3-leg logic

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The 3-leg logic , also tripod logic or tripod logic , consists of three principles that must be adhered to in order to avoid accidents when belaying a climber. They were formulated by Walter Britschgi in order to avoid incorrect operation, especially of semi-automatic machines like the Grigri .

Brake hand principle

The brake hand principle states that one hand must always hold the brake cable. Mainly in the fast of rope in lead climbing it requires practice. In the case of a semi-automatic machine, the blocking function must be switched off. If one hand is used entirely for this, the other to spend the rope, this principle is violated. This has already resulted in fatal accidents and destroyed the illusion that semi-automatic machines completely prevent accidents.

The gasworks method, on the other hand, observes the brake hand principle and allows the rope to be paid out quickly.

Even when draining a hand must be at Grigri the brake cable take, only then the drain lever must be pressed. This is because this is not designed for the dosage of the discharge speed, but only knows the blockade / non-blockade modes. The wrong order has already resulted in accidents with falls and burns on the belayer's hand.

With the Tube, Eighth and HMS, the DAV recommends that the braking hand be closed, i.e. that the thumb and index finger form a ring. Otherwise the brake cable can slip out of your hand in the event of a fall in the event of a slight carelessness, and the grip reflex (see below) can then lead to the braking hand grabbing the wrong cable.

The braking hand principle is also violated if there is too much slack rope, as the braking hand then becomes inoperative.

The braking mechanism of the device

The braking mechanism of the device must work. The positioning of the braking hand is important for tubes , autotubes and abseiling figures . This must be under the belay device , unless the rope is being pulled in. The wrong carabiners can also cancel the braking mechanism. If the carabiner is too small, the belay device can jam; some carabiners with positioning (e.g. the Belay-Master ) can prevent the click-up from slipping into the blocking function.

Reflexes of man

Finally, the natural reflexes must be observed. In a dangerous situation such as a fall, the grasping reflex leads to the belayer grasping what he is holding in his hand even tighter and pulling it towards him. Pulling the lever of a Grigri and GriGri 2 towards you when falling is wrong. Here the Smart is superior to the first two versions of the GriGri, as the braking hand is positioned here under the belay device and the grip reflex causes the braking hand to be pulled towards the body.

Based on this problem, Petzl released the improved GriGri + in 2017. The integrated anti-panic mechanism blocks the rope immediately when the lever is pulled through completely.

Incorrect use of the Grigris

Using the 3-leg logic, incorrect operation of the Grigris, if the lead is not issued according to the gas works method, but one hand holds the locking mechanism and the other hand releases the rope, can be explained as follows:

  • The brake hand principle is violated, no hand holds the brake cable.
  • The braking function can no longer work because it is blocked by a hand.
  • In the event of a fall, neither of these would be a problem if the belayer would stretch both hands away. However, the gripping reflex can lead to the lead hand holding the rope and the earlier braking hand holding the locking mechanism. The result is the climber falling to the ground and the belayer's hand burned.

literature

Individual evidence

  1. ↑ Safely secure with tripod logic. In: DAV Panorama 3/2010, p. 67 ( PDF )
  2. ↑ Video library security devices ( Memento of the original from December 18, 2014 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. , German Alpine Club @1@ 2Template: Webachiv / IABot / www.alpenverein.de
  3. ↑ http://www.bergundstieg.at/file.php/archiv/2004/2/print/64-69%20%28sicherheit%20partner%20sichern,%20teil%201%29.pdf
  4. ↑ Hellberg, Florian u. a .: How much does the device help us? Semi-automatic machines - strengths, weaknesses, differences, in: Panorama 5/2015, pp. 62–63.
  5. ↑ http://www.bergundstieg.at/file.php/archiv/2004/2/print/64-69%20%28sicherheit%20partner%20sichern,%20teil%201%29.pdf