O’Higgins class cruisers (1951)

Armada de Chile – ACS O’Higgins, Capitan Prat 1951-1983/91

The O’Higgins class cruisers were the former USS Brookyn (lead class vessel) and USS Nashville, sold to Chile under MDAP in January 1951 and in service until the 1980s. They answered similar acquisition the same year by Brazil (Barroso) and Argentina with the Belgrano class, of which the latter was sunk in teh Falklands in 1982. Both O’Higgins and Capitan Prat had relatively uneventful careers, apart important collisibs that left them powerless and needed intensive repairs. They had their electronics upgraded before transfer in 1951 and again in 1958 but they were kept in their “stock” condition until the end of their service, as the last all-guns cruisers in active service pretty much until the end of the cold war. In 1971 they were even joined by a third cruiser, Almirante Latorre, former 1945 Tre Kronor. All three were camouflaged, something rare in that era of long range radars. #coldwar #ussbrooklyn #ussnashville #ohiggins #capitanprat #cruiser #chineannavy #chileday #armadadechile

Acquisition

The pride of the Chilean Navy: The cruisers Latorre (ex Tre-kronor), Prat (ex-Nashville), and O’Higgins (ex-Brooklyn) sailing together for an historical photo in the 1970s src navsrource

The most spectacular acquisition of the Chilean Navy in the early cold war were a pair of Brooklyn class cruisers: O’Higgins (ex-Brooklyn) and Capitán Prat (ex-Nashville) (from 1982 Chacabuco). Albeit the design of these ships went back to 1935, they were groundbreaking for US cruiser design at the time, and had be throughly modernized in WW2. Their key feature was a battery of fifteen rapid-fire 6-in guns in three triple turrets. Both were acquired for $37m apiece (10% of the original cost) at the time she ships has been decommissioned, and a contract for transfer led to a limited refreshing overhaul. The final transfer was done on 9 January 1951. They would be active until after the Falklands war. Same type as ARA General Belgrano and Nueve de Julio, both Chile and Argentina had a pair of similar cruisers.
O’Higgins was grounded on 12.8.1974 in Patagonia fjords. Towed back to port but never fully repaired, she became an accommodation hulk, then was extensively refitted and fully recommissioned in 1978. She was decommissioned in January 1991 and sold 10.1991. Her sister did not have any improvements and was decommissioned in May 1982, and sold in April 1983. An oddity in the 1980s, O’Higgins was camouflaged.

The transfer ceremony in Philadelphia, 30 June 1951

Design of the class

Being a “stock” Brooklyn class, both were transferred in the state they were decommissioned from US service. For O’Higgins this was on 3 January 1947, and stricken on 22 January 1951, actually much later than her commission date within the Chilean Navy on 9 January. As CL-40, USS Brooklyn, the namesake class lead cruiser, she was awarded 4 battle stars. Originally laid down on 12 March 1935 and launched 30 November 1936 she saw action in the Atlantic convoys, North African Campaign (Operation Torch), taking part in the Battle of Casablanca where she sank or co-claimed several French destroyers, the cruiser Primauguet and submarine Amazone. Later she took part in the Italian campaign, the Anzio-Nettuno landings in February 1944 and bombardment of the Formia-Anzio area and in August the invasion of southern France, Anvil-Dragoon. After her late 1944 overhaul she was mostly active along the eastern seaboard.

Brooklyn, Nashville and St Louis in Philadelphia, 1951

As for her sister Capitan Prat, she was the ex-USS Nashville (CL-43). Ordered in 1933 and Launched on 2 October 1937 she saw plenty of service in the interwar and WW2, escorting the Doolittle raid on Tokyo in 1942, sinking Japanese picket boats and loosing surprise. Later with Task Force 8 she took part in the Aleutians campaign, and then as flagship of TF 67 in the Guadalcanal Campaign. She then took part in many landings in the New Guinea area Dutch East Indies and Philippines Campaign, Battle of Leyte where she was hit by Kamikaze, then Borneo. When she was decommissioned 24 June 1946, she had been awarded ten battle stars, making her one of the most decorated in her class. Negociations took place in 1950 to sell her to the Chileans (Brazil and Argentina also acquired those) and she was stricken and sold to Chile the same day on 9 January 1951, becoming Capitan Prat. Each was sold at 37,000 $ apiece, 10% of their original cost.

Hull and general design

The Chilean cruisers were still in their “stock” 1945 conditions, and apart new radars, they retained intact their powerful main, secondary and AA artillery.
The Brooklyn class cruisers were quite different than their predecessors in the USN, the New Orleans and Northampton classes with a “fuller” type of hull, flush deck and ending in a transom stern. They were also the result of the 1930 London treaty, which in effect capped the number of heavy cruisers as defined by the 1922 Washington treaty (with 8 inches guns) but authorized a tonnage up to 10,000 tonnes standard. So they were “light cruisers” in name only, with a heavy cruiser hull but no less than five triple 6-inches rapid fire guns. This gave them at the time, the largest firepower of any light cruiser, on par with the Japanese Mogami class in 1934, before they were converted to 8-inches guns in 1940.

The O’Higgins class were thus 10,000 long tons (10,160 t) estimated as design and 9,767 long tons (9,924 t) standard but 12,207 long tons (12,403 t) in 1945, and as sold. Their hull measured 600 ft (180 m) overall and 608 ft 4 in (185.42 m) between perpendiculars for a beam of 61 ft 7 in (18.77 m) so 1/10 ratio and a draft between 19 ft 9 in (6.02 m) mean and 24 ft (7.3 m) max.
They had two main island structures amidships with two raked funnels and masts. The latter was modified to carry extra radars, but they remained small. The ships also retained their fire control systems, also enhanced by radars in 1945. They had a plotting table, no buried central operation, but an efficient ballistic computer. Electronics were upgraded in the 1957-59 refit in the US.

Protection

Being light cruisers, the O’Higgins class were lightly protected:
Belt: 3+1⁄4–5 in (83–127 mm)
Deck: 2 in (51 mm)
Barbettes: 6 in (150 mm)
Turrets: 1+1⁄4–6 in (32–152 mm)
Conning tower: 2+1⁄4–5 in (57–127 mm)
In addition, they had a double hull and underwater compartmentation with bulkheads, with outer compartment filled with thick fuel oil, damping the effect of a torpedo hit. This did not prevented a sinking, as shown by the fate of Belgrano in 1982.

Powerplant

The O’Higgins class cruisers kept the same powerplant without change until the end of their career. It consisted in four shaft propellers driven by four GM or Westinghouse geared steam turbines, and fed by eight Babcock and Wilcox superheated Steam boilers for a total of 100,000 shp (75,000 kW). This gave them a top speed of 32.5 knots (37.4 mph; 60.2 km/h) initially, but between their engines being work out after their WW2 service and wartime addition, 30 knots would be a safe bet. It is no known if their machinery was revised and overhauled before being sold either. It seems in their cold war career they performed well enough. Range was around 10,000 nautical miles based on 1300 tonnes fuel oil.

Armament

As delivered the cruisers kept their previous five triple turrets with 6-inches /47 Mk 16 guns, eight single 5-inches /25 Mk 27 guns and four quad 40mm/60 Mk 2 Bofors, plus six twin 40mm/60 Mark 1 and nine twin 20mm/70 Mk 24 Oerlikon AA guns. This was in 1951 still a “stock WW2 armament”. It was not a problem in the context of South American traditional rivalry, as there was no missile ship in service in either Chile, Argentina or Brazil before decades.
In 1945:
15× 6 in (150 mm)/47 caliber guns (5×3)
8× 5 in (130 mm)/25 caliber anti-aircraft guns (8×1)
4x quad and 2x twin 40 mm (1.6 in) Bofors anti-aircraft guns
18 × single 20 mm (0.79 in) Oerlikon cannons

In 1951:
They had an even large AA park, with four more twin 40 mm Bofors installed and instead of 18 single, ten (nine for Prat) twin 20 mm Oerlikon AA guns, so 20 total to gain deck space. So for the grand total, 38 Bofors, 20 Oerlikon. The Bofors were radar guided.
However this suite showed its age by the late 1950s and an agreement for modernization led to an important refit in 1957-59:
-Six quad 40mm/60 Mk 2 (2 more)
-Two twin 40mm/60 Mk 1
-Six twin 20mm/70 Mk 24
-Landing pad aft, Jet Ranger helicopter.

Sensors

More importantly, they had a relatively modern radar suite, the SPS-4, SPS-6 search radars, and the Mk 13 and two Mk 28 fire control radars.
After their refit of 1957-59 they had the SPS-10 and SPS-12 radars installed. The Fire Control Systems were unchanged.

Air Group

Oriignaly they had two catapults for a pair of Curtiss SOC Seagull spotters/recce floatplanes. They were eliminated in 1946, both the planes and catapults, leaving only the lattice axial crane and lift in the hangar below.
They were fitted in Chilean service with an helipad in 1959, pretty much like on the Belgrano class, but since this part was still lightly constructed, they could only operate a Bell Jet Ranger helicopter, usable only for liaison with the shore and between helipad-equipped ships. They were not usable as ASW helicopters.

*Prat had nine twin Oerlikon guns.