To trigger an avalanche, a coded command is sent from the control centre WAC.3 to the control system of the deployment box to initiate blasting. The deployment box contains 12 prepared explosive charges, which can be individually deployed by remote control. When the explosive charge is dropped, two igniters are pulled and the explosion is set off after a time delay. The charge remains hanging from a cord at a pre-set height above the snow cover, which is completely dropped after blasting. To reload explosive charges the complete deployment box is lifted from the tower by helicopter and brought to a station building or warehouse respectively.
The solar panels, antenna and a flashing lamp are mounted on the outside of the deployment boxes. The dropping mechanism, the electronics and 12 prepared explosive charges are on the inside of the box and protected against the elements. The compact and sealed design means that maximum system reliability is attained.
The explosive charge consists of two orange half-shells with pre-mounted SZ 83 percussion fuse, which are assembled with 5kg of explosives. The charges are assembled by the operator on-site. We deliver the charge containers and the canvas bag for the retaining cable (7.5m) Explosives and other pyrotechnical elements are purchased directly by customers from the appropriate suppliers.
From the operator’s point of view, a blasting installation must be extremely reliable and effective as well as being simple to operate and maintain. The installation in the terrain must be as simple as possible and the interference of the installation must have a low impact on this sensitive environment. The Wyssen avalanche tower fulfils these requirements ideally.
|Wyssen Avalanche Tower LS12-5|
|Weight deployment box complete incl. charges||approx. 600 kg|
|Dimensions Deplyment box (l x b x h)||1600 mm x 1050 mm x 1200 mm|
|Dimensions of tower (h x ø)||8000 mm x 300 mm|
|Inclination of tower||15° in direction of slope
towards the valley
|Number charges per launcher||12 pcs.|
|Amount of explosives per charge||max. 5 kg|
|Drive unit||DC motor|
|Time for rotating one position||approx. 13 s|
|Transmission Gearbox||gear motor|
|Battery in deployment box supplied by solar panlsl||12 V|
The latest software generation including new hardware for operating, monitoring and data storage of the well-proven Wyssen Avalanche Tower LS12-5.
Data connection via mobile network or radio
The deployment box is transported by helicopter to the towers in the terrain. Thanks to the guiding system the pilot is able to perform the placement on the tower on his own without a flight assistant.
The deployment box orientates itself automatically in the correct position. A safety switch detects the correct position, after which the system becomes operational. The operation can verify the placement of the deployment box on the correct tower on the operating interface immediately thanks to the GPS receiver installed. The system will not be activated if placement is incorrect.
When all charges are used or after end of season the deployment box is being retrieved from the tower by helicopter. Thanks to the special Wyssen Heli link no flight assistance is needed in the terrain.
The helicopter company must have an authorisation in order to carry loaded deployment boxes. Depending on the country, the intended flight routes with loaded deployment boxes must be approved by the flight authorities.
The helicopter routes taken by which avalanche tower deployment boxes are transported must be so chosen that from the loading place to the avalanche tower a distance of at least 500m is maintained at all times and in all directions away from any persons not involved in the operation. Flying directly over populated areas, open roads as well as people, technical installations (e.g. mountain cableways, mountain restaurants and relay stations) and open ski runs is prohibited.
Only those persons are permitted to operate and handle the installation who are in possession of a valid certificate for the artificial release of avalanches with explosives and who have attended a certified course by Wyssen Avalanche Control AG. Furthermore, it is very important that the operating staff have the corresponding training and experience for risk assessment, planning of measures, implementation of measures as well being able to assess secondary avalanches and avalanches that could be larger than expected.
Approval for storing explosives: for each tower location authorisation must be requested by the customer from the responsible authorities for storing explosives in the avalanche tower deployment boxes during the period of operation.
It is known from practical experience and from the theory of avalanche release in deep winter, that the effect of a detonation above the snow cover leads to the best results with respect to residual risk of unpredictable avalanches. The explosives used should produce a high detonation speed and a large volume of gas with a high work factor. Tests with numerous experiments show that explosives with the above-mentioned properties and charging positions above the snow cover give the highest effective ranges.
The following table from the WSL Institute for Snow and Avalanche Research SLF Davos Report no. 53/1996 shows the approximate effective ranges for dry new snow of various explosive charge sizes in different positions with respect to the snow surface.
In order to test and to safeguard the avalanche release zone, the whole of the potential release area must be subjected to an additional stress (e.g. by a detonation). This is necessary, because the location of the so-called “hotspots” (super weaknesses) are not known in advance. An acceptable residual risk after blasting operations is only then reached if these “hotspots” have been subjected to a sufficiently high additional stress by high strain rates at the weak layers within the snow cover.
For more information:
|Height of detonation point||Charge size||Radius of effective range
to prevent a natural release
|Radius of effective range
to prevent a release by a single skier
|Blasting above the snow (+3 bis 3.5 m)||4 to 5 kg||120 to 130 m||70 m|
|Blasting above the snow (+2 bis 2.5 m)||1.5 to 2.5 kg||80 to 90 m||50 m|
|Blasting above the snow (ca. +1 m)||4 to 5 kg||80 to 90 m||50 m|
|Blasting above the snow (ca. +1 m)||1.5 to 2.5 kg||60 to 70 m||35 to 40 m|
|Surface blasting||4 to 5 kg||50 to 60 m||30 to 35 m|
|Surface blasting||1.5 to 2.5 kg||35 to 40 m||20 to 25 m|
|Blasting in snow (ca. -0.2 m)||4 to 5 kg||40 m||25 m|
|Blasting in snow (ca. -0.2 m)||1.5 to 2.5 kg||25 m||15 m|
|Blasting in snow (-0.7 m)||1.5 to 5 kg||10 m||5 to 10 m|
|Mortar 12 cm (0 m)||3 kg||40 m||–|
|RPG 8.3 cm (0 m)||0.7 kg||20 to 25 m||10 to 15 m|
|Mortar 8.1 cm (0 m)||0.6 kg||15 to 20 m||10 m|
Source: SLF Mitteilung Nr. 53