"Why the RN's AA accuracy was so poor..." Topic
8 Posts
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4th Cuirassier | 14 Mar 2020 7:37 a.m. PST |
Looking around for pictures of a Mark I HACS I found an interesting summary article. HACS continued to evolve through to the outbreak of the war, with the HACS Mark IV being the latest in service in 1939. In this and all earlier versions, the HACS calculated the required 'aim-off' with the assumption that the target's height, speed and course were constant and that the target's speed had been correctly estimated. As can be easily seen, this design concept falls apart for any other kind of air attack except for high-level bombing. In addition, the inherent lag-times built into the system meant that it was too slow to deal with the higher-speed aircraft that started coming into service late in the 1930s. the gunnery report of HMS Illustrious for the attacks in January 1941 stated that HADFAS and, by extension, the HACS itself, was of no use against dive bombers. It should be noted that during these attacks Illustrious expended about 3,000 rounds of 4.5-inch HE at an average of 12 rounds per gun per minute, yet she suffered eight bomb hits.9 This anecdote may help the reader to understand why she and other British ships of the time suffered so badly from air attacks without inflicting commensurate casualties upon their attackers. A noteworthy problem not readily apparent was that the pre-war British aircraft that the HACS and gunnery crews trained with were significantly slower than contemporary Axis attack aircraft. Thus, the experience the crews had prior to the start of the war was nearly worthless, a fact driven home during the early battles of the war, where few aircraft were destroyed by weapons controlled by HACS link This makes me think I need to rethink the accuracy I assign to early war RN AA…. |
Blutarski | 14 Mar 2020 10:09 a.m. PST |
Tony's Navweaps article is a good one, but omits some details. At the beginning of the Pacific war, the USN had several AA director systems in service – Mk 19, Mk 28/33 and Mk 37. The Mk 37 was a superb piece of kit for the time, but only just coming into service at the time of Pearl Harbor. The Mk 19 was a much older and far more primitive system than the Mk 37. The following data regarding USN naval AA director outfits circa 1942 will give an idea of the distribution of these systems in the Pacific fleet over the course of 1942. May 1942 – Battle of Coral Sea Of 19 ships present for action with USN TFs 16 and 17, > 1 ship had no AA director fitted. > 2 Commonwealth ships had early HACS directors fitted. > 4 had Mk 19 directors. > 10 had Mk 33 directors. > 2 ships had Mk 37 directors. Of the 120 5/38, 5/25 and 4in AA guns present at the battle: > 8 guns had no AA fire control. > 12 guns were under control of early HACS directors > 36 guns were under control of Mk 19 directors. > 56 guns were under control of Mk 33 directors. > 8 guns (approx 7 pct) were under control of Mk 37 directors - – - June 1942 – Battle of Midway Of 28 ships present for action with USN TFs 16 and 17, > 2 ships had no AA directors fitted. > 3 had Mk 19 directors. > 12 had Mk 33 directors. > 11 ships had Mk 37 directors. Of the 164 5/38 and 5/25 guns present at the battle: > 16 guns had no AA fire control. > 16 guns were under control of Mk 19 directors. > 76 guns were under control of Mk 33 directors. > 56 guns (approx 34 pct) were under control of Mk 37 directors - – - October 1942 – Battle of Santa Cruz Of 23 ships present for action with USN TFs 16 and 17: > 1 ship had no AA director fitted. > 3 had Mk 19 directors. > 9 had Mk 33 directors. > 10 had Mk 37 directors. Of the 156 5/38 and 5/25 guns present at the battle: > 8 guns had no AA fire control. > 16 guns were under control of Mk 19 directors. > 44 guns were under control of Mk 33 directors. > 88 guns (approx 56 pct) were under control of Mk 37 directors - – - AS can be seen, even as late as October 1942, the Mk 37 had still not surpassed 50pct in terms of AA director systems fitted to ships of the carrier task forces. That, of course, rapidly changed with the flood of new construction reaching the fleet starting in 1943. FWIW. B |
Blutarski | 14 Mar 2020 10:36 a.m. PST |
Re HACS related background materials, allow me to recommend: British Mechanical Gunnery Computers of World War II by Allan G Bromley Technical Report 223 – January 1984 (I found this document as a free pdf on the web a while ago, but a quick search this morning was unsuccessful in locating it; a more diligent search, however, should turn it up.) - – - HACS: Debacle or Just in Time? by Peter Marland Warship 2017, p.107-125 ("provides a history of the development of the Royal Navy's controversial prewar High Angle Control System (HACS), together with an informed analysis of its strengths and weaknesses.") FWIW B |
HMS Exeter | 14 Mar 2020 4:43 p.m. PST |
link Everybody's AA systems stunk at the start of WWII. That's why the Bismarck was unable to effectively oppose the Swordfish. In order to be effective the AA system had to: Accurately gauge the target range. Accurately gauge the target altitude. Accurately track the target allowing rate of change info. Effectively use this info to anticipate targets future position. Effectively relate this info, in real time, to the weapons mounts. Have a weapon that effectively balances rate of fire with hitting power. Calculate and lay the weapon to hit the target. Fuse the outgoing ammunition to detonate close to the target. And do them all nearly perfectly. At the end of the Pacific War the US had radar range and tracking. A system that auto fused the ammo as it came up to the mount. The superlative 5"/38 and the 40mm. They also had the excellent 20mm, but these weren't as director dependent. And they had proximity fusing, used in varying percentages of the total outgoing ordnance. Had they not, the Kamikaze menace would gave been much worse. |
Blutarski | 14 Mar 2020 5:01 p.m. PST |
The Swordfish attack upon Bismarck was actually kind of an unusual case. A year later, the Swordfish fared much worse during the Channel Dash. B |
4th Cuirassier | 15 Mar 2020 6:26 a.m. PST |
Does anyone have a photo of the Mark I HACS? Hood had these in 1941 and on models ad kits they are usually depicted as a truncated closed cylinder with rangefinder poles sticking out the side. If my reading is correct they were in fact open-topped, which in wargaming scales says they should be painted differently. |
4th Cuirassier | 16 Mar 2020 2:17 a.m. PST |
@ Blutarski Wasn't it fighters rather than improved German AA accuracy that brought that about? It was actually the same officer in charge of both attacks. |
Blutarski | 17 Mar 2020 8:53 a.m. PST |
Hi 4C, Your post drove me to go check my library, as I was working from memory, which cannot be relied upon in every circumstance. According to the book "Fiasco" by J D Potter (a dated secondary source – 1970): Esmonde's Swordfish was initially damaged by a fighter, then lost a lower wing passing through an 11-inch AA barrage put up by one of the accompanying battleships as he made a run against Prinz Eugen. Esmonde was shot down by a direct hit from Prinz Eugen AA immediately after dropping his torpedo. Behind Esmonde was Rose. Cockpit smashed and fuel tank hit by German cannon shells (presumably from fighter). No fire. Torpedo nevertheless dropped. Rose switched to emergency fuel tank. Rose flew directly over Prinz Eugen and through her AA fire at minimum height, force-landing about a half mile beyond. It is unclear from the text whether the aircraft was brought down by fighter attack or by Prinz Eugen's AA. Kingsmill piloted the third Swordfish in Esmonde's flight of three. Aircraft was hit and damaged by fighter attack, but still flying. Further damage suffered by AA fire as they flew over the outer screen of ships. Then again attacked by several FW190's, with a cannon shell wounding Kingsmill and his observer. Kingsmill had to set up a new attack approach, which forced him to again pass through the screen's AA fire. He did manage to launch his torpedo toward Prinz Eugen on this second pass, but AA fire badly damaged the engine, greatly slowing the a/c. As the a/c, now in tatters, slowly lost altitude, the engine caught fire, followed by port wing. Kingsmill managed to ditch just outside the German AA screen. Of the second flight of three Swordfish, led by Thompson, one was apparently seen to blow up while under attack by a German fighter. The circumstances surrounding the loss of other two Swordfish are unknown. Some thoughts on the differences between the Bismarck event and the Channel Dash experience: > In the case of Bismarck, the attacking Swordfish were able to drop out of very low overcast, taking Bismarck by relative surprise. > Bismarck's light AA battery consisted, in part, of manually controlled twin-barreled SEMI-AUTOMATIC 37mm with a very low RoF (hard to believe, but true). > The Swordfish attacking Bimarck were flying into a gale force wind blowing from a forward quarter; this served not only to reduce their true speed over ground to about 50 knots, but also caused the a/c to fly in an awkwardly crab-wise fashion. I'm guessing that both factors served to greatly mislead the aim of the German gunners. > In the case of the Channel Dash attack, the Swordfish were attacking a trio of heavy ships strongly screened by multiple DDs, Flak ships and E-boats. The AA protection (not to dimiss the heavy fighter cover) was a very great deal heavier and denser than that encountered in the case of Bismarck alone. FWIW. B |
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