17.1: Flap Computations
The glider 'ASK21_EN.flz' shall now be used to explain the procedure with this
function. Please open the file 'ASK21_EN.flz'.
Now the screen looks as shown below.
First we enter the settings and a functional description for each group of
flaps. This eases later lucidity. Please select the horizontal stabilizer.
Switch to folder 'Wing' and select in the segment block the subfolder 'Flaps'.
The horizontal stabilizer consist of two segments, please select for each
segment the group of flaps 1 and enter in the input field 'Group of flaps /
Functional Description' the text 'Elevator'.
We proceed in the same way for the wing, use for the left aileron e.g. the
group of flaps 13 and enter the functional description 'Aileron left'. The
right aileron gets the group number 10 and the functional description 'Aileron
right'.
Please select the folder 'Total-Polars Computation' and the subfolder 'Flap
Computations'. First we want to perform a polars computation for the elevator
control. Therefore select the horizontal stabilizer as shown below.
In the list shown below one can enter a group of flaps, the elevator has the
group number 1. So we enter in the top line '1' in column 'Grp. Flaps'. The
flaps functional description is filled in automatically.
If one does not know the number of the group of flaps, one can drag and drop
the flap from the 2D-graphic into the list. Therefore click the flap in the
2D-graphic with the right mouse button, keep mouse button pressed and pull the
flap into the list. Lines with group number '0' are ignored.
Next we define the flap deflection angles for the elevator. The elevator shall
be deflected from -10° to +10°. In the input field 'min. Angle[°]' we enter
'-10' and in the field 'max. Angle[°]' we enter '10'. Next we have to define
the number of steps in which the program shall solve the entered angles. We
enter '20' into the input field 'Number of steps'. The deflection angles of the
elevator will now be incremented by 1°-steps, so that we finally get 20 entries
in our polars table / graphic. As a last resort before starting the polars computation,
the program needs the information, if the angle of attack, the centre of
gravity or the CL shall be fixed. Default is the centre of gravity, the values
for centre of gravity and CL are taken from the folder 'Design Computation'.
One has to control, that reasonable values are available, otherwise one should
first perform a design computation.
The polars computation can now be started by click on the button 'Start
Computations'. First a window will pop up, in which we can enter a remark about
the computation, e.g. 'Test Horizontal Stabilizer'. After confirming the entry
with clicking on button 'OK', the polars computation will be started.
The program first sets all flaps to 0°. The originally settings of the flaps
are backed up, they will be restored after computation. In a loop the elevator
is set step by step from +10° to -10° in 1° decrements.
After the computations one can examine the polars. See: 17.3:
Viewing Polars as Table or Graphic
Computations with multiple Group of Flaps:
Up to now, we have only used one line of the list. It exists the opportunity to
enter multiple groups of flaps, which is useful e.g. for computations with
plain flaps. One can equip the both inner segments of the wing of the ASK21
with flaps. These flaps would form an own group of flaps with description.
See picture below:
The plain flaps are group of flaps 19 and the deflection angle is fixed to 5°.
The computation is started like described above.