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96-460: The Westland Wessex is a British-built turbine-powered development of the Sikorsky H-34 . It was developed and produced under licence by Westland Aircraft (later Westland Helicopters ). One of the main changes from Sikorsky's H-34 was the replacement of the piston-engine powerplant with a turboshaft engine. Early models were powered by a single Napier Gazelle engine, while later builds used

192-610: A Federal Aviation Administration type certificate for the conversion in April 1971. The conversion enhanced safety, allowing the aircraft to continue flight after an engine failure, and greatly improved its hot and high performance; whereas the R-1820 could only provide full power up to an altitude of 700 ft (210 m), the paired PT-6s provide full power up to 6,000 ft (1,800 m), and an S-58T can fly at maximum gross weight up to 5,000 ft (1,500 m). The type certificate for

288-541: A campervan -like conversion—featuring a built-in mini-kitchen and sleeping accommodations for four. Later in that decade, Orlando developed a larger version based on the S-58 and participated in a joint effort with popular American recreational vehicle (RV) manufacturer Winnebago Industries to market both aircraft as the Winnebago Heli-Home . The S-58 version featured a larger kitchenette, sleeping accommodations for six,

384-414: A 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. The effective use of depth charges required the combined resources and skills of many individuals during an attack. Sonar, helm, depth charge crews and the movement of other ships had to be carefully coordinated. Aircraft depth charge tactics depended on

480-420: A "dropping mine". At Admiral John Jellicoe 's request, the standard Mark II mine was fitted with a hydrostatic pistol (developed in 1914 by Thomas Firth and Sons of Sheffield) preset for 45 ft (14 m) firing, to be launched from a stern platform. Weighing 1,150 lb (520 kg), and effective at 100 ft (30 m), the "cruiser mine" was a potential hazard to the dropping ship. The design work

576-422: A 120 lb (54 kg) charge for ships too slow to leave the danger area before the more powerful charge detonated. A hydrostatic pistol actuated by water pressure at a pre-selected depth detonated the charge. Initial depth settings were 40 or 80 ft (12 or 24 m). Because production could not keep up with demand, anti-submarine vessels initially carried only two depth charges, to be released from

672-456: A Wessex would be deployed during the launch and recovery of fixed-wing aircraft as a guard helicopter; during anti-submarine patrols, routine procedure was to have one Wessex airborne to actively screen the ship while a second would be fully armed and prepared for operations, such an arrangement was used during troop transport deployments by HMAS Sydney to Vietnam during the 1960s. Performing search and rescue sorties became another valued role of

768-941: A chute at the stern of the ship. The first success was the sinking of U-68 off County Kerry , Ireland, on 22 March 1916, by the Q-ship Farnborough. Germany became aware of the depth charge following unsuccessful attacks on U-67 on 15 April 1916, and U-69 on 20 April 1916. The only other submarines sunk by depth charge during 1916 were UC-19 and UB-29 . Numbers of depth charges carried per ship increased to four in June 1917, to six in August, and 30–50 by 1918. The weight of charges and racks caused ship instability unless heavy guns and torpedo tubes were removed to compensate. Improved pistols allowed greater depth settings in 50 ft (15 m) increments, from 50 to 200 ft (15 to 61 m). Even slower ships could safely use

864-431: A depth charge undergoes a rapid chemical reaction at an approximate rate of 26,000 ft/s (8,000 m/s). The gaseous products of that reaction momentarily occupy the volume previously occupied by the solid explosive, but at very high pressure. This pressure is the source of the damage and is proportional to the explosive density and the square of the detonation velocity. A depth charge gas bubble expands to equalize with

960-406: A killing radius (resulting in a hull breach) of only 10–13 ft (3–4 m) against a conventional 1000-ton submarine, while the disablement radius (where the submarine is not sunk but is put out of commission) would be approximately 26–33 ft (8–10 m). A larger payload increases the radius only slightly because the effect of an underwater explosion decreases as the cube of the distance to

1056-400: A minibar, and an entertainment system; optional floats were offered for amphibious operations. The aircraft were featured in several American popular magazines and reportedly drew large crowds at RV shows and dealerships, but their high purchase price together with rising 1970s fuel prices resulted in very limited sales; production is not well documented but is estimated at only six or seven of

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1152-487: A more advanced weapon system; the original HAS.1 were re-tasked for SAR duties. A commando assault variant, the Wessex HU.5, was also developed as a battlefield transportation helicopter; it was deployed on the navy's amphibious assault ships , such as the commando carrier HMS  Albion , and used to transport Royal Marines . The Wessex HU.5 was powered by coupled de Havilland Gnome engines, which provided nearly double

1248-533: A more effective average depth of 246 ft (75 m). Vice Admiral Charles A. Lockwood , commander of the U.S. submarine fleet in the Pacific, later estimated that May's ill-advised comments cost the US Navy as many as ten submarines and 800 seamen killed in action . For the reasons expressed above, the depth charge was generally replaced as an anti-submarine weapon. Initially, this was by ahead-throwing weapons such as

1344-553: A pair of de Havilland Gnome engines. The Wessex was initially produced for the Royal Navy (RN) and later for the Royal Air Force (RAF); a limited number of civilian aircraft were also produced, as well as some export sales. The Wessex operated as an anti-submarine warfare and utility helicopter; it is perhaps best recognised for its use as a search and rescue (SAR) helicopter. The type entered operational service in 1961, and had

1440-415: A period of many hours, such as U-427 , which survived 678 depth charges in April 1945. 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

1536-546: A preliminary order for the Royal Navy. For British production, it was re-engined with a single Napier Gazelle turboshaft engine, first flying in that configuration on 17 May 1957. The lighter (by 600 lb or 270 kg) Gazelle engine required some redistribution of weight. The first Westland-built Wessex serial XL727 , designated a Wessex HAS.1 , first flew on 20 June 1958. The first production Wessex HAS1 were delivered to Royal Navy's Fleet Air Arm (FAA) in early 1960;

1632-561: A safe distance away. By the late 1990s all nuclear anti-submarine weapons had been withdrawn from service by the United States , the United Kingdom , France , Russia and China . They have been replaced by conventional weapons whose accuracy and range had improved greatly as ASW technology improved. The first attempt to fire charges against submerged targets was with aircraft bombs attached to lanyards which triggered them. A similar idea

1728-895: A service life in excess of 40 years before being retired in the UK in 2003. In the early 1950s Sikorsky developed the S-58, an improved version of the S-55, which had entered service as the H-19 with the United States. The United States Navy issued a contract in 1952 for the S-58, entering service as the HUS-1, the Army placing a contract in 1955 as the H-34, and the Marine Corp in 1957 (as the HUS-1). In 1962 these names were standardized to using

1824-660: A version of the predecessor of the S-58, the S-55 as the Westland Whirlwind , and they would go on to make a turbine powered version of the S-56 as the Westland Wessex . The Sikorsky S-58 was developed as a lengthened and more powerful version of the Sikorsky Model S-55, or UH-19 Chickasaw , with a similar nose, but with a tail-dragger rear fuselage and landing gear, rather than the high-tail, 4-post pattern. It retained

1920-618: A viable alternative to vulnerable road convoys; operations in this theatre led to the employment of various defensive equipment and countermeasures against the threat posed by small arms and man-portable air-defense systems (MANPADS). Wessex helicopters were also used by the Queen's Flight of the RAF to transport VIPs including members of the British Royal Family ; in this role, the helicopters were designated HCC.4 and were essentially similar to

2016-633: A wide range of weather conditions as well as at night, partly due to its use of an automatic pilot. These same qualities that made the Wessex well-suited to the anti-submarine role also lent themselves to the search and rescue (SAR) mission, which the type would become heavily used for. An improved variant, the Wessex HAS.3, succeeded the HAS.1 in the anti-submarine role; it had a more capable radar and better avionics, greater engine power, improved navigational features and

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2112-440: A wider dispersal pattern when used in conjunction with rack-deployed charges. The first of these was developed from a British Army trench mortar . 1277 were issued, 174 installed in auxiliaries during 1917 and 1918. The bombs they launched were too light to be truly effective; only one U-boat is known to have been sunk by them. Thornycroft created an improved version able to throw a charge 40 yd (37 m). The first

2208-554: Is detonated at a shallow depth and the gas bubble vents into the atmosphere very soon after the detonation are quite ineffective, even though they are more dramatic and therefore preferred in movies. A sign of an effective detonation depth is that the surface just slightly rises and only after a while vents into a water burst. Very large depth charges, including nuclear weapons, may be detonated at sufficient depth to create multiple damaging shock waves. Such depth charges can also cause damage at longer distances, if reflected shock waves from

2304-481: The 90SG . China has also produced such weapons. During the Cold War when it was necessary to inform submarines of the other side that they had been detected but without actually launching an attack, low-power "signalling depth charges" (also called "practice depth charges") were sometimes used, powerful enough to be detected when no other means of communication was possible, but not destructive. The high explosive in

2400-463: The Battle of Karameh , bringing Israeli troops in and out of the theatre as well as evacuating the wounded. This was the last operation of the S-58 as it was retired shortly later, having been replaced by the newer Bell 205 and Aérospatiale Super Frelon . The H-34's lift capacity was just sufficient to lift a Mercury space capsule. In 1961, the hatch of Mercury-Redstone 4 was prematurely detached and

2496-451: The Battle of the Atlantic wore on, British and Commonwealth forces became particularly adept at depth charge tactics, and formed some of the first destroyer hunter-killer groups to actively seek out and destroy German U-boats. Surface ships usually used ASDIC ( sonar ) to detect submerged submarines. However, to deliver its depth charges a ship had to pass over the contact to drop them over

2592-632: The Commando Helicopter Force gets its nickname of the Junglies . Around 55 Westland Wessex HU.5s participated in the Falklands War , fighting in the South Atlantic in 1982. On 21 May 1982, 845 Squadron's Wessex HU.5s supported British landings on East Falkland. The type was heavily used throughout the conflict for the transportation and insertion of British special forces, including members of

2688-569: The HC.2 , differences included an upgraded interior, additional navigation equipment and enhanced maintenance programmes. Both Prince Philip and Prince Charles were trained Wessex pilots; occasionally they would perform as flying crew members in addition to being passengers on board the VIP services. The Wessex was replaced in this role by a privately leased Sikorsky S-76 in 1998. In 1962, an international crisis arose as Indonesia threatened confrontation over

2784-642: The House Military Affairs Committee caused The May Incident . The congressman, who had just returned from the Pacific theater where he had received confidential intelligence and operational briefings from the US Navy, revealed at a press conference that there were deficiencies in Japanese depth-charge tactics. After various press associations reported the depth issue, the Japanese Imperial Navy began setting their depth charges to explode at

2880-619: The MedEvac role, while VIP transports carried significantly fewer people in much greater comfort. A total of 135 H-34s were built in the US and assembled by Sud-Aviation in France, 166 were produced under licence in France by Sud-Aviation for the French Air Force, Navy and Army Aviation (ALAT). The CH-34 was also built and developed under license from 1958 in the United Kingdom by Westland Aircraft as

2976-543: The SUBROC , which was armed with a nuclear depth charge. The USSR , United States and United Kingdom developed nuclear depth bombs . As of 2018 , the Royal Navy retains a depth charge labelled as Mk11 Mod 3, which can be deployed from its AgustaWestland Wildcat and Merlin HM.2 helicopters . Russia has also developed homing (but unpropelled) depth charges including the S3V Zagon and

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3072-730: The Special Air Service (SAS) and the Special Boat Service (SBS). A total of nine Wessex (eight HU.5s and one HAS.3) were lost during the Falklands campaign. Two HU.5s of 845 Squadron crashed on the Fortuna Glacier in South Georgia during an attempt to extract members of the SAS during a snow storm, six of 848 Squadron's Wessex HU.5s were lost when the container ship Atlantic Conveyor

3168-485: The Westland Sea King began to replace the Wessex in this capacity from the late 1970s onwards, although troop-carrying missions would continue into the late 1990s. The Wessex's service career featured long-term deployments to both Hong Kong and Northern Ireland to support internal security operations, performing transport and surveillance missions. In Northern Ireland, the use of helicopters for supply missions proved

3264-404: The turboshaft engined Wessex which was used by the Royal Navy and Royal Air Force . The RN Wessex was fitted out with weapons and ASW equipment for use in an antisubmarine role. The RAF used the Wessex, with turboshaft engines, as an air/sea rescue helicopter and as troop transporter. Wessexes were also exported to other countries and produced for civilian use. Entering service in the 1950s,

3360-429: The "HUS" after its original designation in that service. A total of 2,340 H-34s were manufactured between 1953 and 1970, including the license productions in the UK and France. Although most military forces retired the H-34 by the late 20th century, the type remains in limited civil use in transport and external cargo lift roles, and some have been restored and flown as warbirds . In the early 1950s Sikorsky developed

3456-721: The 21st century, and was one of the longest serving and successful of the H-34 types. Used by RVNAF 219th Squadron to insert MACV-SOG reconnaissance teams into Laos. The H-34 was the primary RVNAF helicopter until replaced by the Bell UH-1 Huey. South Vietnam was taken over by North Vietnam, and the fate of these aircraft Israeli S-58s flew numerous combat missions after the end of the Six-Day War ; these missions were mainly against Palestinians infiltrating Israel or against their bases in Jordan. On 21 March 1968, various S-58s participated in

3552-576: The British-developed Hedgehog and later Squid mortars. These weapons threw a pattern of warheads ahead of the attacking vessel to bracket a submerged contact. The Hedgehog was contact fuzed, while the Squid fired a pattern of three large, 440 lb (200 kg) depth charges with clockwork detonators. Later developments included the Mark 24 "Fido" acoustic homing torpedo (and later such weapons), and

3648-800: The Dominican Republic, Nicaragua, the Six-Day War , the Vietnam War , and the Algerian War , where the French Air Force used it to pioneer modern air assault tactics. It was the last piston-engined helicopter to be operated by the United States Marine Corps (USMC), having been replaced by turbine-powered types such as the UH-1 Huey and CH-46 Sea Knight ; in the USMC, the H-34 was often called

3744-497: The H-34 was originally powered by a radial engine , but was later adapted to turbine power by the British licensee as the Westland Wessex and by Sikorsky as the S-58T. The H-34 was also produced under license in France by Sud Aviation . The H-34 was one of the first successful military utility helicopters, serving on every continent with the armed forces of 25 countries. It saw combat in

3840-404: The H-34, with additional prefixes and letters according to that U.S. designation system. Westland had already made a version of the predecessor of the S-56, the S-55 as the Westland Whirlwind . In 1956, an American-built S-58 was shipped to Britain for Westland to use as a pattern aircraft. Initially assembled with its Wright Cyclone , it was demonstrated to the British armed services leading to

3936-513: The Queen. Related development Aircraft of comparable role, configuration, and era Sikorsky H-34 The Sikorsky H-34 (company designation S-58 ) is an American piston-engined military utility helicopter originally designed by Sikorsky as an anti-submarine warfare (ASW) aircraft for the United States Navy . A development of the smaller Sikorsky H-19 Chickasaw (S-55),

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4032-507: The RAF's Bristol Belvedere helicopters, but was more robust and required less maintenance; thus, when the Belvedere was retired at the end of the 1960s, Wessex squadrons were often tasked with their former duties in support of the British Army on an ad-hoc basis. In large-scale helicopter assault operations, the type could be escorted by the RAF's Hawker Siddeley Harriers . The HC.4 variant of

4128-535: The RN, and 16,451 fired, scoring 38 kills in all, and aiding in 140 more. The United States requested full working drawings of the device in March 1917. Having received them, Commander Fullinwider of the U.S. Bureau of Naval Ordnance and U.S. Navy engineer Minkler made some modifications and then patented it in the U.S. It has been argued that this was done to avoid paying the original inventor. The Royal Navy Type D depth charge

4224-589: The S-55 and S-58 versions combined. Data from Jane's All the World's Aircraft 1958-59 General characteristics Performance Armament Related development Aircraft of comparable role, configuration, and era Related lists Depth charge Depth charges were developed during World War I , and were one of the first viable methods of attacking a submarine underwater. They were widely used in World War I and World War II , and remained part of

4320-444: The S-58, an improved version of the S-55, which had enter service as the H-19 with the United States. The United States Navy issued a contract in 1952 for the S-58, entering service as the HUS-1, the Army placing a contract in 1955 as the H-34, and the Marine Corp in 1957 (as the HUS-1). In 1962 these names were standardized to H-34, with additional prefixes and letters according to that U.S. designation system. Westland had already made

4416-507: The S-58T was sold to California Helicopter International in 1981. In the late 1980s and early 1990s, S-58T helicopters were operated by New York Helicopters in scheduled passenger airline service between JFK International Airport and East 34th Street Heliport , New York . In the early 1970s, Orlando Helicopter Airways developed a novel civil conversion of the S-55/H-19, the Heli-Camper ,

4512-492: The Type D at below 100 ft (30 m) and at 10 kn (19 km/h; 12 mph) or more, so the relatively ineffective Type D* was withdrawn. Monthly use of depth charges increased from 100 to 300 per month during 1917 to an average of 1745 per month during the last six months of World War I . The Type D could be detonated as deep as 300 ft (90 m) by that date. By the war's end, 74,441 depth charges had been issued by

4608-745: The U.S. Army's decision to deploy the CH-21 Shawnee to Vietnam instead of the CH-34, pending the introduction into widespread service of the Bell UH-1 Iroquois . U.S. Army H-34s did not participate in Vietnam, and did not fly in the assault helicopter role, but a quantity were supplied to the Republic of Vietnam Air Force (RVNAF). These saw little use due to a lack of spare parts and maintenance. Its higher availability and reliability due to its simplicity compared to

4704-525: The U.S. Navy designation system for U.S. Navy, United States Marine Corps (USMC) and United States Coast Guard (USCG) aircraft. The U.S. Army and Marine Corps, respectively, ordered it in 1955 and 1957. Under the United States Army 's aircraft designation system, also used by the United States Air Force , the helicopter was designated H-34 . The U.S. Army also applied the name Choctaw to

4800-655: The United States and locally assembled by Sud-Aviation . Later, a further 166 were domestically manufactured by Sud-Aviation; these were operated by the French Army Light Aviation ( Army ), French Naval Aviation ( Navy ) and Air force . The Wessex was used as an anti-submarine and utility helicopter with the Royal Navy and as a transport and search and rescue helicopter with the Royal Air Force. British Wessex saw action in several conflicts: Falklands, Oman, Borneo, Aden, etc. The twin-turbine Wessex served into

4896-471: The Wessex in 1962; those helicopters used for air-sea or mountain rescue duties helped make the Wessex a particularly well known aircraft of the service and contributed to the saving of many lives during its time in service. As one of the RAF's standing duties, multiple Wessex helicopters were permanently kept on standby to respond to an emergency located anywhere within 40 miles of the British coastline within 15 minutes during daytime. At night, this response time

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4992-616: The Wessex was the first helicopter operated by the FAA to be purpose-designed from scratch as an anti-submarine platform. In service, the Wessex was found to be a major improvement over the older Westland Whirlwind . The decision made by Westland to install a modern gas-turbine powerplant gave the Wessex a greater load capacity, was quieter and generated less vibration, the latter quality being highly beneficial when treating casualties during flight. The Gazelle engine allowed for rapid starting and thus faster response times. The Wessex could also operate in

5088-464: 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

5184-753: 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. Later depth charges for dedicated aerial use were developed. These are still useful today and remain in use, particularly for shallow-water situations where

5280-399: The aircraft using its speed to rapidly appear from over the horizon and surprising the submarine on the surface (where it spent most of its time) during the day or night (at night using radar to detect the target and a Leigh light to illuminate it immediately before attacking), then quickly attacking once it had been located, as the submarine would normally crash dive to escape attack. As

5376-463: The aircraft, during the campaign in Borneo the Wessex was typically operated as a transport helicopter, capable of ferrying up to 16 troops or a 4,000-pound payload of supplies directly to the front lines. Alongside the Westland Scout , the Wessex emerged as one of the main workhorses of the campaign, roughly half were operated directly from land bases and would regularly rotate with those stationed on RN vessels stationed off shore. From these operations

5472-408: The anti-submarine arsenals of many navies during the Cold War , during which they were supplemented, and later largely replaced, by anti-submarine homing torpedoes . A depth charge fitted with a nuclear warhead is also known as a " nuclear depth bomb ". These were designed to be dropped from a patrol plane or deployed by an anti-submarine missile from a surface ship, or another submarine, located

5568-491: The armed H-34s, known as "Stingers" were quickly phased out. The TK-1 kit would form the basis of the TK-2 kit used on the UH-1E helicopters of the USMC. An H-34 was featured in the famous early-Vietnam War Time-Life photo essay "One Ride With Yankee Papa 13", photographer Larry Burrows , which depicted stages of a disastrous combat mission in which several crew were wounded or killed. The H-34 remained in service with United States Army and Marine Corps aviation units into

5664-443: The capsule was filled with seawater. The extra weight was too much for the H-34 and the capsule, Liberty Bell 7 , was emergency released and sank in deep water, remaining on the ocean floor until 1999 . Sikorsky set up a production line in 1970 to remanufacture existing S-58 aircraft into the S-58T configuration, replacing the R-1820 engine with a pair of Pratt & Whitney Canada PT6T -3 Twin-Pac turboshafts ; Sikorsky obtained

5760-399: The danger zone before the charges exploded. 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 100 lb (45 kg) anti-submarine bomb, but it was too light to be effective. To replace it, the Royal Navy's 450 lb (200 kg) Mark VII depth charge was modified for aerial use by

5856-431: The distinction of being the last piston-engined helicopter to be operated by the Marine Corps. On 3 September 1973, the last flight of a USMC UH-34 occurred as Bureau Number 147191 which had been formally assigned to Headquarters Squadron, FMF Pacific was flown from Quantico, Virginia to MCAS New River to be placed on static display. France purchased an initial batch of 134 Choctaws; these were shipped in kit-form from

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5952-399: 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 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. Specialized depth charge throwers were developed to generate

6048-453: The first two of 27 Wessex helicopters in September 1963; 817 Squadron was the first to operate the type; the Wessex and its dunking sonar array quickly proved to be the most effective anti-submarine platform as yet seen in the RAN. The Wessex was a major operational shift for the Fleet Air Arm , enabling the RAN to proceed with the conversion of the aircraft carrier HMAS Melbourne as an anti-submarine platform. In typical carrier operations,

6144-402: The helicopter. In 1962, under the new unified DoD aircraft designation system , the Seabat was redesignated SH-34 , the Seahorse as the UH-34 , and the Choctaw as the CH-34 . Roles included utility transport, anti-submarine warfare, search and rescue , and VIP transport. In its standard configuration, transport versions could carry 12 to 16 troops, or eight stretcher cases if utilized in

6240-422: The issue of Brunei , which was not in the newly formed Federation of Malaya . By February 1964, a large number of RAF and RN helicopters, including Westland Wessex, were operating from bases in Sarawak and Sabah to assist Army and Marine detachments fighting guerilla forces infiltrated by Indonesia over its one thousand mile frontier with Malaysia . Having removed much of the anti-submarine equipment to lighten

6336-408: The late 1960s; at this time it was also standard equipment in Marine Corps Reserve , Army Reserve and Army National Guard aviation units, eventually being replaced by the UH-1 Iroquois utility helicopter. Sikorsky terminated all production activities in 1968, a total of 1,821 having been built. All H-34 helicopters were retired from service in the U.S. military by the early 1970s; the type having

6432-477: The latest United States Navy submarines could dive so deep. Unless caught in shallow water, an American submarine could dive below the Japanese depth charge attack. The Japanese had used attack patterns based on the older United States S-class submarines (1918–1925) that had a test depth of 200 ft (61 m); while the WWII Balao-class submarines (1943) could reach 400 ft (120 m). This changed in June 1943 when U.S. Congressman Andrew J. May of

6528-535: The maximum detonation depth to 900 ft (270 m). The Mark VII's 290 lb (130 kg) amatol charge was estimated to be capable of splitting a 7 ⁄ 8  in (22 mm) submarine pressure hull at a distance of 20 ft (6 m), and forcing the submarine to surface at twice that. The change of explosive to Torpex (or Minol) at the end of 1942 was estimated to increase those distances to 26 and 52 ft (8 and 16 m). The British Mark X depth charge weighed 3,000 lb (1,400 kg) and

6624-598: The more advanced and capable Westland Sea King in this capacity. Instead, remaining Wessex helicopters were retained to perform its secondary roles as a plane guard, search and rescue platform, and as a utility transport helicopter. The type was withdrawn from service in 1989. In 2019, one retired Wessex HU.5 was restored to flying condition, after having last flown 30 years ago. After a 10,000 hour expert restoration, HU5 XT761/ G‑WSEX took flight again in Somerset, England. Data from Westland Aircraft since 1915 General characteristics Performance Wessexes portrayed

6720-494: The newer helicopters led Marines to ask for it by name. The phrases "give me a HUS", "get me a HUS" and "cut me a HUS" entered the U.S. Marine Corps vernacular, being used even after the type was no longer in use to mean "help me out". USMC H-34s were also among the first helicopter gunships trialled in theatre, being fitted with the Temporary Kit-1 (TK-1) , comprising two M60C machine guns and two 19-shot 2.75 inch rocket pods. The operations were met with mixed enthusiasm, and

6816-426: The nose-mounted radial reciprocating engine with the drive shaft passing through the cockpit placed high above the cargo compartment. The aircraft first flew on 8 March 1954. The first production aircraft was ready in September and entered in service for the United States Navy initially designated HSS-1 Seabat (in its anti-submarine configuration) and HUS-1 Seahorse (in its utility transport configuration) under

6912-428: The ocean floor or surface converge to amplify radial shock waves. Submarines or surface ships may be damaged if operating in the convergence zones of their own depth charge detonations. The damage that an underwater explosion inflicts on a submarine comes from a primary and a secondary shock wave. The primary shock wave is the initial shock wave of the depth charge, and will cause damage to personnel and equipment inside

7008-545: The power of the original HAS.1 model and significantly extended its range. This enabled it to operate in a wider range of conditions; during the 1970s, the HU.5 also started to be used for the SAR mission. As an anti-submarine helicopter, the Wessex could be either equipped with a dipping sonar to detect and track submarines or be armed with either depth charges or torpedoes ; a single Wessex could not search for and attack submarines as this

7104-424: The pressure of the surrounding water. This gas expansion propagates a shock wave. The density difference of the expanding gas bubble from the surrounding water causes the bubble to rise toward the surface. Unless the explosion is shallow enough to vent the gas bubble to the atmosphere during its initial expansion, the momentum of water moving away from the gas bubble will create a gaseous void of lower pressure than

7200-508: The secondary shock wave can be reinforced if another depth charge detonates on the other side of the hull in close time proximity to the first detonation, which is why depth charges are normally launched in pairs with different pre-set detonation depths. The killing radius of a depth charge depends on the depth of detonation, the payload of the depth charge and the size and strength of the submarine hull. A depth charge of approximately 220 lb (100 kg) of TNT (400 MJ ) would normally have

7296-588: The stern; sonar contact would be lost just before attack, rendering the hunter blind at the crucial moment. This gave a skilful submarine commander an opportunity to take evasive action. In 1942 the forward-throwing "hedgehog" mortar, which fired a spread salvo of bombs with contact fuzes at a "stand-off" distance while still in sonar contact, was introduced, and proved to be effective. In the Pacific Theater during World War II , Japanese depth charge attacks were initially unsuccessful because they were unaware that

7392-400: The submarine if detonated close enough. The secondary shock wave is a result of the cyclical expansion and contraction of the gas bubble and will bend the submarine back and forth and cause catastrophic hull breach, in a way that can be likened to bending a plastic ruler rapidly back and forth until it snaps. Up to sixteen cycles of secondary shock waves have been recorded in tests. The effect of

7488-400: The surrounding water. Surrounding water pressure then collapses the gas bubble with inward momentum causing excess pressure within the gas bubble. Re-expansion of the gas bubble then propagates another potentially damaging shock wave. Cyclical expansion and contraction can continue for several seconds until the gas bubble vents to the atmosphere. Consequently, explosions where the depth charge

7584-408: The target, a U-boat's pressure hull would not rupture unless the charge detonated within about 15 ft (5 m). Getting the weapon within this range was a matter of luck and quite unlikely as the target took evasive action. Most U-boats sunk by depth charges were destroyed by damage accumulated from an extended barrage rather than by a single charge, and many survived hundreds of depth charges over

7680-555: The type served numerous roles in the late 20th century. The type was internationally and commercially. The helicopters used by the French Army Light Aviation (ALAT), including the Sikorsky H-34, aggregated over 190,000 flying hours in Algeria (over 87,000 for the H-21 alone) and helped to evacuate over 20,000 French combatants from the combat area, including nearly 2,200 at night. By the time

7776-530: The type; in 1974, multiple Wessex helicopters participated in the relief effort in Darwin in the aftermath of Cyclone Tracy . While the Wessex proved to be too large to reasonably operate from most of the RAN's destroyers, it was found to be well suited as a troop-transport helicopter from heavy landing ships and larger vessels. By 1980, the Wessex was no longer being used for anti-submarine operations, having been replaced by

7872-546: The visually similar CH-34 Choctaws in Stanley Kubrick 's 1987 film Full Metal Jacket . The helicopters used were Wessex 60s, a civilian version of the Wessex HC.2. These are powered by the coupled-twin de Havilland Gnome with a distinctive long nose and single large turbine exhaust on each side, distinguishing them from the CH-34. XT761 was featured in season 4 of The Crown depicting Tom Byrne as Prince Andrew visiting

7968-460: The war in Algeria had ended, eight officers and 23 non-commissioned officers from ALAT had been killed. The use of armed helicopters during the Algerian War, coupled with helicopter transports which can insert troops into enemy territory, gave birth to some of the modern tactics of airmobile warfare . French evaluations on the reported ground fire vulnerabilities of the CH-34 may have influenced

8064-590: The world. Bristow flew them from various UK airfields and helicopter pads to support the growing North Sea Oil industry until they were withdrawn in 1982. In April 1961, the Royal Australian Navy (RAN) announced that they had selected the Westland Wessex to become the standard service helicopter from their ships and its intention to purchase roughly 30 for anti-submarine patrols, casualty evacuations, and fleet communications duties. The RAN formally accepted

8160-521: Was 200 lb (91 kg) of Torpex with a sinking speed of 14.4 ft/s (4.4 m/s) and depth settings of up to 600 ft (180 m). Later versions increased depth to 1,000 ft (300 m) and sinking speed to 22.7 ft/s (6.9 m/s) with increased weight and improved streamlining. Although the explosions of the standard United States 600 lb (270 kg) Mark 4 and Mark 7 depth charge used in World War II were nerve-wracking to

8256-432: Was a 16 lb (7.3 kg) guncotton charge in a lanyarded can. Two of these lashed together became known as the "depth charge Type A". Problems with the lanyards tangling and failing to function led to the development of a chemical pellet trigger as the "Type B". These were effective at a distance of around 20 ft (6 m). A 1913 Royal Navy Torpedo School report described a device intended for countermining ,

8352-520: Was beyond its carrying capability. It was this limitation that soon led the Royal Navy to search for a more capable helicopter that could provide this capability. This ultimately resulted in Westland proceeding with the adaptation and production of another Sikorsky-designed helicopter in the form of the Westland Sea King . The Wessex was also used as a general-purpose helicopter for the RAF, for troop-carrying, air ambulance and ground support roles. The Wessex

8448-506: Was carried out by Herbert Taylor at the RN Torpedo and Mine School, HMS Vernon . The first effective depth charge, the Type D, became available in January 1916. It was a barrel-like casing containing a high explosive (usually TNT , but amatol was also used when TNT became scarce). There were initially two sizes—Type D, with a 300 lb (140 kg) charge for fast ships, and Type D* with

8544-508: Was designated the "Mark VII" in 1939. Initial sinking speed was 7 ft/s (2.1 m/s) with a terminal velocity of 9.9 ft/s (3.0 m/s) at a depth of 250 ft (76 m) if rolled off the stern, or upon water contact from a depth charge thrower. Cast iron weights of 150 lb (68 kg) were attached to the Mark VII at the end of 1940 to increase sinking velocity to 16.8 ft/s (5.1 m/s). New hydrostatic pistols increased

8640-439: Was detonated in the vertical column of the Y-gun to propel a depth charge about 45 yd (41 m) 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. The K-gun, standardized in 1942, replaced

8736-691: Was first used by the Royal Navy, which introduced the Wessex HAS.1 to operational service in 1961. Having been satisfied by the favourable initial performance of the Wessex but seeking to improve its avionics and equipment, the Navy soon pressed for the development of the improved HAS.3 , which came into service in 1967. Operationally, younger models would be assigned to perform the key anti-submarine warfare and commando transport missions, while older and less capable models would be typically be assigned to land bases for search and rescue (SAR). The RAF became an operator of

8832-584: Was fitted in July 1917 and became operational in August. In all, 351 torpedo boat destroyers and 100 other craft were equipped. Projectors called "Y-guns" (in reference to their basic shape), developed by the U.S. Navy's Bureau of Ordnance from the Thornycroft thrower, became available in 1918. Mounted on the centerline of the ship with the arms of the Y pointing outboard, two depth charges were cradled on shuttles inserted into each arm. An explosive propellant charge

8928-423: Was increased to 60 minutes. SAR-tasked Wessex helicopters were also stationed abroad, such as at Cyprus . The qualities of the Wessex were described as being "ideal for mountain flying". The Wessex often found itself being used on the battlefield as a utility transport; as well as delivering supplies and equipment, the Wessex could also transport small groups of troops. Operationally, the Wessex could lift less than

9024-427: Was launched from the 21 in (530 mm) torpedo tubes of older destroyers to achieve a sinking velocity of 21 ft/s (6.4 m/s). The launching ship needed to clear the area at 11 knots to avoid damage, and the charge was seldom used. Only 32 were actually fired, and they were known to be troublesome. The teardrop-shaped United States Mark 9 depth charge entered service in the spring of 1943. The charge

9120-400: Was sunk and the HAS.3 aboard HMS Glamorgan was destroyed when the ship was struck by an Exocet missile. The last in UK service were retired in 2003, these were HC2 models used by the RAF. A civilian version of the helicopter, the Wessex 60, was also manufactured and supplied to a number of civilian operators, including Bristow Helicopters , one of the biggest rotary-wing operators in

9216-426: Was the first of the RAF's helicopters in which instrument flying, and thus night operations, were possible. Unlike the Navy's Wessex fleet, which was largely composed of early single-engine models, the RAF mandated that its Wessex helicopters should be all twin-engined; this was a major factor in the RAF's decision to reject the adoption of ex-FAA Wessex helicopters as the Navy migrated to the newer Sea King. The Wessex

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