Oktal and Roy Aircraft & Avionic Simulation Inc. – Tiger Helicopter Prototype

Working with HeliSIM, a development team from Oktal, RAAS and Presagis overcame a lack of data to create an ADS-33 qualified prototype of the Tiger helicopter.

 

France’s Oktal has been providing a wide variety of simulation solutions worldwide since 1989.  They focus on four key markets, namely aeronautic & space, automotive & ground vehicles, defence & security, and railway, and produce dedicated research and training solutions for both civil and military groups. 

Recently, working with Montreal’s Roy Aircraft & Avionic Simulation Inc. (RAAS) and Presagis Inc.,  they developed a high fidelity simulator of a Tiger helicopter with ADS-33 qualification for the Direction General de l’Armement (DGA) Flight Testing group of the French Government. 

What is significant about Oktal’s Tiger simulator is that, for proprietary reasons, it had to be built without the necessary data from the aircraft manufacturer.  To meet this challenge, the team was able to design and develop a qualified simulator by gathering non-proprietary physical and performance data and by using HeliSIM from Presagis as their core software for modeling the helicopter.

Simthetiq A-10C Warthog

Working With the Available Data

The Tiger is an attack helicopter with unique design features that improve the view forward for the back gunner.  In particular, although it is based on the standard gunship configuration with the pilot in the front seat, the gunner in the Tiger is in the back.  This design provides advanced capabilities but carries an increased workload.  Consequently, crews coming to the Tiger helicopter require additional training to become familiar with the set up and to manage the workload. 

The primary difficulty that the team faced in building the Tiger simulator was a lack of necessary data.  According to Stéphane Roy, President of Roy Aircraft & Avionic Simulation, “Due to proprietary restrictions, key information was not available to the team, including aerodynamic data characterizations of the helicopter, AFCS control laws, and physical characteristics of the main rotor blade, engine, and landing gear data.” 

In fact, the only data the team had was the flight manual, video of the multi-function display during flight, general specification and performance of the helicopter, and requirement documents that were produced before the helicopter was developed.

Says Roy, "To be able to develop the Tiger simulation, with the limited data that we had, we leverage the flexibility and extensibility offered by HeliSIM framework. We created a qualified model based on the existing HeliSIM models."

Models Built and Modified in HeliSIM

HeliSIM is a software solution for creating high-fidelity rotary wing flight simulations.  Employing HeliSIM allows users to conceive and deploy a complete rotary wing aerodynamic model and to test aircraft design and performance under controlled, simulated conditions.  In addition, users can also specify subsystems behaviour, including flight management systems, autopilot, and flight controls, integrate virtual and/or real hardware devices, and quickly tailor flight simulations.

For the first version of the Tiger simulation, the team addressed the problem of missing data by adjusting existing HeliSIM models to match the target helicopter.  Then, the team from RAAS, in conjunction with Presagis, constructed the missing information using their particular areas of expertise and through various analytic methods.  Finally, they adjusted parameters to match the available performance data through trial and error.

 

Developing to Qualifications

Another difficulty that the team faced was that they did not have the data required to qualify the Tiger simulator in the traditional manner.  A simulator is usually qualified by performing the same tests in the simulator as in the actual helicopter.  But, in this particular case, no flight test data was available for proprietary restrictions.  So, the team based their qualification approach on the procedure used for evaluating the handling qualities of real helicopters as set by the Aeronautical Design Standard Performance Specification Handling Qualities Requirements for Military Rotorcraft (ADS-33E-PRF).

Despite the fact that so much of the data was unavailable to the team, they were still able to develop a simulation for the Tiger helicopter in accordance with ADS-33E-PRF requirements.  As a result, both the tools and simulator are qualified to the ADS-33 standard, a specification that covers land-based rotorcraft that have primary missions ranging from scout and attack to utility and cargo.

In order to validate that the application did, in fact, meet the qualification standard, the final step was to have a real Tiger pilot fly the simulator and perform the maneuvers described in the ADS-33E-PRF.  According to Roy “This approach is extremely beneficial when qualifying a simulation based on our methods because it guarantees that at least one pilot is satisfied with the simulator before more pilots are brought in for their evaluations.”

Tiger Prototype

Oktal’s Tiger simulator is regarded by the DGA Flight Testing as a prototype of a Tiger because it is not a fully dynamic representation.  Explains Roy, “The simulator is close enough for the pilot to fly the simulator without any compensation, which allows him to focus on a specific task, such as human factor feedback for display ergonomics.”  The simulator is, therefore, not used for training but rather as a simulator for aircraft development.

Roy concludes saying, "With HeliSIM as the core modeling software, we were able to develop a comprehensive and effective methodology for building, calibrating, and testing the aircraft models for the simulator. This methodology allowed us to reduce the time spent on parameterization, calibration, and testing. And, in the end, we were able to instrument the model to perform live calibration with the pilot and to maximize the effectiveness of the time spent in the simulator."