Atrevida class Corvettes (1952)

Armada: Atrevida, Descubierta, Diana, Nautilus, Princesa, Villa de Bilbao

The Atrevida class corvettes were the product of the more austere 1950 naval plan in economically crippled and isolated postwar Francoist Spain. Six corvettes were ordered which became the Atrevida class, designed in 1948-49 and laid down in 1950 for the first two, as a Spanish version of the Gabbiano class armed for the Kriegsmarine. However by 1953 MDAP offered Spain the possibility of modifying the design with modern US weaponry and senors, leading to the last four in class, completed 1959-60. They remained active until the late 1970s before being reconverted as OPVs to watch over the Spanish EEZ until decommissioned in 1991-92. Descubierta and Diana were not converted and retired in 1971-73. They were helped later by the Descubierta class corvettes and replaced by the Baleares class Frigates.

Development

The Armada in 1946

The state of the Armada in 1946 was pitiful. Naval construction virtually stopped in 1936 with the civil war, resumed painfully from 1939 but was characterized by massive delayes resulting in prewar design completed post 1945 with acute material shortages. Spanish isolation on the international scene did not helped either and it was arduous to procure modern armaments and sensors, so as a result, she ships were mostly obsolete at completion, like 1930s designed torpedo boats, some destroyers, submarines and cruisers. Franco’s 1943 plan was unrealistic, as it called for an amazing 4 battleships, 4 aircraft Carriers, 8 light cruiser designs, 12 scout Cruisers, 108 Destroyers & Torpedo Boats, 50 submarines and some 100 fact coastal defence ships like MTBs. Needless to say apart gunbopats, corvettes and minesweepers, nothing vame out of it given Spain’s economic realities. So the fleet had still in 1946 the surviving heavy Cruiser Canarias, flagship, the old Méndez Núñez AA cruiser, the Navarra. The backbone of the destroyer force were still the Churruca-class Destroyers modelled on british 1918 V-W class designs, the even older Alsedo-class with a collection of gunboats and versatile warships as the Jupiter-class Minelayers and Frigates and Corvettes for what we are interested in, resulting of the 1943 Plan such as the Pizarro-class Frigates and minesweepers such as the Bidasoa-class.

The 1950 Plan

The Navy launched a realistic Modernization Program (Plan de Modernización) to salvage existing hulls and adapt the navy to the new Cold War. Franco took advantage of the Truman Doctrine, and this government saw Spain from an ex-axis member to a staunchly anti-communist ally. This would result in a $62.5 million in loans and aid. Instead of a global power projection fleet (1943) Spain opeted for an auster but more useful coastal defense plan with mine warfare, and anti-submarine warfare. This plan was elaborated in 1950–1951 when the navy identified 47 specific vessels already built or half-constructed to be retrofitted with modernized equipment, like Canarias, Almirante Antequera-class destroyers, Álava-class destroyers, Audaz-class fast torpedo boats, the Pizarro-class gunboats. New constructions soon also integrated novel ships, the six corvettes in this plan, the Descubierta-class of this topic.

Some programs were cancelled or resuced on scope like the Oquendo class. The navy left them out to maintain the flexibility and later refit them with advanced US weapons and sensors. The 1950 shift laid the exact groundwork for the 1953 Pact of Madrid which took advantage of the resulting Mutual Defense Assistance Pact (MDAP), in which the US could nio supply Spain with modern radars, sonar, and anti-submarine weapons making them into viable Cold War assets. Chiefly this helped transitioning to an obsolete early design for the Atrevida class to far better ASW vessels to the latest international standards, useful in the new NATO role of Spain, especially in the Atlantic. They would be assisted in their role by the modern designed Descubierta class launched from 1962 and replaced truly by the Baleares.

The Atrevida class genesis

The Atrevida class were six corvettes built for the Spanish Navy in the 1950s, part of a large construction programme to re-equip the Spanish Navy, replaced legacy prewar and WW2 vessels now obsolete. They were also a way to relaunch the Spanish shipbuilding industry after the long eclipse of the 1936 civil war and WW2 isolation. That program consisted of 18 destroyers, 6 corvettes, 6 submarines plus MTBs and patrollers. The Atrevida class was to be the corvette part of the program. They were moderately large ships at 75.5 metres (247 ft 8 in) for 927 tonnes standard and since speed was not a prioritity, they were given Sulzer diesel engines for a top speed of only 18.5 knots but making for a long range perfect for escort work and ASW patrols.

The names had been all sported by various ships in the Armada, notably 18th century corvettes Descubierta and Atrevida under command of Captain Alejandro Malaspina and José Bustamante made famous by their scientific expedition across the Atlantic and Pacific. Princesa and Diana were also former sailing corvettes. Nautilus was the the ship on board which Captain Fernando Villaamil circumnavigated the globe. The same was also instrumental in the development of Spanish destroyers and the aptly named 1880s Destructor. Villa de Bilbao was a sailing corvette launched in 1846 (1,312 tons) with 30 guns.

Atrevida and Descubierta were started at Bazán’s (now Navantia) in Cartagena by 1950, financially unassisted. No MDAP funds were allocated yet, but relations with the USA were warming up. Budget restruction thus delayed construction, with the remaining ships laid down only by 1953. Completion went on from 1954–1955, and after this happened, the US Mutual Defense Assistance Programme funding was attributed, allowing to fund the completion of the remaining four ships, with modernised armament and sensors making them more appropriate for anti-submarine warfare. After being rearmed to US standards they rose to 1,013 tonnes standard but this delayed completion until 1959–1960 after which the first two of the Atrevida class were not upgraded to the same standard.

Due to this, they were stricken as early as 1971, Diana in 1973. Atrevida and Villa de Bilbao instead of leaving service in 1979, were refitted for patrol work, sonar and ASW armament removed. They became OPVs bacically, “Patrullero de Altura (PA)”, to roam the Atlantic between Gibraltar and the Canary Islands. They were succeeded in this role by the new Serviola-class from 1991. The to be retired was the lead vessel, Atrevida, eventually stricken after this second career in 1992.

Modernizations

The experience gained with the lead ship in class allowed the remaining ones to entered service, modified, around 1955 after curing most of early design issues. The next five would be included in the 1955 Modernization Program while retaining their original hulls and machinery leading to a series of escorts quickly produced. The only ship not modernized was the lead vessel, an inheritance of material shortages during construction from 1950. It was later deemed not worth the effort to upgrade her.
So in 1959-1960, Descubierta and Atrevida were rebuilt as later ships (F62-65) same standards, but in 1979, Atrevida, Princesa, Nautilus, Villa de Bilbao were rearmed with a 76mm/50 Mk 34, three 40mm/70 SP48 Bofors, a twin 20mm/70 Mk 24 Oelrikon mount, and 20 mines. From 1979 they became essentially OPVs (Offshore Patrol Vessels).

Design of the class

Hull and general design

The Atrevida class measured 75.5 metres (247 ft 8 in) long overall for 68 metres (223 ft 1 in) between perpendiculars, on a beam of 10.2 metres (33 ft 6 in) for a hull ratio of 1/7, and a draught of 2.6 metres (8 ft 6 in). In the initial configuration the first two displaced 927 tonnes (912 long tons) standard, 1,038 tonnes (1,022 long tons) full load.
For their outlook, they were very classic and looked like interwar small destroyer or torpedo boat designs. They had a clipper bow, a long forecastle about 2/5 her full lenght and a classic clipper rounded stern, instead of a more fitting transom stern. They drew influence from references hard to pintoint, but superficially the late WW2 Castle class corvettes or the earlier Italian Gabbiano class for some of their proportions. There was a two-tiered superstructure with an enclosed bridge with portholes followed by an open bridge. They had a single derrick style mast, albeit initially this was a tripod, no radar was planned. No plans or blueprints found (so far)

Powerplant

She relied on a trusted, simple and space-saving powerplant, two Sulzer diesel engines located side by side, rated at a total of 3,000 shaft horsepower (2,200 kW). They drove two 3-bladed fixed pitch propeller shafts, for a top speed of 18.5 knots (34.3 km/h; 21.3 mph) and also carried 100 tons of oil for a range of 8,000 nautical miles (15,000 km; 9,200 mi) at 10 knots (19 km/h; 12 mph). No modernization was ever done in their entire career, on this diesels essentially similar to those of submarines.

Armament

It changed over time: As designed, they basically had leftover axis gunnery, a German 10.5 cm (4.1 in) dual-purpose gun a close-in pair of 37 mm FLAK guns aft in a single twin mount and no less than twelve 20 mm anti-aircraft guns in three quadruple mounts of the Flakvierling type. They also had four depth-charge throwers and rails to carry and drop 20 mines. The crew back then amounted to 132. The first two ships, Descubierta and Atrevida was commissioned as such. They almost looked like enlarged Gabbiano rearmed by the Kriegsmarine. They probably had a sonar, perhaps German, but no sources back this up. They had of course no radar.
The next four ships would be completed, after being redesigned, much later under MDAP funding which opened the pool of US weaponry and sensors to the Armada.
As such they had the following as completed:
One 3-inch (76 mm) Mark 26 semi-automatic anti-aircraft gun
Three 40mm Bofors L/70 guns, placed aft, replacing the twon 37 mm in single positions for the best arc of fire, very much like the Gabbiano class.
Two 178 mm Mk 11 Hedgehog anti-submarine mortars placed forward on the first tier of the structure.
After were now no less than eight depth charge throwers and two depth charge racks, all of US standards.
Although this was an improvement, in the 1970 they were completely obsolete as ASW ships, lacking longer range weapons and an helicopter.
Hence the third rearmament, as OPVs for those concerned:
From 1979 onwards, Atrevida, Princesa, Nautilus, and Villa de Bilbao kept their 3-in(76mm)/50 Mk 34 main gun forward, backed by the same 40mm/70 SP48 Bofors, and just two 20mm/70 Mk 24 for “low threat warning”. The two forward Hedgehogs and the whole aft DCR and DCT suite was removed, but they apparently kept their capacity to lay 20 mines.

Sensors

As competed they had nothing but perhaps a German standard sonar of the GHG type if available, but no radar.
The last four vessels received a radar and sonar suite of US pattern, SPS-5B surface search radar and QHBa sonar.

Above: Early Atrevida class. Below, remaining four with US armament and sensors

⚙ specifications
Displacement	927 tonnes (912 long tons) standard, 1,038 tonnes (1,022 long tons) full load.
Displacement (F63 onwards)	1,013 tonnes (997 long tons) standard, 1,153 tonnes (1,135 long tons) full load
Dimensions	75.5 x 10.2 x 2.6 m m (247 ft 8 in x 33 ft 6 in x 8 ft 6 in)
Propulsion	2× Sulzer diesels 2,200 kW (3,000 shp)
Speed	18.5 knots (34.3 km/h; 21.3 mph)
Range	8,000 nmi (15,000 km; 9,200 mi)
Armament, initial	1× 105 mm, 2× 37 mm AA, 12× 20 mm AA, 20 mines, 4 DCT
Armament, mod	76mm/50 Mk 34, 3x 40mm/70 SP48 AA, 2×24 178mm Hedgehog Mk 11 ASWRL, 8 DCT, 2 DCR
Sensors (mod)	SPS-5B radar, QHBa sonar
Crew	132

Career of the Atrevida class

Atrevida F61

Atrevida (F61) was laid down at Bazán, Cartagena on 26 June 1950, launched on 2 December 1952 and commissioned on 19 August 1954. She was the only ship in class initially built according to the original design, and modernized while the others were built directly to the modified design. Some books and authors refer the class to the lead ship so the Atrevida class (like conways), while others call it the modified Descubierta class. Construction of Atrevida started on June 26, 1950 at the Empresa Nacional Bazán shipyard of Cartagena, she was launched on December 2, 1952, delivered to the Spanish Navy and officially commissioned on April 25, 1955. She was initially based in Cádiz, like the other five built to the modified design, entering the the 41st Corvette Squadron to provide escort and protection for convoys against air and submarine attacks. She was withdrawn from service in 1960 but it was the cost of her modernization, nearly one million dollars ($4,953,167 for all five units) that led to cancel her sister’s Descubierta, suffering from construciton issue, the same process.

Atrevida served as a training vessel while tasked of surveillance and patrol duties in territorial and international waters. In November 1975, she took part in the “Green March” crisis, sent to Las Palmas de Gran Canaria alongside 13 other Spanish vessels. She became an escort and emergency hospital ship for Spanish and Portuguese cod-fishing fleets off Newfoundland (St. John’s), and was outfitted for this. Between 1978 and 1983, she lost her ASW suite. She was reclassified as an offshore patrol vessel (OPV) for monitoring the Spanish Exclusive Economic Zone (EEZ), hull number “PA” and later “P”. She was stationed in Las Palmas de Gran Canaria to patrol the Canary Islands Maritime Zone and towards the south, the Saharan waters and protected national fishing and merchant fleets, as well as providing navigational assistance during emergencies, or safeguarding national economic resources from internaitonal pillage.
She was decommissioned by order of July 11, 1991, by the Admiral Chief of the Naval Staff (AJEMA) Carlos Vila Miranda, stricken from the Register after a proposal by the Naval Staff. On October 7, 1991, she arrived at the La Carraca Naval Arsenal in San Fernando, Cádiz to be disarmed and disposed for scrap. The battle ensign was folded out on February 3, 1992. She was the longest in service in class.

Descubierta F51

Descubierta (F51) was laid down in Bazán, Cartagena on 26 June 1950, she was launched on 9 June 1952 and commissioned on 1 February 1955. She was the only ship in her class not to undergo modernization under MDAP and instead, her early construction issues due to the lack of high-quality materials in post-war Spain led to believe this would not worth it. Once does not build on sand foundations. F-51 served in Equatorial Guinea all her career and continued after independence in 1968. In March 1969, there was a diplomatic crisis between Spain and Equatorial Guinea, so she took part in the evacuation of Spanish residents, alongside the cruiser Canarias, gunboat Pizarro assisted by the tanker Teide (A-11), and transport ships Aragón (TA-11) and Castilla (TA-21). Back to Spain she was decommissioned, and scrapped in 1970, freeing her name for the later namesake corvette class.

Diana F63

Diana (F63) was laid down Bazán, Cartagena on 27 July 1953, launched 29 April 1955 completed 13 May 1960. She served as a training vessel and alternated with surveillance and patrol missions in Spanish waters. She suffered a serious accident when running aground in 1971 near the Rota Naval Base, Cádiz, leading to her premature decommissioning and scrapping in 1973.

Nautilus F64

Nautilus (F64) was laid down at Bazán, Cádiz on 27 July 1953, launched on 23 August 1956 and commissioned on 15 December 1959. She was the first ship in class to be built at La Carraca and served as training vessel with patr-time surveillance and patrol duties in Spanish territorial waters (including the Canarias and Saharan waters) in the 1980s. She was then reassigned to open-ocean patrol duties to monitor the Spanish Exclusive Economic Zone, F was changed to PA and later from 1986, “P” as NATO OPVs. In 1991, she was decommissioned and scrapped.

Princesa F62

Princesa was laid down at Bazán, Cartagena on 18 March 1953, launched on 31 March 1956 and commissioned on 3 October 1959. She was the first ship in class to be built according to the modified design, unlike Atrevida modernized later, and Descubierta never modernized. She served as a training ship and performed surveillance and patrol duties in Spanish territorial waters. On January 12, 1968, she fired warning shots over the Italian fishing vessel Tornado fishing illegally in the waters of the Saharan fishing grounds part of the Spanish territory at the time, which after benn called and warned, refused to stop.
On September 12, 1968, Princesa carried the Olympic flame. It was passed ont Cristóbal Colón de Carvajal, son of the Duke of Veragua and final athlete to carry it for the Spanish Olympic Games. The trip included Las Palmas de Gran Canaria, San Sebastián de La Gomera, San Salvador, passing on the torch to the gunboat Durango. Her commander was later awarded the Medal of Sporting Merit.
In November 1974, she seized the Soviet fishing vessel Orfey while fishing illegally in Canary Islands waters. In the 1980s, she was assigned to offshore patrol duties, monitor the extreme reaches of the Spanish EEZ, with the hull number prefix changed from “F” to “PA” and then “P” under NATO regulations from 1986. In September 1985, she escorted the 1st V Centenary Ocean Regatta from Palos de la Frontera to La Gomera. She was eventually decommissioned in 1991, sunk as target on September 17, 1992 in Sinkex ’92.

Villa de Bilbao F65

Villa de Bilbao (F65) was laid down at Bazán, Cádiz, La Carraca (San Fernando) on 18 March 1953, launched on 19 February 1958 and completed on 2 July 1960 originally intended to be named Favorita. She served as a crew training vessel and performed surveillance and patrol duties in Spanish EEZ waters until the 1980s, when she was reassigned to open-ocean patrol duties, specifically to monitor the Exclusive Economic Zone (EEZ) and this resulted in a change to her hull number with the “F” prefix replaced first by “PA”. From 1986 she received a “P” prefix and finally in 1992, she was decommissioned and scrapped.