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14.3: Stability Measure

Click the folder button 'Design Computation' and click into input field 'Stability Meas. [%] l_my' to enter the desired value. Valid values lie between -100% and +100%. A measure between 5% and 30% is common.

The bigger the stability measure, the more senseless reacts the airplane on disturbances. This might be e.g. a gust, but also the effectiveness of flaps and the horizontal stabilizer decreases.
The stability measure determines the distance between the aerodynamic neutral point and the airplane's centre of gravity. Stability measures smaller 0 indicate instability; the airplane cannot be controlled by hand.
Near the input field are Up/Down-buttons located. They can be used to change the stability measure with mouse clicks.
A click on the right mouse button pops up a menu to set the increment between 0.00001% and 1%.



Below the input fields the button 'Start Computation' is located. If you click this button, the Vortex-Lattice computation will start. An iteration computation with several passes (approximate computation) starts. The program changes stepwise the angle of attack to approximate the desired stability measure. If the program exceeds 90° angle of attack, the computation will abort with an error message.


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