Wool yarn (Instruments of flight)

On a Sailplane, the wool yarn is a wool bit from 10 to 20 cm length, fixed at one of its ends on the canopy, outside and in the medium, in the field of view of the pilot; for the sailplanes two-seater out of tandem, one 2nd wool yarn is placed in the field of view of the back pilot. He behaves like a wind vane and indicates the direction of the relative wind. If the symmetry plane of the fuselage is parallel to the relative wind, the wire is in the axis; if the sailplane is in slip (evolves/moves out of crab), the wire is put transversely, in the bed of the wind.

If, in a turn, the sailplane tends to slip (excessive slope which makes " glisser" the sailplane towards the interior of the turn) the wool yarn will point in the direction opposed to the turn. On the other hand, if, in turn, sailplane has tendency to skid (insufficient slope which makes skid the sailplane towards the outside of the turn), then the wool yarn will point in the direction of the turn. A correction coordinated using the Swing bar and of the handle makes it possible to maintain a flight symmetrical with the wool yarn in the medium.

In all the cases the wool yarn will deviate on the side opposed to the ball; to cure it the pilot will act on the swing bar side relative wind and of the handle of the other with dimensions. It is said that the swing bar " push back the ball and attracts the fil".

The inertia of the wool yarn is quasi null, it is much more reactive than the ball and moreover placed in the field of view.

Let us note finally, that in turbulent environment, and by great slope, it can be disturbed by variations climbing speed of the atmosphere.

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Wool yarn (Instruments of flight)

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