Introducing the Dravion!

Introduction

SSG-AERO has teamed up with Conseil & Technique, Altitude R&D and Didier CAILLEAUX (helicopter pilot) to design and develop a new drone concept : the Dravion.

The concept

Dravion is a french short for Drone + Avion, meaning a Drone and a plane at the same time.
The main idea behind the dravion is to solve the high speed limitations of the quadcopter.

The dravion combines the architecture of the mutlicopter (fixed propellers) with integrated wings, offering an simple yet very efficient architecture:

• As a quadcopter, the dravion offers VTOL capability and multicopter mobility.
• As a plane, the dravion offers reduced consumption in cruise.

Yet the dravion remains simple as its patented concept requires no mobile propeller to transition from one mode to another, a key asset when it comes to certification!

Dravion aerodynamic design

SSG-AERO has been in charge of the aerodynamics of the first demonstrator.
Starting from a blank page, with only propellers and engines, we designed the shape in two month using Ace of Aircraft 3D steady solver on a unbuntu 64 cores server.

With the support of ACE, the initial meshing parameters were quickly set, and we could then easily work on the optimization of the craft, watching the following pattern :

• General performance: lift, drag and longitudinal moment were key to evaluate the speed of the drone, and proved to be very close to the final results as power consumptions match reasonably well the measured data during the tests
• Local optimization: using the native visualization tools, we were able to assess the local mismatches between the geometry and the flow
• Construction requirements: with Conseil & Technique we took into account the construction tools to simplify the whole craft and integrate the propellers and landing system
• Stability: the craft was designed to be naturally stable in all axis to ease the work of the propellers in flight
  

• Propellers impact: when the design started to converge and the weights got more and more realistic, the propellers came into play and were integrated into the simulations. The propellers were modelled using a classic disc actuator model using Ct and Cp curves and setting the rpms for front and rear propellers. The simulations proved to be of major importance as the performances of the drone were strongly influenced by the propellers. The geometry did not require much changes as it proved to be quite tolerant, but the rotation direction of the propellers proved to have a strong impact on the performance of the craft.
  

Integration and optimization

Since 2019, SSG-AERO develops modules inside the COSAPP environment for SAFRAN.
https://cosapp.readthedocs.io/en/latest/

This systems offers integrated solvers and can build complex systems using different physical models.
On the Dravion, we used cosapp to solve the operating points using a structure close to this :

By doing so we were able to predict the performance and behaviour of the complete drone with its propeller, and deduce the performance before feeding the simulator run by Altitude R&D.
This tool proved to predict well the drone performance, and perfectly matched the longitudinal results from the simulator, just as the simulator matched the measured results from the tests.
The next dravion iterations will use this tool to evaluate the aero and propellers improvements, or a change in size.

Demonstrator first flights

Tests

The tests confirmed the predictions!
The Dravion flies fast but burns less energy!

The effect of the propellers has also been validated by the tests!
The team is now working on numerous real world use cases!

More very soon!

Team

Guy VALEMBOIS - CONSEIL & TECHNIQUE / Design & Structure
Romain CHIAPPINELLI - ALTITUDE R&D / Simulation & Control
Didier CAILLEAUX - DC / Pilot
Stéphan AUBIN - SSG AERO / Design & Aerodynamics

Tools

Ace Of Aicraft: www.aero-ce.com/ace-of-aircraft/
COSAPP:  https://cosapp.readthedocs.io/en/latest/