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Historically Germany did not develop their own functional aerial torpedo until 1942 and were forced to use Italian torpedoes once they got over their infighting about the lack of functionality of German torpedo technology. Pre-war there was plenty of opportunity for the Luftwaffe to make the Italian torpedo, as the Germans licensed the technology, but did not manufacture it themselves.Potentials of air-launched torpedoes, however, were discovered commensurately very late, because the German torpedo development had been completely in the hands of the Kriegsmarine since 1932, which had actually purchased the Horten naval torpedo patents from Norway in 1933 and the Whitehead-Fiume patents from Italy in 1938. Germans, essentially, had used a variant of the Norwegian aircraft-dropped torpedo – the 450mm Schwarzkopf F5 with a range of 2000 meters and maximum speed of 33 knots. It was armed with a 200 kg Hexanite explosive warhead. Subsequent German derivative, improved LF 5B travelled at a speed of 40 knots, and was armed with a 180 or 250 kg warhead filled also with Hexanite.
It has to be maentioned, however, that the technical development toward German air-launched torpedoes was pursued in a rather leisurely manner, mainly because it was conducted by the Seeluftstreitkrafte (naval air division of the Kriegsmarine), and the results of trials and reports of combat operations were jealously guarded by the navy. During extensive torpedo-dropping trials, carried out in 1939, both the He 59 and He 115 floatplanes were used, and the failure rate of the torpedoes was a amazing 49 percent!
In 1941, the Luftwaffe decided to pursue its own development trials with the intention of setting up a powerful force of torpedo-bombers. The first torpedo development establishment was formed at Grossenbrode, on the Baltic coast. Several aircraft types were intensively tested and it was soon apparent that the proven and long-established He 111, as well as the faster Ju 88 were the most suitable types.
Apparently the Kriegsmarine had the patent in 1938, so could have started making that torpedo instead of wasting time on developing their own. What they could have had was a functional model in production instead. When the war starts they have a stock on hand. So in 1939 German naval bombers pioneer combat torpedo techniques against Allied shipping, which proves better than level or dive bombing against naval targets.
What does this mean for the conduct of the war in 1939-1941? Historically there were a dearth of successful German naval air attacks on military targets (merchant shipping losses to German bombing was modest at best, mines were much more effective) in this period, as the Germans lacked functional torpedo and were reliant on level bombing with non-specialist units; a prime example is during the Norwegian campaign the KG 100, the specialist pathfinder unit, was used for level bombing against naval targets and remained in Norway until August, attacking shipping. With a functional air-dropped torpedoes the Germans could have put a serious dent into the RN during the Norwegian campaign, not to mention hurt merchant shipping more, as evidenced by the success of German naval air units from 1942 on.
With preparations pre-war, which would make sense, given that the North Sea was a planned conflict zone eventually and the Kriegsmarine was building a navy to fight in that area (Plan Z was all about fighting in the North Sea, as the design of German battleships did not have 'Atlantic' bows for open oceangoing).Luftwaffe unit Kampfgeschwader 26 was anticipated to play the leading role in this new torpedo plan, and Stab, I and III./KG 26 were selected as the specialized torpedo-units, while II/KG 26 remained in the classicist level-bomber role. It sounds almost unbelievable, but the tactical detachment of a few of KG 26’s He 111s to X. Flieger-Korps in the autumn of 1941 for torpedo operations was short-lived due to lack of torpedoes!
In January 1942, the Luftwaffe’s demands for the centralization and control of all German and Italian torpedo development were finally granted. Colonel Martin Harlinghausen was appointed as the head of all Luftwaffe torpedo development, supply, training and operational organizations, with the TorpedoTraining School established at Grosseto in Italy. During the early months of 1942, I/KG 26 underwent torpedo conversion-courses, lasting between three and four weeks. The Gruppe’s He 111H-6’s could carry two torpedoes slung on racks beneath the belly; the standard torpedoes used were the German LT F5 and LT F5W, both of 450-mm caliber, with the latter based on the Italian model made by Silurificio Whitehead di Fiume.
While I/KG 26 underwent conversion at Grosseto, its future and the bases from which it would operate had already been decided. Luftflotte 5, based in Norway and Finland, needed additional bomber support to interdict Allied convoys on the Murmansk/Archangelsk route. In March, Göring ordered Luftflotte 5 to collaborate with the aerial reconnaissance units of the Kriegsmarine and to attack the convoys when they came into range, and also to shift bomber forces from the Finnish front to accomplish this task. Within I./KG 26, based at Banak and Bardufoss, there were 12 crews available for torpedo operations with the Heinkel He 111H-6 planes.
During March and April, various PQ [and retuning QP] convoys were succesfully attacked. Although the Luftwaffe claimed all 35 ships sunk, they had only sunk seven. New lessons had been learned, however, which were to form the basis of later tactics when greater torpedo forces were expected to be available. Coordinated torpedo and bomber attacks sowed confusion among the defensive screen. The most favorable time was at dusk, with the torpedo-bombers coming in from the darker hemisphere aided by the ships' pre-occupation with dive bombers and level bombers by the Ju 88’s of KG 30, thus affording the low-flying Heinkels of KG 26 an element of surprise. The tactic known as "Golden Zange" (Golden Comb) consisted of a mass torpedo attack by as many as 12 He 111’s flying in wide line-abreast, with a simultaneous release of torpedoes to obtain the maximum spread while dividing defensive fire.
Aircrafts have been spaced about 200-300 meters apart, and both LT F5b (improved version) and Italian LT F5W torpedoes were used. The F5W was preferred as the F5b’s whisker-type detonating pistol seldom operated when the target was hit at an sharp angle. Torpedoes were launched at a range of 1000 meters, and usually from a height of 40 meters (125 feet), the parent aircraft flying dead straight and level in order for the weapon to enter the water at the stipulated 12 degrees. AA fire, particularly that of 20mm Oerlikon guns, was considered a greater threat than escorting RN fighters. Observation of torpedo-tracks or hits was next to impossible, as the parent aircraft had to execute violent evasive action as soon as the weapon was dropped. The Ju-88’s of KG 26 had considerably more success than the Ju-88’s of KG 30, and sunk the majority of the merchant ships claimed.
Ill-fated convoy PQ-17 was set upon for five days, in which 23 out of 33 ships were sunk, and Luftflotte V accounting for fourteen of them. This action saw the use of a few He-115 floatplane torpedo-bombers too, but mainly the He-111’s of I/KG 26 and the Ju-88’s of KG 30 were in action.
By the end of July, III/KG 26, under captain Nocken, had completed the course at Grosseto and had transferred its Ju 88A-4 torpedo-bombers to Rennes-St.Jacques. They eventually wound up at Banak along with a considerable anti-shipping force of bombers, torpedo-bombers and reconnaissance aircraft.
So what does this mean for the British in the early war if the Germans were using large numbers of aerial torpedoes with their specialist Luftwaffe and Kriegsmarine naval air units?