Dear Les Hubert,
during WW1, the release altitude and the speed of the floatplanes were quite low and it was possible to launch from an aircraft the same Navy torpedoes designed for TB use. The British first did it operationally in the Marmara Sea in 1915 (Lt C.H.K. Edmond pilot, HMS Ben My Chree) against Turkish shipping.
I hope the book “History of Italian torpedo-plane groups and Buscaglia Unit” by G. Evangelisti and M. Aichner has been translated into English because this matter is thoroughly examined, at least from the R. Italian Air Force side.
In the late thirties the aircraft’s operational speed and the safe release height had raised and so especially conceived aerial torpedoes were produced. At the outbreak of WW2 one torpedo launched by a plane sink up to 80 meters before establishing on its normal pre-set operational deep, which could be anything from two or three meters (contact fuse) up to six or eight meters (magnetic fuse). This was anyway a secondary problem, because the main problems were the shock at the impact with water (tremendous for its sensitive gyroscopes) and, even more important, the angle of water entering. The first was somehow solved producing more solid and light units, the second installing an auxiliary detachable plane on the torpedo tail itself. The system enabled torpedoes to be launched from one hundred meters of height and at a speed of 300 km/h. The Luftwaffe liked the system and bought one hundred Italian aerial torpedoes. For an irony of history they were manufactured by the same Whitehead firm in Fiume (Rieka now) which was the main KuK (Austro-Hungarian) torpedo factory. The Imperial Japanese Navy copied and improved (as usual) the system and trained the torpedo plane crews in low height torpedo releasing in the waters of an home base inlet very similar to Pearl Harbour.
Greetings
Walter M.