Integrated approach to airframe design assemblies

The challenge of defining holes and fasteners for today’s complex airframes is becoming more apparent.  Implementing an efficient fastener management process is crucial to keeping an aircraft program on schedule. Taking an integrated approach to airframe design and manufacturing is critical to
making well-informed design decisions so the hundreds of thousands, if not millions, of fasteners in a single aircraft — and their location, specification, procurement and installation requirements — can be effectively managed and communicated throughout the development process.

Beyond this, the design of aerostructures that include fastened assemblies is unique relative to the design of other kinds of assemblies. Aircraft are highly efficient structures, meaning the joints in the assemblies must carry loads that are as equally distributed as possible. To achieve this,  fasteners must be installed  with very tight tolerances to ensure there is no mismatch in the joint that would cause one fastener to be more highly loaded than another. This requires specialized manufacturing methods to achieve these very tight tolerances and ensure the design performs adequately.

There are many specialized  rules associated with the design of fastened joints, with some unique qualities specific to airframe design. These include distance-to-edge,  fastener pitch distance,  and acceptable grip length ranges, just to name a few. Finally, the holes that the fasteners go into must be defined with special finish operations and variations in assembly states for the design to be manufactured effectively.

All of these unique variables in the definition of a fastener add up to create a huge amount of data. In fact, thousands of pieces of  unmanaged  fastener-related information are generated  in the traditional airframe design-to-manufacturing process. This information must be delivered accurately and completely through multiple revisions of the design in order build the airframe. The tasks necessary to  define and communicate this information are both tedious and complex, and in many cases, they are not automated.

Limitations of CAD and PLM

Traditional PLM systems are not designed to handle the complexity,  rapid change,  and cascading  effects of evolving fastener and joint definitions that are found in an airframe design. PLM systems have grown out of the need for secure access and revision control. This capability has chiefly been applied to individual documents or files, and in the case of engineering data, to 2D drawings and 3D CAD models.

While these systems effectively manage data at the document or file level, they don’t have the capability to address the data inside a CAD file, such as fastener assembly data. There are 50 pieces of non-geometric data that define each fastener location.

Much of this information is lost in the process of defining the fastener using the PLM system alone.

The PLM system might manage the fastener CAD file as an object itself, but much of the design information about the fastener is captured inside the assembly CAD model, or in many cases, can only be understood by looking at the CAD model in an assembly context. This assembly-level data is often incomplete, inaccurate, or not up-to-date in the PLM system. This is where the promise of conventional PLM to manage fastener information falls short. The use of a CAD system to define aerospace fasteners typicallNike Air Max