Crash dive
Encyclopedia
A crash dive is a maneuver performed by a submarine
to submerge 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 operate constantly submerged and are unlikely to be found on the surface.
However, the crash dive is a standard maneuver used during surfacing when a collision is believed imminent.
A crash dive in a diesel
-powered submarine requires careful orchestration of the crew. On German
U-boat
s of World War II
, a crash dive would begin with the Captain or senior lookouts giving the order "Alarm!", which led to a bridge officer activating the alarm bell. All crewmembers would then immediately stop what they were doing and proceed to their diving stations. Once the lookout
s were below deck and the upper deck hatch was secured, the Captain or Chief Engineer would shout the order "Fluten" ("flood the tanks"). With the bow planes at a maximum down angle, the crew would then flood the forward ballast tanks of the submarine and, often, have all available crewmembers move as far forward in the boat as practical (a "trim party"). This extra weight forward gives the ship a bow-down angle so its momentum helps pull it below the surface. A few seconds later the rear ballast tanks are flooded in order to prevent the bow-down angle from becoming extreme enough that the ship's stern rises out of the water. (An accident during the first patrol of U-505 caused just that when she crash dived to avoid an aircraft. Fortunately for the crew, the ship was not spotted during the moments before the crew could regain full control. The crewman who delayed in flooding the rear ballast tanks was subsequently given the nickname "Ostrich
," a reference to the popular myth that the ostrich, when frightened, buries its head in the sand and thereby raises the position of its tail relative to its body.) The entire operation would generally be coordinated by the Chief Engineer
.
Before the 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 ship in a matter of seconds. On submarines with direct drive, the engines are disengaged from the propeller shafts and the electric propulsion motors/generators are switched to motor mode. The motors are run at high speed to maintain the forward momentum. Once all the hatches and induction vents are closed the diving planes are used like the control surfaces of an airplane to pull the ship below the surface and level out at the desired depth, typically between 70 and 90 meters (230 and 295 feet). In a World War II
-era boat, the whole operation could take as little as about 30 seconds with a well-trained and experienced crew. In contrast, an Ohio-class
ballistic-missile submarine may take as long as five minutes to reach periscope depth from the surface.
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. 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)
.
Crash dives were accurately portrayed in the German film Das Boot
.
Submarine
A submarine is a watercraft capable of independent operation below the surface of the water. It differs from a submersible, which has more limited underwater capability...
to submerge 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
Nuclear power
Nuclear power is the use of sustained nuclear fission to generate heat and electricity. Nuclear power plants provide about 6% of the world's energy and 13–14% of the world's electricity, with the U.S., France, and Japan together accounting for about 50% of nuclear generated electricity...
submarines as they operate constantly submerged and are unlikely to be found on the surface.
However, the crash dive is a standard maneuver used during surfacing when a collision is believed imminent.
A crash dive in a diesel
Diesel engine
A diesel engine is an internal combustion engine that uses the heat of compression to initiate ignition to burn the fuel, which is injected into the combustion chamber...
-powered submarine requires careful orchestration of the crew. On German
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
U-boat
U-boat
U-boat is the anglicized version of the German word U-Boot , itself an abbreviation of Unterseeboot , and refers to military submarines operated by Germany, particularly in World War I and World War II...
s of World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
, a crash dive would begin with the Captain or senior lookouts giving the order "Alarm!", which led to a bridge officer activating the alarm bell. All crewmembers would then immediately stop what they were doing and proceed to their diving stations. Once the lookout
Lookout
A lookout or look-out is a person on a ship in charge of the observation of the sea for hazards, other ships, land, etc. Lookouts report anything they see and or hear. When reporting contacts, lookouts give information such as, bearing of the object, which way the object is headed, target angles...
s were below deck and the upper deck hatch was secured, the Captain or Chief Engineer would shout the order "Fluten" ("flood the tanks"). With the bow planes at a maximum down angle, the crew would then flood the forward ballast tanks of the submarine and, often, have all available crewmembers move as far forward in the boat as practical (a "trim party"). This extra weight forward gives the ship a bow-down angle so its momentum helps pull it below the surface. A few seconds later the rear ballast tanks are flooded in order to prevent the bow-down angle from becoming extreme enough that the ship's stern rises out of the water. (An accident during the first patrol of U-505 caused just that when she crash dived to avoid an aircraft. Fortunately for the crew, the ship was not spotted during the moments before the crew could regain full control. The crewman who delayed in flooding the rear ballast tanks was subsequently given the nickname "Ostrich
Ostrich
The Ostrich is one or two species of large flightless birds native to Africa, the only living member of the genus Struthio. Some analyses indicate that the Somali Ostrich may be better considered a full species apart from the Common Ostrich, but most taxonomists consider it to be a...
," a reference to the popular myth that the ostrich, when frightened, buries its head in the sand and thereby raises the position of its tail relative to its body.) The entire operation would generally be coordinated by the Chief Engineer
Chief Engineer
In marine transportation, the chief engineer is a licensed mariner in charge of the engineering department on a merchant vessel. "Chief engineer" is the official title of someone qualified to oversee the entire engine department; the qualification is colloquially called a "chief's...
.
Before the 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 ship in a matter of seconds. On submarines with direct drive, the engines are disengaged from the propeller shafts and the electric propulsion motors/generators are switched to motor mode. The motors are run at high speed to maintain the forward momentum. Once all the hatches and induction vents are closed the diving planes are used like the control surfaces of an airplane to pull the ship below the surface and level out at the desired depth, typically between 70 and 90 meters (230 and 295 feet). In a World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
-era boat, the whole operation could take as little as about 30 seconds with a well-trained and experienced crew. In contrast, an Ohio-class
Ohio class submarine
The Ohio class is a class of nuclear-powered submarines used by the United States Navy. The United States has 18 Ohio-class submarines:...
ballistic-missile submarine may take as long as five minutes to reach periscope depth from the surface.
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. Commander Howard Gilmore earned the Medal of Honor
Medal of Honor
The Medal of Honor is the highest military decoration awarded by the United States government. It is bestowed by the President, in the name of Congress, upon members of the United States Armed Forces who distinguish themselves through "conspicuous gallantry and intrepidity at the risk of his or her...
posthumously during World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
by ordering a crash dive ("Take her down!") while wounded and unable to leave the bridge of USS Growler (SS-215)
USS Growler (SS-215)
, a Gato-class submarine, was the third ship of the United States Navy named for the growler, a large-mouth black bass. Her keel was laid down by the Electric Boat Company of Groton, Connecticut. She was launched on 2 November 1941 , and commissioned on 20 March 1942 with Lieutenant Commander...
.
Crash dives were accurately portrayed in the German film Das Boot
Das Boot
Das Boot is a 1981 German epic war film written and directed by Wolfgang Petersen, produced by Günter Rohrbach, and starring Jürgen Prochnow, Herbert Grönemeyer, and Klaus Wennemann...
.