Amphion class submersibles (1945)

The “A class” or Amphion, were the last submersibles planned by the British admiralty in WW2, designed for Operations in the Pacific. Indeed after Pearl Harbour the realization of a war in the pacific urged the need for a new submarine types with better range, surface speed, diving depht and to reach the latter goal, an all-welded hull. It had also to retain a ten torpedo tubes capability, albeit wartime experience had it rearranged, better accomodations and being “tropicalized”. The Amphion class were laid down in 1943 as many believed they would be ready for the Pacific operations in 1945 but it never happened. Instead they were only launched in 1945 and completed postwar.

Laid down in 1943-45 they were completed in 1945-48. Thus, none was completed in time for war service and 30 on the 56 ordered in 1943 were cancelled. They were the last British submarine planned with a deck gun, and had a long career after streamlining and powerplant modernization, a cold war conversion to new standards. Thanks to this, they formed the core of the early cold war British submarine force until 1974. They represent at the same time the end of the WW2 submarine lineage and start of the cold war lineage. #ww2 #coldwar #royalnavy #submarine #submersible #amphionclass

Development

Science Museum image, Amphion class, 1944

The Amphion class were ordered by the British Admiralty in 1943 for the Pacific theatre, seeing that they would need a new type of submarine to return in the area, since the Atlantic and Mediterranean ahd all priority until then, the RN only capable to sent Force Z in december 1941, promptly disposed of by the Japanese. The Eagle and Light aircraft carriers of the 1942 programme were also in part designed for the Pacific.

As for the new Amphion or A class, they were originally designed to replace the S-class and T-class submarines. The latter were recent, some even still being completed in 1943, but they were seen as too slow, not deep diving enough for Pacific waters. They were however designed around the same hull as the T class and arranged for a fast a simple construction, using much of the materials and equipment used already for the T boats, including thpse cancelled. The bow was what was most criticized from the T class, and the A class started with a brand new flared bow for better surfaced sea performance. They were also given an effective air conditioning system, and had completely redone internal accomodations for better habitability, for a crew between 60 and 68.

The prow of HMS Alliance

Originally, 46 submarines were ordered, only 18 launched, including ten by Vickers-Armstrong (Barrow-in-Furness) sixteen commissioned, and two half-completed hulls being used for crush testing. The class was designed for quick construction and featured an entirely welded hull inlike the mixed constructed T class, the latter pioneering these techniques. More so, they were to be fabricated in sections like the Type XXI, although it is dubious there was any intel about this in 1943. Thus it was calculated to take 8 months from keel-laying to launching (15 months for the T class) but this was done too late, as the setup for construction in 1944 was much delayed. In fact Amphion was only launched in August 1944, Astute in January 1945, both making sea trials in the dying days of the war.
The Amphion class were the last submarines designed in Great Britain during World War II alongside the X-craft designed to sink Bismarck and other axis ships. Wartime experience showed submarines needed in reality larger patrol areas than foreseen, especially in the Far East, but even in the Mediterranean. The A class were also designed to exceed the T class in range while having better accommodations for longer missions.

Design of the class

Hull and general design

The A class significantly larger than the T class, with a displacement of 1,385 tons surfaced and 1,620 tons submerged (versus 1,290 tons surfaced and 1,560 tons submerged for the T class). They were longer at 280.5 ft (85.5 m) over all versus 276 ft 6 in (84.28 m), but narrower at 22.3 ft (6.8 m) versus 25 ft 6 in (7.77 m), but draftier at 16.8 ft (5.1 m) versus 13/14 fr.
The A class approached the double hull type and the circular section welded pressure hull of 4-in plating allowed a design depth of 500ft and test depth of 600ft. It should be noted that they could operate at 500ft, the same figure quoted for Oberon to Rainbow representing an emergency maximum (some damage was to be expected if these exceeded the test depth of 200 to 300ft).

Control room, HMS Alliance

Apart the brand new bow shape, cleaner and more seaworthy, the conning tower was an evolution of the one on the late T class (3rd group) and open with a platform to place a 20 mm AA gun and LMGs.
The torpedo tubes were completely rearranged as well and partly driven by war experience. Instead of a massive 10-torpedo bow spread, there were sixc tubes forard four aft in a more balanced approach, but with non-reloadable external tubes, four in all, in the outer hull.

Powerplant

Not much change compared to the previous T-class. By defauled they sported four 8-cylinder Vickers supercharged diesels and two electric motors. In some vessels however from another yard, namely Acheron, Aeneas, Affray, Alaric, Artemis and Artful had Admiralty supercharged diesels instead, as Abelard, Acasta, Ace and Achates: which had 6-cylinder Admiralty supercharged diesels instead,however the electric engines were the same for all.
This powerplant delivered 4,300 hp surfaced and 1250 hp underwater, but the 6-cylinder variants (Abelard, Acasta, Ace, Achates) were rated for only 3,400 hp and 1250 hp. This was not a success.
They were capable of 18.5 knots (34.3 km/h) surfaced and 8 knots (15 km/h) submerged. To compare, the T class were given 1,250 hp (930 kW) diesels and 1,450 hp electric motors for 15.5/9 knots, so quite an increase of power for surface actions, at the expense of underwater speed. It was thought to be compensated by a greater safety depth of around 600 feet.

Sources diverged about oil carried and autonomy. In general they carried 165 tons of diesel oil in normal conditions, which could be ported up to 219 tonnes. Of this fuel, 60 tons was in internal and 105 tons in external tanks, while an extra 54 tons could be carried in the main tanks. Standard range was excellent, at 10,500 nautical miles at 11 knots surfaced and 90 nautical miles at 3 knots. To compare the T class were capable of 8,000 nmi at 10 knots. So this was also a substantial increase. They had a brand new refrigeration system and two huge air conditioners, and all her accommodation was placed as far away from the engine room as possible.

Armament

HMS Andrew, Aenas and Trespasser at Rotterdam in 1948.

They were the last submarines designed in Britain with deck guns. A 20mm Oerlikon was mounted and the four external TT comprised 2 bow and 2 stern. The torpedo outfit was 20 with 6 reloads for the internal bow tubes and 4 for the stern ones. Alternatively, 18 M2 mines could be carried.
The 4-in Mk XXII was later removed, several boats receiving a 4in/33 QF Mk XXIII in its place. All were intended to have ‘snorts’ though these were not always fitted initially. Compared with previous British submarines, diving time, radar arrangements and sound insulation of auxiliary machinery were much improved. It was found that in certain sea conditions the first boats had a very undesirable rolling motion, and it was necessary to separate the port and starboard main tanks, to relocate the external fuel tanks and to fit a bow buoyancy tank. Excessive vibration of the periscopes had also to be corrected.
There were mild differences in armament, with Alliance, Amphion, Astute having their 4-in/40 QF Mk XXII deck gun and singl 20mm/70 Oerlikon Mk IV, and ten tubes, (4 bow, 2 stern, 2 exterior bow, 2 exterior stern, 20 torpedoes or 18 М2 mines) while the remainder had the 4-in/40 S Mk I, main gun, 20mm/70 Mk VII S/M AA gun, and same.

Torpedo Tubes

The primary torpedo used by the Amphion class was the 21-inch Mark VIII**. The Mark VIII was the first burner-cycle torpedo in service developed from 1925 with a production from 1927. The improved Mark VIII** was the most used in WW2 RN submarines, with 3,732 fired by September 1944, 56.4% of the total of all models and still kicking asses by 1983 in the Falklands war (Belgrano). It was on par with the German G7e in the Atlantic, and US Mark 14 (after corrections) in the Pacific.

This 1,566 kg (3,452 lb) model, 21 ft 7 in (6.579 m) long, carried a 365 kg (805 lb) Torpex warhead and used a Brotherhood burner-cycle engine for a range of 4,570 meters (5,000 yards) at 45.5 knots (84.3 km/h; 52.4 mph) or 6,400 meters (7,000 yards) at 41 knots (76 km/h; 47 mph). It had a greater propulsive efficiency than any contemporary torpedo of similar size. Shortages of the Mark VIII early in the war pushed many T class to be equipped with much older Mark IV models.

The latter was a wet-heater 1916 model Weighting 3,206 lbs. (1,454 kg) for 22 ft 7.5 in (6.896 m) in lenght,
with a 515 lbs. (234 kg) TNT warhead, capable of 8,000 yards (7,300 m) at 35 knots, 10,000 yards (9,150 m) at 29 knots or 13,500 yards (12,350 m) at 25 knots. It was slow, but its range was revised in WW2 with a new setup for all Mark IV* to 6,000 yards (5,500 m) at 40 knots and 9,500 yards (8,700 m) at 35 knots.

The Mark VIII was primarily fitted with a contact pisto detonating upon impact until a non-contact magnetic pistol, the CCR (Compensated Coil Rod) was developed and fitted. Hioweger like for the Mark 14 and German models, it gave endless troubles, being withdrawn. Development problems with postwar torpedoes had the VIII lingring in service with the T class, A class, and all diesel-electric subs, even the first British SSNs until 1971 and slow introduction of the Mark 23 wire-guided torpedo.

⚙ specs. Mark VIII** TORPEDO

Weight: 1,566 kg (3,452 lb)
Dimensions: 21 ft 7 in (6.579 m)
Propulsion: Brotherhood burner-cycle engine
Range/speed setting: 4,570 m/45.5 kn, 6,400 m/41 kn
Warhead: 365 kg (805 lb) Torpex
Guidance: Straight, initial training setup

4-in Mk XXII

All A-class submarines were initially fitted with a single 4-inch (102 mm) deck gun 4 inch QF Mark XII or XXII (interchangeable) on the same S1 mounting above the casing and forward of the conning tower, placed on an elevated position in front of the conning tower in a characteristic breastwork rotating with the gun. It was later removed, several boats receiving instead the gun described below. No gun shield, some were improvized.

4-in/33 QF Mk XXIII

Development of the Mark XXIII started in 1942 as a lighter replacement for the QF 4-inch gun Mark XXII derived from a 1911 model. It entered service after the end of the war in 1945 and fitted to Amphion-class submarines completed from October and some T-class submarines also postwar. This became thus the very last submarine deck gun in the RN.
When the Amphion class were modernized between 1955 and the early 1960s, streamlining the conning towers and casings meant the removal of the deck gun, but still keeping its underlying supports in case it was required to mount it again. These guns saw action in the Indonesia–Malaysia confrontation from 1962 to 1966, refitted with these Mark XXIII guns in counter blockade-running Indonesian junks, HMS Andrew last firing her own on 2 December 1974. Only 31 of these guns were made, and the one from St Andrew was preserved (photo).

⚙ specs. Mark XXIII Deck Gun

Weight: 1,568 lb (711 kg) barrel and breech
Dimensions: 137.6 in (3.495 m), barrel 132.2 in (3.358 m) bore (33 cal.)
Shell: Fixed QF 35 lb (15.9 kg) or 38.5 lb (17.5 kg) 102 mm
Breech: horizontal sliding-block
Mount: 4-0 Inch SII Mounting -10 to +30 degrees/360° traverse
Rate of fire: about 15 rounds per minute at 1,791 ft/s (546 m/s)
Maximum range: 12,080 yd (11.05 km) 35 lb HE shell at 30 degrees:

M type Mark II Mines

The M Mark II designed in WW2 was formerly known as the “Type G” and designed as a submarine launched ground mine. Two replaced a single torpedo and they used a CR magnetic trigger
A contract for 2,000 was placed in 1940 but production was halted in November 1942, with 1,310 made and in storage. They equipped T, S classes as well as the A class postwar.

⚙ specs. Mark II M Type mine

Weight: 1,760 lbs. (798 kg)
Payload: 1,000 lbs. (454 kg) minol charge.
Delivery: Laid at 8 knots in 5-60 fathoms (9-110 m)

HMS Artful, the last completed, flew over by an ASW Avenger AS3, 1950 (before conversion)

Sensors

Type 267W radar:

These were fitted in submarines as an air warning radar operating in VHF-band, and surface warning radar operating in X-band with separate aerials. Only one frequency band wa susable at all times. Two separate aerial outfits could rotate at a time or together, synchrone.
Frequency: 9,65 to 9,7 GHz; X-band 214 MHz, VHF-band.
PRF 500 Hz, pulsewidth 1.2 µs, peak power 30-100 kW (18-60 W average), beamwidth 4.5°/52°, rotation 4.5-5 rpm.

Type 138 Sonar:

Locatunder the forward chin, the Type 129 had a blind stern arc. On the A class from the start it was added a passive and manually-trained listening hydrophone to cover this rear blind arc, and complement the more versaitle Type 129.

Type 152 sonar:

The Type 152X was trialled in HMS Alcide. As a prototype it added a transducer operating at 30 to 65 kHz for mine detection. It went no further than the prototype and instead efforts were made to improve the Types 129 and Type 138 with Types 169 and 168. As refitted and modernized, the Amphion class had the type 267W radar, type 186, type 187, and type 197 sonars to stay relevant until the 1970s.

HMS Amphion as completed, old author’s illustration.

Construction

HMS Abelard and Acasta were launched at Portsmouth DYd,
HMS Ace and Achates were manufactured at Devonport DYd,
HMS Adept was launched at Chatham DYd,
HMS Agate, Aggressor, Agile, Aladdin and Alcestis were from Cammell Laird,
HMS Asgard, Assurance and Astarte were ordered to Scotts,
HMS Andromache, Answer, Antaeus, Antagonist, Anzac, Aphrodite, Approach, Arcadian, Ardent, Argosy and Atlantis were all from Vickers-Armstrong in Barrow,
HMS Admirable, Adversary, Asperity, Austere, Awake and Aztec were from Vickers-Armstrong at its Tyne Yard.
Of these, Ace and Achates hwere launched in 1945, but never completed and instead used for ship target trials. Those and Abelard, Acasta, would have had 6-cylinder Admiralty supercharged diesels as the 8-cylinder type was in short supply. Less powerful at 3400 bhp they would have been a knot slower. A further 20 A class submarines were projected by late 1944, but orders were never placed. On 56 planned in 1943, 16 were completed in 1945-47, 2 cancelled before completion (used as targets) and 28 were scrapped on slip before launch.

modernization to Cold War Standards

After World War II the A class were judged moverall more satisfying than the T class, but like the latter, all were retained for service overseas. Both would be streamlined and modernized, the T class also being exported to vaious Nations. Israel retained their longer than anyone else. The small war emergency, S, U, V class however were not seen as worth retaining in the new context and werd discarded soon. The T and A were rebranded then “Overseas Patrol Submarines”.

As Britain obtained the Type XXI and a late Type IX a snort mast based on the latest German schnorkel was added, as well as a new a radar usable from periscope depth, and a new IR night periscope added to the A and surviving T-class submarines. In the early 1950s the admiralty decided to swap from surface ships to hunt down Soviet submarines. It was a radical change and for this they needed to be at last on par with what the USS had in drove back then, the Project 613 (Whiskey) class. In January 1948 this new operational function was announced officially, and that their precise role would be to hunt down Whiskeys or Zulus slipping out of their bases in Northern Russia to prey on British and Allied merchant lanes.

In April 1948, the Assistant Chief of Naval Staff Rear-Admiral Geoffrey Oliver proposed that British submarines could take an even more offensive rather than only defensive role. IHe suggested that of properly modernized, they attack Soviet submarines off the Northern Russian coast, mining these waters if needed. As the surface fleet was cut down and radically reduced, he commented could allow the Royal Navy a cost-saving, proactive stance with “getting to the enemy on his home ground” as he puts it.

HMS Alliance’s new fin

Thus, the A and T classes were completely redesigned and modernized for this new role between 1955 and 1960. It was necessary to complete rebuild their forward and after hull section and radically streamlined these, but also lengthening, streamlining the upper decks and expecially their conning towers which became a fin. This of course included the removal of deck guns (yet keeping the attachements in case). The goal was to massively improve underwater speed and reduce their noise. For this, the removal of noisy external torpedo tubes was necessary, reducing their torpedo load to six, four forward two aft. It was to be compensated by a new generation of homing torpedoes. It was necessary to give them a greatly improved sonar as well, to listen and detect Soviet submarines as far as possible.
The hull streamlining comprised a fin replaced with a larger 26 feet 6 inch high and far more streamlined sail made of aluminium to not compromise stability. This gave a much better operipheral vision from the bridge and was appreciated; The size was also dictated by the larger snorkel, radars and masts. The purpose of these modifications was to make the submarine quieter and faster underwate and the wireless transmitting aerial was supported on a frame behind the fin, later replaced with a whip aerial on the starboard side of the fin, rotated hydraulically to a horizontal position.

The conversion took about two years, but soon after entering service, HMS Affray was lost in 1951 with all hands and mysterious circumtances. Due to this tragic event, all the Amphion class subs were briefly confined to port, pending investigation. The A class appearance was indeed quite different.
Not all 16 boats were converted, two were discarded. Only Acheron, Aeneas, Alaric, Alcide, Alderey, Alliance, Ambush, Amphion, Anchorite, Andrew, Artemis, Artful, Astute, Auriga were so converted.
As conways 1947-95 states:
Artful underwent modernisation in 1955-56, along the lines of the “T Conversions’, with enlarged batteries and rebuilt bow and stern and streamlined fin, etc but retaining the original motors. All except Awrochs had undergone a similar conversion by 1960. The Mk 8 torpedoes were subsequently replaced by Mk 23, and some boats could carry twenty-six Mk 5 mines. Alliance was put on concrete trestles at HMS Dolphin, Gosport, in 1979 as a permanent submarine memorial.

Revised specs 1955

Displacement: 1,385/1,620 tons surf/submerged
Dimensions 280.5 x 22.3 x 16.8 ft (85.5 x 6.8 x 5.1 m)
Top Speed 18.5/8 kts surfaced/sub
Range: 10,500 nm/11 kts, 16 nm/8 kts surf/sub
Test depth: 500 feet (150 m)
Crew: 61
Armament: 4 × 21 inch (533 mm) bow TTs, 2 stern, 16 torpedoes/26 mines.

Before being scrapped Aeneas was lent to Vickers for trials with the SLAM (Submarine Launched Antiaircraft Missile). This is a TV-guided version of the Blowpipe missile, mounted in the fin and controlled from below, to provide a defence against helicopters. The system was not adopted by the RN and after the tials the boat was scrapped.
They took part in the Indonesia–Malaysia confrontation with some rearmed with their QF 4-inch Mk XXIII gun deck gun or a 20mm autocannon to counter blockade running junks. The A class served for almost three decades, making the backbone of the Royal Naval Submarine Service, gradually replaced with the Porpoise and Oberon classes. The last operational was HMS Andrew decommissioned in 1974, but 1977 is often seen also as the true end of the class, just a few years short of the Falklands war, which is remarkable for a 1942 submarine design.