Argentine submarines in the Falklands conflict. The ARA San Luis attacks the enemy.
ARA San Luis
On April 2, news of the Argentine invasion of the Falklands and South Georgia caught Captain Fernando Azcueta, commander of the submarine ARA San Luis, like most Argentines, by surprise. To some extent, this is evidence of the adventurous policy of the political and military leadership (though at the time, they were acting in the same person—the country was under the military junta led by General Galtieri).
The Argentine military junta. General Galtieri is in the center.
Trying to save an unpopular regime and boost its image on a wave of pseudo-patriotic hysteria, the junta set out to solve a pressing problem for previous governments: the return of the Islas Malvinas (the Spanish name for the Falkland Islands) in one fell swoop. Without any serious preparation (apparently believing the British government would get away with hot air), the junta launched an invasion, ignoring even the Conservative government's plans to cut military spending. After all, in the second half of 1982, plans were underway to sell the aircraft carrier Invincible to Australia, decommission most of the landing ships, and even disband the marine units. In other words, the Falklands could have been taken barehanded.
Summoned to a meeting with the commander of the Argentine Submarine Force (COFUERSUB – Comandante de la Fuerza de Submarinos), Azcueta was ordered to prepare the San Luis for combat operations as quickly as possible. This was no easy task. The submarine's crew was inexperienced, with many newcomers, most of whom had recently returned from summer leave. The submarine had only recently been to sea once (in March). As mentioned, many experienced submariners had been sent to Germany to inspect the new submarines.
Capitán de fragata Fernando María Azcueta
But the main problem was severe fouling of the hull and propeller. This reduced speed (submerged speed did not exceed 14,5 knots), increased noise, and fouling of the sea chest grates and seawater pipes impaired cooling of the diesel engines. One of them completely failed due to a crack in the cylinder block. The engine had not been used since late 1978, but repairs were postponed. Loading and unloading the diesel required cutting and welding a hole in the pressure hull—a technique that the Argentinean fleet I was just starting to master it at that time.
Dry-docking was necessary, but there was no time for it. Furthermore, there was no dock in Mar del Plata, and the submarine had to be transferred to the fleet's main base in Puerto Belgrano. Therefore, a team of divers manually cleaned the hull and propeller, which increased the submerged speed to 20 knots and prevented the diesel engines from overheating. Essential repairs were made, and fuel, fresh water, and provisions were taken on board. Ten AEG SST-4 torpedoes and 14 Honeywell Mk-37 Mod 3 anti-submarine torpedoes were loaded on board.
Loading the SST-4 torpedo
The low reliability of the SST-4 torpedoes was a serious concern for Argentine submariners. Of all the torpedo training exercises conducted by the Argentine Navy's Type 209 submarines using the SST-4 between August and December 1981, only one launch was successful. During the remaining torpedo launches, control cables were broken, the torpedoes sank, and other incidents occurred.
Tactical and technical data of torpedoes
Since 1974, Argentine Type 209 submarines have conducted 19 training exercises with SST-4 torpedoes, and in most cases, various shortcomings were revealed. It should be noted that at the start of the Falklands conflict, no one had any experience with combat use of this type of torpedo.
Furthermore, there were problems with the scheduled maintenance of these torpedoes. They were supposed to be fully overhauled every 10 years, and since they were manufactured in 1972–1973, their guaranteed service life was approaching the end.
Torpedo gyroscopes were required to undergo maintenance every 48 months. Neither of the gyroscopes on the two torpedoes used by the ARA San Luis in combat underwent maintenance.
As for the batteries, they were manufactured between 1971 and 1972 with an expected service life of seven to nine years. Thirteen new batteries were acquired between 1979 and 1982. Of the two torpedoes fired by the San Luis, one had new batteries, and the other had used batteries.
"San Luis" in Mar del Plata
On the night of April 11, after a week of intensive work, the San Luis left base for sea trials. Submerged, she reached 20 knots, and there were no problems with diesel engine cooling. However, the snorkel was leaking water, and the bilge pumps were inefficient and noisy. Despite this, the Submarine Force Command (El Comando de la Fuerza de Submarinos) ordered the patrol. The southward passage proceeded without incident, and on April 17, the submarine's commander received orders to patrol the area east of the Golfo de San Jorge. The submarine remained there for 10 days, awaiting the outcome of Anglo-Argentine negotiations brokered by American Secretary of State A. Haig.
On April 19, during a training exercise, the VM8-24 torpedo fire control computer malfunctioned. The repairs were impossible, and consultations with shore-based specialists were refused out of concern that intensive radio traffic could lead to the submarine losing its stealth. Now, all calculations and data input for torpedo firing could only be performed manually, which significantly reduced its effectiveness. This type of control was recommended for self-defense only. Despite this, command ordered the patrol to continue.
On April 27, orders were received to proceed to the "María" sector, located northeast of Isla Soledad (East Falkland), where the submarine arrived on the 29th. Soon after, the Argentine government announced that, from 7:00 a.m. on April 30, all ships and aircraft within a 200-mile zone could be attacked without warning. The "San Luis" received permission to attack the enemy within the 200-mile Total Exclusion Zone (TEZ) around the islands. The British ships entered the zone at 1:30 a.m. on May 1.
Patrol sectors near the Falkland Islands
Communications with the Argentine submarine were intercepted and decrypted by British radio intelligence, and the approaching task force TF317 was warned of a submarine threat. On the morning of May 1, a naval anti-submarine search and strike group consisting of the frigates F90 Brilliant (Type 22) and F101 Yarmouth (Type 12) was deployed west of the task force. Three Sea King HAS Mk 5 carrier-based helicopters from the aircraft carrier Hermes also conducted continuous anti-submarine searches within their operating area.
Frigate F101 Yarmouth
Helicopter Sea King HAS Mk 5
Aircraft carrier Hermes
On May 1, the San Luis's sonar operators established hydroacoustic contact with a warship. A more precise identification of the ship was made by assessing its electromagnetic emissions using electronic intelligence sensors. It was presumably a Type 42 destroyer or a Type 21 or 22 frigate (according to British sources, the frigates F 173 Arrow and F 174 Alacrity were present at the time). At 8:00 a.m. the following day, a combat alert was sounded—thanks to good sound penetration, the submarine was able to take a favorable attack position. At 10:15 a.m., an SST-4 torpedo was launched from a range of approximately 10,000 meters, but the submarine lost contact with it after 3-4 minutes due to a severed remote control cable. No explosion was heard.
Around the same time, the frigates F90 Brilliant and F101 Yarmouth established contact with the submarine using sonar and one helicopter using a magnetic detector. The frigates, using their deck helicopters (a Lynx HAS Mk1 from Brilliant and a Wasp HAS Mk1 from Yarmouth), supported by three Sea King helicopters from the carrier, began a hunt for the submarine, which lasted approximately 20 hours. During this hunt, Yarmouth fired approximately 30 depth charges from its Limbo launcher. Around 4:00 PM, one of the helicopters dropped a Mk 46 torpedo, which was evaded by setting a decoy (firing cartridges that generated a cloud of gas bubbles).
The San Luis moved slowly towards the coast and at 16 p.m. lay down on rocky ground (to protect the bottom of the boat from damage, it was equipped with a Teflon beam) to reduce noise and conserve energy reserves.
Bomb launcher "Limbo"
Personnel of the San Luis's electromechanical warfare unit and the submarine's commander, Azcueta. The submarine lies on the ground off the coast of the Falklands.
The sounds of British ships and depth charge explosions gradually faded, and at 9:00 PM, the commander, concerned about the proximity of the coast, which limited his maneuverability, decided to head further out to sea. It was then that the poor condition of the bilge pumps became apparent. It took 40 minutes of continuous operation to lift the submarine off the bottom and drain the rapid diving tank. The noise of the pumps triggered a new series of attacks. One of the depth charge explosions was dangerously close. The submarine grounded again, and the enemy soon lost contact with it.
In total, during the search for the San Luis, the helicopters dropped approximately ten Mk11 depth charges and two Mk46 torpedoes. The Sea King helicopters did not return to the aircraft carrier during the search for the submarine, but refueled from the frigates while hovering using the Helicopter In-Flight Refuelling (HIFR) system. One of them remained in the air for 10 hours and 20 minutes.
By the evening of May 1, Brilliant and Yarmouth had moved approximately 90 miles from their carrier task force and continued their search independently overnight. On the morning of May 2, the frigates abandoned their search operation and rejoined the main force of TF317. At 5:00 a.m. on May 2, the Argentine submarine surfaced under snorkel and, taking advantage of the darkness, began charging its batteries. Soon, sonar contact was established with the surface ship, and the charging was interrupted.
On May 4, the San Luis was sent to the Isabel sector, east of Isla de Leones Marinos. This redeployment was apparently motivated by the hope of detecting enemy activity in the area where the destroyer Sheffield had been sunk that day. After three days of fruitless searching, the submarine returned to the María sector.
On May 8, noises with unclear characteristics, presumably those of a submarine, were detected in the stern sector approaching at a speed of 6-8 knots. Fearing an attack, the Argentine submarine's commander ordered the launch of decoys and, under their cover, began maneuvering to close. At 9:42 p.m., a Mk-37 torpedo was launched from a range of 2400 meters, detonating at 9:58 p.m. According to hydroacoustic data, the target continued moving, meaning the explosion was not caused by a hit on the submarine, but by the detonation of a fuse, presumably upon impact with a dense clump of krill or an underwater rock. The target of the May 8 attack remains unclear.
On the afternoon of May 10, the San Luis left the María sector and headed west toward the northern entrance of the Falkland Strait to intercept a ship whose noises were identified as those of a destroyer. After complex maneuvers to close in, the propeller noise of another ship was detected. These were the Type 21 frigates F173 Arrow and F174 Alactity.
At 1:40 a.m. on May 11, an SST-4 torpedo was launched at one of the ships from a range of approximately 5100 meters. After 2 minutes and 12 seconds, the remote control cable snapped, and 6 minutes later, a low-intensity explosion with a metallic sound, unlike a torpedo, was heard. The torpedo likely struck the frigate Arrow's Mk182 towed sonar detector. The ships retreated at full speed, making no attempt to counterattack, as they had not noticed the torpedo attack.
Incidentally, after the Falklands conflict, AEG Telefunken carried out work to eliminate the identified deficiencies in the design of the SST-4 remote control cable detonator and unwinding system.
Frigate F173 Arrow
After the third unsuccessful attack, Azcueta broke radio silence and reported technical problems and weapons failures to command. He was ordered to return to base. On May 19, after 39 days of patrol and 864 hours submerged (equivalent to 36 days), the submarine San Luis arrived at the Puerto Belgrano naval base for repairs to the torpedo control computer, replenishment of supplies, inspection of the torpedoes and replenishment, and crew replacement. However, by the time the conflict ended on June 14, the repairs were not completed.
Despite this, the British were constantly wary of enemy submarine attacks and diverted significant forces to fight a nonexistent enemy. The Falklands conflict demonstrated that diesel-electric submarines still posed a serious threat. Although the Argentine submarines failed to achieve success, they diverted significant forces of the British fleet and kept them under constant pressure throughout the conflict.
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