September 10, 2021, ©. Leeham News: Last week, we looked at the Rig design and manufacture for ground and flight testing.
We are now at the stage in our program (Figure 1) where we shall have scouted and deliberated over our Final Assembly production site (Violet bars). We now need to decide on the site and what facilities we need to build and/or hire.
Most of the close to a million parts for our 19 seat unpressurized utility airliner are designed and produced by subsuppliers. They deliver these to us in an aggregated form to our Final Assembly Site, where all this can be gathered and we can start the assembly of it all into an aircraft. Final assembly line planning usually starts at a very early stage. In fact, some information needs to be available when negotiating with suppliers before launch.
This whole process is nicely described in this picture from ATR, Figure 2. Click on it so you can read the text boxes, which describe what is done and at what time before delivery of the airplane.
ATR builds the fuselage structures and joins them at Naples, Italy, and then ships them to the Final Assembly Line (FAL) in Toulouse.
We will have the nose, center fuselage, and tail sections produced by sub-suppliers and shipped to our chosen FAL site. The same goes for wingbox halves, tailplanes, movables, landing gear, nacelles, engines, and all the systems. We then integrate the parts in steps in our FAL facilities.
The times shown in the ATR graphics can be a guide for our own production. Once our production has worked itself through the initial kinks, down the learning curve, we can assume we will start the initial production of parts at sub-suppliers about a year before customer delivery.
Where we place the FAL is dependent on a number of factors:
Once we have chosen the site, we need to start implementing the FAL. Most likely the complete FAL will not be finished with its tooling to produce our prototypes, so we shall decide on how we join the different parts of the structure with prototype tooling and fixtures.
There are a few things to consider when sizing the campus. What is the expected production rate? How much floor space is needed? How will we receive and store large parts/assemblies? Will the main warehouse be onsite or offsite? What will be the flow of large parts/assemblies? Is there space for future expansions?
Will we use the same site for any servicing, post-production modification, or have a place to manage out of sequence activities (traveled work) to avoid disrupting the mainline? Do we need a separate on-site paint hangar or will that be done off-site? These are some of the questions needing answers when looking for a site.
The sophistication of the tooling and fixtures used for production depends on our planned production rate. We also need to invest in equipment in a timely manner. Product development, production preparation, and production ramp-up require quite a bit of funding. Buying equipment or building facilities that we’ll only need several years after the first deliveries may not make financial sense.
We can see there are assembly jigs and fixtures needed to hold the fuselage sections in place for the ATR fuselage in Figure 3 before the joints are drilled and riveted/fastened using the arc-type scaffolding spanning the fuselage. The same applies to all other structural parts we attach to the aircraft.
We will design the FAL with its different stations together with specialist companies for this kind of production. There are a handful of companies that do assembly toolings for airplane OEMs. We provide these vendors our requirements and leverage their expertise to identify optimal solutions for things like parts flow, jigs, robots, alignment instruments, and IT systems.
For example, there are different systems for the alignment of the large parts and we need help to choose the one that suits our production (laser alignment, local GPS style of alignment, etc). Should the fixtures automatically move the parts to their positions based on sophisticated articulators and advanced software or should we go for a more manual process? All these factors need to be worked through and we need to consider cycle time, production cost, inventory cost, and investment.
The production preparation is the major activity besides detailed design and more and more system testing during this phase.