Misplaced Pages

#778221

62-563: The Short SB.6 Seamew was a British aircraft designed in 1951 by David Keith-Lucas of Shorts as a lightweight anti-submarine platform to replace the Royal Navy Fleet Air Arm (FAA) 's Grumman Avenger AS 4 with the Reserve branch of the service. It first flew on 23 August 1953, but, due to poor performance coupled with shifting defence doctrine, it never reached service and only 24 production aircraft had flown before

124-414: 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

186-422: 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

248-957: 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

310-431: 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

372-401: A device intended for countermining , 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

434-467: A formation display. The fourth Seamew prototype ( XE175 ) was flown by Runciman for a series of sales tours in 1956 to Italy (March), Yugoslavia (April) and West Germany (May). It was this same aircraft in which Runciman was killed when it crashed during the Sydenham (Belfast) Air Display on 9 June 1956, when he attempted a loop. Rumours that the crash had been caused by a material failure were current at

496-768: A higher weapons load. The pilot and observer were located in tandem cockpits located high up in the front of the deep, narrow fuselage, creating a decidedly "curious" profile. They sat atop the Armstrong Siddeley Mamba turboprop in front and the weapons bay to the rear of them. The design had originally called for the tried and tested Rolls-Royce Merlin piston engine but the Royal Navy had made it policy to phase out piston engines, in order that supplies of highly flammable high octane aviation fuel need not be carried in large quantities on ships. The turboprop engine also caused less airframe vibration so that

558-406: 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

620-543: 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

682-602: A patrol plane or deployed by an anti-submarine missile from a surface ship, or another submarine, located 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

SECTION 10

#1732780851779

744-467: 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

806-640: A political scientist and Master of Darwin College, Kent , died in 1996. He was also the brother of Social Work Professor Alan Keith-Lucas . Keith-Lucas is the grandfather of BBC weather girl Sarah Keith-Lucas , who did a "Weatherworld" programme on her grandfather's work on the Short SB.4, the prototype of which is now with the Ulster Aviation Society. Depth charge Depth charges were developed during World War I , and were one of

868-626: A potential hazard to the dropping ship. The design work 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

930-440: 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

992-554: 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

1054-486: 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

1116-508: 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

1178-670: 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

1240-613: 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

1302-647: The Short SB-5 research aircraft. Other projects included the Short Belfast heavy freighter, the Short Skyvan , and the SD-330 and SD-360 freight-commuter series. The Short SB.1 was a shoulder-wing, cantilever, tailless monoplane glider designed by David Keith-Lucas and Professor Geoffrey T.R. Hill and built by Shorts as a private research venture to test the concept of the aero-isoclinic wing; it

SECTION 20

#1732780851779

1364-595: 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

1426-721: The FAA were scrapped at RNAS Lossiemouth , and the other 11, complete and awaiting delivery, were scrapped at Sydenham. The last surviving Seamew, XE180 which had been purchased by Shorts on 31 August 1959 for ground instruction at its Apprentice Training School, was scrapped in 1967. The Rolls-Royce Heritage Trust has preserved a Seamew engine, which is found at its Coventry branch. Data from General characteristics Performance Armament Avionics Aircraft of comparable role, configuration, and era Related lists David Keith-Lucas David Keith-Lucas CBE FRAeS (25 March 1911 – 6 April 1997)

1488-542: 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

1550-837: The Seamew", and that its performance in crosswinds was "outstanding". An order was placed in February 1955 for 60 aircraft (split evenly between the FAA and RAF ), with Seamew XA213 successfully completing carrier trials on HMS Bulwark in July and December 1955. Naval service flight trials with two Seamews were carried out with 700 Naval Air Squadron in November 1956, which included catapult trials and around 200 takeoffs and landings on HMS Warrior . The RAF lost interest after four Mk 2s were built with three of them converted to AS1 standard;

1612-824: The Second World War. Although specifically designed for naval operations, the Seamew was also intended for land-based use by the RAF. It was to be suitable for mass production and operation by the Air Branch of the Royal Naval Volunteer Reserve (RNVR) . This specification was in response to the alarming increase in capabilities of the Soviet submarine forces following the Second World War . Three prototypes were ordered in April 1952 and

1674-640: The Senate of the Queen's University, Belfast . In 1965 he was appointed Professor of Aircraft Design at the College of Aeronautics, Cranfield, later the Cranfield Institute of Technology , and welded together the departments of Aerodynamics, Aircraft Design and Flight into a new College of Aeronautics. In 1972, he became its Professor of Aeronautics and also Chairman of the College, which now forms part of Cranfield University . On retirement in 1976, he

1736-445: 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

1798-468: 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

1860-767: 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

1922-399: 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

Short Seamew - Misplaced Pages Continue

1984-399: 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

2046-464: 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

2108-402: The event of ditching. The weapons bay was 14 ft long and 3 ft wide. By omitting the rotating radar scanner, it could be extended to 17 ft in order to carry longer weapons. The handling characteristics of the Seamew were poor. The prototypes were heavily modified with fixed leading-edge slats, slots added in the trailing-edge flaps, alterations to the ailerons and slats added to

2170-410: The first flight ( XA209 ), piloted by test pilot Sqn. Ldr. Walter J. "Wally" Runciman, took place on 23 August 1953. This same aircraft, also piloted by Runciman, took part in the 1953 Farnborough Airshow three weeks later. In 1954 both XA209 and the second prototype XA213 took part at Farnborough, where the following year both prototypes and two production AS Mk 1 models ( XE171 and XE172 ) gave

2232-496: 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 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

2294-582: The fourth ( XE175 ) was flown by S/L W. "Wally" J. Runciman for a series of sales tours in 1956 to Italy (March), Yugoslavia (April) and West Germany (May). Meanwhile, the FAA decided that the RNVR Avengers would be replaced by Seamews, but only four had been taken on charge by the time the RNVR squadrons were disbanded in March 1957 in keeping with the 1957 Defence White Paper , before any Seamews were allocated to them. Seven aircraft eventually delivered to

2356-544: 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

2418-535: 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

2480-428: The observer had a good field of view for spotting surface vessels even when in level flight. The large, broad-chord wings featured power-folding and pylons for the carriage of rockets , depth charges , flares and small bombs . The large, slab-like tailplane was mounted high on the vertical stabiliser, requiring the rudder to be split into upper and lower sections. The fixed undercarriage legs could be jettisoned in

2542-428: 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

Short Seamew - Misplaced Pages Continue

2604-416: The pilot could be sat directly over it with the absence of a piston engine ignition system which would have interfered with the radar scanner mounted below the engine housing. For simplicity, and so that a nosewheel would not obscure the forward field of the radar scanner, a fixed tailwheel undercarriage was used. The long stroke necessary on the main undercarriage to allow for heavy deck landings while giving

2666-424: 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

2728-457: The project was cancelled. It has been described as a "camel amongst race-horses". The Short Seamew was selected to fulfill Admiralty Specification M.123D for a simple, lightweight anti-submarine aircraft capable of unassisted operation from any of the Royal Navy 's aircraft carriers in all but the worst of conditions, in particular escort carriers which the UK still had in considerable numbers from

2790-411: The radar scanner and propeller adequate clearance from the ground resulted in an alarming attitude on the ground and the cockpits mounted at a seemingly perilous height. For landing the tailwheel extended so it could land at a more level attitude. The pilot and observer sat very far forward in order for the pilot to have a reasonable field of downward vision for takeoff and landing and so that both he and

2852-508: 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

2914-595: 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

2976-400: 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

3038-400: 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

3100-508: The tailplane roots. Although something of an improvement over the initial models, the handling was never wholly satisfactory. Arthur Pearcy wrote "only Short Brothers' test pilot Wally Runciman seemed able to outwit its vicious tendencies and exploit its latent manoeuvrability to the limit." The stall speed of the Seamew was 50 knots and it required only 50% of engine power to maintain flight. Runciman said "take off and landing are simple and straightforward", "it is, in fact, impossible to bounce

3162-408: 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

SECTION 50

#1732780851779

3224-512: The time, but the accident investigation board did not confirm them. The MR Mark 2 for use by Coastal Command was similar in every respect to the AS Mk 1 except that it was optimised for land-based use from hastily prepared airstrips. Naval equipment was deleted although manual wing folding was retained. Slightly heavier than the naval version, the MR Mk 2 had oversize low pressure tyres and could carry

3286-527: 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

3348-534: Was a British aeronautical engineer. David Keith-Lucas was one of the sons of Alys Hubbard Lucas and Keith Lucas , who invented the first aeronautical compass. After the death of Keith Lucas in 1916, his wife Alys changed the family name, and, as Alys Keith-Lucas, edited a short book giving his background together with reminiscences of him and a list of his publications. David Keith-Lucas was educated at Gresham's School , Holt , and at Gonville and Caius College, Cambridge , where he read engineering. David Keith-Lucas

3410-496: Was an apprentice and engineer with C.A. Parsons and Co. from 1933 to 1940, then moved to the aerodynamics office of Short Brothers, Rochester, famous for their flying boats, becoming their chief aerodynamicist in 1944. From 1945 to 1965 he was with Short Brothers and Harland Ltd in Belfast, holding the posts of chief designer, technical director and research director. His work included research on swept-wings which culminated in

3472-543: Was appointed Professor Emeritus and awarded an Honorary Doctorate. In 1942, Keith-Lucas married firstly Dorothy de Bauduy Robertson, and they had two sons and one daughter. In 1979, he and his wife visited Kitty Hawk , North Carolina, where the Wright brothers had made their flights. His wife was killed there in a road accident, and Keith-Lucas himself was seriously injured. In 1981, he married secondly Phyllis Everard Whurr. Keith-Lucas's brother, Professor Bryan Keith-Lucas ,

3534-513: 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

3596-439: 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

3658-543: 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

3720-427: 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

3782-673: Was the first aircraft to incorporate this feature. After initial tests, at the end of which the SB.1 crash-landed as a result of problems while being towed behind the Short Sturgeon , the SB.1 was further developed into the Short SB.4 Sherpa , powered by two Blackburn Turbomeca Palas turbojet engines. In 1951, Keith-Lucas designed the Short SB-6 Seamew as a lightweight anti-submarine platform. While in Belfast, he served on

SECTION 60

#1732780851779

3844-475: Was with aircraft bombs attached to lanyards which triggered them. A similar idea 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

#778221