Preliminary design

In the very initial stages of the design of a non-conventional airplane like this, there are a lot of different paths that can be taken. Maybe the first idea that can cross the mind of an enthusiastic engineer is to develop an innovative concept that perfectly suits to performance needs. Of course, that way could be better in order to achieve the requirements but usually implies to work out new technology and for sure this option will increase dramatically the amount of effort, time and money that the project needs.

A more reasonable or conservative approach is make a less risky bet, using some of the design solutions applied to similar airplanes and focusing the work in a suitable arrangement of these solutions in order to meet the desired requirements and finally achieve a complete new design.

This kind of work philosophy was applied to this project and two main types of airplanes were considered for inspiration: Sailplanes and General Atomics’ UAVS.

Due to the need of a high aerodynamic efficiency, sailplanes wings and body were a reliable design reference. On the other hand, General Atomics’ Predator is a fully proven airplane with similar MTOW and NASA’s Altair prototype seems to have very similar performance requirements.

Here are some photos of the planes that were taken as a reference:

Sailplane during flight

NASA's Altair unmmaned aircraft

Predator US military drone

Researching on internet a valuable amount of data about the reference planes like weight, wingspan or even airfoils can be collected.

At this point the project have the mission requirements defined and a few models to extrapolate data. Building on the simple work philosophy which it was spoken above, just missing enlist the help of a design handbook to begin developing the project. Easy, right?

Well, at the end was not so easy, but after many hours of reading datasheets, making calculations and working with CAD programs, a first design was released.

This is only a basic model with the aircraft elements roughly sized where all the ideas and technical solutions are put together.

Of course this design will need to change in many aspects, because every time that is make a new calculation or a deeper analysis, the results will show that the fuselage must be wider or maybe that the tail surface is not enough to ensure stability. But even if a lot of changes must be implemented at least a core of this design will remain constant due to the general arrangement of the plane has been established and in general terms the associated technical solutions that have been adopted are still valid.