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Image showing legacy aircraft programs.


Any aircraft program prior to the 1990's was defined using 2D CAD which was either "hand-drawn" or drafted using a 2D drafting software.
Either way, the resulting deliverable is an original 2D mylar drawing. Since then, many of these 2D mylars have been archived and have been replaced with some type of scanned image that has been saved into a format such as tiff, PDF, or in some cases, a priority image format.

For today's legacy aircraft modifications, it is imperative that an understanding of how to interpret these older drawings, along with the knowledge of how parts were tooled and fabricated "back in the day", is essential for defining an accurate 3D solid model.

Sample of a 2D drawing from a Legacy Aircraft program

We model directly from supplied 2D media. The benefit of this is that the modeler can catch design flaws on the original drawings that either required manufacturing design change requests (EO's, ECN's, DCN's, etc), or in many cases were never caught or recorded. Interpreting these old drawings is a dyeing art form. It takes an understanding of the tooling processes at the time of the drawing, to interpret what the draftsman/designer was trying to convey on the drawing.

There are two categories of parts on aircraft. They are either "Loft related" or "Non-Loft related'

Non-Loft Related Parts

These are parts that do not come in contact with a lofted surface of the aircraft or if they do have a surface feature on them, the surface can be defined as a simple extruded shape. For more information on aerospace lofting, see our web page on lofted surface offerings.

These types of parts can be modeled directly from supplied 2D media. They can be:

  • Panels

  • Sheet metal parts

  • Composite parts

  • Castings/Forgings

  • Machined parts

  • Cylindrical parts such as landing gear struts


Loft Related Parts:

Simply put, these parts have some feature that is in contact with a lofted surface. On aerospace parts, the surface in question is a "Lofted" surface that is defined on a loft drawing. Each major aerospace company had their own techniques for defining these lofted surfaces but they were always supplied to the draftsmen as 2D section cuts. Below is a typical loft drawing.

Although skin panels are the most obvious examples of these types of parts, any part  can require lofting.

Sample of a 2D lofting drawing from a Legacy Aircraft program

Sample of a 2D Loft drawing

Sample of 3D CAD geometry and surface lofts from Legacy Aircraft program

Before a "lofted part" can be modeled, the corresponding loft data must be converted from 2D section curves into 3D CAD surfaces which are then used to "impart" the surface data into the solid.

The image shows a section of lofted fuselage required to define the solid frame being modeled.

Example of 3D CAD solid model from legacy aircraft program

The resultant frame assembly

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