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Posted by Ralph Wood on May 31, 2026, 12:57:49, in reply to "Re: Taranto and Swordfish"
Sources with correct info will indeed confirm each other. Unfortunately, so will sources with incorrect info... It can certainly be challenging to figure out what is correct.
If you watch the film in the link I gave David, you will have more info on the MK XII torpedo than you can imagine. I looked up cold running torpedoes. They ran on compressed air. Hot running ones ignited the air. The explanation given at about 28:38 in the film I linked indicates to me a hot running torpedo based on my understanding of the terms. The air was mixed with fuel and ignited, then sent to the engine. Is that not hot per this explanation?
https://www.aprilsmith.org/torpedoes.html
"The Mk 1, 2, and 3 Whitehead torpedoes to this point were cold running weapons. Cold running meant that the weapon operated on compressed air. The invention of a super-heater produced the hot running torpedo; this device used a combustion pot to heat the compressed air to increase speed and distance."
They also can be driven up or down to reach their intended depth setting. (They don't have to plunge to exactly the right depth, or to below it only to be guided back up.)
At about 2:38 into the YouTube video you cite is the image I believe you reference. It is a bit blurry, but there is no wooden tail on that torpedo. Those are the contra-rotating props and rudders. Again, if you watch the video I linked, you will see the full function of the British "Air Rudder" device. It is visually much larger...you would know when this is installed. Also, you will see its function is not to hold the torpedo horizontal, but "slightly nose up" in a parabolic falling arc, preventing a completely perpendicular entry plunge. The fact that the (low launched) torpedo of the image you cite has tipped nose-down at all shows the need for a device to keep it horizontal, and from the film I linked, the Air Rudder did not do that. It allowed nose-droop, just preventing a complete nose drop. I am also baffled by the photo I linked of a low flying Swordfish drop. I agree that it does not seem to show any wire. It also is not a candidate for an Air Rudder, however, and doesn't appear to have one of those, either. I'm stumped. "Lucky drop?" 
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Thank you Ralph for your attention to this topic and David for your comments. Commonly available sources often quote each other. hence my questions.
Some concluding remarks. The sources seem to confirm the depth of water and torpedo settings. The torpedoes very likely run cold. I know of two photos of very low flying Swordfish, the one in your source and another one. Neither of these show a wire. What puzzled me is a photo in Youtube video "How an obsolete canvas biplane, , ," by WW2 Echoes: altitude about 3 m (9 ft), wooden tail, no wire and low 10 degree angle. That the reel had drag makes sense but why compensate the effect of one device with another ?
Regarding Pearl Harbor. Whitehead was marketing their torpedo to many possible buyers between 1938-39. Japan's purchase of only two was rejected in fear of apparent copying.
Olli Previous Message
Quote:
"What actually was the desired initial dive for Taranto and how low the aircraft flew ?"
Two sources list the following:
"All torpedoes were to run at twenty-seven knots
and at a depth of thirty-three feet, and all were armed with duplex pistols.40"
"At Taranto the torpedoes were set to run at 27 knots at a pre-set depth of 33 feet. This was calculated to enable the torpedoes to pass under anti-torpedo netting while still allowing the new Duplex magnetic warheads to ‘sense’ a warship above and explode while passing beneath, or detonate on contact. Taranto's battleship harbour had an average depth of 49 feet." (Other sources list 39 or 40 feet.)
As to "desired initial dive," I found that the British knew this much from their exploratory efforts:
"What the Italians did not know was that the British had found a solution. The nose of the torpedo was hooked to a wire wound on a drum beneath the aircraft. Upon launch, the wire pulled the nose of the torpedo up so that after falling from low level, it hit the water in a belly flop instead of a dive. Attack was possible in water as shallow as 22 feet."
(From this source:
https://www.airandspaceforces.com/article/the-air-raid-at-taranto/ )
As to how low they flew, AI reports "as low as 50 feet." This account from the lead plane's observer indicates they were a good deal lower:
"The flight leader of the first attack wave, Lieutenant Commander Williamson, dropped his 1,600 pound torpedo before turning away sharply. Williamson flew so low when dropping the torpedo that the wing tip of his Swordfish hit the water surface during the turn. "I fell out of the plane. We were six feet above the water, so it wasn't a long fall." "
(From this source: https://www.tracesofwar.com/articles/5425/British-attack-on-Taranto.htm )
There's a photo here of a Swordfish dropping with his wheels nearly touching the water. Look for the section titled, "Shallow-Water Torpedoes":
https://www.armouredcarriers.com/operation-judgement-swordfish-attack-taranto-from-hms-illustrious
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Since the 80th anniversary of Taranto raid a Youtube channel has been demonstrating the method used in which a tension wire connects Swordfish and its torpedo in order to ensure a belly flop and thus a shallow initial dive, the tension wire running from torpedo nose to a reel in Swordfish. There was also a wooden aerodynamic tail as both splinters of wood and tension wires are said to have been later floating around. I wonder what is the background of this because the concept involves a wire holding a long and heavy object (CofG close to 50 %) under the aircraft with the other end unsupported. Maybe this matter has already been discussed elsewhere but here are my thoughts.
A wire should not be necessary at extremely low altitude. The torpedo possibly stays near horizontal and in calm conditions skims shortly on the surface. Aircraft's speed is still high compared to any surface craft so bouncing could also happen. Then tail planes and control rods could get damaged. On the other hand unwinding wire should produce no pull upwards at all. The reel should also be above torpedo's nose where Swordfish has its engine. What would detach the wire from both ends and would it not whirl around ?
The wooden tail was to prevent rolling and give the right angle of entry, hardly needed at a very low level. In general, usual means to control depth (in short) was done by adjusting hydroplanes, depth gear and engine. Torpedoes could also be made to run light without fuel and water ("cold") as CMBs did in Kronstadt in 1919. Depth control was critical on coastal waters and improvements were tested in the 1930's. Perhaps RN had developed its own system.
Both initial dive and depth keeping varied greatly. For comparison one 45 cm 800 kg torpedo dived down to 5-6 m before reaching 3 m depth setting (static tube, 1,5 m height). A margin was accepted. I do not know Taranto waters but battleships (9-10 m) could move there and Conte di Cavour was immersed by the barrels of C turret. The height from the ship's bottom (17 m) suggests a fair depth even if embedded in mud. With magnetic exploder a depth setting of 9-10 m plus something plus margin was obviously needed. These torpedoes must have run this deep all the way. To my knowledge in 1940 no device could gradually guide a torpedo deeper.
In developing its Avio torpedo, Whitehead of Fiume conducted shallow water (20 m) trials with an aerodynamic tail. An initial dive of 11,2 m was achieved (angle 32 deg, weight 880 kg, speed 312 km/h, altitude 85 m, 4 m depth setting). What actually was the desired initial dive for Taranto and how low the aircraft flew ?
Olli
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