What is an aircraft without its aerodynamics? It is not difficult to answer this question, surely it is no longer a plane.
In today's “Behind the scenes” article, we will provide you with more insights on the work of our aerodynamic engineering team. In particular, in the following lines, you will find out how the design of UR-1, the first Swiss fully electric race aircraft, was shaped by their work.
UR-1 is a relatively conventional design and proven analytical design rules could be employed for the conceptual design. Computer tools based on simplified (fluid) flow modelling enabled fast prediction of the aerodynamic forces and moments, which is particularly convenient for vehicle optimization in the preliminary design phase. More elaborate simulations were then employed to verify the aerodynamic functionality of the aircraft specific features. For example, the performance of the flaps and the prediction of drag forces.
Sharing outcomes was a natural part of the workflow in designing the UR-1. In this specific case, aerodynamic load data was provided to the structural engineering team, who is in charge of sizing the structure to support the applied loads, as well as providing an input to optimize the outer shape of the aircraft. Once detailed CAD models were taking shape, larger simulations of the air flow around the entire aircraft were done in order to check the aerodynamic performance.
Predicting the flight mechanical behaviour
A crucial stage of the work carried out by the aerodynamic engineering team included prediction of the flight mechanical behaviour. First of all, it was necessary to simulate flight conditions in order to predict the stability of UR-1. By doing this, the team was able to define a first conservative flight envelope . Then, they led some flight tests of remote controlled, scaled models, in order to validate the design tools as well as aircraft stability aspects. After this stage, there is the reality. In that sense, every progress made in the workshop in manufacturing UR-1 parts requires some quality checks, for example to update mass and balance related to flight stability. In conclusion, full-scale aircraft tests will allow the team to validate the handling, progressively extend the limits of the flight envelope and confirm the aircraft performance.
Differences in aerodynamics between an electric aircraft and an ordinary one
Unlike you might think, there aren’t remarkable differences between the aerodynamics of an electric aircraft and an ordinary one. For sure, aerodynamic efficiency is key for flight endurance and speed of a race plane. Even more so for a battery electric aircraft. Therefore, we have opted for a V-tail configuration in order to reduce some of the drag generated by the tail.
Compared to combustion engines, the geometry of electric motors typically fit better in a streamlined fuselage shape. Another notable difference is that an electric motor requires much less cooling air than a combustion engine. Therefore, we do not need a dedicated air intake, which eliminates the associated drag. In conclusion, electric propulsion enables more streamlined shapes, but the design principles are the same as for any other aircraft.
As we will see in the next article, another advantage compared to thermal combustion engines is that an electric aircraft gives more flexibility for example to split the propulsion task over multiple electric motors.