View source for AN/SQS-504

The '''AN/SQS-504 Diver'''<ref>{{cite journal |last1=Finch |first1=David |date=2010 |title=The Canadian Navy: Anti-Submarine Warfare to Undersea Domain Awareness |journal=Journal of Ocean Technology |location=St. John's |publisher=Marine Institute, Memorial University |volume=5 |issue=Special |url=https://www.thejot.net/article-preview/?show_article_preview=184 |pages=29}}</ref> was an early naval medium-frequency active [[variable depth sonar]]<ref>{{cite book |editor-last=Sharpe |editor-first=Richard |title=Jane's Fighting Ships 1989-90 |publisher=Jane's Information Group |date=1989 |page=79 |isbn=978-0710608864}}</ref> (VDS) developed in [[Canada]].

The AN/SQS-504 emerged from a post-[[Second World War]] program to improve the detection of submarines between the [[Thermocline|thermal layers]] in the [[Gulf of Saint Lawrence]].<ref name="Brassington_45-41">Brassington: pages 45-51</ref> A transducer derived from a wartime British Type 144 sonar was placed in a towed body<ref name="Merklinger_2005">{{cite conference |last1=Merklinger |first1=Harold M. |last2=Osler |first2=John C. |title=A few Canadian contributions to underwater acoustics |conference=169th Meeting of the Acoustical Society of America |date=10 September 2005 |location=Pittsburgh |publisher=[[Acoustical Society of America]] |url=http://cradpdf.drdc-rddc.gc.ca/PDFS/unc206/p802858_A1b.pdf |access-date=12 May 2019 }}</ref> and deployed from the stern by the '''AN/SQA-501''' handling gear.<ref name="Brassington_55">Brassington: page 55</ref> The AN/SQS-504 was succeeded by the [[AN/SQS-505]], which used a then-modern transducer and receiver.<ref name="Brassington_559-62">Brassington: pages 59-62</ref>

It was deployed in the 1960s by the [[Royal Canadian Navy]] (RCN), the British [[Royal Navy]] (RN), and the [[Royal Australian Navy]].  The [[United States Navy]] (USN) did not adopt the AN/SQS-504, but the design of the towed body handling gear influenced later USN VDS.<ref name="Merklinger_2010">{{cite journal |last1=Merklinger |first1=Harold M. |date=2010 |title=Navy Research and Development Activities of the Past 100 Years |journal=Journal of Ocean Technology |location=St. John's |publisher=Marine Institute, Memorial University |volume=5 |issue=Special |url=https://www.thejot.net/article-preview/?show_article_preview=184 |pages=65}}</ref>

The success of the AN/SQS-504 has led to claims that VDS was invented<ref name="Brassington_65">Brassington: pages 65</ref> or primarily developed in Canada.<ref>{{cite book |last=Owen |first=David |title=Anti-Submarine Warfare: An Illustrated History |publisher=Seaforth Publishing |date=2007 |isbn=978-1-84415-703-7}}</ref>

==Development==
===Early experiments===
During the [[Second World War]], the thermal layers in the [[Gulf of Saint Lawrence]] severely decreased the detection range of hull-mounted [[sonar]]. From 1944 to 1948, Canadian institutions used sonar and [[bathythermograph]]s to investigate the effect of oceanic and seasonal conditions on underwater sound propagation. After war, the [[Defence Research and Development Canada|Naval Research Establishment]] (NRE) conducted sonar ranging trials in the [[Bay of Fundy]] and [[St. Margarets Bay, Nova Scotia]] with British [[Type 144 sonar]].<ref name="Brassington_45-47">Brassington: pages 45–47</ref><ref name="Merklinger_2005"/> In December 1948, the NRE reported that in the summer the waters of the [[Scotian Shelf]] was divided into three temperature layers, and a sonar lowered into the cold middle layer might have good detection range against submarines within that layer.<ref name="Brassington_50">Brassington: page 50</ref>

In 1949, the RCN issued requirements for a towed sonar for operations in the shallow waters of the Gulf of Saint Lawrence and off [[Halifax, Nova Scotia]].<ref name="Brassington_51">Brassington: page 51</ref> The Defence Research Board of Canada (DRBC) organized a development program for a towed dipping sonar in April 1949. Early trials were conducted using an experimental dipping sonar called "Hot Dog", a harbour defence sonar capsule lowered over the side or rear of a stationary ship by electrical cable. The trials confirmed the possibility of achieving long detection ranges and the reduced efficacy of hull-mounted sonar against targets in the middle layer. The RCN requested top priority for the project in October 1952, and the development effort became "Project DUNKER".<ref name="Brassington_49">Brassington: page 49</ref> RCN requirements were revised in 1954; it now called for a sonar that could be deployed at variable depths, and so would be useful in wider range of conditions.<ref name="Brassington_52">Brassington: page 52</ref>

===Towing body===
The next step was the development of a towing body and [[Cable fairing|faired cables]] suitable for operational use on RCN warships at a speed of {{convert|15|to|20|kn|lk=in}}. The first experimental towing body, "Toby", was [[torpedo]]-shaped; after being lost it was replaced by "Toby II", which incorporated an [[aluminium]] nose with a fixed Type 144. A Winged Housed Air Towed Sonar (WHATS), developed by the [[EDO Corporation]] for [[blimp]]-towed sonars, was also adapted for experiments. NRE designed the "Canadian Body" (Canby) and contracted the [[Fairey Aviation Company]] to build it; Canby was trialled in October 1953.<ref name="Brassington_51"/>

Ultimately, the towing body that was adapted for service was the "Trilby". Trilby was based on a RN {{convert|100|in|cm|adj=on}} sonar dome<ref name="Brassington_51"/> and developed in close cooperation with the [[David Taylor Model Basin]] (DTMB) in the United States;<ref name="Merklinger_2005"/> its shape was radically different than Canby, allowing it to house a larger transducer that could also be trained all around. Trilby was first trialled in 1955.<ref name="Brassington_51"/> The after ends of the tails fins were sharpened "knife sharpness" to eliminate tail flutter which jammed the sonar receiver.<ref name="Brassington_56">Brassington: page 56</ref>

The development of cable fairing was required to solve serious tow-off problems. Trials only began in spring 1952 after delays caused by [[Cold War]] and [[Korean War]] rearmament. The tow-off problem was solved in early 1953 by completely redesigning the fairing<ref name="Brassington_51"/> with the help of DTMB.<ref name="Merklinger_2005"/> Over-the-stern towing was found to be superior to over-the-side towing—the latter was then being pursued by the USN.<ref name="Brassington_51"/>

===Transducer===
NRE developed a new "searchlight" sonar called "Canadian ASDIC Search Towed 1" (CAST/1),<ref name="Merklinger_2005"/><ref name="Brassington_51"/> using the Type 144 as a starting point.<ref name="Merklinger_2005"/> The transducer used a high-activity low-impedance piezoelectric ceramic developed by NRE; the ceramic, called NRE-4, was [[barium titanate]] with small quantities of [[cobalt]].<ref name="Tollefsen"/> NRE-4 allowed transmission power 300-times greater<ref name="Merklinger_2005"/> than the steel-quartz transducer in the Type 144.<ref name="Tollefsen">{{cite journal |last1=Tollefsen |first1=Cristina D. S. |date=Summer 2018 |title=Canadian Innovations in Naval Acoustics from World War II to 1967 |journal=Acoustics Today |volume=14 |issue=2 |location=Hyannis |publisher=[[Acoustical Society of America]] |url=https://acousticstoday.org/issues/2018AT/Summer2018/Summer2018.pdf |pages=29}}</ref> British and American ceramics were not available due to industrial supply issues. Initially, the connecting cable's electrical conductors burned failed after a few hours of use; this was resolved by adopting design and testing procedures for such cables from the [[Ministry of Northern Development and Mines|Department of Mines]] in [[Ontario]].<ref name="Merklinger_2005"/> CAST/1 also had a split beam direction finding system.<ref name="Brassington_51"/>

===Handling gear===
Development of the AN/SQA-501 handling gear occurred from the early 1950s to 1960. Early development used parts salvaged from DRBC experiments and naval stocks. During one trial, the cable release clutch failed to function when the cable or body became caught underwater; the cable pulled itself off the drum and destroyed the gearbox. The clutch was upgraded to release under higher strain. The parallel mechanism was also redesigned to prevent jamming during a recovery operation.<ref name="Brassington_55-56">Brassington: pages 55-56</ref>

===CAST/1/R and CAST/1/X===
CAST/1 was placed into the towed body to create the "Canadian ASDIC Search Towed research 1" (CAST/1/R) VDS.<ref name="Merklinger_2005"/><ref name="Brassington_51"/> CAST/1/R was successfully tested in the [[Bermuda]] area in December 1955.<ref name="Brassington_51"/>

A related development was the "Canadian ASDIC Search Towed experimental 1" (CAST/1/X) VDS;<ref name="Merklinger_2005"/><ref name="Brassington_51"/> CAST/1/X used modified Canby handling gear, and an experimental version of CAST/1 that operated on a "train-ping-listen" sequence. CAST/1/X was completed and installed on {{HMCS|Crusader|R20|6}} in June 1956. It conducted successful submarine target trials in September and November that same year.<ref name="Brassington_51"/> CAST/1/X out-ranged the Type 144 used by the RCN by a factor of five.<ref name="Brassington_54">Brassington: page 54</ref>

In 1958, the CAST/1/X, aboard ''Crusader'', performed comparative tests with the British experimental Type 192x VDS, aboard {{HMS|Brocklesby|L42|6}}. The CAST/1/X performed similarly to the much larger Type 192x. The British subsequently abandoned the Type 192x and adopted the Canadian system as the Type 199.<ref name="Merklinger_2010"/>

CAST/1/X was re-engineered to meet naval standards to become the AN/SQS-504.<ref name="Brassington_55"/>

==Problems in service==
Deficiencies in the AN/SQA-501 handling gear, which made operating the AN/SQS-504 difficult to impossible, became apparent within a few years of entering service. Problems included poorly designed [[hydraulics]], damage to the AN/SQS-504 because it was slightly too wide to fit between the saddle arms, and an overall haphazard design.<ref name="Brassington_59">Brassington: page 59</ref> In 1964, the RCN formed a small team that worked to fix the AN/SQA-501, although time and material were not formally allocated.<ref name="Brassington_59"/> This followed a hoist failure on {{HMCS|St. Laurent|DDH 205|6}} which prevented the recovery of the AN/SQS-504 for 18 hours during JETEX 64.<ref name="Mayne_325">Mayne: page 325</ref>

A further difficulty was the range of RCN [[Anti-submarine warfare|anti-submarine]] (ASW) weapons. The AN/SQS-504 had a range of {{convert|5000|to|7000|yd|m}}, but upon entering service the RCN was equipped with the much shorter-ranged [[Limbo (weapon)|Limbo]] mortar and [[Mark 43 torpedo]].<ref name="Mayne_323">Mayne: page 323</ref>

Even as the AN/SQS-504 entered service, the RCN was already looking for longer-ranged sonar to vector ASW helicopters against faster and deeper diving [[Soviet]] [[nuclear submarine]]s. In 1960, the RCN initiated Project DIANA ONE which ultimately resulted in the AN/SQS-505 hull and VDS sonar and the AN/SQA-502 handling gear.<ref name="Mayne_324-325">Mayne: pages 324–325</ref><ref name="Brassington_62-64">Brassington: pages 62–64</ref>

==Variants==
The British '''Type 199''' is an AN/SQS-504 with RN rigging.<ref>{{cite book |editor-last=Harding |editor-first=Richard |title=The Royal Navy 1930-1990: Innovation and Defense |publisher=Routledge |date=2004 |page=281 |isbn=978-1-135-75371-9}}</ref>

==Operators==
;{{AUS}}
*{{sclass2|River|destroyer escort}}<ref name="Jeremy_8">{{cite report |last=Jeremy |first=John C. |date=July 1989 |title=Naval Shipbuilding - Some Australian Experience |url=http://www.rina.org.uk/hres/1988-4%20Jeremy%20-%20Naval%20Ship%20Construction%20-%20Some%20Australian%20Experience.pdf |publisher=[[Royal Institution of Naval Architects]] (Australian Division) |location=Sydney |accessdate=12 May 2019 |pages=8}}</ref> (Type 199)<ref name="Tollefsen"/> (retired)

Only {{HMAS|Stuart|DE 48|6}} and {{HMAS|Derwent|DE 49|2}} were fitted. The sonar was unsuccessful in Australian service and later removed.<ref name="Jeremy_8"/>

;{{CAN}}
*{{sclass|Annapolis|destroyer}}<ref name="Moore_81">Moore: page 81</ref> (retired)
*{{sclass|St. Laurent|destroyer}}<ref name="Moore_82">Moore: page 82</ref> (retired)
;{{UK}}
*{{sclass|Leander|frigate}} (Type 199)<ref name="Moore_602">Moore: page 602</ref> (retired)

==See also==
*[[AN/SQS-505]], an improved Canadian hull and VDS sonar system developed in the 1960s
*[[Canadian Towed Array Sonar System]], a towed array sonar developed in the 1980s

==References==

===Notes===
{{reflist|30em}}

===Sources===
*{{cite journal |last1=Brassington |first1=D.G. |date=1985 |title=The Canadian Development of VDS |journal=Maritime Warfare Bulletin - Commemorative Edition, 1985 |location=Halifax |publisher=Canadian Forces Maritime Warfare School |url=http://www.cntha.ca/static/documents/papers/VDS_Development.pdf |pages=45–65}}
*{{cite thesis |type=PhD |last=Mayne |first=Richard Oliver |date=April 2008 |title=The Annapolis Riddle: Advocacy, Ship Design and the Canadian Navy's Force Structure Crisis, 1957-1965 |publisher=[[Queen's University at Kingston|Queen's University]] |url=https://qspace.library.queensu.ca/bitstream/handle/1974/8298/Mayne_Richard_O_finalsubmission_200804_PhD.pdf?sequence=1&isAllowed=y}}
*{{cite book |editor-last=Moore |editor-first=John |title=Jane's Fighting Ships 1979-80 |publisher=Jane's Information Group |date=1979 |isbn=978-0-531-03913-7 |url-access=registration |url=https://archive.org/details/janessfightingsh00john }}

[[Category:Military electronics]]
[[Category:Sonar]]
[[Category:Military equipment of Canada]]