Editing Depth charge (section)

==Delivery mechanisms==
{{See also|Anti-submarine unguided projectiles}}
[[File:Mk VII depth charge.jpg|thumb|Loading a drum-type Mark VII depth charge onto a {{sclass2|Flower|corvette|1}}'s K-gun]]
[[File:USN Y-Gun Depth Charge Thrower.jpg|thumb|Y-gun depth charge thrower]]
The first delivery mechanism was to simply roll the "ashcans" off racks at the stern of the moving attacking vessel. Originally depth charges were simply placed at the top of a ramp and allowed to roll. Improved racks, which could hold several depth charges and release them remotely with a trigger, were developed towards [[Armistice with Germany|the end of the First World War]]. These racks remained in use throughout World War II because they were simple and easy to reload.

Some Royal [[Naval trawler|Navy trawlers]] used for anti-submarine work during 1917 and 1918 had a thrower on the [[forecastle]] for a single depth charge, but there do not seem to be any records of it being used in action.<ref name="t40"/> Specialized depth charge throwers were developed to generate a wider dispersal pattern when used in conjunction with rack-deployed charges.<ref name="t40"/> The first of these was developed from a [[British Army]] [[trench mortar]].<ref>{{Harvnb|McKee|1993|p=51}}</ref> 1277 were issued, 174 installed in auxiliaries during 1917 and 1918.<ref name="m52">{{Harvnb|McKee|1993|p=52}}</ref><ref>{{Harvnb|McKee|1993|pp=51–52}}</ref> The bombs they launched were too light to be truly effective; only one U-boat is known to have been sunk by them.<ref name="m52"/>

[[Thornycroft]] created an improved version able to throw a charge {{cvt|40|yd}}.<ref name="m52"/> The first was fitted in July 1917<ref name="m52"/> and became operational in August.<ref name="t40"/> In all, 351 torpedo boat destroyers and 100 other craft were equipped.<ref name="m52"/> Projectors called "Y-guns" (in reference to their basic shape), developed by the U.S. Navy's [[Bureau of Ordnance]] from the Thornycroft thrower,<ref name="m52"/> became available in 1918. Mounted on the centerline of the ship with the arms of the ''Y'' pointing outboard, two depth charges<ref name="m52"/> were cradled on shuttles inserted into each arm. An explosive propellant charge was detonated in the vertical column of the Y-gun to propel a depth charge about {{cvt|45|yd}}<ref name="m52"/> over each side of the ship. The main disadvantage of the Y-gun was that it had to be mounted on the centerline of a ship's deck, which could otherwise be occupied by superstructure, masts, or guns. The first were built by [[New London Ship and Engine Company]] beginning on 24 November 1917.<ref name="m52"/>

The K-gun, standardized in 1942, replaced the Y-gun as the primary depth charge projector. The K-guns fired one depth charge at a time and could be mounted on the periphery of a ship's deck, thus freeing valuable centerline space. Four to eight K-guns were typically mounted per ship. The K-guns were often used together with stern racks to create patterns of six to ten charges. In all cases, the attacking ship needed to be moving fast enough to get out of the danger zone before the charges exploded.

[[image:Sunderland db rack 2.JPG|thumb|Depth bombs hung under the wings of an RAF [[Short Sunderland]] flying boat]]
Depth charges could also be dropped from an aircraft against submarines. At the start of World War II, Britain's primary aerial anti-submarine weapon was the {{cvt|100|lb}} anti-submarine bomb, but it was too light to be effective. To replace it, the Royal Navy's {{cvt|450|lb}} Mark VII depth charge was modified for aerial use by the addition of a streamlined nose fairing and stabilising fins on the tail; it entered service in 1941 as the Mark VII Airborne DC. Other designs followed in 1942.

Experiencing the same problems as the RAF with ineffective anti-submarine bombs, Captain [[Birger Ek]] of [[Finnish Air Force]] squadron [[LeLv 6]] contacted a navy friend to use Finnish Navy depth charges from aircraft, which led to his unit's [[Tupolev SB]] bombers being modified in early 1942 to carry depth charges.<ref>{{harvnb|Karhunen|1980|p={{page needed|date=September 2012}} }}</ref>

Later depth charges for dedicated aerial use were developed. These are still useful today and remain in use, particularly for shallow-water situations where a [[torpedo|homing torpedo]] may not be effective. Depth charges are especially useful for "flushing the prey" in the event of a diesel submarine hiding on the bottom.