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The TI was the last naval torpedo of German design in operational use with the traditional standard wet heat method of propulsion. The torpedo was powered by an engine fed by a mixture of compressed air and steam. Decaline fuel was burning in a combustion chamber, creating steam from fresh water. The torpedo's speed was determined by the level of pressure (three settings for 30/40/44 kn) from the low-pressure regulator feeding air to the bottom of the combustion chamber. The resulting superheated steam powered a four cylinder reciprocating engine, in turn powering a pair of contra-rotating propellers.

Though this system of propulsion gave the TI great speed and endurance it had the distinct disadvantage of being very noisy and leaving a long wake of bubbles, common to most torpedoes of the period, with the exception of the Japanese surface-launched Type 93 and submarine-launched Type 95, which were fuelled by an enriched oxygen wetheater engine. For U-boats, this relegated the TI for use mainly at night, when its wake was least noticeable, so as to not give away the element of surprise and the location of the submarine that fired it. During daytime, the electrical propulsioned torpedoes were favoured.

For the period 1934-1940 the only available warhead for the TI and TII were the Type Ka, with two available pistols: The Pi G7A-AZ and the Pi G7a-MZ. The former was a direct-acting mechanical pistol, while the latter had an additional influence-mechanism (magnetic). Both mechanisms were flawed and contributed to the german "Torpedokrise"(torpedo crisis) which lasted from the start of the war and through 1942. The mechanical deflection arms was designed too short, and the magnetic igniting-mechanism couldn't be properly tuned for the natural magnetic fields in the northern hemisphere and narrow fiords. These issues led to premature or late detonations, as well as failing to detonate even when hitting the target, in numerous cases during this period until properly working pistols were introduced with first the mechanical Pi1, and later the combined mechanical/magnetic Pi2. Also, the depth mechanism had a design-issue leading to leakage of vacuum when stored on the U-boats, causing the torpedo to run deep. The problems were common for the TI and TII torpedoes, but the TI also had issues with weak engine blocks (cracking at 44 kt setting), and the TII had issues with poorly performing batteries.

The problems were so serious, Admiral Dönitz said, "...never before in military history has a force been sent into battle with such a useless weapon."[1] In general, all issues were resolved by 1942 when new depth mechanisms and new pistols had been developed and put into service. The TII was then also replaced by the TIII with improved batteries.