25 | July | 2024

J2 Announces a Major Breakthrough in the Modelling and Analysis of The Flying Qualities of UAS Type Aircraft

The UK SME, J2 Aircraft Dynamics Ltd, developers of the software suite, the j2 Universal Tool-Kit, have been recognised in a PhD dissertation originating from the Airforce Institute of Technology or AFIT. The dissertation reports on the application of j2 software to deliver a piece of work that focused attention on the development of a repeatable process and methodology used to assess the flying qualities of Unmanned Aerial Systems or UAS platforms.  This led to a repeatable method used to accurately assess and quantify aircraft performance parameters during specific events leading to key factors in flying quality assessments necessary to begin the framework for an unmanned flying qualities standard.

In the thesis the author used j2 software to accelerate the model build and analysis process focused on three hypothetical UAS aircraft, ranging from 125 Kgs up to 1.6 tonnes gross weight, without the need to write any code and without reference to any controlled or classified data. In addition, the j2 Universal Tool-Kit was used to undertake key flying qualities analysis looking at upsets and other operational situations to assist in improving the overall understanding of their impact on the safe operation of the aircraft.

Lt Col Kara Greene, the author of the thesis said, “without this software, I do not know how this research would have been accomplished.”

j2 software was used to build the digital models using data such as – weight, sizing, moments of inertia and aerodynamic coefficients, from non-restricted sources and publicly available information and then go fly the models in the j2 software, repeatedly, through a series of set manoeuvres.

Lt Col Greene went on to say, “The j2 Universal Tool-Kit allowed all three sample aircraft to perform the same manoeuvres in a similar manner.  This not only allowed the variation in the control inputs for each aircraft to be analysed, but also a comparison of the three different aircraft’s performance of the same manoeuvre.”

Parameters such as weight, six moments of inertia and aerodynamic coefficients were input into the j2 Universal Tool-Kit aircraft model design template.  Once the model had all the necessary parameters, some initial sanity checks and control derivatives were reviewed.  Of particular note, the lift, drag, and moment curves were reviewed over a range of longitudinal step inputs to ensure a comparison could be made to operational UAVs.”

Paul Jenkins, Snr VP at j2 Aircraft Dynamics, was delighted with the dissertation Lt Col Greene had published especially the authors comment that, “after entering the required model characteristics, all the aerodynamic derivatives were then calculated within the j2 Universal Tool-Kit software.” and that this, “differentiates j2 from other modelling programs as the others require the derivative coefficients first before then calculating the aircraft performance characteristics.

Lt Col Greene went on to say, “This study provides yet another example demonstrating the usefulness and validity of models created in the j2 Universal Tool-Kit and demonstrates that this software is a useful tool in the development of the methodology for evaluating the flying qualities of UAVs/UAS’s. The end result is the determination that j2 Aircraft Dynamic’s software has the ability to reconstruct a flight path using a high fidelity model and fits the flight data within acceptable tolerances.”

The j2 module, j2 Virtual, provides an embedded 3D viewer and this proved to be one of the most beneficial capabilities of using the j2 Universal Tool-Kit, the ability to visualize the aircraft flight/manoeuvre in a three dimensional viewing screen.  Lt Col Greene said, “as a model is run through extended manoeuvres or flight, the data output can become overwhelming.  This is when the visualization capability becomes essential.”

J2 virtual can be used to visualise how such handling sensitivities look from a range of different viewing points using a virtual chase plane with viewpoints fully adjustable in flight.

John Jeffery, j2 CEO said, “I am really pleased that we [j2] were able to help Lt Col Greene produce her dissertation and very much appreciate her kind words.  J2 are always trying to help aerospace students understand more about how their aircraft behaves without the need to spend months developing code and models.  This was fully realised within Kara’s thesis and I wish Kara all the best in the future

Footnotes: The award of PhD provides a clear measure of the scientific acceptance of the process and methods used to deliver this work and certainly provides a valuable start point as more UAS, PAV/eVTOL platforms come under scrutiny with regards to flying qualities assessments.

Lt Col Greene has retired from the Air Force and now works for Engineering Systems Incorporated or ESi as a consulting engineer in aircraft accident reconstruction.

For more information or to open a dialogue with j2 Aircraft Dynamics contact Paul Jenkins as follows:

Email: paul.jenkins@aircraft.com

M: +44(0)7908818724

Ph: +44(0)845 0529489

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