PRANDTL-D

In 1933, Ludwig Prandtl published one of the first analytical studies on what we today know as aero-structural optimization. Having just developed lifting line theory and the bell shaped lift distribution in 1923, Prandtl determined that to minimize bending moment along the wing (and hence minimize wing weight), one should use a more "bell-shaped" lift distribution:

However, as stated by Munk in 1925, one of the results of moving the lift distribution inward is a reduction in adverse yaw. When looking at these two papers together, one can theorize that the optimal lift distribution for aero-structural efficiency may also be the optimal lift distribution for coordinated turning. This hypothesis was the starting point for the PRANDTL-D project.

When I joined the team in the summer of 2013, the first airframe had been constructed and the critical task was validating the existence of proverse yaw, or the tendency for the aircraft to yaw into the roll. After an initial failure in the data acquisition system, my iPhone was strapped onto the CG of the vehicle with a gyroscope app running. The resulting rate data indicated that proverse yaw had indeed occurred. The video below summarizes this initial investigation phase of the project:

As a member of the PRANDTL team, I was responsible for numerous tasks. First, I assisted in flight operations, most often acting as the energy delta for the big bungee cord we were using as a high start:

Additionally, I provided much of the modeling capability of the team, using tools such as AVL, XFOIL and XFLR5 to predict stability and control derivatives for the vehicle. After flight, I was also responsible for analyzing the raw data, generally using MATLAB and SIDPAC, and comparing the results with my predictions.