There are many reasons why firms need to model the exterior contour of existing aircraft outer mold lines (OML). Most aircraft flying today were not designed in a modern 3-D CAD system. Even with a current 3-D digital design, the actual as-built contour deviates from the intended shape, at least on some level.

In 2009, Direct Dimensions Inc. of Owings Mills, Maryland, was approached by Texas A&M University’s Flight Research Laboratory (FRL) with a challenging yet typical 3-D problem. The FRL, while primarily an active teaching facility, also offers both flight and wind-tunnel test services. This particular project was for a customer who had contracted the FRL to perform feasibility and conceptual design studies for a flight-test program using a business-jet-class aircraft.

This type of “virtual” aerodynamic testing, called “computation fluid dynamics” (CFD) analysis, requires a dimensionally accurate “as built” 3-D CAD model of this specific Gulfstream airplane. The FRL would also need additional 3-D models showing the plane in various configurations, such as with and without the engine and with and without the vortex generators.

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