German Navy torpedo type G7A at the Norwegian Armed Forces Museum in Oslo
(photo by MoRsE)
U-Boats carried two different types of torpedoes.
- G7a: powered by compressed air, which left the trail of bubbles, a popular scene in movies. The torpedo could be set to various distances and various speeds depending on the target. This was done by the First Watch Officer during a surface attack using an aiming device which resembled a pair of binoculars.
- the G7a had a speed of 44 knots for distances of 6,000 meters or less. 40 knots for 8,000 meters and a speed of 30 knots for its maximum distance of 14,000 meters. If a torpedo ran out of compressed air before hitting something it just sank.
- G7e: electrically powered torpedoes, which didn’t leave a trail of bubbles.
Improved versions of these torpedoes were issued to the U-Boat fleet in mid-1942.
Subsequently, a torpedo which homed in on the sounds made by a ship’s propellers was introduced. This acoustic torpedo was a variation of the G7
The Allies quickly came up with counter measures.
A variation of the G7 which became famous for being the first acoustic homing torpedo he German Uboatwaffe also used (GNAT=German Navy Acoustic Torpedo, also known as the G7s, T5 and code named Zaunkönig) it had a sinking success rate of about 19%.
Allies immediately introduced effective countermeasures the most successful being “the foxer.”
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