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Case History – Cassidian

Cassidian, previously EADS, in Manching adopted the J2 Aircraft Dynamics Software in 2010 to increase the speed with which they could deliver detailed design analysis results and improve on the overall quality of the design process.

The Goal

Cassidian’s goal was to model mass, inertia and control systems whilst harnessing the knowledge in its legacy modelling system. Cassidian selected the j2 Universal Tool-Kit because the software was able to integrate seamlessly with their existing aerodynamic modelling code base which was running in FORTRAN. This was a vital link as significant and valuable knowledge resided in the legacy modelling system. Additional mass, inertia and control systems could then be “superimposed” onto the aerodynamic models, through the j2 Universal Tool-Kit, to provide complete aircraft systems solutions.

Cassidian Validation

Stage 1 – Model Validation

The first stage of this process was to demonstrate the integration and analysis capability using an existing aircraft and comparing the results with flight test data. Two models were built to compare these cases:

  • Model 1: Initially j2 Aircraft Dynamics were provided with a comprehensive set of data tables, and equations that defined the aerodynamic characteristics of the aircraft across the complete flight envelope. This included the introduction of an Experimental Axis System used within Cassidian as part of their model definition. J2 constructed a model within j2 Builder using the data including the look-up tables, derivatives and expressions that already existed.
  • Model 2: The second model was constructed using a FORTRAN library containing the aerodynamic data, and integrated with the same mass, inertia and CG characteristics as the previous model. Both models were run over a range of steady state conditions and results compared. Wherever discrepancies between the two models were found, further analysis actually showed that all errors occurred in the original legacy FORTRAN library which therefore required updating and recompiling. Because of the flexibility of the j2 Developer interface, the updated FORTRAN libraries were immediately integrated into the j2 model and the cases re-run and evaluated instantly.

Steady state cases were then evaluated over a range of data points and compared to actual flight test data. Further Classical linear analysis was performed on both models to identify modes of motion, frequency and damping characteristics and results assessed against actual flight test data.


Both models showed very high and acceptable levels of fidelity when compared to the real aircraft.

Stage 2 – Dynamic Behaviour Analysis

An actual crash scenario test case was selected that could not have been evaluated using the existing, legacy, Cassidian software tools. This scenario was to model the effect of a lateral gust on the aircraft during final approach with rudder free. The j2 Universal Tool-Kit analysis showed an unstable, uncontrolled response on the aircraft resulting in a crash which was consistent with what had occurred with the real aircraft. As a further demonstration of the j2 software capability, additional cases were run at higher aircraft approach speeds instantly. The outcome was that at a higher final approach speed the aircraft would have remained stable and in control.

These cases were presented to the Cassidian engineers and management using the functionality embedded in j2 Visualize(charting) and j2 Virtual(3-D playback facilities) to provide a real understanding of aircraft behaviour.

Network Integration

The j2 Universal Tool-Kit was able to be set up as a client/server application with floating licenses enabling engineers of different disciplines to add data to models and evaluate aircraft from anywhere on the permitted network. Furthermore all models, analyses and updates are automatically tagged with user information, version control and configuration management data to enable full traceability on the complete process.

The integrated networked multi user approach was something that was not previously possible with the legacy tools.

Training and Implementation

The final stage was to complete the training of the Cassidian engineers over a 1 week period including model building, the integration of the existing FORTRAN aerodynamic libraries and analyses.

Client Value Return

Such was the success of the j2 software, Cassidian have found that they have greatly accelerated the speed with which they can go and crucially have removed a number of error sources associated with import/export regimes using the previous legacy system.

Stephan Hitzel (Dr.-Ing., Expert Aerodynamic Design and Numerical Methods at Cassidian said:
“Our evaluation of the j2 software revealed a considerable potential in quality and turn-around time improvement in the conceptual and detail design. There is no doubt that now we have adopted j2 we can significantly shorten the design and analysis cycle within Cassidian. It also opens up further gains elsewhere in the design process to regard and to exploit the true multidisciplinarity of aircraft systems.”


  • The use of J2 software at the Detailed Design stage enables design teams to evaluate more cases and trade-off studies than with their existing solution in the same time frame and no additional resources. This results in the following key benefits to Cassidian:
    • Designers no longer have to write code in order to run multiple analyses.
    • The powerful analytical toolset can run many test cases instantly.
    • A controlled team working environment for each discipline coming together to work on a complete aircraft project.
    • Design teams can look at detailed certification manoeuvres and failure analyses across the complete flight envelope.
    • The J2 software has a mature installation process and is easily networked onto any company system without access or permission issues arising.
    • Whilst the FORTRAN library models are trusted, when errors occur it is difficult to identify them. The exposed tables, derivatives and formulae within the j2 Builder environment mean that aspects of the model causing problems can be easily found and corrected without the need to recompile any code.

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