Also known as "Ato," this torpedo was issued throughout the war and was considered to be very reliable.  It was developed almost directly from the 50 cm (20") G7 of World War I and differed from those of other nations by using Decalin (decahydronaphthalene) instead of kerosene for fuel.  Producing this torpedo took about 3,730 man hours per torpedo in 1939 but this fell to 1,707 hours by 1943.  This was significantly more than what it took to produce the electric G7e.

The 44 knot speed was found to overload the engine and was not used during the early years of the war.  The early models used in 1939 had ranges about 20% less than those given above.  Used a four-cylinder radial engine that drove a single six-bladed propeller.

The Federapparattorpedo (spring-operated torpedo) or FAT variation had a simple guidance system that allowed a series of long or short legs or loops at the end of a configurable length of straight course.

Starting about mid-1944, the Lagenunabhängiger Torpedo (LUT) variation was introduced which was a more sophisticated version of FAT.  LUT could be fired at any target angle and could follow a curved path to its target.  LUT had problems with the targeting gear not disengaging at launch, resulting in "tube runners" and appears to have been rarely used after December 1944.

Warhead weight for these torpedoes confilicts in many references.  I have seen numbers as low as 617 lbs. (280 kg) and as high as 948 lbs. (430 kg).  It is possible that the lower numbers were for torpedoes issued early in the war and then heavier warheads were introduced during the war.

Also known as "Eto," this unit used a 100 hp electric motor that drove a pair of contra-rotating two-bladed propellers.  The above range and speed could be reached only if the batteries were preheated to 30 degrees Celsius.  These torpedoes had to be serviced every three to five days in order to maintain their reliability.  Slower than the wet-heater G7a type, but trackless and relatively quiet.  Took about 1,255 man hours to produce each torpedo.

Battery voltage was 124 Vdc immediately after charging and decreased to 115 volts two days later.  The voltage dropped to 104-106 Vdc during the run.

The most common variations were as follows:

T2:  This version had two batteries, each having 26 cells and rated at 93 amp hours in total.
T3:  Same as T2 but with influence fuze.
T3a:  Same as T2 but with a larger battery capacity of 125 amp hours.
T3b:  The propulsive part of the Marder Submarine.  Max speed of 2.5 knots.
T3c:  The torpedo for the Marder Submarine.  The forward battery was eliminated and buoyancy was neutral.
     Weight:  2,937 lbs. (1,332 kg)
     Range / Speed:  4,370 yards (4,000 m) / 18.5 knots.
T3d Dackel:  A very long range / slow speed version intended for use in harbors or restricted bays.  Could be programmed with specific circling or legs at the end of a straight run.  Negative buoyancy was almost zero because of the very low speed.  About 300 were adapted and issued starting in July 1944.  About 80 or 90 were actually fired, most against shipping in the Seine Bay.
    Length:  36 feet (11 m)
    Weight:  4,885 lbs. (2,216 kg)
    Range / Speed:  62,300 yards (57,000 m) / 9 knots.
    Explosive Charge:  620 lbs. (281 kg)
T3e Kreuzotter:  Another Midget Submarine Torpedo.
    Weight:  2,961 lbs. (1,343 kg)
    Range / Speed:  8,200 yards (7,500 m) / 20 knots

Warhead weight for these torpedoes confilicts in many references.  I have seen numbers as low as 617 lbs. (280 kg) and as high as 948 lbs. (430 kg).  It is possible that the lower numbers were for torpedoes issued early in the war and then heavier warheads were introduced during the war.

Many records on these torpedoes were lost when the Gotenhafen experimental station was demolished to prevent capture by the Soviet Union.  Serious experiments on homing torpedoes began in 1936.

T4 Falke:  The first passive homer.  Homing was by a simple noise measurement.  Intended for use against merchant ships so the low speed was acceptable.  Originally known as G7eS, with the “S” signifying “Sonderartsführung” (special manner of behavior).
T5 Zaunkönig 1 (wren):  Known as GNAT to the British.  For use against convoy escorts.  Designed to home in on cavitation noise of around 24.5 kHz which was equivalent to propellers on an escort traveling at 10 to 18 knots.  First successful combat use in September 1943.
T5a:  A modified T5 used by S-boots (E-boats).
T5b:  Same range as T5a but used by submarines
T10 Spinne:  A standard torpedo modified to use wire guidance.  First issued in 1944 but the results were not satisfactory.
T11 Zaunkönig 2:  Improved T5 less influenced by Foxer (towed noise maker).