Flutto class Submarine (1943) – Naval Encyclopedia

Regia Marina: 48 Planned 1942, built 1942-43
Tipo I, II, III: 8 completed.

The Flutto-class submarines were the last in the 600 Series, and Regia Marina’s most important numerically. They were built with modifications brought by wartime experience and simplified. Seaworthiness was good, with improved internal arrangements, greater hull strength, better AA and the fastest diving time, more powerful diesels. A total of 48 were ordered, made in three series or “Types”. But only 8 were operational in late 1942 or 1943. They arrived to late to make a difference before the Armistice of Cassibile in September.
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The end of a cycle. Next stop: Italian midget subs of WW2.

Development

The Flutto-class (Tritone class in Italian sourcces) submarines were essentially repeats of the preceding Acciaio, following a long line with the Adua, Perla, Sirena and Argonauta, all “Bernardis” single hull designs with blisters and minor upgrades and modifications. This incremental approach, instead of sometimes the greater risks made on larger classes paid off in the end as each iteration solved issues highlighted by previous classes. The German style of conning tower “bridge” was, with the Acciaio before, the surest way to identify these, but otherwise they were very comparable. Their hull profile was also rather similar, and they repeated the same radiogoniometer controllable from inside, had the new air conditioning equipment, now made safer since the Adua class, to operate off Africa, and their fuel reserves were optimized.

The simplifications made to the hull were mostly internal, with simplified shapes here and there, some refinements of previous boats cancelled, everything that can help reducing building time. The whole class was created to address the increasingly critical shortage of submarines available for service in the Mediterranean in the Regia Marina. The partial double-hull design was closer to the preceding Argo class rather than Acciaio, but incorporated a slightly revised German-style conning tower. Powerful diesel engines and greater operational range were also their key assets. There were also differences within the series with the second being longer and with a slightly higher displacement.

Construction

Orders were placed for 48 total, the largesst submarine program ever in Italian history. They were ordered by the “usual suspects” at Cantieri Riuniti dell’ Adriatico or CRDA shipyards in Monfalcone, Odero Terni Orlando (OTO) Muggiano shipyards, and Tosi shipyards in Taranto. As seen above they were ordered in three series, the first comprising 12 boats, the second 24, the third 12. In the end, only eight boats from Series I entered service in 1942. Some Series II boats were captured while still on the slipways, completed for the Kriegsmarine but sunk or scuttled. Below is the detail: Starred ones had been commissioned and saw service.

Tipo I:

Tritone, Gorgo, Flutto, Marea, Vortice, Nautilo, Murena, Grongo, Sparide, Spigola, Cernia, Dentice
The first six were built at the CRDA shipyards in Monfalcone, while Murena, Grongo, and Sparide were constructed at the Odero-Terni-Orlando shipyards in Muggiano; the final three were laid down at the Tosi shipyards in Taranto. All the boats built in Monfalcone entered service with the exception of Nautilo. Tritone, Gorgo, Flutto were lost in action. Marea and Vortice survived the war the former a war reparation (WR) to USSR, the latter modernized for the Marina Militare. At the time of the armistice the three boats from La Spezia and Nautilo were completed and nearly operational and captured by the Germans or scuttled by the Italians. The three from Taranto laid down much later (Spigola on June 10, 1943, Cernia on July 12, Dentice on August 23) never reached even launching stage and construction was suspended on 9 September, they were later scrapped.

As for construction time, let’s have a look if these simplifications bore fruit: Tritone, the first built, was laid down at CRDA on 15 april 1941, launched on 3 June 1942 and entered service 10 october. That makes 20 months. To compare, Alabastro of the previous class, also from CRDA, was laid down on 12 march 1941, launched on 18 December 1941 and entered service on 9 May 1942, so 15 months. If these numbers are correct, it seems this had little effect, and there is no way to tell if a few months could have been spared, given the circumstances: Italy in 1943 was in an unfavourable industrial position and just could not deliver the goods realistically. Not only they were bottlenecks due to the shortage of some equipments, but by 1942 allied bombings on industrial sites was real: It transitioned from strategic bombing based in North Africa and Malta to direct tactical and strategic support for the invasions of Sicily (July 1943) and the Italian mainland (September 1943), neutralizing Axis air power and crippling Italian infrastructure.

Not only railways bringing equipments were frequently stopped, but everything that was shipped was also at risk. All activity at Taranto virtually stopped by September 1943 with the allies gaining air superiority there and above Salerno for Operation Avalanche, Baytown, and Slapstick. Bombings over the northwestern “industrial triangle” of Milan, Turin, and Genoa—to destroy Axis war production, break civilian morale, and force Italy’s surrender. Raids peaked between 1942 and 1944. So the Kriegsmarine, which managed to gain all the Series I and II still incomplete was not in a favourable conditions to complete them, as any progress was low priority and done at a snail’s pace with little Italian cooperations, or at gunpoint. Genoa and Naples were also badly bombed. This brought activity in these yards to a crawl. There was also widespread labor unrest: Factory workers subjected to bombings frequently responded with organized underground strikes, demanding an end to the war.

Tipo II:

By far the largest, it was equivalent to four average squadrons (of 6 subs each), all named after materials from the periodic table:
Alluminio, Amianto, Antimonio, Bario, Cadmio, Cromo, Ferro, Fosforo, Iridio, Litio, Magnesio, Manganese, Mercurio, Oro, Ottone, Piombo, Potassio, Rame, Rutenio, Silicio, Sodio, Vanadio, Zinco, Zolfo.
15 were to be built at the CRDA shipyard in Monfalcone, six at OTO in La Spezia, and three at Tosi in Taranto. The first to be laid down were the six of La Spezia: Alluminio, Antimonio, Fosforo, Manganese, Silicio, Zolfo all on December 9, 1942. None launched, let alone completed.

The three from Taranto, Magnesio, Mercurio, Amianto were never even laid down, nor were six of Monfalcone, Oro, Ottone, Cadmio, Vanadium, Iridio, Rutenio.
Of the remaining one laid down at Monfalcone, Bario on March 15, 1943, Litio on March 31, Sodio on May 3, Rame and Ferro on June 2, Zinco and Piombo on August 2, Cromo on September 1 were all captured by the Germans when the armistice came and three were launched, Bario, Litio, and Sodio, on January 23, February 19, and March 16, 1944, respectively. They were pressed in Kriegsmarine as U.IT.17, U.IT.18, and U.IT.19. However, all were savaged by an air raid on March 16 194. Litio and Sodio sank, Bario was damaged, but never repaired and remained so until May 1, 1945, when she was scuttled by opening the cocks, so she sank without much more damage, ensuring she could be salvaged and rebuilt postwar, renamed Pietro Calvi.

Tipo III:

The third series, consisting of twelve units, remained at the design stage. None was ever laid down, as space was lacking. If so, that would have been from mid to late 1943. They were named Attinio, Azoto, Bromo, Carbonio, Elio, Molibdeno, Osmio, Osigeno, Plutonio, Radio, Selenio, Tungsteno.
On this chapter, there are 118 elements on the periodic table and a good portion was already used by previous series. The choice of naming submarines after materials is quite unique to the Italian Navy and it’s not sure if it had any effect of the “esprit the corps”. It might have been more judicious to name these after submarine captains awarded the Medaglie D’oro, as this was already the choice made for a class of destroyers, albeit the pool to choose from was probably reduced, or jus those that just died in action, provided this was no seen as a bad luck choice.

Cold War Service

Bario was salvaged after the war, rebuilt, modernized and streamlined in the “GUPPY” style, renamed “Calvi” and seeing a second, much longer career in the Marina Militare. Vortice followed a similar path as well as Giada forming a class of modern diesel-electric subs active in the cold war. But there were three on 48 submarines which for the majority never saw service or only ranging from barely a year to a few months.

Design of the Flutto class

Hull and general design

Rough draft comparison between the Flutto (bottom) and Acciaio (top). To take with a grain of salt.

The Flutto class as seen above was a repeat of the Argo class built in 1938-39 in Italian sources, but with more powerful diesels and a longer hull and thicker pressure hull enabling them to dive to 120 meters or 400 feet as well. This was appreciable diven the growing allied superiority in the Med by 1942. The general design was the same except the German style conning tower in its final form. They were the “mediums” that effectively reached 1016 tonnes submerged. At 63.15 meters or 207 feet long, they were still shorter than the Type VIIC (67.20 m (220 ft 6 in)), and at 6.98 m (22 ft 10.8 in) slightly beamier than the Argo class (6.93 m (22 ft 9 in)), and much beamier than the Type VIIC at 6.20 m (20 ft 4 in). They had a less favourable lenght-to-width ratio and les powerful diesels than their German equivalents (3200 hp total) so no wonder they only managed 16 knots versus 17.7 knots. The VICC/41 were in addition capable of diving much, much deeper, at 220 m, increasing survavibility.

Otherwise they diverged from the Acciaio by the shape of their forward diving planes and aft ones, the rudder, the struts, details of the keel, and they had water more scoops, including a double row forward to dive faster. The conning tower was however similar in the “German style” with an open watch forward position, a weave breaker circling it at the level of the deck, an open aft AA platform, a classic portico to support the protection steel cable running all the way from the net-cutting structure forward, a proper conning tower bell down to the pressure hull containing the attack and watch periscopes. Routinely with good training a Flutto class could dive in between 90 and 120 second versus 60 sec. for a Type VIIC. The VIIC/41 was even faster.

Powerplant of the Flutto class

The recipe remained the same here, trying to improve on the diesel power. They had two shafts Diesel engines rated for 2,400 hp (1,800 kW), or 1200 hp each which was way more than the previous Fiat 700 hp diesels fitted on the Acciaio class or 1,400 hp (1,000 kW) total. The idea was to gain one knot to 16 knots or more in order to be able to use the latest Überwasser-Nachtangriff Taktik, forming in 1942 the core operational phase of the broader Wolfpack (Rudeltaktik). For the few Flutto class that actually saw action, this was appreciable, but less that the 18 knots of the Type VIIC. So top speed surfaced was 16 knots (30 km/h; 18 mph) and 8 knots (15 km/h; 9.2 mph) submerged versus 7.7 knots (14.3 km/h; 8.9 mph) on the Acciaio.

For submerged speed, no change, they adopted the same CRDA Electric motors rated for 800 bhp (600 kW) or 400-horsepower (298 kW) each, albeit there was a slight boost here too with better batteries. It seems also measures were taken to better insulate these electric motors for silent running.
Range was a mixbag depending on sources. The Tipo I had apparently 52 tonnes tonnes of diesel oil for 13,000 nautical miles at 8 knots (15 km/h; 9.2 mph) surfaced or 2.000 nm at 16 kts, and 80 nmi (150 km) at 4 knots (7.4 km/h; 4.6 mph) submerged but this varied wildly among sources. For example the Tipo I were also creditd of 7 nautical miles at 8 knots (max speed underwater) or 74,5 nm at 4 knots. However fuel capacity was greatly reduced on the Tipo II, down to 5,400 nmi (10,000 km; 6,200 mi) nautical miles at 8 knots. As for the max depth it was superior to the Acciaio, at 120-130 meters.

The Tipo 1 was built in a difficult context leading to scores of issues. Submerged speeds and ranges both submerged and surfaced fell short of expectations, along with higher fuel consumption and diverged betwene yards. A new type of fixed-pitch propellers were originally installed, but they caused such significant issues except on the Gorgo which had older models due to shortage, that in February 1943, decision was made to replace all with variable-pitch propellers at least on Flutto, Marea, Vortice, and Nautilo.

Armament of the Flutto class

It was the same as the Acciaio class: One deck gun 100mm/47 M1938 on deck, two twin 13.2 mm Breda M.1931 in the CT, six 533mm or 21 inches torpedo tubes, four in the bow, two in the stern.

Cannone da 100/47 Mod. 1938

Placed on the forward deck, on a raised platform or bandstand well integrated into the hull, acting as wave breaker, to avoid sea spray. The previous 100 mm/47 (3.9″) Modello 1935 already benefited from developments and improvements made on the earlier Modello 1928 manufactured by OTO. By 1941, the Modello 1938 was standard. These boats carried 149 rounds.

Specs

Gun Length oa: 194.5 in (4.940 m), 8-10 rpm.
Fixed Ammunition (HE) 30.4 lbs. (13.8 kg) 2,756 fps (840 mps)
Range: 35° 13,800 yards (12,600 m), OTO 1932
Weight 4.6 tons (4.7 mt) -5 /+32 or 35°.

Breda Mod. 31 13.2 mm AA

The anti-aircraft defence on the Tipo I counted two twin Breda M1931 13.2 mm L/76 heavy machine guns, placed aft of the conning tower. Each mount weighed 695 kg, but ensured an elevation of -10° to 90°. They fired 125 g unitary rounds, with a muzzle velocity of 790 m/s, maximum range of 6,000 meters and effective range of 2,000 meters. Their rate of fire was 500 rounds/min, so 2,000 rounds when both twin mounts fired in concert, however. They carried a total of 10,000 rounds. It seems before or during the war, this progressed to two twin mounts for extra AA firepower according to many sources.

20mm/70 Scotti-Isotta Fraschini Modello 1939

In alternative, and for the Tipo II by default, the twin 13.2mm mounts Breda were replaced by two Scotti-Isotta Fraschini Modello 1939. Indeed the Breda 20 mm experienced bottlenecks. Development started in 1930 through a collaboration between designer Alfredo Scotti an Officine Meccaniche A. Grandi, to create a versatile anti-tank and anti-aircraft gun. It had a gas-operated automatic mechanism, fixed barrel, gas-actuated breech-locking system patented by Scotti in 1931. The first was chambered for a 20x110mm cartridge for 15-round box magazines or 60-round drum magazines with gravity feed, single-barrel or twin-barrel static mount. Tested in 1932 it lost in competition in 1935 againsty the Breda 20/65 Mod. 1935 chambered for the better 20x138B cartridge. However, manufacturing rights were licensed to Isotta-Fraschini which continued development for a new ground-based version chambered for 20x110mm until 1937 and then the 20x138B cartridge with identical feed clips as the Breda Mod. 35.

At last it met success, with production orders from the Regia Aeronautica and Regia Marina as the “Scotti-I.F based on the 20/70 Mod. 38”. It was compatible with a wide variety of mounts.
It was followed by the Scotti-I.F. Mod. 39 (adopted here) featuring a dual gas-regulation valve and made under licence by C.E.M.S.A as the Scotti-O.M. Mod. 41 for the Royal Army. Thos of the Navy had the same types of mounts. After 1943 the Wehrmacht used them as the 2 cm Scotti (i). It was also adopted by the Dutch Army and in 1938, by Nationalist Spain. The British also captured some. Itw as dubbed the “Italian Oerlikon” but apart its 70 calibre, the two were not related.
Specs
Mass 70.5 kg, length 2,270 mm, barrel 1,400 mm, rifling 8 grooves, right-hand twist.
Caliber 20 mm for 20 × 138 mm B rounds 136 g (330 g full), rate 230 rounds/min
Muzzle velocity 830 m/s
Best Range 5,500 m
Feed system Production models: clip-fed.
Elevation -10°/+85°, Air-cooled

12x 533 mm (21 inches) torpedoes

The Adua class submarines repeated the previous class for the stabndardized torpedo armament, six overall including four in the bow, and two in the stern, all reloadable for the pressure hull, and a reserve of 12 torpedoes including the six already in the tubes. Same as before albeit some sources states an increased reserve torpedo load for commerce raiding.
Models available in 1942:
-W 270/533.4 x 7.2 Veloce: 1,700 kg, 7.2 m WH 270 kg, 3,000-4,000 m/50 knots or 12,000 m/30 knots.
-W 270/533.4 x 7.2 “F”: 1,550 kg, 6.500 m, WH 250 kg, speed 3,000 m/43 knots or 10,000 m/28 knots
-W 250/533.4 x 6.5: 1,550 kg, 7.200 m, WH 270 kg, 4,000 m/48 knots or 12,000 m/30 knots.
-Si 270/533.4 x 7.2 “I”: 1,700 kg, 7.2 m, WH 270 kg, speed 3 km/42 kts or 7 km/32 kts, 9,2km/30 knots, 12km/26 kts
-W 250/533.4 x 6.72: 7.2m, WH 270 kg speed 4km/49 kts or 8km/38 kts.
-Si 270/533.4 x 7.2 “M”: 1,7 ton, 7.2 m, WH 270 kg speed 4km/46 kts, 8km/35 kts or 12km/29 kts.
They were also given also a pair of hydrophones and possibly the German GHG sonar.

Maiale Conversion

Two Tipo 1 boats, Murena and the Grongo, were fitting-out to carry assault craft (the Maiale or SLC). They received four cylinders for “human torpedoes” instead of three, born from larger dimensions and wartime experience. The cylinders were located close to the conning tower, two either side for balance and with refinements for handling and deploying the operators. However never never saw action for the the X Mas flotilla.

⚙ specifications Type I as built
Displacement	930 long tons (945 t) surfaced, 1,093 long tons (1,111 t) submerged
Dimensions	63.15 x 6.98 x 4.87 (207 ft 2.2 in x 22 ft 10.8 in x 15 ft 11.7 in)
Propulsion	2 shaft diesel 2,400 bhp, 2 EM 800 hp
Speed	16 kts (30 kph; 18 mph) surfaced, 8 kts (15 kph; 9.2 mph) submerged
Range	5,400 nmi at 8 kts surf, 80 nmi at 4 kts sub.
Max depth	120 m (400 ft)
Armament	1x 100mm deck gun, 6x 533mm TTs, 2×2 13.2mmm AA
Crew	49

Tipo 2

The “Improved Tritone” (Tritone migliorato) had their hull was slightly lengthened, the bow shape modified to address flaws identified in the Tipo 1: a tendency to settle by the stern when fully loaded, an overload trim that caused the bow to dip underwater during surface navigation. The anti-aircraft armament was altered, with the twin 13.2mm Breda replaced by two 20/65mm guns on single mounts.

⚙ specifications Type II as built
Displacement	766 tonnes surfaced, 913/1113 tonnes submerged
Dimensions	64.20 x 6.98 x 4.93 m
Propulsion	2 shaft FIAT diesel 2,400 bhp, 2 CRDA EM 800 hp
Speed	16 kts surfaced, 8 kts submerged
Range	52t diesel oil, 13,000 nmi at 8 kts surf., 80 nmi at 4 kts sub.
Max depth	120 m
Armament	1x 100mm deck gun, 6x 533mm TTs, 2x 20mm/70 Scotti AA*
Crew	50

*On single “retractable” mounts.

Appearance and Camouflage

Like the previous Acciaio class, basic Vertical surfaces were painted in the “Grigio Piombo Ponte”, basically ‘lead grey’. The light grey showed a bluish hue under the Mediterranean light, but it was soon superseded by the “Grigio-Azzuro Chiaro” which mixed light blue to the grey and matched better the sky’s color. During the war they were almost all camouflaged, with a variety of style. It could be a spotted camo in some cases with the military “Verde Scuro” or a mix between it and the Grigio Plombo, darker in tone. But straight shapes, triangles or large areas paintd in dark grey, same Grigio Piombo Ponte, was the norm.

Career of the Flutto class

Series I

Cernia (never launched)

Cernia was laid down at Tosi, Taranto in July 1943, work suspended, never launched, BU on site postwar (cancelled 1.1944).

Dentice (never launched)

Dentice was laid down at Tosi, Taranto, 8.1943. Work suspended, cancelled 1.1944, never launched, BU postwar on slip.

Flutto (1942)

Flutto was laid down at CRDA, Monfalcone on 12.1941, launched on 19.11.1942 and commissioned on 3.1943. She saw action in a few patrols and was lost in July 1943 when trying to disrupt convoys to and from Operation Husky, off Sicily. On 11 July 1943 by night she was on patrol, surfaced in the Straits of Messina when spotted, when attacked and torpedoed by three British Motor Torpedo Boats, MTB 640, 651 and 670. She went down with her entire crew of 49. Career more developed in a future update.

Gorgo (1942)

Gorgo was laid down at CRDA, Monfalcone on May 1941, launched 31 January 1942, launched on November 1942. She trained until 11 November under Ragusa, Innocenzo, had trials and was based at Pola, Montfalcone, then Taranto from December. Her first patrol was on 6-14 January 1943, towards African coast and off Cape Carbon. At 02:06 hours the night of 7-8 she spotted a large shadow through the periscope from 6,000 metres and identified this as a 15,000-ton vessel in convoy. She surfaced, intercepted her and launched at 02:22 hours, four torpedoes of the G7e type from 1,000 metres. These electric torpedoes sped up at 28.5 knots but were spotted as they left a very visible phosphorescent track. They also had an irregular course. They all missed. At 02:25 hours she turned to port to fire her stern tubes but was spotted by an escort vessel and had her CT straddled by 20mm fire, she crash-dived at 90 metres and received depth charges but escaped. On the 13th at 00:51 hours she spotted a convoy of two steamers with a corvette from 4,000 metres, closed to 3,000 meters bu was detected and dove deep 01:05 hours, receiving four depth-charges damaging her then four more later so she abandoned her patrol.

She was repaired at Calgliari and Naples, and made another patrol from 4 April. On the 26th, she spotted steamers, closed for an attack, but never was in position. Later she was ordered to sail to intercept a convoy of 30 ships for Sicily, she altered course but never spotted it. On 2 June she patrolled the Balearic Islands. This 3rd war patrol for 58 sorties total was also the last. While back off the Algerian coast she was reported missing, believed to have been sunk off the Algerian coast by USS Nields (DD-616) on 21st May but this is contested. What is certain is that at 18:50 hours on 2 June, she was ordered to regain base and never acknowledged reception.

Grongo (1943)

Grongo was laid down at OTO, Muggiano on April 1942, 6 May 1943. She was never completed, scuttled incomplete 9.9.1943. Raised and Scrapped postwar.

Marea (1942)

Marea was laid down at CRDA, Monfalcone on 12.1941, launched on 10 December 1942 and commissioned in May 1943 under Sub-Lieutenant (later Lieutenant) Attilio Mario RUSSO. After training in the upper Adriatic, on August 1st she reached Naples and 2 days later sailed for her first combat patrol off the Gulf of Policastro in Calabria, trying to cut off supplies to the VIII British Army and the prepared landings near Reggio and Villa S. Giovanni. No spot, she was back to Naples. On the 7th she sailed for a 2nd patrol to the Gulf of Salerno (screen of 10 submarines for Operation Zeta) to catch up possible landing operations. At 18:30 on the 8th, radio Algiers announced the armistice. MARICOSON (Italian Submarine Command) ordered her to immediately submerge to 80 meters, surface on the 9th at 8:00 AM, flying the national flag and a black signal off the forward periscope and proceed to Bone in Algeria to surrender to the British.

She was then relocated to Malta and on October 6th, back to Taranto, then Brindisi to prepare for co-belligerence. She was selected for two “Special Missions”, both successful: One on the 3rd-9th of November, landing six spies at Cortellazzo near the Piave, the second on December 23rd-29th. After refitting in Taranto by February 1944, she was transferred to Bermuda for ASW training until May 1945. In total she performed 139 training missions notably to and from Bermuda, but also New London and Key West. Whe leaving US waters she was part of a parade, saluted by Admiral Ernest J. King. She was inactive until stricken on February 1st, 1948. Under a Merchant Marine flag she was sent to Albania, Valona on February 7th 1949 and attributed to the Soviet Union as И-41 or I-41. She was scrapped in the 1960s.

Murena (1943)

Murena was laid down at OTO, Muggiano in April 1942, launched on 11 April 1943 and commissioned in August 1943 but never active. Scuttled incomplete on 9 September 1943. Raised and scrapped postwar.

Nautilo (1943)

Nautilo was laid down at CRDA, Monfalcone on January 1942, launched on 20.3.1943 and commissioned in Jnly 1943. Following the Italian armistice, Nautilo was scuttled in Venice harbour on 10 September 1943 to avoid capture. She was then refloated by German forces, recommissioned in the Kriegsmarine as UIT-19. She was once again sunk on 9 January 1944 in Pola during an RAF air raid Royal. She was raised postwar by the new Yugoslav Navy (Jugoslavenska ratna mornarica) and moved to the Uljanik Shipyard to be repaired from 1947 to 1949. She was recommissioned in 1949 as “Sava” (pennant P-802). With Mališan (P-901) and Tara (P-801) also former Italian subs, she formed the basis of the new Yugoslav submarine fleet.
In 1958 she was relegated to training duties. She had a new major refit in 1958-1960, seeing her 100 mm deck gun removed, conning tower reshaped and streamlined as well as part of the hull. She continued serving as a training submarine until stricken in 1971. She became ultimately became a Croatian night club in Dubrovnik, the “Yellow submarine”.

Sparide (1942)

Sparide was laid down at OTO, Muggiano on April 1942, launched on 21 February 1943 and officially commissioned on August 1943 but never active. She was scuttled on 9 September 1943 to avoid capture at La Spezia. Salvaged by the Germann, she became the UIT-15. Never operational. Lost in an air attack on Genoa on 4 September 1944 and stricken on 27 March 1947.

Spigola (never launched)

Spigola was laid down at Tosi, Taranto in June 1943, never launched, work suspended in November 1943, cancelled 1944. BU from February 1948.

Tritone (1942)

Tritone was ordered from CRDA, Monfalcone, laid down on 5.1941, launched on 3.1.1942 and commissioned on 10.1942. She was lost during her first mission on January 19, 1943, while attempting to attack an enemy convoy under command of Lieutenant Commander Paolo Monechi. Remaining at periscope depth, she used the German method adopted in 1942, trying to penetrate by night the escort line and attack transports at close range. But that tactic was known by the allies and they were aware that it might have been used by the Italians as well, so she was detected, subjected to a vigorous, relentless depth-charge attack, forcing her to surface to avoid sinking. She then was lit up, and came under artillery fire from the Canadian corvettes HMCS Antelope and Port Arthur. She had no chance. She quickly sank with only half her crew escaping and 26 men going down including 3 officers, 22 petty officers and sailors, and a civilian worker still on board for fixes. The 25 survivors were rescued and became POWs. Aside this, the made six transit cruises for a total of 1,839 miles surfaced, 54 miles submerged.

Vortice (1943)

Vortice was laid down at CRDA, Monfalcone on January 1942, launched on 23 February 1943 and she was commission in June 1943 under command of Lieutenant Marco Revedin, she was transferred to Taranto, training until September. On 7 September under Lieutenant Giovanni Manunta, she left Taranto for her first mission taking part in the “Zeta Plan” to opposed the landing at Salerno, posted in a line of 10 subs east of Sicily in the Ionian Sea. The next day, the armistice was announced and Captain Manunta surrendered his boat at Augusta. On September 16th, she left port with five other submarine and reached Malta the next day. On October 6th she headed back to Naples, berthed to produce electricity for port facilities. In February 1944 she was sent to Bermuda, based in New London for ASW exercises until V-Day. She was supposed to be handed over to France but the latter declined the transfer and she ordered to be scrapped after decommission in February 1948. However an agreement was found through NATO and it was insted decided to have her modenrized in 1953-54, recommissioned in 1954 as a training sub for antisubmarine training until her final decommission on 1 July 1967, stricken on 1 August, and scrapped. From February 1948 she was the “PV1”. From January 1952 she adopted the NATO number S502.

Series II

Alluminio (never launched)

Alluminio was laid down at OTO, Muggiano in December 1942, never launched, work suspended, captured by Germany on 9 September 1943. Never completed or commissioned. BU on slip postwar.

Antimonio (never launched)

Antimonio was laid down at OTO, Muggiano in December 1942, never launched or completed, captured by Germany 9.9.1943. Never commissioned. BU on slip postwar.

Bario (1944)

Bario (MM: Pietro Calvi, NATO S503) was ordered from CRDA, Monfalcone, completed at Tosi, Taranto, laid down 3.1943, captured by Germany on 9 Sept. 1943, renamed UIT7 and commissioned on 23 June 1944 but never deployed. She was later sunk (scuttled). Postwar she was raised, rebuilt from 1957 to 1961 in two phases and in between recommissioned on 21.6.1959 and 16.12.1961. She served as the training sub Pietro Calvi until decommissioned and discarded in January 1972.

Cromo (never launched)

Cromo was laid down at CRDA, Monfalcone on September 1943, never launched or completed, captured by Germany 10.9.1943. Later scrapped on slip.

Ferro (never launched)

Ferro was laid down at CRDA, Monfalcone on June 1943, never launched or completed, captured by Germany 10 September 1943, renamed UIT12, never completed or commissioned. Scrapped on slip postwar.

Fosforo (never launched)

Fosforo was laid down at OTO, Muggiano on December 1942, never launched or completed, captured by Germany 9 September 1943. Scrapped on slip postwar.

Litio (1944)

Litio was laid down at CRDA, Monfalcone in March 1943. Captured by Germany on 10 September 1943, renamed UIT8 and launched on 19 February 1944. Never completed. Scuttled, raised postwar and BU on slip.

Manganese (never launched)

Manganese was laid down at OTO, Muggiano on December 1942. Never launched, construction suspended, captured by Germany on 9 September 1943. Never completed, BU on slip postwar.

Piombo (never launched)

Piombo was laid down at CRDA, Monfalcone in August 1943. Never completed, captured by Germany 10 September 1943, registered as UIT13. Never operational. Scrapped on slip postwar.

Potassio (never launched)

Potassio was laid down at CRDA, Monfalcone 5.1943, never launched or completed, captured by Germany 10.9.1943 (UIT10). Never operational. Scrapped on slip postwar.

Rame (never launched)

Rame was laid down at CRDA, Monfalcone 6.1943, never launched or completed, captured by Germany 10.9.1943 (UIT11). Never operational. Scrapped on slip postwar.

Silicio (never launched)

Silicio was laid down at OTO, Muggiano 12.1942, never launched or completed, captured by Germany 9.9.1943. Never operational. Scrapped on slip postwar.

Sodio (1944)

Sodio was laid down at CRDA, Monfalcone on May 1943, captured by Germany on 10 September 1943 (UIT9), launched on in June 1944 but never completed. BU on slip postwar.

Zinco (never launched)

Zinco was laid down at CRDA, Monfalcone on 8.1943, never launched or completed, captured by Germany 10.9.1943 as UIT14. Never operational. Scrapped on slip postwar.

Zolfo (never launched)

Zolfo was laid down at OTO, Muggiano on 12.1942, captured incompleted by Germany on 9 September 1943. Never operational. Scrapped on slip postwar.