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all the information I have to enter in the software?» The data sources are: the press articles, the
manufacturer’s website, the aircraft owner’s manual, and a 3-view drawing. We have developed a
digitizer to exploit 3-view drawings. You scan a picture and generate a bitmap file. Then you import the
file in ADS. You georeference this image. This is done by giving the aircraft length and the wing span
for example. And then you can exploit this image and retrieve a length, a length ratio, an angle, and a
surface. This is very simple and very accurate. And you cannot imagine how many information you
can extract from a plain drawing.
During the design process we advise you to analyze at least 10 aircraft before starting your own
design.
When you have analyzed about 10 aircraft, you start to design your own aircraft using the design
module of ADS. You have to input about 70 items. A progress bar shows the input you have already
entered and how many are remaining. We invite you to consult the On-line help window to enter the
Optimal Aircraft Design
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right value, you may catch some information from engines, airfoils and tires database. All the
information you have to enter is necessary to compute the performances of the aircraft, its empty
weight, the specific drags, the centre of gravity position and the 3D model. When everything has been
defined, you start the run. The calculation will take a while. During this time, ADS computes the main
dimensions of the aircraft, its performances during the cruise, the takeoff, and the climb. If we design a
twin-engine aircraft, the performances will also be computed with one engine inoperative. The centre
of gravity positions are computed. The stability is determined and the 3D model is generated.
When the results are displayed, the first thing we have to do, is to check the 3D model and watch if the
3D model looks like an aircraft. Let’s say a few words about the 3D model. This module runs like a
light expert system. For example, in the acquisition window, you have never introduced information
about the landing gear except the tire size. The length of the gear has been defined from the propeller
diameter and the minimum propeller ground clearance. The lateral position is defined so that the angle
formed by a line connecting the wing tip and the contact point of the main gear with the ground and
the horizontal is greater than a minimum value. The longitudinal position of the gear is defined
according to the centre of gravity position of the aircraft. The shape of the fuselage is generated to be
aerodynamically clean and to localize the main bulkhead at the trailing edge of the wing, … The
results are presented in the same manner. The characteristics of the wing, the tails and the fuselage
are presented in some specific windows. The specific weights are also given. The performances for
cruise, climb and takeoff are displayed. The speed polar is given in a table as well as in a graph. The
centre of gravity is displayed in a graphical way. The specific CG are displayed. The CG position of
the aircraft at empty weight and at all-up weight are displayed. The fore and aft limits are also
displayed. The CG can never go beyond these limits if it is to remain stable as well as controllable.
When you have designed an aircraft and you think that the selected configuration is the right
configuration, you have to check its feasibility. This is done using the Statistical module. You compare
your design with all the others that are contained in the database. You select one or two parameters
and you visualize the information in a graph. If your new design is better than the best aircraft you
probably have been too optimistic with the data you entered in the acquisition window (too low friction
coefficient, …). On the other hand, if your design is far worse than the worst, you may question
yourself if it is worthwhile to spend time and money to develop something that would not be possible to
sell. If you are between these two limits you will probably succeed in your design. This final check is
vital in the design process.
Let’s say a few words about the databases
You have aircraft, engine and airfoil databases included in ADS. To access to the engine database,
click on the left menu. You select an engine in the list. And all the information about this engine is
displayed in the window. This information concerns the dimensions of the engine, the different
systems that are part of it, its weight, its performances. The performances curves are also displayed.
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