Long-term chemical-mechanical igniter

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Chemical-mechanical long-term detonators ( LZZ ) are a type of time detonator . In the air war of World War II , they have been widely used in bombs of the British Royal Air Force and United States Army Air Forces used (USAAF). They were supposed to hinder fire-fighting and rescue work or make it impossible and, as a result of the detonation, even hours after the end of the air attack , hit people who had left their shelters . The insidiousness of these bombs was therefore particularly denounced by Nazi propaganda . Whether their use was a crime against humanity is still discussed today (see also Hague Land Warfare Regulations of 1907, Art. 25).

Non-detonated bombs (including those with conventional impact fuses ) are in an extremely dangerous condition due to aging processes. The position of these duds must not be changed under any circumstances. After reporting to the police, the ordnance disposal service is informed, which either defuses the bomb or detonates it in a controlled manner.

Colloquially , the LZZ are also called acid detonators , although the acetone used belongs to the ketones and is not an acid , but a solvent.

Working principle

Delay fuses were usually built into the rear of the bomb (floor fuses) so as not to be damaged on impact. The firing pin is held in place by one or more celluloid disks , over which there is a glass ampoule filled with acetone . The glass ampoule is destroyed during or during the drop, the escaping acetone dissolves the celluloid platelets and, depending on the number or thickness of the panes, the firing pin is released after a few hours or days and detonates the bomb. In order to avoid that aerial bombs are defused by unscrewing the detonator before the delay time had expired, dismantling barriers were installed in a few cases, which detonated the bomb immediately when attempting to defuse it.

United States

With American bottom fuses for GP and SAP bombs from 100 to 2000 pounds of the type M123, 124 and 125 (older models) or M123A1, M124A1 and M125A1 (newer models), the glass ampoule was dropped in free fall through one of one Wind turbine- driven release spindle destroyed. A minimum height of 100 feet (approximately 30 meters) or, for older models, up to 1,800 feet (550 meters) was required for this process. The delay of the release mechanism could be adjusted to a delay of 1 to 144 hours (6 days) using a celluloid ring or hollow cylinder with variable wall thickness. After the firing pin is released, it strikes the detonator with the initial explosive and detonates the main charge.

The detonators are largely identical in structure and only differ in the length and function of the trigger spindle, which leads through the tail unit of the bomb, which was different in size depending on the size of the bomb. On the newer A1 models, the release spindle was driven directly by an 8-blade wind turbine, while the older models had a gearbox and 4 blades. These detonators react very specifically to temperature fluctuations: temperatures above 10 ° C accelerate the process, below 10 ° C the process is inhibited. At a temperature of around -4 ° C, with a nominal delay of 1 hour, the detonation only takes place after around 2½ hours - at a temperature of around 32 ° C, the detonator triggers after 52 hours with a preset time of 144 hours. Exceeding certain temperature thresholds during transport could also lead to spontaneous detonation, which is why the detonators were delivered partially assembled without detonator and a temperature indicator and were only installed immediately before use.

In addition, all of these detonators have a removal lock that could not be removed after the detonator was installed in the bomb. To prevent accidental detonation in the aircraft, the wind turbine and the trigger spindle were blocked by a safety wire. This wire was pulled out during the drop - a subsequent disarming, not even for trained personnel, was planned in the construction - the bomber crews were instructed not to drop bombs that were not dropped over enemy territory or over deep waters.

United Kingdom

The British pencil fuses (Switch No. 10) worked according to a different chemical principle . B. were used in the assassination attempt on July 20, 1944 on Adolf Hitler .

German Empire

Long-term detonators were also used by the German Air Force . These either had a comparable chemical-mechanical function (LZtZ (57)) with delay times of up to 100 hours or a mechanical clockwork with a running time of up to 72 hours (LZtZ (17)). The expansion lock was brought about by a separate additional igniter (ZusZ 40), which was installed under the LZtZ (17) or was already integrated in the LZtZ (57).

particularities

Since the heavy explosive bombs often made an arc-shaped movement at a shallow angle of impact, especially in sandy and clay soil, they often remained in the ground with the point up. Since acetone evaporates quickly, the remaining amount could no longer completely dissolve the celluloid platelets and the bomb became a dud . Since it cannot be seen from the outside whether z. For example, if the detonator is damaged or blocked or has just not yet triggered, these duds represent a latent danger.

Problems in this day and age

Due to the aging process, all duds are in an extremely dangerous condition today; Smallest external influences such as vibrations can lead to an explosion. Corrosion can also trigger the igniter. Such a self- detonation occurs about once a year on the territory of the former German Reich .

The defusing of duds with chemical-mechanical long-term detonators is extremely difficult due to the unknown condition of the detonators and possible dismantling barriers. If possible, procedures are used that are “under security”, i. H. remotely controlled. Nevertheless, the bomb must be uncovered and the devices necessary for defusing it must be attached to the detonator or the bomb. As a result, tragic accidents occurred again and again (e.g. Wetzlar 1990 during the defusing itself, Salzburg 2003 and Göttingen 2010 during the preparation) in which the defusers were killed.

Self-detonations that became known since 1999

  • June 26, 1999 in Nidda- Harb
  • September 28, 2000 at Siegerland Airport near Burbach
  • May 10, 2001 in Bodman-Ludwigshafen
  • March 17, 2003 in Salzburg (Austria, in preparation for defusing)
  • October 7, 2004 in Linz (Austria, during construction work above the bomb)
  • February 3, 2005 in Offenbach
  • April 5, 2007 in Kassel
  • September 19, 2008 in Vienna (Austria)
  • June 30, 2009 at Nidda- Harb
  • June 1, 2010 in Göttingen (circumstances not yet clarified, three dead)
  • June 15, 2011 near Unterföhring north of Munich (exact date unknown, crater was discovered after the detonation).
  • November 5, 2011 in Theinstetten near Ybbs an der Donau (Austria)
  • August 25, 2012 in the Danube in Vienna
  • July 21, 2013 at Alten-Buseck
  • June 24, 2019 near Limburg

Successful defuses

On March 16, 2011, a bomb with a chemical-mechanical long-term detonator was found at Duisburg's inner harbor , which could be defused without incident. A similar situation occurred on August 23, 2011 in Koblenz . The discovered aerial bomb with a long detonator led to an evacuation initiated immediately, as the bomb threatened to explode. The disarming itself was carried out by means of a device from 100 m away.

On November 29, 2012, an aerial bomb with a long-term detonator was discovered during construction work in the clinic district in downtown Dortmund . After extensive evacuation measures, it was defused late in the evening of the same day.

October 16, 2019, a bomb with a chemical-mechanical long-term detonator was found in a residential area in Hamburg-Schnelsen, which could also be defused without incident. Evacuation took place within a radius of 300 m; Roads and Hamburg Airport were closed for several hours. In Oranienburg since 1990, 200 bombs have been rendered harmless with a chemical-mechanical long-term detonator. On November 27, 2015, four 250 kg bombs were defused one after the other on a property measuring just 700 square meters; two of them lay directly on top of each other.

Controlled explosions (selection)

Controlled detonation of an aerial bomb with long-term detonator on August 28, 2012 on the property of the former Schwabinger 7 pub in Munich

Web links

Individual evidence

  1. ↑ a b c d e f g h i j k Hans Frenken: Long-term detonators. (PDF; 230 kB) Association of German Fireworkers and Defense Technicians, April 2012, archived from the original on April 2, 2015 ; accessed on March 15, 2015 .
  2. ↑ http://bulletpicker.com/tail_-delay_-m123a1.html
  3. ↑ http://bulletpicker.com/pdf/TM%209-1325-200,%20Bombs%20and%20Bomb%20Components.pdf#page=195
  4. ↑ http://bulletpicker.com/tail_-delay_-m123a1.html
  5. ↑ http://bulletpicker.com/pdf/TM%209-1325-200,%20Bombs%20and%20Bomb%20Components.pdf#page=197
  6. ↑ Bremen Police: Accidents involving ordnance on construction sites from 1985 to 2015 (accessed April 17, 2018; pdf; 1.4 MB).
  7. ^ Opinion by Prof. Spyra from February 12, 2008 ( Memento from March 7, 2016 in the Internet Archive ).
  8. ↑ The defusing of the ten hundredweight bomb failed . Wetzlar New Newspaper . August 11, 1990. Archived from the original on February 22, 2014. Retrieved on February 12, 2014.
  9. ↑ DESMINATION AND DESOLATION SERVICE Secure, rescue, dispose of. Federal Ministry of the Interior , February 12, 2014, archived from the original on February 21, 2014 ; accessed on February 12, 2014 .
  10. ↑ Air bomb: wanted cause . Daily mirror . June 2, 2010. Archived from the original on June 5, 2010. Retrieved June 3, 2010.
  11. ↑ Air bomb explodes right next to the promenade. tz , June 15, 2011, archived from the original on September 21, 2012 ; accessed on August 31, 2012 .
  12. ↑ The bomb exploded. Niederösterreichische Nachrichten , November 29, 2011, archived from the original on August 31, 2012 ; Retrieved August 28, 2012 .
  13. ^ Vienna: Violent explosion in the Danube ( memento from January 23, 2016 in the Internet Archive ), last accessed on August 28, 2012.
  14. ↑ World War II bomb exploded in Buseck , last accessed on July 22, 2013.
  15. ↑ [1] , last accessed June 24, 2019.
  16. ↑ hessenschau de, Frankfurt Germany: bomb crater in Limburg. Accessed June 28, 2019 (German).
  17. ^ Bomb defused in Duisburg . wdr.de . March 16, 2011. Retrieved March 16, 2011.
  18. ↑ Explosive situation: Koblenz bomb was defused from a distance of 100 meters ( memento from August 30, 2012 in the Internet Archive ) in: Rhein-Zeitung , August 25, 2011
  19. ^ Bomb successfully defused in Dortmund - the chronicle ( Memento from December 1, 2012 in the Internet Archive ) . On: derwesten.de on November 30, 2012
  20. ↑ 200. Bomb rendered harmless since the fall of the Wall. City of Oranienburg, December 14, 2016, archived from the original on November 16, 2017 ; accessed on May 7, 2017 .
  21. ↑ Four bomb blind people successfully defused in Lehnitz. City of Oranienburg, November 27, 2015, archived from the original on November 16, 2017 ; accessed on May 7, 2017 .
  22. ↑ Graz was paralyzed by an aerial bomb. Kleine Zeitung , March 26, 2011, archived from the original on April 14, 2014 ; accessed on March 26, 2014 .
  23. ↑ Bomb detonated in a controlled manner. Rheinische Post , July 27, 2012, accessed on July 27, 2012 .
  24. ↑ Bomb detonated in downtown Munich. Süddeutsche Zeitung , August 28, 2012, archived from the original on August 30, 2012 ; Retrieved August 28, 2012 .
  25. ^ Bomb blown in Viersen. n-tv , September 18, 2012, archived from the original on September 19, 2012 ; Retrieved September 18, 2012 .
  26. ↑ Archive version: Bomb successfully blown up in Duisburg. Rheinische Post , November 27, 2012, accessed on November 27, 2012 .
  27. ↑ Bomb at the Cologne Uni-Center detonated in a controlled manner. Rheinische Post , January 31, 2014, archived from the original on January 31, 2014 ; accessed on January 31, 2014 .
  28. ^ A3 near Offenbach: World War II bomb tears crater in motorway. Frankfurter Allgemeine Zeitung , August 20, 2014, archived from the original on August 19, 2014 ; Retrieved August 20, 2014 .
  29. ↑ The World War II bomb was blown at 6.45 p.m. Westdeutsche Allgemeine Zeitung , April 3, 2016, archived from the original on March 3, 2016 ; Retrieved March 3, 2016 .
  30. ↑ Huge crater in Nuremberg after being blown up - nearby buildings must be checked. In: Münchner Merkur . February 17, 2019, accessed August 14, 2019 .
  31. ↑ Bomb found in Bergkamen: First detonation fails - second attempt succeeds. In: Westfälischer Anzeiger . August 13, 2019, accessed August 14, 2019 .
  32. ↑ Radio Essen: bomb in the north quarter. Retrieved August 29, 2019 .