Balao-class submarine

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USS Balao
USS Balao in 1944
Class overview
Name: Balao class
Builders: Portsmouth Naval Shipyard, Cramp Shipbuilding Company, Mare Island Naval Shipyard, Electric Boat Company, Manitowoc Shipbuilding Company[1]
Preceded by: Gato class
Succeeded by: Tench class
Built: 1942–1946[2]
In commission: 1943–1975[2]
Completed: 120[1]
Cancelled: 70[1]
Active: 2[1][3]
Lost: 11[1]
Retired: 109[1]
Preserved: 8[1]
General characteristics
Type: Diesel-electric submarine
Displacement: 1,526 tons (1,550 t) surfaced,[1] 2,391–2,424 tons (2,429–2463 t) submerged[1]
Length: 311 ft 6 in–311 ft 10 in (94.9–95.0 m)[1]
Beam: 27 ft 3 in–27 ft 4 in (8.3 m)[1]
Speed: 20.25 knots (38 km/h) surfaced,[4] 8.75 knots (16 km/h) submerged[4]
Range: 11,000 nautical miles (20,000 km) surfaced @ 10 knots (19 km/h)[4]
Endurance: 48 hours @ 2 knots (3.7 km/h) submerged,[4] 75 days on patrol
Test depth: 400 ft (120 m)[4]
Complement: 10 officers, 70–71 enlisted men[4]

The Balao class was a successful design of United States Navy submarine used during World War II, and with 120[6] units completed, the largest class of submarines in the United States Navy. An improvement on the earlier Gato class, the boats had slight internal differences. The most significant improvement was the use of thicker, higher yield strength steel in the pressure hull skins and frames,[7] which increased their test depth to 400 feet (120 m). Tang actually achieved a depth of 612 ft (187 m) during a test dive,[8] and exceeded that test depth when taking on water in the forward torpedo room while evading a destroyer.[9][10]


The Balaos were similar to the Gatos, except they were modified to increase test depth from 300 ft (90 m) to 400 ft (120 m). In late 1941, two of the Navy's leading submarine designers, Captain Andrew McKee and Commander Armand Morgan, met to explore increasing diving depth in a redesigned Gato. A switch to a new High-Tensile Steel (HTS) alloy, combined with an increase in hull thickness from 916 inch (14.3 mm) to 78 inch (22.2 mm), would result in a test depth of 450 ft (140 m) and a collapse depth of 900 ft (270 m). However, the limited capacity of the trim pump at deep depths, and lack of time to design a new pump, caused Rear Admiral E. L. Cochrane, Chief of the Bureau of Ships, to limit test depth to 400 ft (120 m). Fortunately, in 1944 a redesigned Gould centrifugal pump replaced the noisy early-war pump, and effective diving depth was increased.[11]

The Balaos incorporated the conning tower fairwater and periscope shears reduction efforts that were being retrofitted to the Gatos and the preceding classes in the original design, refining the reductions and reducing the fairwater to the smallest practical size. By the time the boats began to be launched, lessons learned from patrol reports had been worked into the design and the bridge and fairwater proved to be efficiently laid out, well equipped, and well liked by the crews.[12]

For the masts and periscope shears, the original arrangement for both the Government and Electric Boat designs had (forward to aft) the two tapered cone shaped periscope support shears, followed by a thin mast for the SJ surface search radar, and then by a thin mast for the SD air search radar. There were minor differences in how the periscopes were braced against vibration, but both designs were nearly identical. About halfway through their production run, Electric Boat altered their design, moving the SJ radar mast forward of the periscopes, then altered it again a few boats later by enlarging the SD radar mast. Late in the war, many Balaos built with the original design had the SD air search radar moved slightly aft onto a thickened and taller mast. These mast arrangements, along with the tremendous variation in the gun layout as the war progressed account for the numerous exterior detail differences among the boats, to the point that at any given time no two Balaos looked exactly alike.[13]


The propulsion of the Balao-class submarines was generally similar to that of the preceding Gato-class. Like their predecessors, they were true diesel-electric submarines: their four diesel engines powered electrical generators, and electric motors drove the shafts. There was no direct connection between the main engines and the shafts.

General Motors Model 16-248 V16 diesel engine

Balao-class submarines received main engines from one of two manufacturers. Fairbanks-Morse supplied Model 38D8⅛ opposed piston engines, and General Motors' Cleveland Diesel division supplied Model 16-248 and 16-278A V16 engines. Earlier Fairbanks-Morse boats received a 9-cylinder version of the Model 38D8⅛, while boats from Sand Lance onward received 10-cylinder engines. Earlier GM boats received Model 16-248 engines, but beginning with Perch Model 16-278A engines were used. In each case, the newer engines had greater displacement than the old, but were rated at the same power; they operated at lower mean effective pressure for greater reliability. Both the F-M and GM engines were two-stroke cycle types.

Two submarines, Unicorn and Vendace, were to receive Hooven-Owens-Rentschler (H.O.R.) diesels, which proved unreliable on previous classes, but both boats were cancelled.

Two manufacturers supplied electric motors for the Balao class. Elliott Company motors were fitted primarily to boats with Fairbanks-Morse engines. General Electric motors were fitted primarily to boats with General Motors engines, but some Fairbanks-Morse boats received GE motors. Allis-Chalmers motors were to be used in SS-530 through SS-536, but those seven boats were cancelled before even receiving names.

Earlier submarines carried four high-speed electric motors (two per shaft), which had to be fitted with reduction gears to slow their outputs down to an appropriate speed for the shafts. This reduction gearing was very noisy, and made the submarine easier to detect with hydrophones. Eighteen late Balao-class submarines received low-speed double armature motors which drove the shafts directly and were much quieter, but this improvement was not universally fitted until the succeeding Tench class.[14] The new direct drive electric motors were designed by the Bureau of Ships' electrical division under Captain Hyman G. Rickover, and were first equipped on Sea Owl.[15] As the diesel engines were not directly connected to the shafts, the electric motors drove the shafts all the time.

Deck guns[edit]

Many targets in the Pacific War were sampans or otherwise not worth a torpedo, so the deck gun was an important weapon. All Balaos began their service with a 4-inch (102 mm)/50 caliber Mk. 9 gun. Due to war experience, most were re-armed with a 5-inch (127 mm)/25 caliber MK. 17 gun, similar to mounts on battleships and cruisers but built as a "wet" mount with corrosion resistant materials. This conversion started in late 1943, and some boats later had two of these weapons. Spadefish, commissioned in March 1944, was the first newly built submarine with the purpose-built 5-inch/25 submarine mount. Additional anti-aircraft guns included single 40 mm Bofors and twin 20 mm Oerlikon mounts, usually one of each.[16]

Service history[edit]

World War II[edit]

Periscope photo of a Japanese merchant ship sinking.

The Balaos began to enter service in mid-1943, as the many problems with the Mark 14 torpedo were being solved. They were instrumental in the Submarine Force's near-destruction of the Japanese merchant fleet and significant attrition of the Imperial Japanese Navy. One of the class, Archerfish, brought down what remains the largest warship sunk by a submarine, the Japanese aircraft carrier Shinano (59,000 tons). Tang, the highest-scoring of the class, sank 33 ships totaling 116,454 tons, as officially revised upward in 1980.[17]

SS-361-364 were completed by Manitowoc as Gatos, due to an unavoidable delay in Electric Boat's development of Balao-class drawings. Manitowoc was a follow yard to Electric Boat, and was dependent on them for designs and drawings.[18]

Nine Balaos were lost in World War II, while two were lost in postwar accidents. Additionally, Lancetfish commissioned but incomplete and still under construction flooded and sank pierside at the Boston Navy Yard on 15 March 1945, after a yard worker mistakenly opened the inner door of an aft torpedo tube that already had the outer door open. No personnel were lost in the accident and she was raised, decommissioned, and never completed or repaired.[1][19][20] Her 42 days in commission is the record for the shortest commissioned service of any USN submarine. Postwar, she was laid up in the Reserve Fleet until stricken in 1958 and scrapped in 1959.

Balao-class losses[edit]

In United States service, nine Balao-class boats were lost during World War II; two were lost post-war because of accidents. One boat in Argentine service was lost to enemy action during the 1982 Falklands War.

Name and hull number Date Notes
USS Capelin December 1943 Cause of loss unknown, possibly naval mine or attack by the Japanese minelayer Wakataka
USS Cisco 28 September 1943 Lost to air attack and gunboat Karatsu (ex-USS Luzon)
USS Escolar 17 October - 13 November 1944 Probably lost to enemy mine
USS Shark 24 October 1944 Attacked by the Japanese destroyer Harukaze
USS Tang 25 October 1944 Sunk by a circular run of own torpedo
USS Barbel 4 February 1945 Air attack
USS Kete March 1945 Cause of loss unknown, possibly to mine or enemy action
USS Bullhead 6 August 1945 Air attack
USS Lagarto 3 May 1945 Attacked by Japanese minelayer Hatsutaka
USS Cochino 26 August 1949 Accidental fire
USS Stickleback 28 May 1958 Collision with USS Silverstein
ARA Santa Fe (formerly USS Catfish) 25 April 1982 Disabled by helicopter attack and captured by ground forces during Operation Paraquet, the British recapture of South Georgia during the Falklands War. After the war, she was scuttled in deep water

Postwar service history[edit]

Postwar, 55 Balaos were modernized under the Fleet Snorkel and Greater Underwater Propulsion Power (GUPPY) programs, with some continuing in US service into the early 1970s.[21] Seven were converted to roles as diverse as guided missile submarines (SSG) and amphibious transport submarines (SSP). 46 were transferred to foreign navies for years of additional service, and Tusk remains active in Taiwan's Republic of China Navy as Hai Pao.

Naval Reserve trainer[edit]

Interested in maintaining a ready pool of trained Reservists, the Navy assigned at least 58 submarines from 1946 to 1971 to various coastal and inland ports (even in Great Lakes ports like Cleveland, Detroit, and Chicago), where they served as training platforms during the Reservists' weekend drills. At least 20 Balao-class boats served in this capacity. In this role, the boats were rendered incapable of diving and had their propellers removed. They were used strictly as pierside trainers.[22][23]

Foreign service[edit]

The large numbers of relatively modern, but surplus U.S. fleet submarines proved to be popular in sales, loans, or leases to allied foreign navies. 46 Balao-class submarines were transferred to foreign navies, some shortly after World War II, others after serving nearly 30 years in the US Navy. These included 17 to Turkey, 2 to Greece, 3 to Italy, 2 to the Netherlands, 5 to Spain, 2 to Venezuela, 4 to Argentina, 5 to Brazil, 2 to Chile, 2 to Peru, 1 to Canada and 1 to Taiwan.[24]

GUPPY and other conversions[edit]

At the end of World War II, the US submarine force found itself in an awkward position. The 111 remaining Balao-class submarines, designed to fight an enemy that no longer existed, were obsolescent despite the fact they were only one to three years old. The German Type XXI U-boat, with a large battery capacity, streamlining to maximize underwater speed, and a snorkel, was the submarine of the immediate future. The Greater Underwater Propulsion Power Program (GUPPY) conversion program was developed to give some Balao- and Tench-class submarines similar capabilities to the Type XXI. When the cost of upgrading numerous submarines to GUPPY standard became apparent, the austere "Fleet Snorkel" conversion was developed to add snorkels and partial streamlining to some boats. A total of 36 Balao-class submarines were converted to one of the GUPPY configurations, with 19 additional boats receiving Fleet Snorkel modifications. Two of the GUPPY boats and six of the Fleet Snorkel boats were converted immediately prior to transfer to a foreign navy. Most of the 47 remaining converted submarines were active into the early 1970s, when many were transferred to foreign navies for further service and others were decommissioned and disposed of.[25]

Although there was some variation in the GUPPY conversion programs, generally the original two Sargo batteries were replaced by four more compact Guppy (GUPPY I and II only) or Sargo II batteries via significant re-utilization of below-deck space, usually including removal of auxiliary diesels. All of these battery designs were of the lead-acid type. This increased the total number of battery cells from 252 to 504; the downside was the compact batteries had to be replaced every 18 months instead of every 5 years. The Sargo II battery was developed as a lower-cost alternative to the expensive Guppy battery.[26] All GUPPYs received a snorkel, with a streamlined sail and bow. Also, the electric motors were upgraded to the direct drive double-armature type, along with modernized electrical and air conditioning systems. All except the austere GUPPY IB conversions for foreign transfer received sonar, fire control, and Electronic Support Measures (ESM) upgrades.[27]


GUPPY I[edit]

Two Tench-class boats, Odax and Pomodon, were converted as prototypes for the GUPPY program in 1947. Their configuration lacked a snorkel and was not repeated.

GUPPY II[edit]

USS Catfish in GUPPY II configuration

This was the first production GUPPY conversion, with most conversions occurring in 1947-49. Thirteen Balao-class boats received GUPPY II upgrades. This was the only production conversion with Guppy batteries.

GUPPY IA[edit]

This was developed as a more cost-effective alternative to GUPPY II. Nine Balao-class boats were converted in 1951-52. The less expensive Sargo II battery was introduced, along with other cost-saving measures.

Fleet Snorkel[edit]

USS Sabalo after a Fleet Snorkel conversion

The Fleet Snorkel program was developed as an austere, cost-effective alternative to full GUPPY conversions, with significantly less improvement in submerged performance. Nineteen Balao-class boats received this upgrade, six immediately prior to foreign transfer. Most Fleet Snorkel conversions occurred 1951-52. Notably, the original pair of Sargo batteries was not upgraded. Each boat received a streamlined sail with a snorkel, along with upgraded sonar, air conditioning, and ESM. The original bow was left in place, except on three boats that received additional upper bow sonar. A few boats initially retained a 5"/25 deck gun, but this was removed in the early 1950s.


This was generally similar to GUPPY IA, except one of the forward diesel engines was removed to relieve machinery overcrowding. Thirteen Balao-class boats received GUPPY IIA upgrades in 1952-54. One of these, Diodon, had previously been upgraded to GUPPY II.

GUPPY IB[edit]

This was developed as an austere upgrade for two Gato-class and two Balao-class boats prior to transfer to foreign navies in 1953-55. They lacked the sonar and electronics upgrades of other GUPPY conversions.


Nine submarines, six of them Balaos, were upgraded from GUPPY II to GUPPY III in 1959-63 as part of the Fleet Rehabilitation and Modernization II (FRAM II) program. All except Tiru, the pilot conversion, were lengthened by 15 feet in the forward part of the control room to provide a new sonar space, berthing, electronics space, and storerooms. Tiru was lengthened only 12.5 feet, and both forward diesel engines were removed.[28] The other GUPPY IIIs retained all four engines. A taller "Northern" sail was included, to allow improved surfaced operations in rough seas; this was also backfitted to some other GUPPYs. The BQG-4 Passive Underwater Fire Control Feasibility Study (PUFFS) sonar system, with its three tall domes topside, was fitted. Additionally, fire control upgrades allowed the Mark 45 nuclear torpedo to be used.

Radar picket[edit]

The advent of the kamikaze demonstrated the need for a long range radar umbrella around the fleet. Radar picket destroyers and destroyer escorts were put into service, but they proved vulnerable in this role as they could be attacked as well, leaving the fleet blind. A submarine, though, could dive and escape aerial attack. Ten fleet submarines were converted for this role 1946-53 and redesignated SSR as radar picket submarines. Burrfish was the only Balao-class SSR. Experiments on two Tench class submarines showed that placement of the radars on the deck was inadequate and that more room was needed for electronics. Thus Burrfish was given the appropriately named Migraine I conversion, which placed a Combat Information Center (CIC) in the space formerly occupied as the crew's mess and galley. The after torpedo room was stripped and converted into berthing, and the boat lost two of her forward torpedo tubes to make room for additional berthing and electronics. The radars were raised up off the deck and put on masts, giving them a greater range and hopefully greater reliability. Unfortunately, the SSRs proved only moderately successful, as the radars themselves proved troublesome and somewhat unreliable, and the boats' surface speed was insufficient to protect a fast-moving carrier group. The radars were removed and the boats reverted to general purpose submarines after 1959. Burrfish was decommissioned in 1956 and, with her radar equipment removed, transferred to Canada as HMCS Grilse (SS-71) in 1961.[29]

Guided missile submarine[edit]

USS Cusk fires a Loon missile

The Regulus nuclear cruise missile program of the 1950s provided the US Navy with its first strategic strike capability. It was preceded by experiments with the JB-2 Loon missile, a close derivative of the German V-1 flying bomb, beginning in the last year of World War II. Submarine testing of Loon was performed 1947-53, with Cusk and Carbonero converted as test platforms in 1947 and 1948 respectively. Initially the missile was carried on the launch rail unprotected, thus the submarine was unable to submerge until after launch. Cusk was eventually fitted with a watertight hangar for one missile. Following a brief stint as a cargo submarine, Barbero was converted in 1955 to carry two surface-launched Regulus missiles and was redesignated as an SSG, joining the Gato-class Tunny in this role. She made strategic deterrent patrols with Regulus until 1964, when the program was discontinued in favor of Polaris.[30] A number of fleet boats were equipped with Regulus guidance equipment 1953-64, including Cusk and Carbonero following the Loon tests.

Transport submarine[edit]

A helicopter touches down on Sealion as a transport submarine

Sealion and Perch were converted to amphibious transport submarines in 1948 and redesignated as SSPs. Initially, they were equipped with a watertight hangar capable of housing a Landing Vehicle Tracked (LVT), and retained one 5-inch (127 mm)/25 caliber deck gun for shore bombardment. Both torpedo rooms and one engine room were gutted to provide space for embarked Special Operations Forces (SOF) and their equipment. Snorkels were fitted. Due to the extra personnel, to avoid excessive snorkeling they were equipped with a CO2 scrubber and extra oxygen storage. Initially, a squadron of 12 SSPs was considered, capable of landing a reinforced Marine battalion, but only two SSPs were actually converted. Perch landed British commandos on one raid in the Korean War, and operated in the Vietnam War from 1965 until assignment to Naval Reserve training in 1967 and decommissioning in 1971, followed by scrapping in 1973. Perch was replaced in the Pacific Fleet transport submarine role by Tunny in 1967 and Grayback in 1968. Sealion operated in the Atlantic, deploying for the Cuban Missile Crisis and numerous SOF-related exercises. She was decommissioned in 1970 and expended as a target in 1978. The LVT hangar and 5-inch gun were removed from both boats by the late 1950s. They went through several changes of designation in their careers: ASSP in 1950, APSS in 1956, and LPSS in 1968.[31][1]

Sonar test submarine[edit]

Baya was redesignated as an auxiliary submarine (AGSS) in 1949 and converted to a sonar test submarine in 1958-59 to test a system known as LORAD. This included a 12-foot (3.7 m) extension aft of the forward torpedo room, with 40-foot (12 m) swing-out arrays near the bow. Later, three large domes were installed topside for a wide aperture array.[32]

Cargo submarine[edit]

Barbero was converted to a cargo submarine and redesignated as an SSA in 1948. The forward engine room, after torpedo room, and all reload torpedo racks were gutted to provide cargo space. The experiment was short-lived, and she was decommissioned in 1950. In 1955, she was converted to a Regulus missile submarine and redesignated as an SSG.[33]

Operational submarines[edit]

As of 2007 Tusk, a Balao-class submarine, was one of the last two operational submarines in the world built during World War II. The boat was transferred to Taiwan's Republic of China Navy in the early 1970s. The Tench-class ex-Cutlass is the other one. They are named Hai Pao and Hai Shih, respectively, in Taiwanese service.[34][35]


A total of 125 US submarines were cancelled during World War II between 29 July 1944 and 12 August 1945. References vary considerably as to how many of these were Balaos and how many were Tenches. Some references simply assume all submarines numbered after SS-416 were Tench class; however, USS Trumpetfish (SS-425) and USS Tusk (SS-426) were completed as Balaos.[36][37] This yields 10 cancelled Balao-class, SS-353-360 and 379-380. The Register of Ships of the U. S. Navy differs, considering every submarine not specifically ordered as a Tench to be a Balao, and further projecting SS-551-562 as a future class.[1] This yields 70 cancelled Balao class, 43 cancelled Tench class, and 12 cancelled future class. Two of the cancelled Balao-class submarines, Turbot and Ulua, were launched incomplete and served for years as experimental hulks at Annapolis and Portsmouth Navy Yard. Two of the cancelled Tench-class boats, Unicorn and Walrus, were also launched incomplete, never commissioned, but listed with the Reserve fleet until scrapped in 1958. The cancelled hull numbers, including those launched incomplete, were SS-353-360, 379-380, 427-434, 436-437, 438-474, 491-521, and 526-562.


Eight Balao-class submarines are open to public viewing. They primarily depend on revenue generated by visitors to keep them operational and up to U.S. Navy standards; each boat gets a yearly inspection and a "report card". Some boats, like Batfish and Pampanito, encourage youth functions and allow a group of volunteers to sleep overnight in the crew's quarters. The following is a complete list of Balao-class museum boats:

See also[edit]



  2. ^ a b Friedman through 1945, pp. 285–304.
  3. ^ Time to decommission old subs
  4. ^ a b c d e f g Friedman through 1945, pp. 305–311.
  5. ^ a b U.S. Submarines Through 1945 pp. 305–311
  6. ^ Lenton, H.T. American Submarines (New York: Doubleday, 1973), p.5.
  7. ^ Peter T. Sasgen (2002). Red Scorpion: The War Patrols of the USS Rasher. Naval Institute Press. p. 17. 
  8. ^ Richard H. O'Kane (1977). Clear the Bridge! The War Patrols of the USS Tang. Presidio Press. p. 40. 
  10. ^ Farley, Robert (18 October 2014). "The Five Best Submarines of All Time". The National Interest. 
  11. ^ Friedman through 1945, pp. 208-209
  12. ^ A Visual Guide to the U.S. Fleet Submarines Part Three: Balao and Tench Classes 1942–1950 pp. 2-3, Johnston, David (2012) Navsource Naval History website
  13. ^ Johnston, pp. 3-10
  14. ^ Bauer and Roberts, p. 275
  15. ^ Friedman through 1945, pp. 209-210
  16. ^ Johnston, pp. 3-6
  17. ^ O'Kane 1989, p. 458
  18. ^ Friedman through 1945, p. 209
  19. ^ Friedman through 1945, p. 297
  20. ^ Silverstone, p. 199
  21. ^ { GUPPY and other diesel boat conversions page]
  22. ^ Reserve Training Boats at
  23. ^ Friedman since 1945, pp. 228-231
  24. ^ Friedman since 1945, pp. 228-231
  25. ^ GUPPY and other diesel boat conversions page
  26. ^ Friedman since 1945, p. 41
  27. ^ Friedman since 1945, pp. 35-43
  28. ^ Friedman since 1945, p. 37
  29. ^ Whitman, Edward C. "Cold War Curiosities: U.S. Radar Picket Submarines, Undersea Warfare, Winter-Spring 2002, Issue 14
  30. ^ Friedman since 1945, pp. 177-183
  31. ^ Friedman since 1945, pp. 86-88
  32. ^ Friedman since 1945, pp. 65-68
  33. ^ Friedman since 1945, p. 89
  34. ^ Museum documents an operating US, WW II built submarine in Taiwan
  35. ^ Jimmy Chuang (Apr 17, 2007). "World's longest-serving sub feted". Taipei Times. p. 2. 
  36. ^ Silverstone, pp. 203-204
  37. ^ Gardiner and Chesneau, pp. 145-147


External links[edit]