Wren (torpedo)

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Wren was the code name for a torpedo of the German Navy with acoustically controlled self-steering. The official type designation was TV or G7es . The allied abbreviation for the torpedo was GNAT ( German Navy Acoustic Torpedo ).


The wren was developed in the Second World War by the Gotenhafen torpedo testing facility of the Kriegsmarine under the leadership of the Physikalisch-Technische Reichsanstalt ( Berlin-Charlottenburg ), other institutes and industry. The forerunner was the G7e / T IV with the code name "Falke", which had been introduced in March 1943, but was only used on three boats, since the wren, which was faster, was already available in September of the same year, via one had a greater range and could be equipped with both magnetic and impact fuses.

After at least two boats - U 377 and U 972  - had probably been sunk by their own acoustic torpedoes, the regulations stipulated that the use of Wren torpedoes stipulated that the submarine had to go to a depth of at least 60 meters immediately after being shot down so as not to draw the wren back to the submarine with its own screw noises. After being shot down from the stern tubes, the boat had to be absolutely quiet.

During the war, the Allies developed the Foxer as an antidote. This was a noise generating Schlepptäuschkörper , which was towed behind the ship and should serve the Wren as FLARE. The Foxer often reached its destination, but abrupt changes in screw speed also caused the torpedo to lose its source of noise. Nevertheless, German submarine crews mostly blamed the Foxer for the failures and often referred to Foxer devices as "damn paddle buoys".

Despite some successes, especially against pursuing destroyers and corvettes, the wren often detonated behind the enemy ship because the acoustic guidance was still very imprecise. This was particularly evident during the first large-scale operation of the wren from September 20 to 24, 1943 in the attacks on convoy ON-202, against which the "Leuthen" group, consisting of 20 submarines, was deployed. The commanders assumed a hit for every torpedo detonation they heard and reported the sinking of a total of nine merchant ships and twelve escort ships after the battle; in fact, only six merchant ships and, of the security vehicles, only one destroyer, one frigate and one corvette had been sunk.

The allied antidote, the foxers , also turned out to be disadvantageous, as launching and hauling in was time-consuming and dragging the noise buoys reduced the speed to 14 knots (26 km / h) and the maneuverability of the escort vehicle in general. In addition, the noises emitted could only alert enemy submarines to a convoy, and the noise level made the sonar devices useless for the duration of the mission.

An improved variant was the Zaunkönig II , which could detect escort vehicles even at lower speeds.


The wren was equipped with a passive acoustic target control system. This consisted of two listening receivers with magnetostriction transducers , which picked up the sound waves from the ship's propellers and transmitted the receiving direction to the rudder via a pneumatic-electric autogiro system.

The wren was an attitude-independent torpedo type ; In other words, it could be shot down from any position of the submarine towards the enemy and, after a specified safety route , looked for its target based on the screw noise of the enemy ship.

Technical specifications

  • Nomenclature:
    • Official designation: T 5
    • Torpedo model: G7es
    • Code name: Wren I
  • Dimensions:
    • Ø: 534.6 mm
    • Length: 7163 mm
    • Weight: 1495 kg
  • Mileage:
    • Drive: electric motor
    • Speed: 24 kn
    • Range: 5.7 km
  • Warhead: 274 kg of gunwool 36

Wren II

T11 of the U 534

In early 1944 the improved "Wren II" was introduced. The official designation was T 11. It differed from its predecessor in that the acoustic self-steering was improved in terms of target accuracy and that it responded to engine noises from ten instead of twelve  knots . However, only 38 copies were built, of which at least the three from the U 534 boat lifted in 1993 have been preserved.


The high point of acoustic self-steering was the "Geier" torpedo . It had active acoustic self-steering by means of echo tracking , was tested for the first time in the summer of 1944 and put into service in the fall of that year. Due to the complicated assembly, only between 50 and 100 torpedoes have been delivered. Theoretically, the precision was much higher than that of the wren, and the "Foxer" flares became ineffective. Nevertheless, due to the immature technology and the poor war situation, the successes were low. The steering of the "Geier" got a (very imprecise) third dimension after an adjustment by the weapons officer on the torpedo . So you could have shot the torpedo with the steering against submerged submarines .


  1. ^ Franz Kurowski : War under water. Submarines on the 7 seas 1939–1945. Pawlak, Herrsching 1984, ISBN 3-88199-156-5 , p. 320.
  2. Jürgen Gebauer, Egon Krenz: Marine Encyclopedia. Brandenburgisches Verlagshaus, Berlin 1998, ISBN 3-89488-078-3 .

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