it), resistance to UV light, fatigue (both from pressure, load, and thermal varations), and then there is the expence of raw materials and ease of manufacture. Well to think that aluminum will not come out ahead on a least some of the elements in this incomplete list is naive at best.

Why aluminum is one of the weakest materials in common use. One might think, from reading many of these posts, that we should have abandoned it shortly after the bronze age. Even steel, for all its commercials, is quite weak given the alternatives, as long as we're sticking to a single design criteria. Why even lowly glass is much stronger than steel and even exhibits good corrosion resistance. Why don't we make everything out of glass? It's stronger. Ahhh. But glass is brittle, low toughness. So it's VERY dificult to control and predict failure. That's why metals are great. You don't have to think real hard. Their flaws are predictable, they tolerate large cracks (multi foot long cracks are not uncommon in airframes), they're easy to manufacture (for the most part, extreamly easy in the case of aluminum), and by in large metals are cheap (to name a few qualities).

Raytheon is wise to proceed with challenges that are managable. A small airframe is much simpler than a large one. The other nice thing about buisness jets is, in addition to being less complicated, they have higher margins. Even better for Raytheon, they'll be able to charge a premium for their offering because it will be much cheaper to operate, practically sipping fuel in a time of swiftly increasing fuel costs. I can practically guarantee that Raytheon will probably loose money on every plane for something like the first 6 months. It took something like a year for Boeing to bring the all composite tail of the 777 into the profitable range. What was Boeing going to make the tail for the 777 out of if the composites didn't work out? Aluminum.

Another thing to consider is that composites are much more difficult to repair, but this increased cost of ownership is almost always offset by the reduction in fuel consumption.

That said, its all about the right tool for the right job. If I were to espouse the use of hammers in microsurgury, they would certainly be considered unproven in that circumstance, and I might be a crackpot. No one has made an all composite airframe for a mass produced business jet at a profit. I would call that unproven. It doesn't mean you can't make a nice wing spar, a golf club, or even a bridge. Just means Raytheon is gunning to be the first in this respect.

To that end, kudos to Raytheon. Buy their stock. I think its a good do-able plan. Sure they'll have some challenges; I bet they'll solve the problems that come up. And in the process they'll learn a little something, pass that on, and the sum of our knowledge grows. Even if they fail, we'll win. And who doesn't love that?

So prove it

[Spamalamadingdong]

The nice thing about carbon fiber is that it's as strong as steel and only about a third of the weight. If Raytheon wanted to, they could just over-build their first designs to make abso-freaking-lutely certain that it wasn't going to break, and they would still have a lighter and smoother product than the competition. Lighter = more of the total weight can be payload and fuel, giving longer range and/or more payback. Smoother = less drag, less power and fuel required to push it through the air, saving money. Every way you look at it, isn't it a win?
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Re:So prove it

[GreyOrange]

Also this stuff doesn't have to worry about the varieties of aluminum eating fungus that recently have been found. Now they have to worry about the inner enviroments of these things for weirder types of organisms that like to break down carbon based structers.

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also used as...

[spacefem]

You forgot bicycles. Top of the line road bikes are commonly made from carbon fiber these days, as are some mountain bikes (but not many). There are durability problems, professional cyclists tend to go through bikes like they're free (well, to those guys, they are) but for most serious bikers they're worth it. I can see this being the same way, I'm sure the savings in weight will make up for the initial cost eventually.

And of course, we all have to admit it looks very cool.

Composites

[return 42]

I used to read a fair amount about aviation and I seem to recall that a lot of kitplanes are made with composites. Not much carbon fiber, that's expensive, but generally a foam core (light and space-filling) covered with various resins (stiff). You end up with a very light, strong airframe that beats the hell out of conventional metal designs. That's how the Rutans circumnavigated the globe on one tank of gas.

Thing is, kitplane designers and builders do this sort of thing out of love. They're basically the hackers and overclockers of the aviation world. The general aviation companies are scared silly of liability, which is only sensible in today's climate, and they also don't dare risk their shareholder's money on anything that doesn't have a twenty year track record. So you end up with a situation much like computing before GNU/Linux: commercial products with mediocre performance and exciting projects that no one wants to invest big money in.

I don't know what will happen to break the logjam, but it will be very interesting when it happens.

The problem is not structural, it's thermal

[thirdrock]

Most of the resins used in Carbon Fibre Composites are not thermosetting, they are thermoplastic.

Some cfc's have been made that can resist temperatures up to 600deg.far, but they are much more expensive than the cfc's that are used in race-cars, yachts, bicycles etc.

A modern commercial jet travels an speeds in excess of 600mph (I cant remember the top speed of 747), which creates a high surface temperature on the skin of the aircraft due to the air resistance. The U2, which flew at 60,000ft where it's very cold and the air is very thin, still needed to use titanium instead of aluminium because of the heat generated by air resistance.

The structural quantities of cfc's are well known, but the thermal qualities, and the effect of temperature on structural qualities are largely un-tested.