Building an aircraft...

[BigHitDH]

Hi,

I've often wondered this....

When you build a machine the size of a modern airliner, where do you start?

Obviously, the ribs and stringers + skin is what gives the sturucture it's strength, but how does the structure support it's own weight until major sections are completed?

I know when building Ocean liners they first lay down the "keel beam", and everything else is bolted to that - is the process for aircraft similar?

Designing the "system" to build an aircraft seems like a greater challenge than designing the aircraft itself!


Thanks in advance for any insight you can give.

[Genghis the Engineer]

You don't.

The aircraft is made in a number of sub-assemblies, usually in different places (often different countries), the largest of which initially is a single nacelle or a fuselage section perhaps 30ft long.

Then all these pieces are brought together into an assembly site (in the good old days this was called a " 'recting shop " but nowadays is called something mundane like "assembly hall" ).


The other point is that unlike a ship, which is built up from the keel, an aeroplane (or it's parts) are generally built up within "jigs", which are large mechanical constructions within which the shape of the aeroplane parts are built up - you can see this on the photo below, where jigs used for wing-to-fuselage assembly and tail-fitment assembly are still fitted.

One the full aircraft shell is together, systems are fitted, then seats, trim, instruments, and finally engines.

Ultimately, once an aircraft is designed, the jigs actually become more important to the manufacturer than the drawings.

G

[BigHitDH]

Thanks

Thankyou Genghis, an excellent answer!

So, following from your answer: When say, for example, converting a 747 pax aircraft to a dedicated freighter with the opening nose, is it possible to literally "unbolt" the nose section forward of a particular station and bolt a new one on?

Thanks again.

[Genghis the Engineer]

In a manner of speaking, but it's not straightforward. All sorts of power and fluid systems will inevitably pass through any section of a modern large aircraft. So, a great deal of redesign will be needed of that section taking all this into account, and the task will be large and require a lot of skilled man-hours with the amount of replacement, re-routing, etc. that goes into this. This applies both to the design stage, and to the fitting of it.

But being simplistic, yes.

G

[Basil]

None of the B747 pax > freight conversions I've seen had the nose door.

[Dr Illitout]

From my experience in aircraft maintenance. The aircraft manufacturer takes the the componant that fails most often. Hangs it from the roof of the assembly shed on a piece of cotton and then builds the aircraft around it!!.

[bbbaldy]

I assume when you say unbolt the nose of the aircraft for a front loading freighter conversion you mean at the manufacturing joint (But Joint) .On the type of freighter I have worked on the nose was not seperated at the butt joint. Also it is the original nose section that is re used after extensive modification.