Avalanche release by helicopter

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The release of an avalanche by helicopter is, in addition to the manual release of avalanches, the most frequently used method of releasing avalanches in the Alps . The particular advantage of triggering an avalanche with a helicopter is that the avalanche's starting zone can be selected individually and according to the respective situation and the triggering can thus be enlarged.

general requirements

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The requirements for triggering an avalanche by helicopter differ from country to country (examples):

  • Approved helicopter (e.g. with double turbine and / or artificial horizon),
  • specially trained staff. Local must be present in the helicopter,
  • Approval for blasting work by helicopter or ignition with gas mixtures,
  • Explosives or ignition devices for gas mixtures are approved for this use,
  • Transport baskets / nets removed from the runners (when dropping / abseiling explosives from the helicopter),
  • Approval for the mission flight by the avalanche commission or authority, etc.,
  • Avalanche release sites must be determined before the flight,
  • Communication between all persons must be possible during the flight (e.g. via the on-board communication system Intercom),
  • During the flight, it must be possible for the chief of operations (e.g. those authorized to blast) to communicate with all barricades and other people involved on the ground,
  • there must be no people in the release area of ​​the avalanche or the scattering and pressure effect area from the detonation in the case of explosives (fly information round),
  • The avalanche release has to take place in slow, steady flight and individually in order to ensure a safe release.

For the height of the trigger point, the explosives and the amount of explosives as well as the ignition of the explosive or gas mixture, see: Avalanche triggering by explosives and artificial avalanche triggering .

Authority to issue orders and liability

The avalanche commission or a similar institution usually arranges for an avalanche triggering action for a specific area . A person authorized to blast , cable car company, road supervisor , etc. is generally not authorized to carry out avalanche explosions.

With regard to the execution of blasting work, however, the person authorized to blast is solely responsible and authorized to issue orders. It determines how the explosives and detonators are transported by whom, how much explosives are used, where the corresponding charge is dropped or detonated, how the locking and safety measures are to be implemented, who will accompany him and who will detonate the explosive charge, etc. For the use of this system in Austria, an explosives authority with special training in avalanche blasting from a helicopter is required.

Only the pilot is authorized to issue orders with regard to all aeronautical orders. He can z. B. also order the immediate dropping of all explosive charges or simply drop the triggering device by gas mixture ignition.

Avalanche release with explosives

Procedure and requirements

It can only be used when visibility is good and there is safe access to the launch site.

The individual charge per blast is usually around 4 to 10 kg. The charge is chosen to be larger if there is a risk that the explosive charge will sink into the snow, thereby eliminating a significant part of the detonation effect.

In order to minimize the risk of duds, the thrown charges can / must be provided with two detonators (two detonators, two safety fuses) (redundant detonation). When using detonators , the protective caps must be attached during transport in the helicopter so that accidental ignition is safely excluded. Marker lighters must be vibration-proof for use in the helicopter. The selected length of the safety time fuse must ensure that after an explosive charge has been dropped, the helicopter can reach a safe location before the charge detonates. Explosive charges must always be thrown off, even if the ignition has apparently not taken place or the effectiveness of the ignition cannot be reliably determined.

The explosive charge can be secured on a rope, then possible failures can be recovered from the avalanche slope. This controlled lowering of explosive charges and thus the use of optimized surface or snow blasting is z. B. no longer used in Austria.

If the explosive is thrown, it must not slide down the slope in an uncontrolled manner before it ignites. The explosive cartridges are z. B. pierced crosswise with two wooden skewers so that the explosive remains on the sloping snow surface.

Helicopter pilots and blasting officers may need to have special training. In Austria z. B. Basic training and retraining every five years required.

Failure elimination

RECCO strips

In order to be able to find failures ( duds ) more easily, the explosives can be equipped with a RECCO strip. Failures are to be recovered as quickly as possible. However, a minimum waiting time must be observed (in Austria e.g. 15 minutes after ignition until recovery).

Eliminating failure (explosives) by helicopter is a particularly difficult external task, as the person or persons who rescue them are hanging on a rope under the helicopter. In principle, only a helicopter that complies with Regulation (EU) 379/2014 is to be used for this. It is dangerous to hang up to try to fail at the mountain site and is also prohibited in some countries, as an avalanche can be expected at any time.

The time fuses attached to an explosive charge must be cut off near the explosive immediately after recovery in order to reliably prevent re-ignition.

Avalanche release by gas mixture ignition

The triggering of avalanches by gas mixture ignitions using devices that are attached to the helicopter must be carried out in accordance with the instructions of the manufacturer of the device. There are currently two devices in use: Daisybell and Avalanche Blast .

General

Both systems work according to a similar principle, a hydrogen / oxygen mixture ( oxyhydrogen ) is ignited on site at the potential avalanche starting zone about up to 5 meters above the snow cover. As with the use of explosives, the pressure wave can trigger an avalanche.

System advantages

The system with gas mixture ignition has advantages over the release of an avalanche with explosives (examples):

  • simple gas storage,
  • no manipulation with explosives required,
  • usually no specific training or approval required for use,
  • Installation and use possible even in places that are extremely difficult to access,
  • Ignition above the snow cover, therefore pressure wave on the snow cover,
  • no duds ,
  • Remote ignition (safety for operating personnel),
  • simple and inexpensive handling,
  • very short triggering consequences.

Daisybell

In the Daisybell® system, a bell-shaped device weighing around 600 kg with gas bottles hangs on a 20 to 30 meter long rope under the helicopter. The hydrogen / oxygen gas mixture is ignited as close as possible above the snow cover (ideally 0.5 to 5 meters). The distance between the bell-shaped device and the snow cover is recorded by laser distance measurement and the correct trigger position is determined and reported to the helicopter. The ignition bell is filled with hydrogen and oxygen before it is immediately used on site and is also automatically ignited immediately after readiness for operation is displayed.

All work processes are controlled from the helicopter. There are less than 10 seconds between release and ignition. 50 to 55 releases can be made with one unit, with only a very short waiting time between two successive shots. The resulting compressive force is comparable to a 0.8 m³ Gazex ignition tube .

Avalanche Blast

In the Avalanche Blast system, a latex balloon with a diameter of about 1.2 to 1.6 meters is inflated and ignited by a hydrogen / oxygen mixture. The hydrogen / oxygen gas mixture is ignited as close as possible above the snow cover (0.5 to 3 meters). Up to eleven ignitions can be carried out one after the other.

The system was made ready for series production by Werner Greipl as a prototype and by Elikos in Val Gardena in winter 2003/2004.

advantages and disadvantages

advantage

The particular advantage of triggering an avalanche with a helicopter is that the avalanche's starting zone can be selected individually and according to the respective situation, thus increasing the success of the triggering. Even if an avalanche does not go off, another attempt to trigger it in the vicinity can be started very quickly.

disadvantage

  • Flying weather and good visibility must be given. As a result, it is sometimes not possible to limit the size of the avalanche by triggering it early (e.g. during snowfall).
  • The flight lesson with a helicopter is relatively expensive. Nevertheless, the release of an avalanche by helicopter is still the most frequently used method alongside manual release. However, it can be assumed that in a few years an avalanche release with drones will almost completely replace manned helicopter flights.
  • The disadvantage of triggering an avalanche from the helicopter by dropping the explosive charge is that the explosive charge comes to rest on the snow cover or sinks into the soft snow cover and does not, as would be optimal, detonate 0.5 to 3 meters above the snow cover.

Detection

Whether the detonation and the triggering success occurred and to what extent and at which point of detonation / ignition point must be checked (visual inspection) and documented. Under certain circumstances, the avalanche commission or authority must also be informed about the success of the avalanche release.

If explosive charges are dropped in a series, the time fuses must be dimensioned in such a way that it is possible to check whether all explosive charges have detonated.

See also

Web links

Individual proof

  1. ↑ Lukas Stoffel: Comparison of the blasting methods: Gazex, Avalanche Guard / Mast Inauen-Schätti, Wyssen Sprengmast, Avalancheur , Comparison of methods for artificial avalanche release, WSL Institute for Snow and Avalanche Research SLF, January 24, 2013, p. 3.
  2. ↑ § 25 Paragraph 5 Blasting Work Ordinance, Federal Law Gazette II No. 358/2004.
  3. ↑ Christoph Skolaut, Florian Rudolf-Miklau: State of knowledge about the use of artificial avalanche triggering in Austria. In: State of the Art for Artificial Avalanche Triggering. July 2014, p. 13.
  4. ↑ Philippe Berthet-Rambaud, Louis Noel, Bruno Farizy, Jean-Marc Neuville, Stéphane Constant, Pascal Roux: DEVELOPMENT OF AN HELICOPTER-BORNE GAS DEVICE FOR AVALANCHE PREVENTIVE RELEASE , International Snow Science Workshop 2008.
  5. ↑ MAK: Daisy Bell - safe release of avalanches by helicopter in Mountain Manager 8/2008, p. 74 f.
  6. ↑ Manufacturer: Gummiwerk Czermak & Feger.
  7. ↑ THE LATEX BALLOON in its diverse application, here on avalanche detonation, website: ballonpoint.com.
  8. ↑ Lukas Stoffel: Comparison of the blasting methods: Gazex, Avalanche Guard / Mast Inauen-Schätti, Wyssen Sprengmast, Avalancheur , Comparison of methods for artificial avalanche release, WSL Institute for Snow and Avalanche Research SLF, January 24, 2013, p. 2.