Monday, August 27, 2012

Why Your Next Airplane Design Will be Your Best

Why your next airplane design will be the best?  Aircraft design is an iterative process.  This is why Boeing, Airbus and even NASA need lots of scientists, engineers and mechanics to carry out the engineering process. Here's an exercise, fold a sheet of paper into a paper airplane and get it to fly to your satisfaction the very first time (how many times did it take?)

Because aircraft design is an iterative process, it becomes critical that every iteration or design step is efficient. In addition, each iteration in the design should advance the project in the right direction (this is called convergence ).  In the modern aerodynamics design, tools such as analytic methods,  computational fluid dynamics, wind tunnels, scaled models and flight testing are necessary to ensure a fast rate of convergence.

Why your next design will be the best?

1.  There are a number of airfoil analysis software currently available to help you to quickly and accurately analyze cross sectional shapes for wings, struts, rudders, landing gears, flaps and other components.  You can use  these tools to select shapes that provide good lift at the expense of low drag.  Another consideration (especially for wings) is the use of airfoils that produce high lift without huge destabilizing pitching moments (this reduces the tail drag).  Some airfoil tools are free (see Xfoil).  Other are efficient and accurate and help you to finish this crucial first iteration ahead of the pack (see,

VisualFoil 5 can compare the performance of many airfoils on a single graph.

2.  Once you have cross sectional shapes, the next step is the skeleton airplane.  The skeleton airplane is essentially just wings, winglets, canards, flaps, tail and rudder.  The skeleton airplane should be a good enough approximation to the actual aircraft to help you to compute lift, drag, longitudinal and lateral stability, angle of trim, 3 DOF trajectories, component loading (for stress calculations) and drag reduction (winglets).

Getting the most out of the skeleton aircraft is key to the next step in the design process. Free tools such as AVL (Athena Vortex Lattice Method) allows you to analyze the skeleton aircraft using a horse-shoe vortex lattice approach.   If entering each component using a text file leaves you behind schedule, MultiSurface Aerodynamics (MSA) provides a modern user interface that expedites the design process (based on vortex rings method). MSA is the ideal tool to compute and identify form and induced drag from different wing components and design/position winglets, canards and the tail-plane (see and

MultiSurface Aerodynamics can quickly perform loading & Stability Analysis

3.  As a design engineer your imagination and experience are your biggest assets. By this time in the process, you have formulated your ideas and analysis findings into a 3D solid model that resides in a CAD program (Rhino, Solid Works, Autodesk Inventor, NASA's Open Vehicle Sketch Pad  This is the stage where efficiency is most critical because you must test the design as a unit. A good way to proceed is to use computational fluid dynamics or CFD methods. Traditional CFD methods requires that you construct a mesh for each design iteration that you wish to test.  This is often difficult and time consuming especially for 3D models (see

The more parameters you can test, the better the design. If your next design is to be your best, you will benefit from Stallion 3D, a novel and accurate tool that eliminate the mesh generation process. This allows you to efficiently analyze and optimize your CAD models for this final step in the aerodynamics conceptual design process. The following video shows all the steps required to enter and analyze your aircraft design in Stallion 3D.
Stallion 3D can go from solid model to results in as little as 1.5 hours on a laptop computer.

More information about Stallion 3D can be found at

Thanks for reading.

Friday, August 24, 2012

NASA's OpenVSP Hangar

NASA Open Vehicle Sketch Pad now has a hangar area with many 3-D models that you can use for inspiration and guides for your own original designs.  The url is:  The hangar currently lists 74 models for download.

 I used Stallion 3D to analyze some of the models in the hangar.  Simply export the model from  Open Vehicle Sketch Pad in the .stl format and Stallion 3D can read in and analyze the geometry.  The software can  model subsonic, transonic and supersonic external flow fields.  More information can be found at
The following are some pictures from Stallion 3D.

Surface pressure on the surface of the F5 model at a speed of 290 m/s.

Velocity near the surface of the Q2-Model at V=100 mph.

Pseudo-Top-Gun Scene using the F15 for the F14 and the F5 standing in as the MIG. The airplanes were analyzed at a speed of 290 m/s.

Hypersonic waverider model at mach number of 6 (surface Mach number)

Surface pressure for the waverider model at M=6

More information about NASA's Open Vehicle Sketch Pad can be found at
More information about Stallion 3D can be found at

Thanks for reading.