ASDIC, Radar and IFF Systems Aboard HMCS HAIDA - Part 3 ...

The 124 oscillator was mounted in a retractable dome.Jim Fairnie of Victoria B.C. describes Asdic operations on this type of vessel. "On some River Class ... ASDICEQUIPMENTTYPES-SECTIONA Thissectionfocusesontechnicalandoperationalinformation ofselectedAsdicorSonarsets.DuringWorldWarII,Asdicfittingscould beclassifiedasfollows: TYPEOFSHIP ASDICTYPE Bangors 128 Corvettes 123 Cruisers n/a Fairmiles 127D/134A/134C/134D Frigates 128 RiverClassDestroyers 124 TribalClassDestroyers 144/147 Note,thatHMCSHaidawasonlyfittedwithafewofthesets describedinthissectionofthisdocument.Whentheequipmenttypeis applicabletoHaida,acommentwillbefoundinthetext.Theyearofintroduction issuffixedafterthetypenumber.Adefinitiveworktitled'SeekandStrike' byWillemHackmannlistsalltheBritishAsdicsetsproducedfrom1918 to1960. Type123and123A(1934) JohnCoatesrecalledhisfirstexperienceswithtype123Asdic. "IcommissionedthefirstCanadianCorvette,HMCSChamblyasthesenior Asdicrating.Thisshipwasfittedwiththe123Asdicsetasweremost corvettes--primitivebutreliable.Itsmajorshortcomingwasitsinability togaugethetarget'sdepth.Thiswasacriticalfactorbecausedepthcharges didnotcauseseriousdamageunlesstheyexplodedwithintwentyfeetof thehullofasubmarine.BothJohnandHarryCarson,Ex-C.P.O.1stClass ofDartmouthN.S.providesanexcellenttechnicaldescriptionofthe123 set."Theoscillator,whichoperatedinthe14to22Kcsband,wasfitted inafixeddomeandcontrolledfromanAsdichutmountedabovethebridge. Locatedinthehut,werearangerecorderandacompassbinnaclecontaining amagneticcompassandatrainingwheel.Thewheelcontrolledabeamof lightthatshonethroughamaskbelowthecompassface.Thisbeamindicated thedirectiontowhichtheoscillatorfacewaspointing.Beforesailing, theoperatoralwayscheckedthatthefaceoftheoscillatorwaslinedup withthelightbeam.ThisAsdicsethadonlyonecompassandindicating positionanditwasimpossiblefortheCaptaintokeeponeeyeontheinformation fromthehutwhilecontrollingtheshipfromthebridge.The123and123A Asdic'sweredesignedtohavetheoperatorinastandingposition.  WithotherAsdicsets,theoperatorhadtheluxuryofsittingonathinly cushionedbench. TheASDICdomeonaCorvettewaslocatedjustaftofthebowtransition. (Drawing byLathamJenson.FromTinHats,OilskinsandSabots)  AlsosecuredtothetrainingwheelwasaBowdenwiredrive. Thisdrivewasverticallyorientedandthecablepassedthroughthenavigation compartmentandallothercompartmentsdirectlybelow,untilitreached thetraininggearboxintheAsdicwell.MostAsdicratingsreferredto thisdeviceas'handraulictraining'.Thedomewasfixedtothebottom ofthekeelwithheavynuts.Itwascoveredwithsteelfairingplatesto produceasmoothsurfacetoreducewaternoisewhentheshipwasunderway. Bydesign,itwasnotnecessarytohousethedomeasitcouldwithstand aservicespeedof18knots,aspeedthatwasmorethanthemaximumspeed ofacorvette.Whenthetransducerwasfullylowered,itsfacewasaligned withtheStaybritewindowsofthedome. CHRONOSCOPE:VeryearlyASDICsdidnothavearangerecorder.Instead, theoperatorwouldstarta6secondstopwatch.WhentheinitialASDICpulse washeard,thewatchwasstarted.Whentheechowasheard,thewatchwould bestopped. The rangeofthetargetwouldthenbereadfrom theredscale. Thesestopwatcheswereprobablymadebyseveralmanufacturers andwerecalibratedforsaltwateroperation.Soundtravelsapproximately 1,650yds/secinseawater.   Thechronoscopecouldbeusedforrangingineventofarecorder break-down.Thisinstrumentrequiresthesamelevelofcarethatwould begiventoapersonalpocketwatch.  Waltham'sAdmiralty#6Pattern,circa1940, isoneexampleof acompanythatmadethisproduct. Theunitdepictedhereis areplica.(ImageprovidedbyKojiKamori) Astheoscillatorexpandedorcontracted,theresultantsound wavewaspropagatedthroughthewatercontainedwithinthedome.Inturn, theStaybritewindowwouldimpartthesoundenergytotheouterseawater. Whenanechowasreceived,theexpansionorcontractionofseawaterwarped theoscillatorfaceaccordingly.Thisactiongeneratedaveryweakvoltage intheoscillatorthatwasappliedtoanamplifierandarecordingdevice. Sendingandreceivingwascontrolledwithakeyoralternatelywiththe RangeRecorder.Normally,theoperatorpressedthekeytotransmit,then releasedittoreceive.Ontransmission,impuritiesinthewaterwould sendbackthousandsofsmallechoesthatwerecalledbackgroundreverberations. Whentheoperatornolongerheardthereverberationsorbackgroundnoise, hewouldsteptheoscillatoranother5degrees,thenpressthehandkey. Theadvicewastonottoholdthekeydownforlongerthanasecond,however, therewasnotime-outcircuittopreventitfrombeinghelddownforever. ThechiefoftheAsdicdepartmentknownastheHigherSubmarineDetector (HSD)wouldtakeovertheset.Wearingearphones,hewoulddirectthesearch andcalculatethefiringtimeforanti-submarineweapons.WhentheAction Stationbellsounded,itwassolouditcouldwakethedead.Intheevent therewasafalseActionStationalarm,ashappenedfrequently,theAsdic crewweresubjectedtoridiculebytheothercrewmembers.Onmanyoccasions, thealarmwastherealthing.Inthisoccurrence,everyonewaspleased inknowingtheAsdicratingshadtheirearsopenwhiletherestofthe crewslept.OffthecoastofIreland,theseawaterisverypure.Attimes, noreverberationscouldbeheardwhensteamingthroughthisarea.This causedsomeconcerntooperatorswhowerenewtothelocality.Manysummoned theHSDtoassessthesituation.Inthisinstance,alltheHSDcoulddo istotakealookformthebackofthebridgetoseeiftherewasawake. Ifso,theoperatorwasinstructedtopingthewake.Muchtotheiramazement anechowouldbereceivedfromthewakebutnoreverberations.Thisprocedure verifiedthattheAsdicwasoperatingproperly." Whenbeinghunted,someGermansubsusedabubblemakingdeviceknown as'Pillenwerfer'.Thisalwaysreturnedanexcellentechobuttherewas noDoppler.Itproducedaperfectgraphontherangerecorderandthere wasalwaysthetemptationtodepthchargethetarget.Inpractice,itwas notagoodideatodepthchargedoubtfulechoes.Asmartsubmarinecommander, withalotanerve,wouldheadintotheareaofthedepthchargeexplosions. Heknew,thatwithinthisarea,nothingcouldbeidentifiedonAsdicfor fivetotenminutes,especiallyifthechargeshadbeenriggedfordetonation at250to500feet.Asafesheltercouldbehadevenifitwasonlytemporary. Inthe123set,theSend/Receivekeywasamovingarmarrangement.When thekeywaspressed,asmallmotorwasenergisedwhichthenmovedthearm fromareceivecontacttoasendcontact.Thisenergizedacoilandcapacitor bankthat,inturn,producedthepulseofelectricalenergyrequiredto firetheoscillator. IftheRangeRecorderwasoperating,thestyluswouldtravelfromthe leftsideoftherecorderface,tojustbeyondthepointwheretheecho wasmarkedonthepaper.Theflybackcontactwouldengageandthestylus wouldmovetotheleftsidewhereitwouldengagethestartcontactsand anothertransmissionwouldbeinitiated.Theslopeoftheechotraceon therecorderpaperwouldindicatethespeedoftheechocomingtowardor goingawayfromtheship.TheRangeRecorderOperatorwouldslopehisline oflighttomatchtheechotraceandcontinuouslyadjustthealignment untilthefiringbarontheoppositeendofthelineoflightmadethe firingcontact.Thisengagedthefiringmechanismoftheweaponssystem thatwasfitted. TheAS14rangerecorderwasusedwiththe123 ASDIC.Themaximumrangeonthisrecorderwas2,500yards.Clickonimage toenlarge.(CollingwoodHeritageCollection) Tochangetheoperatingfrequencyofthe123set,onewould havetoaccessthetransmittingpanel.Mountedhere,wasatoroidalwound coilwithabankofcapacitorsinthecentre.Thesecapacitorswerelinked withaheavycircularbarthatcouldbere-positionedsothatitadded orremovedcapacitorsfromthecircuit.Movingthebaradjustedtheresonant frequencyofthecoil/capacitorbankthuschangingtheoutputfrequency. Amatchingtransducerinthefrequencyrangeof14Kcsto22Kcswould havetobeinstalledaseachoscillatorwasmanufacturedtooperateat onlyonefrequency.Frequencyco-ordinationwasrequiredsothatescorts guardingaconvoywouldnothavetheirAsdicsetsinterferingwitheach other.Theoscillatorofthe123setwascomposedofthinquartzcrystals, cutintolengths,andthencementedandsandwichedbetweentwocircular steelplates.Thethicknessoftheplatesdeterminedtheoutputfrequency. Asubsequenttechnicalrefinementinthe123ASDICcproducedthemodel 123A.The'A'meantaminorimprovementintheamplifierandtheintroduction ofanautomaticsendkey. Ifitwasnecessarytochangeatransducer,atestwouldbedoneon thedometoseeifitwaswatertight.Thenutsholdingdownthecoverplate wouldbeslackenedoffandifnowaterappeared,theywouldberemoved alongwiththecoverplate.Next,thetransducerandoscillatorshaftwould beremovedandthedomewouldbesealedupwithablankcoverplate.After thetransducerwasreplaced,anotherwatertighttestwasperformedand theprocedurewasthenreversed. AsdiccouldbeusedtotransmitMorsecodeunderwater.Thiswasknown asSupersonicTelegraphy(SST).ItwasseldomusedandonlybetweenAsdic fittedshipsinharbourorifashipwasexercisingwithasubmarine.This communicationwasuni-directionalasthesubcouldnotreplyexceptby sendingupaflare.Morsecodeusedinthismannerwassentinplaintext andwasnotusedwhenengaginginsubmarinedetectionandattackprocedure. WhensendingMorseonanAsdicset,thedotsanddashesweresentmuch slowerratewhencomparedtowireless.Hence,specialtrainingwasrequired tousetheSSTtechnique.InAsdictrainingschool,instructorsfrowned uponusingSSTsinceitdetractedfromthemainpurposeoftheset--to searchforsubmarines. Someoperatorswereremarkableatbeingabletotelloneecho fromanother.Insomewaters,tidalripsandtemperaturegradientsreturned Dopplerechoesandsortingthisoutbecameimportant.Ifanoperatorplayed itsafebyreportingeverydubiousechotothebridge,heeventuallylost credibilityandnothingthathereportedwasbelieved.Thissituationnever wentonindefinitelyasthepoorsoulusuallyaskedforatransfer.It wastherecruitingprocessattheAsdicschoolsthatwasatfaultinmost cases.Somepeoplejustdidnothavethe'ears'forAsdicworkortheattention span.OnHaidatherewasacasewheretheHSDrequestedtoexchangeone oftheAsdicoperatorsforacook.Incivilianlife,thecookhadbeen atypewritermechanicthatmadehimsomewhatsuitableforthejob.The resultwasagoodcookandagoodoperator. Whileinconvoy,operatorsusedAsdictolistentotheenginesandpropellers ofothershipswhichwasveryhelpfulduringfogconditionsoronnights wheneverythingwaspitchblack.Tosaythatconvoyswerewellprotected byAsdicwouldbeanunderstatementespeciallyintheearlyyearsofthe war.Typically,aconvoyconsistingof30to50merchantshipscreated aperimeterdistanceof16to18miles.Intheory,theescortswerepositioned sothattheirAsdicbeamsoverlapped,providingunbrokencoverageofthe convoyperimeter.Therealityofthesituationwasdifferent.Anescort groupusuallyconsistedofonedestroyerandthreeoffourcorvettes,barely enoughtoprovidepropercoverageespeciallywithAsdicwhoserangelimits averagedaround2000yardsundernormalconditions.Whenconvoysdidhave sufficientescorts,notalltheAsdicsetswereusedsimultaneously.If twoshipswereoperatinginthesameareaandonthesamefrequency,there weretwooptions.Theprimaryoptionwouldmeanshuttingdownoneofthe Asdics.Secondarily,theoperatingfrequencycouldbechanged.Ifanactive setbrokedown,anotherescortshipcouldprovidesurveillanceuntilrepairs werecompleted.   EarlyASDICslsuchastnetype123,hadtheirtransducerstrainedby awheelmountedontheASDIChutbinnacle.(PhotocourtesyNational MaritimeMuseum)  123D Theimproved123knownasthe123Dwasdevelopedbyadding asecondmagneticcompassandbearingindicatoronthebridge,andaloudspeaker systemforthesonaroperatortocommunicatedirectlywithbridgepersonnel. Theupgradeappearstohaveoccuredsometimebetween1942and1943for someships,butwasneverfullycarriedoutinfavourofothermoreimproved sonarsets. Sideprofileofthe123Dbinnacletrainingcontrol.Thelampwould projectabeamoflighttowarsthecompassrose thusindicatingthe bearingofthetarget.  (CollingwoodHeritageCollection   123Dbridgearrangement.Clickonimagetoemlarge. (Collingwood HeritageCollection.. RelabelledbyKoji Kanori) Type124 (1934-37) ThissetwasfittedintoRiverClassdestroyersandwasanupdatedversion ofthe121set.Theseshipswereequippedwithagyrocompassthusthe trainingmechanismwaselectricallycoupledtothegyro.Thebearingof theoscillatorwasindicatedbyaneedlemovingaroundtheperimeterof acompass.Sincetheoscillatorwasdriveninslavewiththebridgecontrol, itwasimperativethateverythingwaslinedupbeforesailing.The124 oscillatorwasmountedinaretractabledome.JimFairnieofVictoriaB.C. describesAsdicoperationsonthistypeofvessel."OnsomeRiverClass destroyers,theAsdichutwasasoundproofcompartmentlocatedattheaft endofthelowermessdeckandwasonlyusedwhencruising.Actionstations wereinacompartmentattheaftendoftheupperbridge.InotherRiver Classdestroyers,allAsdicoperationswerecarriedoutfromthecabin onthebridge.ThiswasthecaseforHMCSOttawain1945asIwastheHSD atthetime." Type127D (1937) AccordingtoRearAdmiral BobWelland(Ret'd),thiswas thesetusedinFairmiles."Ithadtwotransducersfixedintoabombshaped casingandwasaffixedtotheship'sbottom.Onetransducerlookedahead andtheotherlookedabeamonbothsides.Therewasnobackplateonthe abeamtransducer,sobothsidesofthetransducersentoutthesamebeam. Thesearchprocedurewastousetheabeamtransmittersfornormalsearch. Whenanechowasheard,theshipwasturnedtopickupthetargetagain. Therewasafiftypercentchanceofturningthewrongway.Whentheecho wasrecovered,itsbearingwastakenandtheaheadtransmitterwasswitched onfromthebeamtransducer.Thetargetwasthentrackedbyweavingto andfroacrossthetarget.Someskippersbecameveryproficientatthis manoeuvre." 127DASDIC.controlequipmentfittedintheASDIC hutofHMCSRimouski,November1943.(PhotocourtesyCorvettesofthe RoyalCanadianNavy1939-1945)..  CloseupoftheA/S3BRangerecorderusedwith the127set. (hmsmedusa.org.uk) Type128and128A(1937) FrigatesandBangorswereequippedwiththe128set.Thiswas theretractabledomeversionoftheBritish127setandwassuperiorin performancetothe123Asinceitreliedonagyrocompassinsteadofa magneticcompassforbearingindication.Prioritywasgivenforthefitting ofthe128setinBangorsbecauseitwasoriginallyintendedthattheir primaryrolewastobeminesweeping,ataskthatrequiredaccuratenavigation tomarksweptchannels.Corvettes,whichweresupposedtobejack-of-all trades--suchasescort,minesweeper,andpatrolcraft,wouldhaveto sufficewiththelessaccurate123setwhichemployedamagneticcompass. From1941andonwards,bothclassesofshipsweretransferredtoocean escortduties.Itwasthecorvette,burdenedwithanoldergenerationAsdic, thatwasgiventhetaskofprotectingthemostvitalescortgroups,while theBangorsservedwiththelessimportantWesternLocalgroup.OnBangors, theAsdichutwaslocatedontheforwardandstarboardsideofthebridge. Trainingcontrolwasthesameasthatofa124set.InFebruaryof1943, theBritishAdmiraltyannouncedthatthe128setinRoyalNavyBangors wasbeingsupersededby128A.Type128Ahadatrainingmechanismthatwas manipulatedelectricallyratherthanmechanicallyandwaskeptontarget automaticallybytheshipsgyrocompass.TheRCNquicklyapprovedthesame changeforitsownBangors,however,ithadtowaitforaBritishpolicy statementbeforeworkcouldstart.Therewerenineteenversionsofthe 128setproducedduringWorldWar2. 132HydrophoneSet Thiswasthefirstdefensivesetandwasespeciallysuited forcruisersandotherlargewarshipssuchasaircraftcarriers.Forexample, takeacruiser.Duetoitssizeandspeed,itcouldnotaltercoursewithin theturningcircleofasubmarinesotheinstallationofAsdicwouldbe pointless.Thecruiser'smaindefencewasspeed.InplaceofAsdic,the cruiserwasfittedwithahydrophonelisteningsetthatcontinuallyswept theseatryingtolocatethehydrophoneeffect(H/E)fromasubmarine. Ithadalargeretractingdomethatoperatedelectricallywithtwotransducers operatingindependentlyofoneanother.Onewasusedon15Kcsfordetection andtheotherwasusedforlisteningon10Kcs.Eachhaditsownelectronics andrangerecorderswithscalesof5,000and2,500yardsrespectively. H/E,orcavitationnoiseisproducedfromthemotionofaturning propellerregardlessofwhetheritisasurfacevessel,asubmarineor atorpedo.Cavitationnoisesoundslikeapulsednoteandcanbeheard atagoodrangedependingonthesizeofthepropellerandthespeedof rotation.Forexample,atorpedoproducedaveryhighpitchedandfast rotationnoise.WhentorpedoH/Ewasheard,theoperatorwouldsweepback andforthrapidlyacrosstheloudestH/Eandreportthecentrebearing andmovement.TheOfficeroftheWatch(OOW)wouldthenaltercoursein anefforttopresentthesmallestpossibletargettothetorpedo.Onescorts, ifa'bowon'attackwasdetected,theOOWwouldincreasespeedandcarry outadepthchargeattack.Iftheassaultwas'sternon,'hewouldalter awayuntilthetorpedopassedfromastern,thenaltercoursetocarryout adepthchargeattack. OnCruisers,theprocedurewasslightlydifferent.IfH/Ewasdetected, sayontheforwardbeam,thetypicaltacticwastoaltercourse,passover thesubmarine,dropapatternofdepthcharges,thencontinueonacourse toclearthesubmarine.Whiledoingthis,informationonthesubmarine's positionwouldbepassedtotheescortwhowasmorecapableindealing withthesubmarine.IftheH/Ewaspickedupaftofthebeam,thecruiser wouldincreasespeedandalterawayfromthesubmarinewhilepassinginformation aboutthesubmarine'spositiontotheirescort. BobWelland,relatessomepersonalexperiencewithtorpedodetection. "TheAsdicoperatorswerealwaysalertfortorpedoes,anditbecamemore importantwhentheGermansintroducedanelectricallypropelledmodelknown as'Gnat'.ItspropellernoisecouldbeheardouttoamileandtheAsdic wasefficientatpickingitup.Ialwayshadtheoperatordoa360degree listeningsweepeveryfewminutes.Thissweep,withnopinging,onlytook abouttensecondstoexecute.DuringHaida'slastconvoyruntoRussia, thisprocedureproveditself.Wedodgedtwotorpedoes,havinghadtime toturntheshipintotheAsdicdetectedrush-noise."AftertheHSDreported thatthetorpedoeshadpassed,wewentontoattacktheU-boat." Type134 Firstintroducedin1939,thetype134ASDICusedahand-operated, retractable,tadpoleshapeddomewhichcouldnotbehoused.Insidethe domeweretwo,fixed, rubbercoveredtransducers.Thesingle-faced transducerfacedforwardwhilethedouble-facedtransducerfacedathwartships.  Thisdome,patternA400,consisted ofagunmetalandStaybritesteel frameworkcoveredwithaStaybritesteelskin.Thebodywassplitvertically intotwohalveswhicharelocatedbymeansofpinsonthefaceoftheafter sectionwhichfitintocorrespondingholesintheforwardsection.  Powertothesetwasprovidedbynine12voltbatteries. Thehigh powercircuitsinthesetconsumed1.5kwofpowerwhilethelowpower citcuitsconsumed200watts. The134 employedaHFMA(High-FrequencyMotorAlternator)and aresonantcircuittoproducethesoundpulseinthe14to22kHzband. Powersupplies forthe134setwere thesameasType127.Six variantswereproduced:134A(1941)formotorlaunches;134B(1942)which hadasingletrainabletransducer;Type134C(1942)whichwasadouble-faced trainabletransducerandAVC(AutomaticVolumeControl);Type134E(1944) hadcompassstabilizedtraining. Type134Shadareflectingplate inthedomeforechosoundingandpossibleuseforwreckdetection.Type 134F(1952)wasmodifiedtodetectsmallobjects. InFebruary1945,theRCNorderedthatallthetype134AASDICsets inthetype‘B’Fairmilesbeupgradedtoeither134Cor134Dmodels. AS3/Drecorderdiagram. This was thematingrecordertothe134Cset.Thedisplaywasapaperrecorderwith amechanicaldeviceontopwhichwouldcomputethecorrecttimetodrop depthcharges. 134Cwiringdiagram. 134C.Frontcoverof manualBR1663.Note thetrackingnumberintheupperrighthandcorner. ASDICtechnology wassecretduringWWII, soalldocumentationhadtobeaccounted for.  Clickonimagetoenlarge.Images providedbyAlanWatson Type135 Adocumentfrom1952indicatesthat RCN gatevesselswere equippedwithType135ASDIC, commonlycalledHarbourDefenceASDIC (HDA).ThistechnologywasdevelopedbytheRoyalNavy lateinWWI andwasfirstusedin1939.The135setfirstenteredservicein1942. Itwas aspecial,sea-bedmountedformoftheshipborneASDIC.  TheUShadaccesstothistechnologyandcalledtheirHDAa"Herald"- HarborEchoRangingAndListeningDeviceifleftontheseabed.Itcases wherethe seabedandtideswereunsuitable,theASDICcouldwould besecuredtothesideoftheship. The135setusedamagnetostrictiontransduceroperatingat15KHzand suspendedonalongshaft.ThecircuitrywasbasedontheModel758echo sounder.Aprintoutwasprovidedonatype758synchronousrecorder. ContributorsandCredits: 1)TinHats,OikskinsandSeabootsbyLathamB.Jenson. RobinBrassStudio2000.ISBN1-896941-14-1. 2)134recorderhttps://www.hmsmedusa.org.uk/medusa-history/special-equipment-for-d-day/ 3)134Cimages AlanWatson[alan(at)trinitystar.plus.com] BackToTableofContents October23/21