Rope break
The term breakage means the glider sport the unpredictable rupture of the tow rope in the winch launch or aero-tow . When the aircraft breaks, the towing force on the aircraft suddenly goes to zero, and the remnant of the rope, which is hanging diagonally backwards from the aircraft, puts a strain on the aircraft due to the weight and drag of this piece of rope and the parachute that remains folded. The wing loading decreases sharply immediately, the pulling component in the forward direction disappears immediately. The plane continues its climb a few seconds under the action of its own momentum with degradation of driving only a short distance away. When the winch takes off, the pilot does not react immediately, and the flight speed falls below the minimum, resulting in stalling and tilting.
The likelihood of a rope break increases with the duration of the load due to the number of starts and with the strength of the load at each of the previous starts, additional loads from kinks, repairs and, of course, especially with the amount of tensile force in the rope at the currently considered winch start.
Trigger of a rope break
A rope break is mostly triggered by material fatigue on the steel or plastic ropes, which are up to 2000 m long and are exposed to high loads, especially at high starting frequencies. However, it also happens that climbing too steeply, especially immediately after taking off (so-called cavalier start ), exceeds the load limit. Even if a rope break is very uncomfortable and dangerous incidents can occur if the pilot reacts too slowly or incorrectly, if the load limit is exceeded it is the lesser evil compared to the destruction ( dismantling , dismantling ) of the aircraft structure and the resulting crash . For this purpose, all tow ropes must have a predetermined breaking point , which should break before the rope or the aircraft are damaged.
Reaction to a rope break during winch start
From the rapidly decelerating climb, a regular gliding flight at a suitable speed (80-100 km / h depending on the aircraft type) must be initiated by immediately pushing the control stick in order to continue flying safely. At the same time, the remaining rope still attached (on the winch maximum: pre-rope, predetermined breaking point, intermediate rope, rope brake parachute and torn tow rope) must be released by pulling the (yellow) clutch several times (usually three times) and thus thrown off. This avoids additional weight, additional air resistance and the risk of serious landing accidents due to the remaining rope getting caught.
The appropriate reaction to a rope break is trained in all possible constellations during training so that control of this situation is ensured.
Depending on the altitude at the time of the rope break, a distinction is made between two cases:
The breaking of the rope above the decision height
If the aircraft has almost reached the normal release height at the time of the rope break, only the remainder of the rope is released and the flight continues as normal. The wire rope failure occurs in an earlier start phase (100-150 m), is a truncated Place Round flown d. In other words, it is curved in the direction of the wind and landed by a shorter, but otherwise identical, traffic area.
Breaking the rope below the decision height
Depending on the length of the airfield and thus the area available for landing as well as the wind strength, the decision height can be quite different. It is about 100 m. Below this height you do not have enough time in gliding to fly a shortened traffic pattern. Then a steep descent is initiated immediately, where possible landing aids , z. B. flaps are used and / or the side glide (slip) is used. The landing then takes place in the take-off direction at the airfield. However, this form of landing requires a fairly long space. The often propagated turnaround is a stress factor, which unfortunately can quickly end in accidents with inexperienced pilots if not first consciously flown away from the field and the crossing (which is necessary especially with tight and therefore steep curves) is kept. In addition, a tailwind landing places additional demands on the target country ability of the pilot. Therefore, a safe outside landing in the take-off direction or only slightly deviating from it is the better alternative to breaking on or near the landing field despite the increased return effort (dismantling the aircraft, loading the trailer, upgrading on the field). For take-offs from unfamiliar places, exploring potential landing fields (e.g. using satellite photos) is an essential part of flight preparation.
Repair of the rope
A broken rope can be put back together by splicing . To do this, the two torn, often frayed ends are shortened to a regular cross-section of the rope by cutting and from here a piece is divided into its strands. These are then reassembled crosswise so that a section of the rope is duplicated. Theoretically, the strength of the original rope is more than restored, but it has proven useful to fix the ends of the splice with ferrules. Such a precisely executed splice is initially much stronger than the rest of the rope, but its thickness makes it significantly more bulky and wears out faster.