# Type B submarine

The Cruiser submarine Type-B (巡潜乙型潜水艦, Junsen Otsu-gata sensuikan) was a class of submarine in the Imperial Japanese Navy (IJN) which served during World War II. The Type-B submarines were similar to the Type-A apart from not having the headquarters installation.

## Class variants

The Type-B submarines were divided into four classes:
* Type-B (乙型（伊十五型）, Otsu-gata, I-15-class)
* Type-B Mod.1 (乙型改一（伊四十型）, Otsu-gata Kai-1, I-40-class)
* Type-B Mod.2 (乙型改二（伊五十四型）, Otsu-gata Kai-2, I-54-class)
* V22A Type (第5115号艦型, Dai-5115-Gō kan-gata, 5115th vessel-class). The 5115th vessel-class submarines were not built and remained a design only.

### Type-B (I-15 class)

Project number S37. Twenty boats were built between 1937 and 1944 under the Maru 3 Programme (Boats 37 - 42) and Maru 4 Programme (Boats 139 - 152).

### Type-B Mod.1 (I-40 class)

Project number S37B. Six boats were planned under the Maru Kyū Programme (Boats 370 - 375), all boats were completed. On the outside this class looked the same as the I-15 class; however, they were built from high-tensile strength steel and equipped with diesel engines of a simpler design.

### Type-B Mod.2 (I-54 class)

Project number S37C. Twenty-one boats were planned under the Maru Kyū Programme (Boats 627 - 636) and Kai-Maru 5 Programme (Boats 5101 - 5114). Eighteen boats were cancelled in late 1943, because the IJN was setting the Type E submarine [ja] (戊型潜水艦, Bo-gata sensuikan) as 1945's main submarines.
* Boats in class
| Boat No. | Boat | Builder | Laid down | Launched | Completed | Results | Fate |
| 627 | I-54 | Yokosuka Naval Arsenal | 1 July 1942 | 4 May 1943 | 31 March 1944 | Damaged USS Santee on 25-10-1944 (?) | Sunk east of Leyte by USS Helm and USS Gridley on 28 October 1944. |
| 629 | I-56 | Yokosuka Naval Arsenal | 29 September 1942 | 30 June 1943 | 8 June 1944 | Damaged USS LST-695 on 24 October 1944. Damaged USS Santee on 25 October 1944 (?). | Conversion to a Kaiten mother ship began in early October 1943 and completed in November 1944. Sunk by USS Heermann, USS Uhlmann, USS Mertz, USS Collett and aircraft from USS Bataan east of Okinawa at 26°42′N 130°38′E﻿ / ﻿26.700°N 130.633°E﻿ / 26.700; 130.633 on 18 April 1945. |
| 631 | I-58 | Yokosuka Naval Arsenal | 26 December 1942 | 9 October 1943 | 7 September 1944 | Sank SS Wild Hunter on 28 July 1945, possibly by Kaiten Sank USS Indianapolis on 30 July 1945 Damaged USS Thomas F. Nickel on 12 August 1945 by Kaiten (?) | Converted to a Kaiten mother ship before completion. Decommissioned on 30 November 1945, scuttled off the Gotō Islands on 1 April 1946 as part of Operation Road's End. Wreck found in 2017. |
| 633 - 636 | | | | | | | Cancelled in 1943 |
| 5101 - 5114 | | | | | | | Cancelled in 1943 |

### V22A Type

Project number S49A. Eighteen boats were planned under the Kai-Maru 5 Programme (Boats 5115 - 5132). However, all boats were cancelled in late 1943, because the IJN concentrated on production of Type-E submarine (戊型潜水艦, Bo-gata sensuikan) from 1945.
* Boats in class
| Boat No. | Boat | Builder | Laid down | Launched | Completed | Fate |
| 5115 - 5132 | | | | | | Cancelled in 1943 |

## Characteristics

| Type | Type | Type-B (I-15) | Type-B Mod. 1 (I-40) | Type-B Mod. 2 (I-54) | V22A Type |
| Displacement | Surfaced | 2,198 long tons (2,233 t) | 2,230 long tons (2,266 t) | 2,140 long tons (2,174 t) | 2,330 long tons (2,367 t) |
| Displacement | Submerged | 3,654 long tons (3,713 t) | 3,700 long tons (3,759 t) | 3,688 long tons (3,747 t) | No data |
| Length (overall) | Length (overall) | 108.70 m (356 ft 8 in) | 108.70 m (356 ft 8 in) | 108.70 m (356 ft 8 in) | 106.50 m (349 ft 5 in) (waterline) |
| Beam | Beam | 9.30 m (30 ft 6 in) | 9.30 m (30 ft 6 in) | 9.30 m (30 ft 6 in) | 9.64 m (31 ft 8 in) |
| Draft | Draft | 5.14 m (16 ft 10 in) | 5.20 m (17 ft 1 in) | 5.19 m (17 ft 0 in) | 5.32 m (17 ft 5 in) |
| Depth | Depth | 7.90 m (25 ft 11 in) | 7.90 m (25 ft 11 in) | 7.90 m (25 ft 11 in) | No data |
| Power plant and shaft | Power plant and shaft | 2 × Kampon Mk. 2 Model 10 diesels 2 shafts | 2 × Kampon Mk. 1A Model 10 diesels 2 shafts | 2 × Kampon Mk. 22 Model 10 diesels 2 shafts | 2 × Kampon Mk. 2 Model 10 diesels 2 shafts |
| Power | Surfaced | 12,400 bhp | 11,000 bhp | 4,700 bhp | 11,000 bhp |
| Power | Submerged | 2,000 shp | 2,000 shp | 1,200 shp | 2,400 shp |
| Speed | Surfaced | 23.6 knots (43.7 km/h) | 23.5 knots (43.5 km/h) | 17.7 knots (32.8 km/h) | 22.4 knots (41.5 km/h) |
| Speed | Submerged | 8.0 knots (14.8 km/h) | 8.0 knots (14.8 km/h) | 6.5 knots (12.0 km/h) | 8.0 knots (14.8 km/h) |
| Range | Surfaced | 14,000 nmi (26,000 km) at 16 knots (30 km/h) | 14,000 nmi (26,000 km) at 16 knots (30 km/h) | 21,000 nmi (39,000 km) at 16 knots (30 km/h) | 14,000 nmi (26,000 km) at 16 knots (30 km/h) |
| Range | Submerged | 96 nmi (178 km) at 3 knots (5.6 km/h) | 96 nmi (178 km) at 3 knots (5.6 km/h) | 105 nmi (194 km) at 3 knots (5.6 km/h) | 80 nmi (150 km) at 3 knots (5.6 km/h) |
| Test depth | Test depth | 100 m (330 ft) | 100 m (330 ft) | 100 m (330 ft) | 100 m (330 ft) |
| Fuel | Fuel | 774 tons | 814 tons | 842.8 tons | 735 tons |
| Complement | Complement | 94 | 94 | 94 | No data |
| Armament (initial) | Armament (initial) | • 6 × 533 mm (21 in) Torpedo tubes (6 × front) • 17 × Type 95 torpedoes • 1 × 140 mm (5.5 in) L/40 11th Year Type naval gun • 2 × Type 96 25mm AA guns | • 6 × 533 mm (21 in) TTs (6 × front) • 17 × Type 95 torpedoes • 1 × 140 mm (5.5 in) L/40 11th Year Type Naval gun • 2 × Type 96 25mm AA guns | • 6 × 533 mm (21 in) TTs (6 × front) • 19 × Type 95 torpedoes • 1 × 140 mm (5.5 in) L/40 11th Year Type Naval gun • 2 × Type 96 25mm AA guns | • 8 × 533 mm (21 in) TTs (8 × front) • 16 × torpedoes • 1 × 14 cm/40 11th Year Type naval gun • 4 × 25mm AA guns • 8 × naval mines |
| Aircraft and facilities | Aircraft and facilities | • Catapult and hangar • 1 × Watanabe E9W1 Slim seaplane | • Catapult and hangar • 1 × Yokosuka E14Y2 Glen seaplane | • Catapult and hangar • 1 × Yokosuka E14Y2 Glen seaplane | • Catapult and hangar • 1 × floatplane |