The design report

Although these values met requirements for this phase of design, soon calculations had
to be in more detail and thus AVL had to be used to calculate and perform in depth
analyses on aerodynamic performance and stability.
AVL (Athena Vortex Lattice) version 3.26 was mainly used to calculate and analyse
aerodynamic performance characteristics of the aircraft. Values obtained from AVL
were also used to ensure stability in all dimensions. There were a few assumptions
involved at this stage of design as AVL was only a freeware and had limited functionality.
Shapes and geometry entered as part of the design had to be of minimal complexity and
consideration to extrusions such as landing gear or location of motors were not taken
into account either. The software itself had an easy to follow interface in command
prompt but did not have a particular graphical user interface. The input files were made
as accurate as possible by adding detailed coordinate points of the fuselage in order to
replicate its shape and size accurately. Airfoil files were then exported from Profili into
text files. These files had to be manipulated in order to be used for AVL analyses. The
output files were used to extract key numerical values important to our design and
stability analysis. AVL considered the airfoil shapes of the horizontal tail and the wing
and since no airfoil file was linked up for the vertical tail, it was taken to be a plate by
default as the program was designed to do so.
Once the files required for AVL analyses were in place, they had to be run on the
program to ensure the aircraft displayed accurately to a reasonable extent. The final
design of our aircraft was similar to that which is shown below in figure 3.2.301.
Figure 3.2.301 – The aircraft as displayed on AVL.