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the Design with “given means”.
The number of parameters used will increase and the input data will become more accurate. Certain
information will be sourced directly from product databases. The “flexible engine” is substituted by a
real engine which closely matches the properties of the “rubber engine”. Values, which in the previous
stage were selected by statistical analysis, will be verified by extensive algorithms. The increase in lift
for the type of flaps used will be computed. The total drag will be defined more precisely as the sum of
specific drag components. A weight estimate will be made. All flight conditions will be explored. The
stability will be checked. Finally, a 3D model will be generated which will enable the results of the
design process to be verified and appreciated visually.
Level 3
The final stage in the process is the design with “given geometry”.
One goal is to show what the effect would be of parameters that are “off-target”. What will be the
impact on the aircraft performance if the weight of the aircraft turns out to be slightly different? What
margins are acceptable? Where is the limit to be set?
It is also possible to show the impact of modifications to an existing aircraft. What is the overall impact
on the aircraft of a wing modification? Change in weight, change in drag, change in performance,…
The improvements obtained in reality can often be very different from what was initially expected or
aimed for.
Optimal Aircraft Design
Optimal Aircraft Design SPRL Tél.: (32) 81 21 26 87 TVA.: BE 887 679 266
Rue de l’Yser, 31 Fax.: (32) 81 21 26 87 Banque : ING 363-0097122-65
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Belgique Code BIC : BBRUBEBB
It is also possible to analyze the performances (take-off, climb and cruise) of a given aircraft for
different flight conditions (flight weight and flight altitude).
Optimal Aircraft Design
Optimal Aircraft Design SPRL Tél.: (32) 81 21 26 87 TVA.: BE 887 679 266
Rue de l’Yser, 31 Fax.: (32) 81 21 26 87 Banque : ING 363-0097122-65
5020 Namur E-Mail: info@oad.aero IBAN : BE18 3630 0971 2265
Belgique Code BIC : BBRUBEBB
3 Work done in the research department of a company
Now imagine that you are at the head of a research department of a company. A customer comes to
you and asks you to design a new twin-engine aircraft. Its specifications are listed here under. He has
very strict requirements on particular things and gives you freedom in other areas.
You enter the data in ADS. You get one solution.
Then you decide to change one parameter. You will shift the wing backward to improve the visibility for
the pilot and passengers. The longitudinal position of the wing will be changed from 20% to 50% of the
fuselage length. ADS computes. Of course there is a problem. The centre of gravity is too much
forward, and you have to solve the problem:
1. Change from tractor to pusher. ADS computes. The modification improves the design but it is
not sufficient.
2. Change from a standard configuration to a 3-surfaces configuration. We define the
characteristics of the canard surface using the historical value proposed by the On-line help.
ADS computes. Again this modification improves the design. If we increase the size of the
horizontal tail we will probably succeed.
3. We increase the size of the horizontal tail. ADS computes. Now it is OK. You can propose a
second solution.
Optimal Aircraft Design
Optimal Aircraft Design SPRL Tél.: (32) 81 21 26 87 TVA.: BE 887 679 266
Rue de l’Yser, 31 Fax.: (32) 81 21 26 87 Banque : ING 363-0097122-65
5020 Namur E-Mail: info@oad.aero IBAN : BE18 3630 0971 2265
Belgique Code BIC : BBRUBEBB
After 10 “clicks” we can come up with a new design that fulfills the customer’s specifications. Of
course, you may imagine that this design will be probably more expensive than the first one. We have
added additional components (canard surface), we have increased the size of the tail. Now the
question is:”Is there another solution, different from the last one which improves the visibility without
adding additional components on the aircraft?”
Remember what is the problem if the canard surface is removed. ADS computes. The CG is located
too much forward. What can we do to solve the problem? … We can try to sweep the wing forward.
We change from 5° to –5°. ADS computes. Now it is OK. You can propose a third solution.
Very quickly, with ADS, you are able to define the main characteristics of different designs
(performances, weight, CG, stability, …) and select the most appropriate configuration.
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