German aerial torpedo LT.F5w (Italian torpedo type W)
German air doctrine had considered the attack of enemy shipping by the Luftwaffe. Part of the Luftwaffe’s prewar plans was the employment of torpedoes launched from aircraft. German torpedo development had started as early as 1926; however, the development itself was in the hands of the navy, and progress was considerably slow with the Luftwaffe did not yet giving the issue its required attention.
The aerial torpedo LT I A1 F5b (Lufttorpedo LT I A1 F5b) was a weapon known before the outbreak of the war. The first torpedo construction was based on patents, which were acquired from Norway and Italy. This torpedo did not prove very reliable and produced failure rates of nearly 50%. To employ it conditions had to be very favorable. Besides being unreliable, the torpedo also would take a significant dive after being released which limited employment in coastal waters and forced earlier interception of ships, thus limiting the employment by land-based aircraft.
The development effort for this torpedo did not improve significantly and by February 1938, the navy bought an aerial torpedo from the Italians. The navy had accepted the fact that it would take until 1942 to have about 100 torpedoes of the new type manufactured. Therefore, at the outbreak of the war, the navy had no effective aerial torpedo. To overcome this problem and regardless of its unreliability, the production of the faulty LT I A1 F5b carried on and the stocks were increased, to reach a total of 152 in June 1939. A little more than a year later, the total number amounted to 362 torpedoes.
The first torpedo operation by the Naval Air Force was carried out on 7 November 1939. Activity in the western sea area had been high and Naval Air Commander West demanded to launch a “Kette” (3 a/c) of aircraft with torpedoes. This employment in a “Kette” was not uncommon, since the aircraft would widen to a parallel formation prior to the attack and the parallel tracks of the torpedoes would increase the probabilities of hitting the targets. Nevertheless, the attack was unsuccessful due to evasive maneuvering of the target.
After the ice which blocked the seaplane harbors was gone, preparations for the invasion of Norway were already underway and flying had considerably slowed down. This interval gave the Naval Air Commander an opportunity to test the performance of the aerial torpedo with the He 115 s. The operations were carried out as armed reconnaissance in “Ketten” or “Rotten” shortly before dark. The operations, a total of five were carried out, led to the conclusion that the torpedo was in satisfactory working condition.
While the navy had two wings assigned to deliver the LT I A1 F5b, the Luftwaffe considered this weapon an expensive alternative to their conventional way in engaging in anti-shipping operations, with the dropping of bombs. For delivery, the aircraft types He 59 and He 115 were employed, with a limited maneuverability. The torpedo would bring the aircraft to their maximal payload for take off and only a few missions were flown. Furthermore, delivery tactics were dangerous and exposed the attacker to enemy anti-aircraft fire which was becoming more effective. Due to the close release distance to the target, the attacker had to over fly the target afterwards. Additionally, the conversion from He 59 to He 115 and its use as a torpedo bomber created significant problems until the outer design of the torpedo was adjusted. Therefore, the results by fall 1941, largely due to limitations of technique and equipment, were meager.
In 1941, when the Luftwaffe started showing interest in torpedoes, interservice rivalry hampered the progress of the development. The navy did not provide critical experience gained to the air force and the development of the torpedo came to a standstill until the end of that year, which forced the Luftwaffe to pursue dive bombing for anti-shipping attacks.
The late introduction of a fully functioning torpedo after two years of war significantly decreased Germany’s anti-shipping capabilities. Luftwaffe interest in the torpedo weapon came at a late stage of the war and valuable development and training time was lost due to little attention and interservice rivalry. Until the beginning of 1942, the achievements with the torpedo’s use were few.
After the unreliable LT I A1 F5b torpedo was finally replaced with the better Italian F5w torpedo, this attack option actually became more effective and had to be taken into consideration by the allies as a significant threat. By July 1942, the Germans had an effective weapon against targets at sea, but indecisiveness of the Chief of staff General Hans Jeschonnek and rivalry between navy and Luftwaffe delayed the use of the torpedo in significant numbers until spring.
In 1942, Germany asked Japan for several of their Type 91 aerial torpedoes and blueprints for them. Japanese submarine I-30 arrived at Lorient in August 1942, carrying, among other things, what Germans had asked: Type 91 aerial torpedoes and plans for making more.
It is true Germany and Japan were far looser allies than US and UK were, but that didn’t mean they never shared technology. For two countries that basically had to rely on submarine transport to deliver each other technologies and experts, Germany and Japan put quite some effort on keeping each other updated.
Over the course of the war, Japanese delivered(or attempted but failed to deliver) Germany Type 91 and 95 torpedoes, torpedo tubes, an automatic trim system, the excellent naval reconnaissance aircraft Yokosuka E14Y, as well as critical stock of rare materials that among others included rubber, tungsten, and zinc, while in exchange Germany delivered(or attempted but failed to deliver) Würzburg radars, machine guns, Metox and Naxos radar detectors, G7a and G7e torpedoes, two submarines, Enigma machines, 20mm AA guns, Zeiss FlaK fire control systems, a Walter rocket engine, blueprints for the Me 163 and 262 aircraft, and more.
Germany wouldn’t be able to make an awful lot of use of even the world’s best aerial torpedo in 1939, for the Luftwaffe’s torpedo bomber arm was neglected and miniscule. It is incorrect that Germany had no aerial torpedoes at the start of the war, but their one torpedo was so bad they might as well not have had it: the 450mm LT I A1 F5 torpedo, a copy of the Norwegian Horten torpedo, which was an excellent, cutting edge weapon… in 1930, when the concept of ‘aerial torpedo’ was still in its infancy.
So, Germans looked for closer to home solutions rather than two oceans away from Germany, like Japan, and went for Italy. The workhorse of German torpedo bomber arm for the first couple years of the war was the very capable Italian Fiume W torpedo, which Germans designated F5w.
The problem with the Fiume was that Italy and its formidable torpedo bomber arm also used that weapon, and in Mediterranean it was being expended in not-inconsiderable quantities. As the Germans intensified torpedo bomber operations, imports from Italy began to grow insufficient. In 1941, the problem was alleviated by the entry of the 450mm LT I A1 F5b torpedo in production- a perfectly serviceable, if not spectacular, weapon- though it would grow to be an excellent torpedo by the introduction of the LT II model in 1944.
But in 1942, it was still only a decent weapon. The start of that year saw Hitler declare production of aerial torpedoes a matter of national importance. Among the various steps taken to empower the German torpedo bomber arm and increasing German aerial torpedo production was requesting blueprints for the excellent Type 91 torpedo from Japan, and Japan answered. Between 1942 and 1944, the Type 91, designated Luftorpedo LT 850, had an important role in German torpedo arm, especially after the Fiume torpedoes became difficult to procure after the Italian surrender.
The L-40 aerial torpedo
Dr. Mario Zippermayr. Dr. Zippermayr, sometimes spelled incorrectly as “Zippermeyer”, was born an Italian of Austrian parents and educated in German speaking institutions. His interests ranged from perfecting color photographic film to the medical benefits of ozone therapy. He is remembered for his wide-ranging weapons research.
Dr. Zippermayr’s solution to the problem of the aerial torpedo. The standard German aerial torpedo was released at about 50 meters (slightly over 150 feet) from the ocean’s surface by an aircraft in horizontal flight at an air speed of about 300 km. per hour or about 180 m. p. h. To release higher or faster would cause the torpedo to impact the water at too great a speed, damaging the torpedo’s steering mechanisms. The Germans suffered substantial losses to their attacking aircraft using these weapons and tactics. The low altitude and low speed simply left the attacking aircraft venerable.
What was needed was a new torpedo with a new attack methodology. The Germans needed a torpedo that could be fired from a distance, at a high altitude, and at jet-plane speeds. They wanted the new torpedo to be launched at 1.5 kilometers from the target, at any height, at any angle and at speeds up to 700 km per hour (435 m. p. h.).
Dr. Zippermayr reworked the internal components of the new aerial torpedo with these goals in mind. But what is most interesting were his aerodynamic solutions for the new torpedo. This solution was a new gliding surface that automatically balanced the torpedo in flight. This gliding surface was a new wing with a special shape. It was attached to the top edge of the torpedo and its wings were “V” shaped as seen from the front or rear. This wing design automatically confirmed stability on the flying craft since its center of gravity was directly below what we might call its point of suspension, the midpoint between the V-wing surfaces. Tests were performed in which the torpedo was dropped from an aircraft flying at speeds up to 720kph and from heights of over 1000 meters. The Arado 234 was envisioned as using this weapon. The work was carried out from January, 1944 until the end of the war. .
German Aerial Torpedo Data
the following aerial torpedo data is taken from Appendix 9 (p. 246) of Manfred Schiffner’s book
German Torpedo LT1200 F5 F5b
Length (m) 5.57 5.16 5.16
Diameter (mm) 533.4 450 450
Weight (kg) 1295 750 750
Propulsion type Walter Steam Steam
Warhead weight (kg) 300 200 200
Range (m) 2500@46kts 7500@22kts 2500@36kts
2100@50kts 3500@33kts 2000@40kts
Drop speed (km/h) 360 250 250
Drop height (m) 70+/-30 40+/-10 40+/-10