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[vagos]

Mετα το ωραιο και χρησιμο post του Vatsouk, βρηκα και αυτο :





“There are plenty of stories, tales, and rumours about stable spirals. We would like to explain the situation, what we think about the rumours, and what matters for certification.

During the certification test flights, the paraglider is accelerated into a spiral by pulling the brake on one side until a descent rate of –14 m/sec is reached. Then, the brake is released rather fast and completely while the weight of the pilot is following passively the harness’ / wing’s movement. If the paraglider does not stop the spiral by itself, the spiral is considered stable and the wings does not pass the certification.

However, it is possible that a wing meets these criteria, but when the brake is released during a spiral with a descent rate of MORE than 14 m/sec, the paraglider keeps on spiralling. The descent speed might further increase, reaching considerable rates! The loss of altitude might reach 75 meters in one 360-degree turn.

The power needed on the outer brake to terminate the spiral can be really considerable. In addition, the pilot might be shocked due to radical and high acceleration forces. As a result, he might get the impression that it is impossible to stop the spiral.

However, I am sure that there are no spirals that can’t be terminated at all or only with excessive effort. But there are definitely wings on the market, which aggressively keep on accelerating and require energetic action from the pilot.

Yet, every pilot should be aware that unfavourable circumstances may lead to a compulsory use of the outer brake – regardless of paraglider model. We generally say that a pilot should not blindly rely on his wing to finish the spiral automatically. Be mentally prepared to use the outer brake with a lot of power – always! If not, your flying can be dangerous.

A fully controlled steep spiral is a demanding manoeuvre. The pilot must not only know about the reaction of his wing, but also about the reaction of his body. So we highly recommend approaching slowly into steep spirals – ideally in an SIV course."