In this day and age with CNC machining, how are airplane parts still ridiculously expensive?

Even with CNC, which I'm sure Textron uses extensively, you're not going to save much on 143 parts per year. They make sense when volumes are involved. Anyway, if they already have the molds for the castings, it's cheaper to keep doing that. Machining landing gear wheels from bar stock, for instance, involves enormous waste of expensive metal, and removing that metal takes time, too. So they cast or forge the wheel and CNC finish-machine it and drill the holes, then roller-harden the bead area.

Welded-up parts are labor-intensive. Engine mounts and some landing gear parts, for instance. Nobody is going to build a hugely complex CNC machine to make a few hundred mounts per year. Riveting skins together is similarly complex, though the sheets can be CNC cut and punched. Van's does it.

And we also seem to expect that Cessna stock parts for our 1971 airplanes, but no reasonable person expects GM to stock parts for a 1971 Chevy. Order some out-of-stock part for such an airplane and see what it will cost; that's a reflection of the time it takes to pull up a drawing and get some guy to fabricate it for you. A guy, by the way, who has never made it before, since the last guy that made them retired a long time ago. It could take him several tries. They're not going to make ten of those parts if they sell one every four years.
 
Dan Thomas said:
Even with CNC, which I'm sure Textron uses extensively, you're not going to save much on 143 parts per year. They make sense when volumes are involved. Anyway, if they already have the molds for the castings, it's cheaper to keep doing that. Machining landing gear wheels from bar stock, for instance, involves enormous waste of expensive metal, and removing that metal takes time, too. So they cast or forge the wheel and CNC finish-machine it and drill the holes, then roller-harden the bead area.

Welded-up parts are labor-intensive. Engine mounts and some landing gear parts, for instance. Nobody is going to build a hugely complex CNC machine to make a few hundred mounts per year. Riveting skins together is similarly complex, though the sheets can be CNC cut and punched. Van's does it.

And we also seem to expect that Cessna stock parts for our 1971 airplanes, but no reasonable person expects GM to stock parts for a 1971 Chevy. Order some out-of-stock part for such an airplane and see what it will cost; that's a reflection of the time it takes to pull up a drawing and get some guy to fabricate it for you. A guy, by the way, who has never made it before, since the last guy that made them retired a long time ago. It could take him several tries. They're not going to make ten of those parts if they sell one every four years.
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Maybe when 3d printing of metals become cost effective we will see somthing great.

I remember hearing about a guy that specializes in high performance mods on Porsche cars.

One thing I remember him saying is that there is the tech right now that he uses to print out the actual exhaust headers on the flat six engine. It's a composite material that is strong, stiff and light weight, and has great compression strength, so much so you can run the header over with a truck and it doesn't break.

Imagine all the parts you could print for a GA air plane. Exhaust systems, baffling things of that nature.

And then when the tech on metal printing gets better, imagine the possibilities.
 
Croomrider said:
That process is still very expensive, and it depends on the quantity being produced. Each process generally has a minimum lot charge for setup, so gets cheaper with more parts. However, nobody wants to spend the money and then stock the parts without at least doubling their money.
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That would be illegal without PMA.
 
LOL. I've been boycotting GE since the 1980's when they produced/sold refrigerators with centrifugal compressors that failed right after warranty was up. They actually extended warranties for it but only included replacement part and not labor. F GE
 
murphey said:
Unfortunately, most airplanes are still hand-made and labor intensive. GE has been doing some prototyping with 3D printing on scaled-down components but so far, not cost-effective. I used to work at Boeing and made the Obligatory Pilgrimage to Seattle (altho I didn't work for Boeing Airplane) for a tour of one of the factories. I am not kidding when I say even the airliners are still handmade. If you've seen the video of the 777 or 787, you'll see people putting the pieces together.
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Boeing is in the process of placing the FAUB (fuselage automated upright build) system into the 777 build line. Right now it is assembling every other straight fuselage section on the line. As soon as it it found to be trouble free, it will be building 100% of those sections. Plans are being made to use the technology on other parts as well.

A new method for building 777 fuselages is being developed as part of Boeing’s ongoing technology investment strategy.

“This is the first time such technology will be used by Boeing to manufacture commercial airplanes, and the 777 program is leading the way,” said Elizabeth Lund, vice president and general manager of the 777 program and Everett, Wash. site.

Known as the Fuselage Automated Upright Build, or FAUB, this Advanced Manufacturing technology improves workplace safety and increases product quality.

With FAUB, fuselage sections will be built using automated, guided robots that will fasten the panels of the fuselage together, drilling and filling the more than approximately 60,000 fasteners that are today installed by hand.
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http://www.boeing.com/features/2014/07/bca-777-fuselage-07-14-14.page
 
CNC machining a couple parts is usually not the most cost effective way of doing it.
 
weirdjim said:
No, the owner self-certifies it to 21.303 (b)(2).
Jim
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I think we've been here before.

21.303 pertains to PMA application.

Are you saying that an owner wanting to produce parts for his aircraft must apply for PMA? And if not, why is 21.303 relevant?
 
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GlennAB1 said:
That would be illegal without PMA.
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Not sure what PMA is, or what you are talking about. My post was giving a general description of what is involved in using CNC to manufacture parts. My company produces hundreds of different parts for the aerospace industry, but we work to customer prints and specifications. We do not reverse engineer aerospace parts, but we have customers that do.
 
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