Name: Oberon class

Builders: Vickers-Armstrong, Cammell Laird, Chatham Dockyard, Scotts Shipbuilding and Engineering Company
Operators: Royal Navy, Royal Australian Navy, Royal Canadian Navy, Brazilian Navy, Chilean Navy

Preceded by: Porpoise class
Succeeded by: Upholder class
In commission: 1960–2000

Completed: 27 Retired: 27 Preserved: 8 complete, 3 partial, 1 awaiting conversion

General characteristics for Royal Navy submarines

Type: Attack/Patrol submarine

Displacement: Surfaced: 2,030 t (2,000 long tons), Submerged: 2,410 t (2,370 long tons)

LOA: 295.2 ft (90.0 m) B: 26.5 ft (8.1 m) Draught: 18 ft (5.5 m)

Propulsion:

2 × 1,840 hp Admiralty Standard Range V16 diesels
2 × 1,280 kW generators
2 × 3,000 hp electric motors, diesel-electric
2 shafts

Speed: Surfaced: 12 knots (22 km/h; 14 mph) Submerged: 17 knots (31 km/h; 20 mph)

Range: 10,350 nautical miles (19,170 km; 11,910 mi) at surface cruising speed

Test depth: 650 ft (200 m)

Complement: 7 officers 62 sailors

Sensors and processing systems: Type 1002 surface search and navigation radar Type 187 Active-Passive attack sonar Type 2007 long range passive sonar

Electronic warfare & decoys: MEL Manta UAL or UA4 radar warning[citation needed]

Armament: 6 × 21 in (533.4 mm) bow tubes, 20 torpedoes 2 × 21 in (533.4 mm) short stern tubes, 2 torpedoes Forward torpedo payload could be replaced with 50 × mines

The Oberon class was a ship class of 27 British-designed submarines operated by five different nations. They were designed as a direct follow-on from the Porpoise class: physical dimensions were the same, but stronger materials were used in hull construction, and updated equipment was fitted.

The submarines were built between 1957 and 1978 by four shipyards: Cammell Laird (4), Chatham Dockyard (6), Scotts Shipbuilding and Engineering Company (11) and Vickers-Armstrongs (6). Thirteen of the submarines were operated by the Royal Navy, six by the Royal Australian Navy, three by the Brazilian Navy, three by the Royal Canadian Navy/Canadian Forces Maritime Command (plus two ex-Royal Navy boats later acquired for non-commissioned roles), and two by the Chilean Navy.

The Oberons operated during the height of the Cold War, with duties including surveillance, tracking of other ships and submarines, delivery and retrieval of special forces personnel, and serving as targets for anti-submarine training. Submarines of the class were in service until 2000. As of 2015, eight of the submarines are preserved intact as museum vessels, another three are partially preserved (with some exterior portions of the submarine on display), and one is in private ownership and awaiting conversion for display. The rest have been sold for scrap, including one former museum vessel.

Design and construction

The 295.2-foot (90.0 m)-long Oberon class was based heavily on the preceding Porpoise class of submarines,[2] which were in service from 1956 to 1988. Changes from the Porpoise design were primarily to improve the strength and stealth of the submarine. Instead of UXW steel, the hull was built from QT28 steel, which was easier to fabricate and stronger, allowing the submarine to dive deeper. Glass-reinforced plastic was used in construction of the casing.

The fin and equipment masts of HMAS Onslow

Electronics, sonar, and radar systems were also upgraded to the latest standard. The submarines were equipped with a type 1002 surface search and navigation radar, a type 187 active-passive attack sonar, and a type 2007 long-range passive sonar.

The Oberons were constructed at a variety of shipyards in the United Kingdom: the six Australian and two Chilean submarines by Scotts Shipbuilding and Engineering Company (the latter were built after the Scott Lithgow merger); the three Brazilian submarines by Vickers-Armstrongs; and the three Canadian submarines at Chatham Dockyard.

Construction of the British submarines was shared amongst four dockyards: the three mentioned above and Cammell Laird.

Armament

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Barr and Stroud Attack Periscope Type CH74 – RAN Oberon class submarine
Torpedo fire control consoles aboard HMCS Onondaga

The Oberons were originally armed with eight 21-inch (533.4 mm) torpedo tubes: six tubes in the bow, and two short tubes for antisubmarine defence in the stern. The submarine normally carried a payload of 20 torpedoes for the forward tubes; a mix of Mark 24 Tigerfish and Mark 8 torpedoes, while only the two preloaded Mark 20S torpedoes were carried for the stern tubes. Naval mines could be carried instead of torpedoes: the torpedo payload would be replaced with up to 50 Mark 5 Stonefish or Mark 6 Sea Urchin mines.

The forward torpedo tubes are constructed in two sections bolted together across the bulkhead at the fore end of the torpedo compartment. The 116-inch (290 cm) long inner section is constructed of 0.5-inch (1.3 cm) rolled steel fitted with welded flanges and support brackets. The outer section is constructed of a similar tube 175 inches (440 cm) long but with a reinforced 1.125-inch (2.86 cm) thick section behind the main bulkhead. The internal door hinges at one side with two locking mechanisms, a swing bolt opposite the hinge and a rotating locking ring attached to the tube which presses down on the ten projecting lugs around the door. The outer end of the tube is sealed with a domed bow cap. Bow shutters close across the bow caps so as to preserve the streamlined shape of the bow when the cap is closed.

The bow caps and shutters are mechanically linked to a hydraulically operated drive rod from within the torpedo compartment. The bow cap opens first behind the shutter, which then folds back against it forming a smooth exit tube. Interlocks prevent the doors at both ends being opened at the same time but the inner door is also provided with a test cock to check whether the tube is full of water before opening and remains held nearly closed by the swing bolt after the locking ring is released. The tube internal diameter is 22.5 in, wider than the torpedo, which is designed as a loose fit inside the tube. Torpedoes could be fired either electrically or with compressed air.

The aft torpedo tubes passed through the ballast tank at the rear of the submarine. A 31-inch (79 cm) section projected into the boat through the bulkhead, forming overall a relatively short tube of 12 feet (3.7 m), but of 25-inch (640 mm) diameter.

With the retirement of the Mark 20S torpedo in the 1980s, the stern torpedo tubes were decommissioned and thereafter used for storing beer.

Chilean service

The Chilean government required two Oberon-class submarines to be built by Scott's Shipbuilders Engineering Co., Ltd. The first was built in 1971 and launched on 22 December 1972 and given the name O'Brien, arriving at Punta Arenas on 10 August 1976. The second submarine, built in 1972, launched on 26 September 1973, was given the name Hyatt. The submarine arrived at Punta Arenas on 10 February 1977. These two submarines were able to achieve a speed of 12 knots surfaced and 17 knots submerged. With a length of 90 meters and a displacement of 2,030 tons surfaced and 2,410 tons submerged, the submarines had a 6,000 bhp engine to power them. The submarines were fitted with eight 21-inch torpedo tubes. Both submarines remained in service until 31 December 2001 where they were replaced by Scòrpene-class submarines.