Directional stability

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The directional stability (including price stability ) the assets describes each vehicle, especially a plane , its straight course to maintain. It describes the stability around the vertical axis when driving over the ground.

The most important role as a stabilizer for the course plays the vertical fin of the aircraft vertical tail , it brings the machine to be in flight like a wind vane to provide parallel to the wind direction.

It is crucial that yourself

  • far more lateral contact surface is located behind the center of gravity than in front of the center of gravity,
  • the stabilizing side contact surface behind the center of gravity is sufficiently far away from the vertical axis and thus engages with a favorable, long lever arm .

Then the aircraft will always position itself “in the airstream ” like the wind vane .

Explanation (greatly simplified)

The picture shows an airplane (from above and from the side) that originally flew in the direction of the old course , so that the airstream came from the front. Due to a disturbance in the flight attitude, the nose of the aircraft is now pointing in the direction of the disturbed course ; however, due to the inertia , the aircraft initially retains the original flight direction.

Direction640.png

As a result, now that the wind is not the aircraft more accurately from the front, but obliquely blow on the side.

The effects are shown in the diagram below: The side wind generates a torque that attempts to turn the front part of the aircraft further clockwise and further aggravate the disturbance of the flight position. The wind force on the rear of the aircraft creates a counter-clockwise torque, so it tries to turn the aircraft back into the original direction. Since the side of the attack surface behind the vertical axis is much larger and also acts mainly on a longer lever arm, the second moment predominates, and this resultant turns the aircraft back from the disturbed flight position to the old course until the airstream comes back from the front .

See also

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