THE DEFENCESAIR DETECTION (I)

The Nazis developed a complex net to defend the Reich and occupied Europe from air raids. This superb detection net goes from observation of incoming attacks to the latest and more sophisticated elements of electronic radar and radio to track enemy planes and to assist the AA (anti-aircraft) guns in their role against the Allied ‘Terror-bombers’.

At the beginning of the war, German air detection was based on primary methods and systems like the observation sites.

[Here, a Luftwaffe officer (note the shape of the Eagle in the uniform’s chest) teaches young Flakhelfers to use a range finder device and binoculars, the simplest method to know the range and height of incoming bombers from local ground level.]

[Photo: Bundesarchiv.]

After plotting enemy aircraft the site will pass this essential information to the defence and fighter direction centres to defend the Reich territories. This method was highly successful during the Battle of Britain in the summer of 1940 employed by the British Royal Observer Corps (ROC). At night, it had obviously no usefulness.

The air-defence instruments also consisted of sound location equipment. The Germans used a complex system, called Horchgerät, during early stages of the war, and revitalized during the Summer and Fall 1943 after their radar defence net failed as a consequence of the introduction of the first electronic countermeasures like ‘Window’ (ERC & ECM) by the British.

[A Horchgerät viewed on October 1939 at the outskirts of Berlin, more specifically a Ringtrichter-Richtungshörer (RRH) zur Einweisung der schweren Flak.]

[Photo: Bundesarchiv.]

[Photo: Sammlung Berliner Verlag/Archiv.]

The system idea was to hear the sound of the engines of the incoming aircraft and track their height, warning the defences of an incoming enemy raid. For typical aircraft speeds of that time, sound location only gave a few minutes of warning.

It consists of four acoustic horns, a horizontal pair and a vertical pair, connected by rubber tubes
to stethoscope type earphones worn by the two technicians left and right. The stereo earphones enabled one technician to determine the direction and the other the elevation of the aircraft.

[A Flakhelferin am Horchgerät poses for the camera in January 1943.]

[Photo: Bundesarchiv.]

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