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A crash dive is a maneuver by a submarine in which the vessel submerges as quickly as possible to avoid attack. Crash diving from the surface to avoid attack has been largely rendered obsolete with the advent of nuclear-powered submarines, as they normally operate submerged. However, the crash dive is also a standard maneuver to avoid a collision.
A crash dive in a diesel-powered submarine requires careful orchestration of the crew. On German U-boats of World War II, a crash dive began with the Captain or senior lookouts giving the order "Alarm!" which led to a bridge officer activating the alarm bell. All crew members then immediately stopped what they were doing and proceeded to their diving stations. Once the lookouts were below deck and the upper deck hatch was secured, the Captain or Chief Engineer shouted the order, "Fluten" ("flood the tanks"). With the bow planes at a maximum down angle, the crew then flooded the forward ballast tanks. Often, all available crew members moved as far forward in the boat as practical (a "trim party"). This extra weight forward gave the boat a bow-down angle so its momentum helped pull it below the surface. A few seconds later, the crew would flood the rear ballast tanks to prevent the bow-down angle from lifting the boat's stern out of the water. [note 1] The entire crash dive was generally coordinated by the Chief Engineer. [1]
Before hatches and air induction vents fall below the surface they must be closed. Before that, the diesel engines must be stopped or they will suck the air out of the boat in a matter of seconds. On submarines with direct drive, the crew disengages the diesel engines from the propeller shafts and switches to electric motor propulsion. The motors run at high speed to maintain the forward momentum. Once all hatches and induction vents are closed, the diving planes (like the control surfaces of an airplane) pull the boat below the surface and level it out at the desired depth—typically between 70 and 90 metres (230 and 300 ft). [1] In a World War II-era boat, the whole operation could take as little as 30 seconds with a well-trained crew. [2] In contrast, an Ohio-class ballistic-missile submarine may take as long as five minutes to reach periscope depth from the surface. However, it is capable of doing so faster if required; the smaller, more agile attack submarines can dive quite rapidly. The crash diving rate of a missile submarine is also not relevant since it can stay submerged for very long periods of time, and is not expected to ever cruise on the surface when in range of enemy units of any type. A WWII era submarine (technically a submersible since it is only capable of diving for limited periods of time) is by design forced to spend much of its time on the surface, and therefore needs to be able to "escape" by diving when an enemy is spotted.
In extreme emergencies, submarines have had to crash dive so quickly that lookouts were left on-deck. Such was the only survivor of U-68 when the four lookouts were left top-side as she crash dived among exploding aerial bombs. [3] Commander Howard Gilmore earned the Medal of Honor posthumously during World War II by ordering a crash dive ("Take her down!") while wounded and unable to leave the bridge of USS Growler (SS-215).
U-boats were naval submarines operated by Germany, particularly in the First and Second World Wars. The term is an anglicised version of the German word U-Boot, a shortening of Unterseeboot, though the German term refers to any submarine. Austro-Hungarian Navy submarines were also known as U-boats.
Tench-class submarines were a type of submarine built for the United States Navy (USN) between 1944 and 1951. They were an improvement over the Gato and Balao classes, only about 35 to 40 tons larger, but more strongly built and with a slightly improved internal layout. One of the ballast tanks was converted to carry fuel, increasing range from 11,000 nautical miles to 16,000 nautical miles. This improvement was also made on some boats of the previous two classes. Further improvements were made beginning with SS-435, which are sometimes referred to as the Corsair class. Initial plans called for 80 to be built, but 51 were cancelled in 1944 and 1945 when it became apparent that they would not be needed to defeat Japan. The remaining 29 were commissioned between October 1944 (Tench) and February 1951 (Grenadier). The last submarine of the Tench class, as well as the last submarine which served during World War II, remaining in service with the U.S. Navy was USS Tigrone (AGSS-419) which was decommissioned on 27 June 1975.
BAP Pacocha (SS-48) was a submarine of the Marina de Guerra del Perú named for the 1877 Battle of Pacocha, in which the Peruvian ironclad Huascar clashed with the Royal Navy. Formerly USS Atule (SS-403), a Balao-class submarine with a GUPPY IA upgrade, she had been sold to Peru and commissioned on 28 May 1974. She was rammed and sunk by a fishing trawler on 26 August 1988.
The Royal Navy's T class of diesel-electric submarines was designed in the 1930s to replace the O, P, and R classes. Fifty-three members of the class were built just before and during the Second World War, where they played a major role in the Royal Navy's submarine operations. Four boats in service with the Royal Netherlands Navy were known as the Zwaardvisch class.
The K-class submarines were a class of steam-propelled submarines of the Royal Navy designed in 1913. Intended as large, fast vessels with the endurance and speed to operate with the battle fleet, they gained notoriety and the nickname of "Kalamity class" for being involved in many accidents. Of the 18 built, none were lost through enemy action, but six sank, with significant loss of life, in accidents. Only one ever engaged an enemy vessel, K-7 hitting a U-boat amidships, though the torpedo failed to explode with what has been described as typical "K" luck; K-7 escaped retaliation by steaming away at speed.
HMS Affray was a British Amphion-class submarine. It was the last Royal Navy submarine to be lost at sea, on 16 April 1951, with the loss of 75 lives.
A ballast tank is a compartment within a boat, ship or other floating structure that holds water, which is used as ballast to provide hydrostatic stability for a vessel, to reduce or control buoyancy, as in a submarine, to correct trim or list, to provide a more even load distribution along the hull to reduce structural hogging or sagging stresses, or to increase draft, as in a semi-submersible vessel or platform, or a SWATH, to improve seakeeping. Using water in a tank provides easier weight adjustment than the stone or iron ballast used in older vessels, and makes it easy for the crew to reduce a vessel's draft when it enters shallower water, by temporarily pumping out ballast. Airships use ballast tanks mainly to control buoyancy and correct trim.
O 20, laid down as K XX, was a O 19-class submarine of the Royal Netherlands Navy that saw service during World War II. O 20 along with her sister ship O 19 were the first boats in the world to be equipped with a submarine snorkel that allowed the submarine to run its diesel engines while submerged.
The British U-class submarines were a class of 49 small submarines built just before and during the Second World War. The class is sometimes known as the Undine class, after the first submarine built. A further development was the British V-class submarine of 1942.
A teardrop hull is a submarine hull design which emphasizes submerged performance over surfaced performance. It was somewhat commonly used in the early stages of submarine development, but was gradually abandoned in the early 20th century in favour of designs optimized for high performance on the surface as a result of changes in operational doctrine. Although naval doctrine changed, design practices remained until the later parts of World War II when the German Kriegsmarine suffered ever-growing losses of submarines in the Battle of the Atlantic.
Farfadet (Q7) was the lead ship of her class of four submarines built for the French Navy at the beginning of the 20th century. She was of the Maugas type. Farfadet accidentally sank in July 1905 at Bizerte with the loss of 14 men of her crew; two men survived. She was later refloated and recommissioned as the Follet. She was stricken in November 1913.
The Balilla class were the first submarines to be built for the Italian navy following the end of World War I. They were large ocean-going cruiser submarines designed to operate in the Indian Ocean based in Italy's East African colonies. The design was double-hulled and based on the German Type UE 2 U-boats, one of which, U-120 was supplied to the Italians as a war reparation. A 425 horsepower (317 kW) auxiliary diesel engine was installed as an extra generator.
The Hrabri class consisted of two submarines built for the Kingdom of Serbs, Croats and Slovenes – Yugoslavia from 1929 on – by Vickers-Armstrong in the United Kingdom. Launched in 1927, the boats were named Hrabri (Brave) and Nebojša (Fearless). Their design was based on that of the British L-class submarine of World War I, and they were built using parts from L-class submarines that were never completed. The Hrabri-class were the first submarines to serve in the Royal Yugoslav Navy (KM), and after extensive sea trials and testing they sailed from the UK to the Adriatic coast of Yugoslavia, arriving in April 1928. They were armed with six bow-mounted 533 mm (21 in) torpedo tubes, two 102 mm (4 in) deck guns, one QF 2-pounder L/39 anti-aircraft gun and two machine guns. Their maximum diving depth was restricted to 55 metres (180 ft) by Yugoslav naval regulations.
Prométhée (Q153) was a Redoutable-class submarine of the French Navy, launched in 1930 at Cherbourg. On 7 July 1932, while sailing on the surface during sea trials, she suddenly sank off Cape Lévi, Manche. 62 of her 69 crew were lost with her, causing an outpouring of grief in France. The wreck was located the following day, but attempts to rescue any survivors and refloat the vessel were in vain. Survivors' statements indicated that the sinking was likely due to a sudden opening of the diving purges.
Xifias was a Greek submarine which served during World War I. It was the third submarine to enter service in the Greek navy, and the second and last vessel of the Delfin class. It was taken over by the French in 1916, and decommissioned in 1920 without seeing action.
German submarine U-576 was a Type VIIC U-boat of Nazi Germany's Kriegsmarine during World War II. She carried out five patrols, sinking four ships of 15,450 gross register tons (GRT) and damaging two more of 19,457 GRT. She was sunk on 15 July 1942 by depth charges from two US aircraft and gunfire from a merchant ship, near the East Coast of the United States. The wreck was discovered in August 2014.
Nebojša was the second of the Hrabri-class submarines; built for the Kingdom of Serbs, Croats and Slovenes– Yugoslavia by the Vickers-Armstrong Naval Yard in the United Kingdom. Launched in 1927, her design was based on the British L-class submarine of World War I, and was built using parts from an L-class submarine that was never completed. The Hrabri-class were the first submarines to serve in the Royal Yugoslav Navy (KM), and after extensive sea trials and testing Nebojša sailed from the UK to the Adriatic coast of Yugoslavia, arriving in April 1928. The submarine was armed with six bow-mounted 533 mm (21 in) torpedo tubes, two 102 mm (4 in) deck guns, one QF 2-pounder L/39 anti-aircraft gun and two machine guns. Its maximum diving depth was restricted to 55 metres (180 ft) by Yugoslav naval regulations.
I-183 was an Imperial Japanese Navy Kaidai type cruiser submarine of the KD7 sub-class commissioned in 1943. During World War II, she was sunk with all hands by United States Navy fleet submarine in April 1944.
The French submarine Z was an experimental submarine built for the French Navy in the first decade of the 20th century. Designed by Gabriel Maugas, it was the first French submarine to be completed with a diesel engine and the only one with four sets of diving planes. It was commissioned for its sea trials in 1904, although its propulsion machinery was unreliable and it was never fit for service with the fleet. It may have been completed in 1905. An extensive refit for Z was planned in 1907, but this was cancelled as too expensive. Disposal of the submarine was first proposed the following year, although it was not stricken from the navy list until 1910. Z was sold for scrap in 1911.
I-33 was an Imperial Japanese Navy B1 type submarine. Completed and commissioned in 1942, she served in World War II, making one war patrol that included the Battle of the Eastern Solomons, before sinking accidentally in September 1942. Refloated and repaired, she sank again in a diving accident during post-repair sea trials in June 1944.