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Schematic representation of the incident during the winch launch.
Schematic representation of the incident during the winch launch.

Incident during winch launch, ASK-23, PH-774, glider field Soesterberg

Status : Closed

The ASK-23, a single-seater glider, was occupied by a soloist. It was ready to take off from runway 31, using a winch launch. In this launch direction, the landing field is to the right of the take-off field. Due to the north wind, the winch cables had been reeled out on the north side of the runway, which meant that they were positioned between the takeoff field and the landing field. After an ASK-21 with an instructor and a student on board had landed far down the landing field, on the south side, the soloist indicated that he was ready for take-off, after which the winch cable was pulled taut. The instructor in the ASK-21 that had just landed noticed that the left wing of his aircraft was lying across two winch cables, including the one that was being drawn taut. When the instructor saw that the cable was being winched-in and was gaining speed, he and the student quickly got out of the ASK-21 and lay down on the ground. The winch cable cut into the tip of the ASK-21’s left wing. When the ASK-23 lifted off the ground, the cable lifted the wing of the ASK-21, which then rotated approximately 180 degrees on its vertical axis, hit the ground hard and came to a stop. The winch cable detached itself from the ASK-23 prematurely, at an altitude of approximately 50 metres, because it had been caught up by the wing of the ASK-21. The soloist then flew straight ahead and made a safe landing. The instructor and the student were unharmed. The left wing of the ASK-21 was badly damaged.

The following three factors contributed to the occurrence. First, the wing walker, signals operator, and soloist did not consider the ASK-21’s position in the landing field to be unsafe, so they gave the go-ahead for the ASK-23’s takeoff. The club in question had no clear guidelines for determining when runways are clear and when take-offs can subsequently be initiated. Second, the cables had been reeled out further into the field than those involved had assumed. Nor had anyone at the takeoff point noticed that the ASK-21 (which was located far down the landing field) was lying across two winch cables. Third, the ASK-23’s winch launch was not supervised by an instructor and/or a launch leader – both of whom were doing something else at the time of the occurrence.

The safety committee of the gliding club involved carried out an investigation into the occurrence, and shared the results with the Dutch Safety Board. One of the committee’s recommendations concerned the use of a safe sector, which should be free of obstacles during take-offs.

This serious incident can be found in the quarterly aviation report over the 4th quarter of 2020.

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