AN understanding as to how the J2 UNiversal Tool-Kit can be used for the complete development of aircraft and provides more capability than just dynamic modelling

1. The J2 Universal Tool-Kit - More than
Dynamic Modelling
AIRCRAFT MODELLING AND PERFORMANCE PREDICTION SOFTWARE
Key Aspects
INDUSTRIES MOST COMMON POINTS
We Already Have the Capability
We Don’t Do that Analysis Yet
I use Matlab/Simulink
MOVING TO THE NEXT STAGE
Beyond Flight Modelling
FLIGHT TESTING
Performing flight trials from conceptual design
WHY NOT FLY?
What do pilots think of the latest design?
CONCLUSION
More than Dynamic Modelling

2. Jane’s “All the World’s Aircraft” has documented over 950 aircraft projects from over 550
manufacturers across the globe. In performing it’s market research to develop requirements and
understand the industry perspective on software design tools, J2 Aircraft Dynamics have spoken,
directly and indirectly, to over 200 of these manufacturers.
In addition to our research, we have over 15 years experience in aircraft design and control including
handling qualities evaluation and envelope expansion of the Eurofighter Typhoon Aircraft, design
and control system development of Reconnaissance, Radar Jamming and Flying Target UAVs, Thrust
Vectoring and conventional aircraft. Each aircraft class offers their own unique requirements on
handling qualities, stability and control, and manoeuvring. We have analysed Business Jets and a
variety of unconventional aircraft and missile systems.
This extensive research and experience base underpins the overall capabilities of the J2 Universal
Tool-Kit. We have not yet come across any other solution that comes close to achieving the benefits
offered by the J2 solution.
From our conversations and research and our discussions with Manufacturers, Consultants,
Government Agencies, and Universities worldwide on the J2 Universal Tool-Kit, the 3 most common
points that are made are:
“We already have the ability to model and simulate our aircraft”
“We don’t use simulation of our aircraft at the early stages of the design”
“We already have Matlab”
With this in mind, the purpose of this document is to help to understand the current situation, and
to outline/define how the J2 Universal Tool-Kit can be used to return significant value/provide
significant savings in time, costs and improved productivity. Take the time to know where you can
accelerate your knowledge and understanding and know where you can significantly reduce your
costs of design

3. INDUSTRIES MOST COMMON POINTS
We Already Have the Capability
All serious/major manufacturers have some form of simulation capability. This is often legacy code
that has been written by engineers for some project past that has been updated and modified over
time to fit each new project. In very large organisations, a separate software group may have been
commissioned to write a more general solution. However, in all cases this solution utilises
comprehensive data for defining the aircraft coefficient information, as well as mass and inertia
details. In the worst case scenario the aircraft data is actually embedded in the code itself (hard
coded and typically written in FORTRAN) and any changes to the aircraft design require a
modification to the code and corresponding re-compilation. In better situations, the aircraft data is
stored in text files that are loaded into the software at run-time.
In all cases the amount of data and structure of the code means that engineers are reluctant to use
simulation early in the design cycle when the design is in a state of flux as they would have to
generate masses of information and produce numerous copies of code to be able to analyse the
design changes, and model the impact of modification and sensitivity studies. This is viewed as too
big a task.
If the J2 Universal Tool-Kit is used as an inherent part of the early design process data can be
detailed or simple; it can come from any data source at any point in the lifecycle. The models are
built up from a logical hierarchy which maps onto the aircraft structure providing an easy to use and
understandable aircraft model.
The use of J2 Universal also unlocks significant savings on design hours and a considerable increase
in fidelity of the flight model and assessment of design changes, even at the early stages with no
additional hours wasted on re-writing and compiling code.
Comparing the J2 Universal Tool-Kit Approach to one of the Existing Approaches to
Dynamic Modelling
Logical Structure to Aircraft Model Definition Multiple pages of aircraft specific code to define the
aircraft model data

4. The speed with which engineers can
construct aircraft models and variations
can come down from weeks/months to
hours/days. This results in them being
able to construct more models and
evaluate more cases in a significantly
Integration of User Defined Libraries to the Aircraft
reduced time. The ability to build the Model
aircraft from any data source means that
models can be “flown” much earlier in the
design lifecycle increasing fidelity and
confidence which in turn can unlock
significant value and benefit.
In some cases though, internal
development has introduced a smooth
process for generating data and turning it
into software code. In this situation, such
comprehensive data models can be
included in the J2 Universal Tool-Kit
through open interfaces that provide a
simple drag ‘n’ drop approach to including
manufacturers data libraries. This then
unlocks the benefits summarised above.
Mapping Model Parameters to Library Inputs

5. This same data model has many uses and can be used for many analyses not just flight simulation
and dynamic modelling. Static stability can be assessed, as well as classical linear characteristics
about any flight condition such as eigenvalue, poles and zeros and root locus analysis.
Eigenvalues across Airspeed Showing Modes of Motion Root Locus
At the same time the modes of motion are automatically calculated to assess any type of classical
figure of merit
Evaluating Short Period Characteristics against ESDU 92006

6. We Don’t Do that Analysis Yet
As mentioned in the introduction, many companies do not perform their dynamic modelling analysis
until much later in the design cycle. Whilst this has become an accepted process it does not mean it
is the best way to proceed. When performing any analysis on an aircraft for the first time, it will
always uncover aspects that were not known or not previously predicted. These aspects will, in turn,
result in potential design changes even after CDR which can lead to unwanted and often significant
cash burn and budget overrun.
This outcome is due to the complex nature of aircraft and all the contributing factors and is
especially true when investigating handling qualities, and stability and control. There are so many
factors to consider (aerodynamics, weights, structures, propulsion) that simple approximations
cannot identify all the characteristics. It is therefore always necessary to perform dynamic response
modelling to fully understand the situation. With the J2 Universal Tool-Kit it is possible to perform
dynamic modelling at the very beginning of the aircraft design lifecycle, greatly reducing the risk of
surprises and unwanted cash burn on fixes.
Cost of Changes
Number of Changes
Changes using J2
Traditional Changes
Cost of Change
Mission Preliminary Flight
Detail Design Manufacture Delivery
Specification Design Trials
Development Process
Comparison of the Changes made and the Cost of Each Change due to Traditional Design Process
and Using the J2 Universal Tool-Kit
If we now look at how aircraft are developed, it can be seen that the cost of modifying the airframe
goes up exponentially throughout the process. A traditional approach to stability and control,
handling qualities, and behavioural analysis can incur major changes very late on in the project
design cycle due to the late approach to dynamic modelling. By bringing this analysis forwards in the
design cycle, a much greater understanding of the aircraft can be developed and although more
changes may be required in the early stages this is where changes can be accommodated easily and
cheaply, so having a reduced impact on the design. The resultant savings can be seen below.

7. J2 Approach
Traditional Approach
Cost of Changes
Advantage
Mission Preliminary Flight
Detail Design Manufacture Delivery
Specification Design Trials
Development Process
Total Cost of Changes when comparing the Traditional Approach and the J2 Universal Tool-Kit
Experience shows that 80% of the project costs are
defined during the first 20% of the project.
The J2 Universal Tool-kit provides the opportunity to
know as much about the aircraft as early as possible to
avoid expensive late fixes and significant cash burn.
I use Matlab/Simulink
In this situation, it is felt that companies have moved forwards from the more traditional in-house
developed FORTRAN solutions. The truth is, in many situations companies have just changed their
language from a structured high order language, such as FORTRAN to Matlabs scripting language.
Matlab/Simulink is an excellent tool for developing control systems and matrix manipulation.
However, the user requires significant domain knowledge to develop a solution. In the case of
dynamic modelling, users have to trim 1 case at a time and then run the responses 1 case at a time,
they have to then run the response manoeuvre from the created initial conditions and then develop
read/write routines to store and retrieve the data. Creating plots requires further scripting activities
all of which takes time away from the designers’ available hours.
Matlab/Simulink is very widely used in the aerospace industry, so the J2 engineers naturally decided
to take a look at how to improve the process by working with Matlab/Simulink. The key was to
integrate the best of Matlab/Simulink with the best of the J2 Universal Tool-Kit. This was done by

8. creating a series of Simulink components that enable the two tools to merge seamlessly, enabling
users to quickly build logical ordered easy to understand data models in the J2 Universal Tool-Kit and
merge these using Flight Control Systems developed within Matlab/Simulink.
Seamless Integration of J2 Universal Tool-Kit into Matlab/Simulink Models
These models can then be analysed using the J2 Universal Tool-Kit providing multiple case batch run
capability, automatic data storage and retrieval and visualisation.

9. Visualizing Closed Loop Matlab/Simulink Models
The visualisation enables the user to view and compare multiple parameters in real time to fully
understand the aircraft’s behaviour and the impact of design decisions. Comparison between
different aircraft, configurations or with/without an FCS can all be viewed either in graphs and traces
or in real-time at the click of a button.
Merging this capability with Matlabs control system
design really gives you, the user,
the best of both worlds.

10. MOVING TO THE NEXT STAGE
Beyond Flight Modelling
The above arguments are primarily focused on companies performing small changes from their
existing analysis capability to use the J2 Universal Tool-Kit in the same way. Effectively trying to
persuade them to go from 1 seat of their existing solution to 1 seat of the J2 Universal Tool-Kit.
However, the J2 Universal Tool-Kit is much more than a simple like for like swap of their existing
process of flight dynamic modelling for an easier, faster and better solution.
The J2 Universal Tool-Kit enables companies to utilise an integrated collaborative platform for their
design and analysis process and to change their fundamental approach to aircraft design, enabling
the flight test and certification program to be investigated from the very beginning. This will produce
growing confidence and increased fidelity throughout the design and analysis cycle and will result in
the aircraft get certified sooner and know that they have developed the best solution possible to
meet the mission requirements.
In a traditional process, aerodynamics are developing the airframe, passing that information to
structures and weights groups who are calculating their information. At the same time the design is
changing. Once everyone is happy with the data they eventually send it to Flight Mechanics for
analysis. FM investigates behaviour and then sends the data models to be evaluated by FCS. The
design is then updated based upon the findings and the whole process repeated.
Aerodynamic Design
Structural Design
Weights Analysis
Flight Mechanics
FCS Design
Classical Waterfall Approach to Design
This process can lead to frantic activity when new data is delivered and periods of frustrating
inactivity when the analysis is complete and the next set of data is being generated. Inherent in this
approach is the ability to introduce errors through data transfer techniques, as well as introducing
further errors through attempts to streamline the process by starting work on incomplete data.
With the J2 Universal Tool-Kit these issues are totally
eliminated due to the centralised database and the way
in which each discipline can interact directly with the J2
solution.
Throughout the design lifecycle of the aircraft each discipline can continually add information and
analyse the most current design. The central database provides version control and configuration

11. management so even when analysis is started on an intermediate solution, as the solution evolves
and takes shape, so the analysis can be simply re-run with the most up to date solution
automatically. This dramatically tightens up quality control of the iterative loops of the design cycle
to the point of complete interdisciplinary concurrent design.
Aerodynamic Design
Structural Design
Weights Analysis
Flight Mechanics
FCS Design
Reducing Timescales with a Data Centric Environment
The key benefits of these improvements are that other disciplines can utilise the data and results
developed from analysis performed by other engineers with the same model without the need to
perform their own trim and response analyses.
For example
Structural Engineers can extract the loads information from the flight test cases already run
by Flight Mechanics.
Aerodynamics can develop tolerance models for sensitivity studies and FCS can re-use their
analyses to assess the robustness of the controller.
Weights group can change CG locations of the whole aircraft or individual components, and
Flight Mechanics can compare the different scenarios and how it affects stability and
handling qualities.

12. CL
CLo
CL
Tolerances to the Lift Curve Slope
Applied to the Baseline Aircraft and Documented

13. FLIGHT TESTING
Performing flight trials from conceptual design
“Imagine the possibilities if you could take any aircraft concept and immediately understand how it
will behave, and be able to perform all flight trials and certification flights instantly”.
This is not a dream. Using the J2 Universal Tool-Kit unlocks this potential and is exactly what you can
do.
When presented with a Mission Specification and Requirements for an aircraft, one of the first
stages suggested is to understand how the aircraft is to be tested and certified/validated. How are
flight test going to perform their process? These validation manoeuvres can be built into the J2
Universal Tool-Kit right at the beginning of the design stages and the aircraft can be “flown” through
the complete flight test program at any stage in its development cycle. What is even more beneficial
is the ability to rapidly create variations of the original aircraft model enabling the complete flight
envelope to be “flown” over numerous aircraft and all the results then compared. The benefit is
that the impact of configuration changes, aerodynamic tolerances, and sensitivity studies can all be
performed by only creating the data once.
These comparisons can be represented graphically or through real-time visualisation to really
understand what is happening to the aircraft.
Comparing the Impact of Design Changes on FAR 23 Aircraft Roll Characteristics

14. From conceptual design, as the aircraft evolves, it is possible to simply re-run the analyses
automatically using the latest design and latest version of the data without having to re-create the
test cases. By the time the design has reached CDR the configuration is settled and engineers
already have great confidence that the aircraft will satisfy design goals and receive certification.
However, even at the final stages of the design, through to the actual flight trials, the J2 Universal
Tool-Kit provides continual support to the engineers. Data from the flight test data recorder can be
loaded into the J2 solution to enable an observer to follow the aircraft and view the flight from the
comfort of their own desk using the unique 360 degree visualisation plug-in. This data can then be
used to perform re-prediction analysis of the flight model using original pilot inputs to evaluate and
assess the model against the real aircraft. This can be further used to refine and validate the model.

15. Visualizing Flight Test Data and Comparing Predicted Flight to Flight Tests.

16. WHY NOT FLY?
What do pilots think of the latest design?
To obtain pilot opinions of aircraft in
early stages of design classically requires
the development of real time code,
look-up tables and interpolation
routines and any number of steps just so
that it can be connected into a
simulator. The effort involved often
negates the benefits as the aircraft’s
design has moved on by the time the
solution is developed. But Pilot opinion
is important, this is why the Copper-
Harper Rating, and Pilot Opinion
Contours have been developed and are
used in evaluating aircraft.
This is not the case with the J2 Universal
Tool-Kit. In this case the real-time
capability is already integrated; the
dynamic model has already been
developed, so in order to run pilot-in-
Desktop Simulation with the J2 Universal Tool-Kit
the loop simulation of any aircraft within
the database requires a few simple
mouse clicks. In this respect, pilots can
give instant reaction and feedback to
different designs and different options.
This feature can be used as a simple
desktop simulator for basic handling
evaluation, or can be integrated across
the network directly into a full mission
simulator using standard CIGI graphics
interface and cockpit inputs/controls.
All this can be achieved without the
need to write any aircraft specific code,
so pilots can fly the aircraft instantly.
Automatic Integration of the J2 Universal Tool-Kit
into a G-Cueing Full Motion Simulator

17. CONCLUSION
More than Dynamic Modelling
All the functionality described above is not the result of utilising different tools to manually develop
responses or trims. There are no complex text files that need to be mastered before anything can be
achieved or software and scripts to be written to start the first analysis.
The full capability is available from a single integrated toolset that utilises easy to use graphical
interfaces and built-in domain knowledge to produce rapid prototyping and developing of aircraft
through comprehensive stability and control, handling qualities and behavioural analysis. The J2
Universal Tool-Kit focuses on engineers being able to arrive at results and produce data faster and
more efficiently, so they can spend more time designing the aircraft and less time designing the
tools.
From concept to completion, it is possible to build and fly the complete flight test program;
integrating data across disciplines automatically without the need to transfer files and the J2
Universal Tool-Kit improving design cycle QC and maintaining consistency through a data centric
approach. All engineers can have access to results for further post processing. Where existing tools
and processes exist, the best of these can be integrated into the complete J2 Universal tool-kit to
ensure continual workflow and no reduction in productivity due to changeover.
As has been demonstrated above, all this capability does not just sit with a single flight dynamics or
simulation engineer, but is utilised throughout the company bringing all departments together for an
improved design process. The functionality and the way the data is managed, demonstrates that the
J2 Universal Tool-Kit is much more than a dynamic modelling solution.
For this reason alone many companies and research establishments across the world have adopted
or are adopting the J2 Universal Tool-Kit into their design process. These include:
EADS
Embraer
Korean Air
National Aerospace Laboratories India
Cranfield University
Arizona State University
Allow J2 Aircraft Dynamics to demonstrate how your organisation can realise these benefits and
improve on the design lifecycle process.

18. IT TOOK J2 AIRCRAFT DYNAMICS’ AEROSPACE ENGINEERING AND AIRCRAFT
DESIGN SPECIALISTS OVER 10 YEARS TO BUILD THE ‘CODE’ THAT ENABLES THE
UNIVERSAL TOOL–KIT TO INVESTIGATE ALL ASPECTS OF AIRCRAFT HANDLING
AND PERFORMANCE.
WE HAVE DONE ALL THIS SO THAT YOU DON’T HAVE TO.
This state-of-the-art, but easy-to-use software PLUG-INS
suite gives you unprecedented power to design
J2 Builder
and ‘fly’ multiple configurations of the complete An easy-to-use graphical interface that
flight envelope in a 3-D virtual environment – all rapidly develops aircraft models and
at the click of a mouse! When using the J2 builds multiple variants for comparison
Universal Tool Kit, you can save hundreds of
thousands of dollars by streamlining your J2 Elements
process, maximizing your analysis capability and Enables automatic calculation of total
aerodynamic coefficients and derivatives
reduce the risk of serious project flaws. through integrated strip theory.
J2 Developer
At the heart of J2’s A Software Development Kit (SDK) for all
software is the J2 users to write their own components and
Universal Framework, libraries with an interface into J2 Aircraft
Models.
a cutting-edge
configuration control J2 Freedom
Provides flight dynamics simulation of
and data management aircraft data models, allowing you to
platform that hosts all evaluate the complete flight envelope.
steps of the design
process. Everything J2 Active
we offer begins and An open COM interface that instantly
interacts with this key integrates your existing design packages
with the power of the J2 Universal Tool-
framework.
kit.
J2 Matlab Toolbox
Get the full capability of J2 with Simulink
Now it’s time to investigate our range of plug- Model files. Manoeuvres from within J2
ins. ‘Mix and match’ their additional design and can be flown on Simulink Models. Run all
analysis capabilities using floating licenses. Take analyses from within J2 Universal Tool-
control of a bespoke package that perfectly fits Kit.
J2 Visualize
your requirements. This way, you get Instant understanding and evaluation of
the right functionality and maximise the return aircraft behaviour through data
visualization and graphic displays.
on your investment.
J2 Virtual
View any results in a virtual 3-D real-
ARE YOU READY TO RETHINK THE WAY YOU world, to understand what exactly
DEVELOP YOUR AIRCRAFT? happens during unexplained/complex
manoeuvres
J2 Pilot
To find out more about J2 Aircraft Dynamics, Using the J2 Pilot plug-in’s automatic
interfaces/models you can fly aircraft on
our software and our consultancy services, visit your. You can also use J2 Pilot interfaces
www.j2aircraft.com to merge the finished design into pilot
training simulators.