154:) B. S. Smith at Fairlie. The primary purpose, unsurprisingly for Fairlie, was to avoid a disadvantage with ASDIC; the minimum range of ASDIC left a 'hole' immediately ahead of the ship where submarines could not be tracked. A U-boat skipper could wait for this hole, then manoeuvre out of the path of the approaching destroyer. Gravity-dropped depth charges were large, slow-sinking and could only be dropped directly astern. A technique developed during the First World War had been to 'throw' charges sideways, with powered launchers, such as the Thornycroft mortar. By firing enough charges, a large pattern could be fired in the hope that the target would still be somewhere within it. The charges were so heavy that few reloads could be carried and the manual reloading time was so long that any submarine would have escaped before a second salvo. By firing these mortars ahead instead and by using a smaller, streamlined and faster-sinking projectile, the hope was to destroy a target submarine before ASDIC contact had been lost.
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with a more robust mounting on the ship. A similar problem beset the
Thornycroft projector which used heavy charges and was limited to only five, an inadequate pattern, if they were to be thrown far enough to still be ahead of the ship when they detonated. Fairlie's mortar bombs carried only 20 lb (9.1 kg) of explosive filling and used a lead ballast weight to keep them nose-down for faster sinking. A production bomb was expected to need around 60 lb (27 kg) of filling and to avoid the 'wasted' mass of pure ballast. They were detonated by a nose
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to which they were supposedly not taking part. They had faith in their ASDIC detection and the ability to aim a small number of powerful weapons close to a target but lacked political support to develop this further. The
Thornycroft weapon was too heavy to be automatically controlled and Hedgehog believed it to be unnecessary. Eventually the
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and were fired in pairs from each side, with a 0.1 second automatic delay between pairs firing, to reduce the recoil load on the mount. The launcher was well thought out for ease of operation and could be tilted horizontally, to allow re-loading with a simple trolley, rather than the vertical lift on
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and
Thornycroft team who favoured mortars (like Fairlie) but wanted them to be very heavy and the DMWD that had no faith in any ability to aim such a weapon and so favoured quantity over quality with large numbers of small Hedgehog projectiles. Fairlie were caught between these, in an offensive field
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Parsnip or 'Mortar A' was a response to the concerns over the small size of
Hedgehog and was a revival of the Fairlie Mortar, now with two rows of ten mortar tubes, each projectile carrying a 60 lb (27 kg) charge. Parsnip's tubes were aligned to fire a circular pattern, half from each row,
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the mortar onto the ASDIC bearing. The initial
Fairlie projectile was lightweight, limited by the power of the propellant charge and the strength of the deck to support the mortar. This was recognised to be too light for service use and a developed version would need to be heavier, more powerful and
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that the
Thornycroft had required, and which would have made it impossible to reload in most mid-Atlantic conditions. The propellant, at least for the trials, was a separate breech-loading cartridge, being easier to store separately from the less-sensitive but heavier projectiles, and allowing for
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period. These were one or two installations of three-barrelled forward-throwing heavy mortars. They were controlled directly by the ASDIC system, first the Type 147 sonar and tracked the target continuously. When the target was at the optimum location, they were fired automatically. They were
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controllable in bearing, depth and (for Limbo) range. The three mortars had a fixed relationship to each other, giving a triangular pattern around the target. The projectile was a heavy depth charge, of around 400 lb (180 kg) weight with 200 lb (91 kg) of
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in May. Fairlie's main work up to this time had returned to ASDIC, with the Type 144Q ASDIC in late 1942, then the Type 147. The Q attachment gave a paper recording of the target bearing, with a much narrower beam in plan view than the 144 set. The 147 set with its
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The mortar used two racks of ten tubes, mounted on the forecastle. The tubes were in line fore-and-aft, mounted on a swinging frame. Based on their work with ASDIC, this was roll-stabilised against the ship's motion and could also be used to
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coast before the war but was dispersed northwards to escape the fighting and risk of bombing, to the Fife
Boatyard in Scotland. The boatyard would provide facilities for ASDIC development and sometimes, with nearby
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Hedgehog took the opposing view to
Fairlie's vision: it used a large number of lightweight projectiles, and a 'scatter-gun' approach to targeting. This was much simpler to achieve; the projectiles were
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but was not large enough to build ships as a strategic shipyard. As the research establishment was established to develop the ASDIC sensor, rather than offensive weapons, this led to conflict with
247:'sword' transducer produced a horizontal 'fan' beam that could give a depth estimate. Both of these improved targeting for a weapon, unlike Hedgehog, capable of making use of this information.
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in
February 1943. Performance was thought to be adequate but Hedgehog was already well-established and the next generation, Squid, was almost ready for its trials on
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The
Fairlie Mortar's legacy was as a concept for small numbers of powerful, well-aimed weapons and as a step towards the development of
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projecting 24 small bombs from a platform, eventually became the predominant British ship-borne anti-submarine weapon in the war.
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The Fairlie Mortar was unsuccessful, as much due to politics as to technical failings. Although it may have been tested on
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had long been the navy's torpedo school and saw itself as having responsibility for offensive weapons.
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140:. Developments over the next few years were characterised by disagreements between the three groups.
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46:, each containing 20 lb (9.1 kg) of explosive. The Fairlie Mortar was not a success and '
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in September 1943, when a Hedgehog misfired and killed 16 of the crew, causing extensive damage.
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and the charges were intended to detonate simultaneously around the target, giving a combined
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42:. It projected small anti-submarine bombs simultaneously, ten from each side of the ship's
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easier trials of different propellant charges and projectile weights.
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Depth Charge!: Mines, Depth Charges and Underwater Weapons, 1914–1945
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charge was increased to 35 lb (16 kg) of the more powerful
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filling. They were shaped to sink quickly and predictably and had a
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British Destroyers & Frigates: The Second World War & After
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became embroiled and B. S. Smith was removed from control in 1942.
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to develop an anti-submarine weapon, the Fairlie Mortar, whilst
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Atlantic Escorts: Ships, Weapons & Tactics in World War II
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The Fairlie Mortar was developed by the civilian scientist (
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In January 1940, Fairlie was allowed a partnership with
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124:', based on Thornycroft's First World War mortar. The
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The Fairlie Mortar was developed by the Royal Navy's
334:"Explosive send off for Fairlie sub base after WW2"
653:World War II naval weapons of the United Kingdom
126:Department of Miscellaneous Weapons Development
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263:, the dominant anti-submarine mortar of the
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132:) were advocating the multiple
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58:Fairlie research establishment
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83:, a base for the trials ship
231:The apparatus was tested on
34:was an unsuccessful British
66:-research establishment at
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259:or 'Mortar B' and in turn
181:Director of Naval Ordnance
563:DiGiulian, Tony (2019).
397:, pp. 115–116, 119.
120:to develop the similar '
602:. Casemate Publishers.
581:. Seaforth Publishing.
548:. Seaforth Publishing.
68:Fairlie, North Ayrshire
648:Anti-submarine mortars
617:Lavery, Brian (2012).
596:Henry, Chris (2005).
565:"Britain ASW Weapons"
36:anti-submarine mortar
27:Anti-submarine weapon
496:Proc, Jerry (2019).
481:Proc, Jerry (2019).
130:Wheezers and Dodgers
38:design of the early
513:, pp. 119–120.
471:, pp. 54, 119.
428:, pp. 116–120.
274:clockwork time fuze
136:that would become
116:collaborated with
110:Vickers-Armstrongs
630:978-0-85-790542-0
609:978-1-84-415174-5
588:978-1-84-832015-4
555:978-1-84-415702-0
122:Five Wide Virgins
16:(Redirected from
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533:Bibliography
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623:. Birlinn.
245:beamforming
165:impact fuze
118:Thornycroft
642:Categories
288:References
282:shock wave
172:Kingfisher
99:Portsmouth
87:Kingfisher
44:forecastle
240:Ambuscade
235:Ambuscade
233:HMS
209:HMS
92:HMS
85:HMS
81:Ardrossan
575:(2012).
542:(2007).
265:Cold War
211:Escapade
187:Hedgehog
138:Hedgehog
48:Hedgehog
218:Parsnip
74:on the
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606:
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225:davits
205:Torpex
176:Vernon
151:boffin
114:Vernon
103:Vernon
94:Vernon
76:Dorset
270:Minol
261:Limbo
257:Squid
128:(the
64:ASDIC
50:', a
625:ISBN
604:ISBN
583:ISBN
550:ISBN
30:The
198:TNT
160:lay
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