Air­borne Anti-Sub­ma­rine War­fare

Siko­rsky Air­craft has been se­lected by the In­dian Navy to ful­fil its multi-role he­li­copter re­quire­ment for anti-sub­ma­rine and an­ti­sur­face war­fare mis­sions.

SP's NavalForces - - FRONT PAGE - Rear Ad­mi­ral Dr S. Kul­shrestha (Retd)

STAND­OFF ANTI-SUB­MA­RINE CA­PA­BIL­I­TIES CON­TINUE to be of vi­tal in­ter­est to the navies across the world. The cur­rent en­vi­ron­ment of lit­toral war­fare has once again brought in to sharp fo­cus the threat of the lurk­ing diesel sub­ma­rine and the means of tack­ling it by the use of he­li­copters and air­craft. Some of the note­wor­thy anti-sub­ma­rine war­fare (ASW) plat­forms are dis­cussed in brief in the suc­ceed­ing para­graphs.

Siko­rsky CH-148 Cy­clone

The Siko­rsky CH-148 Cy­clone is a twinengine, multi-role ship­board he­li­copter be­ing de­vel­oped by the Siko­rsky Air­craft Cor­po­ra­tion. CH-148 is de­signed for ship­board op­er­a­tions and is in­tended to re­place the CH-124 Sea King. It is equipped to search and lo­cate sub­marines dur­ing ASW. The In­te­grated Mis­sion Sys­tem and the Sonobuoy Acous­tic Pro­cess­ing Sys­tem are be­ing de­vel­oped by the Gen­eral Dy­nam­ics Canada. The sonar is an L-3 Hel­ras, the radar is a Tele­phon­ics AP­S143B, the Elec­tro Op­tic Sys­tem a Flir Sys­tems Safire III, and the ESM a Lock­heed Martin AN/ ALQ-210. CMC Elec­tron­ics pro­vides the flight man­age­ment sys­tem CMA-2082MH Air­craft Man­age­ment Sys­tem. It car­ries 2 x MK-46 tor­pe­does on a bomb rack BRU-14 mounted in fold­ing weapons py­lons and a door-arm mounted gen­eral pur­pose ma­chine gun.

Siko­rsky S-70B Sea­hawk

Siko­rsky Air­craft has been se­lected by the In­dian Navy to ful­fil its multi-role he­li­copter re­quire­ment for ASW and anti-sur­face war­fare (ASuW) mis­sions. The cur­rent re­quire­ment pro­jected is 16 with an op­tion from ad­di­tional 8. It has been de­vel­oped from the US Army’s UH-60A Black Hawk. The SH-60B car­ries a com­plex sys­tem of sen­sors in­clud­ing a towed mag­netic anom­aly de­tec­tor and air-launched sonobuoys. Other sen­sors in­clude the APS-124 search radar, ALQ-142 ESM sys­tem and op­tional nose-mounted for­ward look­ing in­frared tur­ret. It car­ries the MK-46, MK-50, or MK-54 tor­pedo, AGM-114 Hell­fire mis­sile, and a sin­gle cabin-door-mounted M60D/M240 7.62mm (0.30 in) ma­chine gun or GAU-16 .50 in (12.7mm) ma­chine gun. The In­dian Navy’s S-70B vari­ant is ex­pected to fea­ture avion­ics and flex­i­ble, open ar­chi­tec­ture weapons man­age­ment sys­tems, which are equipped with an ad­vanced sonar, 360-de­gree search radar, mod­ern air-to-sur­face mis­siles and tor­pe­does for ASW mis­sions.

Agus­taWest­land AW101

The Agus­taWest­land AW101 is a medi­um­lift he­li­copter used in both mil­i­tary and civil applications. The AW101’s nav­i­ga­tion sys­tem in­cludes a GPS re­ceiver and in­er­tial nav­i­ga­tion sys­tem, VHF Omni di­rec­tional ra­dio range, in­stru­ment land­ing sys­tem, tac­ti­cal air nav­i­ga­tion sys­tem and au­to­matic di­rec­tion find­ing. For safety, the air­craft is equipped with ob­sta­cle and ter­rain avoid­ance warn­ing sys­tems and traf­fic col­li­sion avoid­ance sys­tem. The AW101 is equipped with the Blue Kestrel search and de­tec­tion radar, which is ca­pa­ble of 360-de­gree scan­ning and can de­tect small tar­gets as far as 25 nau­ti­cal miles. Most vari­ants of the AW101 are equipped with self-de­fence sys­tems. Two hard points are present on the un­der­side of the air­frame on which it can carry four Sting Ray tor­pe­does or MK-11 Mod 3 depth charges.


The Air­bus/Agus­taWest­land pro­duced NH90 is de­signed to ful­fil a NATO staff re­quire­ment for a multi-role, medi­um­sized mil­i­tary he­li­copter for both land and mar­itime op­er­a­tions. NH90 is the first he­li­copter in the world to be equipped with full fly-by-wire flight con­trols. NH90 is ei­ther fit­ted with Rolls-Royce Tur­bomeca RTM322 or Gen­eral Elec­tric T700E power plants. The NH90 fea­tures a range of cus­tomis­able avion­ics sys­tems, de­pen­dent on cus­tomer se­lec­tion and pur­pose. The naval vari­ant is out­fit­ted with dip­ping sonar and sonobuoy pro­cess­ing equip­ment.

Boe­ing P-8 Po­sei­don

The Boe­ing P-8 Po­sei­don is a mil­i­tary air­craft de­vel­oped for the US Navy by Boe­ing De­fense, Space and Se­cu­rity. The P-8 con­ducts ASW, ASuW and ship­ping in­ter­dic­tion, along with elec­tronic sig­nals in­tel­li­gence role. The P-8 can carry tor­pe­does, depth charges, SLAMER mis­siles, Har­poon anti-ship mis­siles, and other weapons. It is able to drop and mon­i­tor sonobuoys. In­dian Navy has ac­quired eight P-8I which have been adapted as per In­dia’s op­er­a­tional re­quire­ment.

ASW Ar­ma­ment

The ASW ar­ma­ment car­ried to­day by mar­itime air­craft and he­li­copters in­cludes light­weight tor­pe­does, depth charges and bombs. Depth charges have again come into fo­cus be­cause of the ASW threat in lit­torals. These can be very ef­fec­tively utilised for flush­ing out the lurk­ing diesel sub­marines. Two depth charges are wor­thy of men­tion, these are the MK-11 depth charge of UK and the BDC 204 depth charge of Swe­den.

The MK-11 depth charge was de­vel­oped by Bri­tish Aero­space (now BAE Sys­tems) for air de­liv­ery from mar­itime air­craft and he­li­copters. The MK-11 depth charge was de­signed for shal­low wa­ter op­er­a­tions against sub­marines on the sur­face or at periscope depths. It is fully com­pat­i­ble for car­riage and re­lease from a wide range of ASW he­li­copters and fixed-wing mar­itime pa­trol air­craft. The Mod 3 ver­sion in­cor­po­rates a 4mm mild steel outer case and nose sec­tion, which is de­signed to with­stand en­try into the wa­ter at high ve­loc­i­ties with­out dis­tor­tion. It has been cleared for car­riage on Lynx, Mer­lin, NH90, Sea King and Wasp he­li­copters.

The BDC 204 depth charge was de­vel­oped by Bo­fors Un­der­wa­ter Sys­tems (now Saab Dy­nam­ics) for air de­liv­ery from mar­itime air­craft and he­li­copters of the Swedish Navy. The depth charge can be de­ployed in pat­terns, with dif­fer­ent depth charges set to det­o­nate at dif­fer­ent depths to achieve pro­found shock and dam­age to sub­marines. They have been cleared for car­riage on the Boe­ing Ver­tol 107 he­li­copter and CASA C-212 Avio­car mar­itime pa­trol air­craft.

Air Launched Tor­pe­does

Few of the prom­i­nent air launched tor­pe­does are de­scribed be­low:

Stingray is a LWT man­u­fac­tured by BAE Sys­tems. It has a di­am­e­ter of 324mm, weight of 267 kg, and length of 2.6 me­tres. Its speed is 45 knots with a range of 8 km and its war­head is 45 kg of Tor­pex. It can dive up to 800 me­tres. Stingray is fed with tar­get data and other as­so­ci­ated in­for­ma­tion prior to its launch, after en­ter­ing wa­ter it searches for tar­get au­tonomously in ac­tive mode and on ac­quir­ing the same at­tacks it. It is car­ried by Nim­rod air­craft. Stingray Mod 1 is re­ported to have a shaped charge war­head and im­proved shal­low wa­ter per­for­mance.

MK-46 Mod 5 tor­pedo is the main­stay of US Navy’s air launched light­weight tor­pe­does. It is man­u­fac­tured by Al­liant Tech Sys­tems. It has a di­am­e­ter of 324mm, length of 2.59 me­tres, with a weight of 231 kg. It runs on Otto fuel, has a range of 11 km with a speed of 40 kts, and can dive up to 365 me­tres. It has a PBXN-103 war­head of 44 kg. It has an ad­vanced dig­i­tal com­puter con­trol sys­tem with a built in logic and tac­tics for search and re-at­tack. It has ef­fec­tively per­formed in both deep and shal­low wa­ters and can at­tack the nu­clear as well as the smaller diesel sub­ma­rine. Over 25,000 MK-46 tor­pe­does have been sup­plied to cus­tomers un­til date. In­ter­est­ingly the Chi­nese YU-7 tor­pedo is said to have been de­vel­oped from the MK-46 Mod 2.

The MK-54 light­weight tor­pedo is a hy­brid of tech­nolo­gies taken from MK-46,

Depth charges have again come into fo­cus be­cause of the ASW threat in lit­torals. These can be very ef­fec­tively utilised for flush­ing out the lurk­ing diesel sub­marines.

MK-48 and MK-50 tor­pe­does. It is sup­posed to have hom­ing and war­head of the MK-50 and propul­sion pack­age of the MK-46 tor­pedo. It has in­cor­po­rated COTS pro­cess­ing tech­nolo­gies for an ad­vanced guid­ance and con­trol sys­tem. It is stated to have so­phis­ti­cated shal­low wa­ter ca­pa­bil­i­ties for lit­toral threats. The MK-54 tor­pedo has been fi­nalised for P-8I air­craft by In­dia.

The A244/S de­vel­oped by WAAS and cur­rently man­u­fac­tured by the Euro Torp con­sor­tium is a 324mm-di­am­e­ter, 2.8-me­tre-long, and 244-kg weight tor­pedo. It has a cruise/surge speed of 30/39 knots, with a range of 6 km and depth up to 600 me­tres. Its hom­ing head can func­tion in mixed, ac­tive or pas­sive modes. It has spe­cial sig­nal pro­cess­ing to dis­tin­guish tar­get from de­coys.

A244/S Mod 3 is the lat­est up­grade of the A244/S. It has more pow­er­ful propul­sion bat­tery, with an in­creased num­ber of cells, which en­sures a 50 per cent in­crease in the en­durance of the weapon to 13.5 km. It has an Ad­vanced Dig­i­tal Sig­nal Pro­ces­sor mod­ule to counter so­phis­ti­cated tor­pedo coun­ter­mea­sures. The hom­ing head has pre­formed multiple trans­mis­sion and re­cep­tion beams and multi-fre­quency op­er­at­ing ca­pa­bil­ity. It can clas­sify and track sev­eral tar­gets si­mul­ta­ne­ously, and dis­crim­i­nate be­tween the tar­get and coun­ter­mea­sures.

MU90/Im­pact is in mass pro­duc­tion for 6 ma­jor NATO and al­lied coun­tries. The MU90/Im­pact tor­pedo is 323.7mm NATO Stan­dard cal­i­bre, 2.85mm long with a weight of 304 kg. It is pow­ered by an alu­minium-sil­ver ox­ide sea­wa­ter bat­tery us­ing dis­solved sodium-diox­ide pow­der as elec­trolyte with a closed-loop elec­trolyte re-cir­cu­la­tion sys­tem, the tor­pedo is pro­pelled by an elec­tron­i­cally con­trolled high-RPM brush­less mo­tor driv­ing a skewed multi-blade pump jet propul­sor al­low­ing a con­tin­u­ously vari­able tor­pedo speed au­to­mat­i­cally se­lected by in built logic of the tor­pedo. The con­trol and guid­ance elec­tron­ics has em­bed­ded op­er­a­tional and tac­ti­cal soft­ware in­clud­ing the sig­nal pro­cess­ing, the data pro­cess­ing, and the tor­pedo guid­ance al­go­rithms, which en­able the MU90 to con­tin­u­ously self-adapt its con­fig­u­ra­tion and tac­tics. The in­er­tial sys­tem is based on ‘ strap-down’ tech­nol­ogy en­abling all-at­ti­tudes ca­pa­bil­ity in­clud­ing bot­tom fol­low­ing ca­pa­bil­ity. The war­head con­sists of V350 ex­plo­sive, fully in­sen­si­tive, shaped charge war­head, with an im­pact type ex­ploder in­cor­po­rat­ing two me­chan­i­cal and six elec­tri­cal in­de­pen­dent safety de­vices.

Low Cost Anti Sub­ma­rine Weapon (LCAW) A200/A is a minia­ture tor­pedo de­vel­oped by WASS. LCAW has been de­vel­oped as an in­ter­me­di­ary be­tween air launched tor­pe­does and con­ven­tional depth charges. It is a low-cost op­tion, which pro­vides propul­sion and guid­ance to a depth charge with­out the costs of a tor­pedo. The air dropped ver­sion A200/A is de­ployed from aerial sonar­buoy dis­pensers. The weapon is pri­mar­ily de­signed to en­gage tar­gets in shal­low wa­ter, like midget sub­marines. The A200/A ver­sion has a length of 914.4mm, weight of 12 kg, and a di­am­e­ter of 123.8mm. The war­head is a 2.5 kg PBX shaped charge and the LCAW has an op­er­at­ing depth from 15 me­tres to 300 me­tres. It has a speed of about 18 knots with a range of 2 km.

In­dian Navy

The In­dian Navy has or­dered eight in num­ber of the P-8I Nep­tune ver­sion of the Boe­ing P-8 Po­sei­don. The air­craft in­cludes six ad­di­tional body fuel tanks for ex­tended range from Mar­shall Aero­space. In-flight re­fu­elling is via a re­cep­ta­cle on top of the for­ward fuselage, just aft of the cock­pit. In or­der to power the ad­di­tional elec­tron­ics, the P-8 has an 180 kVA elec­tric gen­er­a­tor. The P-8 uses data fu­sion soft­ware to com­bine its var­i­ous sen­sors for tar­get track­ing.

The Bharat Elec­tron­ics Lim­ited Data Link II com­mu­ni­ca­tions al­lows the P-8I to ex­change tac­ti­cal data be­tween In­dian Navy air­craft, ships and shore es­tab­lish­ments. The P-8I fea­tures an in­te­grated BELde­vel­oped IFF sys­tem. In­dia has pur­chased AGM-84L Har­poon Block II mis­siles and MK-54 all-up-round light­weight tor­pe­does for the P-8I. The air­craft car­ries Raytheon APY-10 multi-mis­sion sur­face search radar and is likely to have ad­vanced air­borne sen­sor sur­face search radar and SIG­INT pack­age in the fol­low-on pro­gramme. It has five in­ter­nal and six ex­ter­nal sta­tions for AG­M84H/K SLAM-ER, AGM-84 Har­poon, Mark-54 tor­pedo, mis­siles, mines, tor­pe­does, bombs and a high alti­tude anti-sub­ma­rine war­fare weapon sys­tem. Six have been de­liv­ered and re­main­ing two will be de­liv­ered this year.

IN has se­lected Siko­rsky Air­craft Corp., a sub­sidiary of United Tech­nolo­gies Corp, to ful­fil the multi-role he­li­copter re­quire­ment for ASW/ASuW. Ne­go­ti­a­tions will now com­mence to pro­cure 16 S-70B Sea­hawk he­li­copters, with an op­tion for eight ad­di­tional air­craft along with a com­plete lo­gis­tics sup­port and train­ing pro­gramme. IN has a re­quire­ment for 120 NMRH in the 9-12.5 tonnes cat­e­gory. The NMRH is en­vis­aged to carry out the ASW as well as the ASuW roles.

(Top) Sting Ray Mod 1 light­weight tor­pedo; (above) P-8A Po­sei­don as­signed to the Bureau of Air Test and Eval­u­a­tion Squadron (VX) 20 repli­cates the char­ac­ter­is­tics of an MK-54 tor­pedo

PHO­TO­GRAPHS: BAE Sys­tems, US Navy

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