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Aircraft Aerodynamics with LinAir

Two software packages were used to characterize aerodynamics of each RPT. The first one, LinAir, is a simple and yet very reliable program that computes aerodynamic properties based on the model created from several individual elements (panels). It is capable of generating the effect of varying the angle of attack and sideslip angle (鈥渧irtual wind tunnel鈥�), as well as introducing turn rates and deflecting the control surfaces. LinAir was developed back in 1982 by Ian Kroo from Stanford University and has been used since then by many companies such as Boeing, AeroVironment, Northrop, Lockheed, and NASA to quickly assess different novel design concepts.

As an example, Figs.D,E show a P10B RPT model composed of 22 panels

• 3 panels to represent a vertical span of the fuselage (in the x-z plane)
• 3 panels to represent a horizontal span of horizontal fuselage (in the x-y plane)
• 2 panels to represent a left wing
• 2 panels to represent a right wing (see a description of one of them in Fig.Db)
• 1 panel for a left aileron
• 1 panel for a right aileron
• 2 panels for a horizontal stabilizer
• 2 panels for a left elevator
• 2 panels for a right elevator
• 2 panels for a vertical stabilizer
• 2 panels for a rudder

Figure D. The P10B model in the LinAir environment.

Figure E. Different views of the P10B LinAir model.

Figure F shows an aerodynamic force distribution for all 22 panels and serves as the good means of visual model verification (for a symmetric configuration the force contribution should be symmetric with most of the forces positive).

Figure F. Force contribution of the P10B model panels.

Once the base (nominal) model is created and verified, it is modified to create a few more models with the control surfaces (aileron, elevator, and rudder) deflected, so that the complete model is comprised of at least ten input files (one neutral plus three for each of the three control surfaces with different deflection angles).

Next, the angle of attack (alpha) and sideslip angle (beta) sweeps are executed for each of these input files. All data for each sweep are stored in a separate file in a table format. Figure G shows an example of visualizing these data in MATLAB.

Figure G. The P10B aerodynamic derivatives derived from the alpha and beta sweeps.

As an illustrative example, Table B provides aerodynamic and controls coefficients computed for P10B RPT with two wing configurations using LinAir.