PFR - Aerospace Engineering Sciences Senior Design Projects ...

Project Final Report – CUDBF April 30 th , 2009
ASEN 4028: Aerospace Senior Projects
Static Margin
0.2
0.15
0.1
0.05
0
-0.05
-0.1
-0.15
Static Margin as a function of Taper Ratio and Sweep Angle
Sweep Angle of 25 o
Sweep Angle of 20 o
Sweep Angle of 15 o
Sweep Angle of 10 o
Sweep Angle of 5 o
-0.2 Sweep Angle of 0 o
-0.25
-0.3
1 2 3 4 5 6 7 8 9 10
Taper Ratio * 10 -1
Figure 12: Determining Wing Geometry
The leading edge sweep angle was narrowed down to between 15 degrees and 25 degrees such
that a positive static margin was assured. The choice of configuration is discussed in the
Mechanical Design Elements section for aerodynamics.
5.1.2 Airfoil Selection
In order to choose the best suited airfoil for a flying wing configuration, several hundred airfoils
on the UIUC database as well as the DBF Osborne databases were analyzed. All the airfoils
were plotted in the airfoil analysis tool XFOIL [8] . The three best airfoils were chosen based on
their drag polars and variance in coefficient of moment with angle of attack. The main driver for
the airfoil selection was the coefficient of moment as a function of angle of attack. Since the
configuration chosen for this aircraft is a flying wing design, the longitudinal static stability of
the aircraft is very important. Flying wings have the tendency to be unstable in pitch; therefore,
selecting an airfoil with optimal lift characteristics as well as a coefficient of moment very close
to zero was extremely important.
The variation in moment coefficient with angle of attack and the variation of the lift coefficient
with angle of attack for the three best airfoils are shown in Figure 13. The top three airfoils
shown are the HS520, Eppler216 and the HS602.
32