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aerial torpedo duds

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#1 gregoryk


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Posted 07 September 2007 - 03:08 PM

The problems with the 21" US torpedoes are very well-documented and adjusted for in most naval rules, including GQ. But were the aerial torpedoes plagued with the same detonator problems, or did they have different ones? The Battle of Midway was not about the torpedoes from the planes having problems, it was the planes themselves. The switch to the TBF seemed to solve that, and the aerial weapon system seemed to work fine thereafter. Question: should the "DUD" penalty be applied to US 18" aerial torps?Gregory

#2 Lonnie Gill

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Posted 07 September 2007 - 08:27 PM

Gregory,Good question. Yes, the Dud adjustment should apply to US aerial torpedoes.The US Mk. 13 aerial torpedo was basically a 21" (actually 22.4") type torpedo rather than the 18" lightweight used by most other navies. It was lighter than the Mk 14 submarine torpedo and the even heavier Mk 15 surface ship torpedo, with a shorter range and smaller warhead, but was generally similar to the other US 21" torpedoes and shared some mechanisms and designs - and problems.US torpedo problems were threefold: 1) they ran 6 - 10+ feet deeper than set 2) the magnetic exploder mechanism didn't work as has been written up in many accounts and 3) the contact exploder would generally fail if it hit perpendicular to the target or other than at a narrow angle. Each of these problems took time to recognize and sort out from the rest. Since the Mk13 aerial torpedo shared mechanisms and (I think) exploders with the other 21" torpedoes, the same problems would have been present. Added to which are the additional problems that came from the stress of aerial drops, potential tumbling gyros,etc.Confirming that problems existed was naturally more difficult in high stress situations resulting from aerial drops contested by a sky full of AA and opposing fighters. Certainly debriefers would have been sceptical. Problems would have been further masked as it was sometimes easy to mistake the splash from a dud hitting a hull with a real torpedo explosion under fire. But, it would seem the same problems existed for all three versions of the US torpedoes. It is instructive that DD launched Mk 15 torpedoes scored almost no hits until August 1943. Instructions reached the SoPac area in July about the depth set problem and shortly after authorized deactivation of the magnetic exploder. A few weeks later, in the very next surface clash, US DDs scored a decisive success at Vella Gulf. I have not done a statistical analysis, but I think the pattern was similar for aerial torpedoes. It's a wonder they got any hits at all in 1942 - mid 1943. Once the problems were dealt with, the aerial torpedo became a viable weapon for the rest of the advance across the Pacific.Incidentally, pre-war TB crews spent more time practicing high level bombing (hoping to use gravity to enable bombs to penetrate thick battleship deck armor) than practicing torpedo runs. Actual torpedo drops were very few and far between. After all, real torpedoes were quite expensive and training was on a tight budget. US torpedo bomber crews developed proficiency through on-the-job training, under fire.LONNIE

#3 Lonnie Gill

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Posted 27 November 2007 - 10:53 PM

Over the past month I have done some additional research on the question of US aerial torpedo duds which leads me to amend my previous post. Special thanks to Coastal for pointing out the fine articles on US torpedoes written by Fredrick J. Milford. His Part Two article on "the great torpedo scandal, 1941 -43" is the best description of the US torpedo problems I've seen. I have found data on one or more of the problems in various other sources, but Fred put it all together in one place with clear explainations. Well done! His article can be found at http://www.geocities...592/ustorp2.The US Mk 13 aerial torpedo did not use the Mark 6 magnetic influence exploder that caused so many problems with the submarine Mk 14 and surface ship Mk 15 torpedoes. Further, the contact exploder failures of those torpedoes were the result of increasing speeds from the 30 - 33 Kts of the earlier Mk 8 through Mk 12 torpedoes to 45 - 46Kts at short range [common for submarine attacks]. The Mk 13 aerial torpedo remained set for 33 Kts, within the contact exploder's original design stress parameters. Thus, the Mk 13 did not suffer from two of the three problems that beset other US torpedoes. Running deeper than set - the other issue - may have been a problem with shallow targets such as DDs until identified in 1943.Slow and low launch limits were troublesome early on, along with limited pre-war training as indicated in my earlier post. The development of drop rings and wartime torpedo bomber training focused on aerial torpedo launches overcame these issues. On balance, the Mk 13 proved reasonably reliable without the exploder problems. Thus, I have exempted aerial torpedoes from the US early war dud adjustment in Amendment 1.LONNIE

#4 Klebert Hall

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Posted 28 November 2007 - 12:49 PM

Running deeper than set - the other issue - may have been a problem with shallow targets such as DDs until identified in 1943.

My dad flew the Avenger in the Pacific from early '43. His experience was that they never even tried to use torps against DDs. Generally, they'd glide-bomb with a 2000 pounder, or sometimes use rockets.He actually never dropped a torpedo in action, all the big ships he attacked during the war were in port. He missed his chance at Phillippene Sea as he'd had to ditch a week or so previously (due to REMF idiocy) and had no plane.-Kle.

#5 Dave Franklin

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Posted 03 December 2007 - 09:36 AM

I read somewhere that the IJN air dropped torp could be dropped from up to an altitude of 500 ft at up to 200 knots air speed, while the US torp was likely to fail if dropped from more than 150 feet and little more than 100 knots air speed (or maybe that was 100 feet and 150 knots?).As I wrote this, thinking I might advicate the dud roll still being included for the US if those rather limited parameters were not observed, I took a quick look at the Tactical Air Ops rules/tables. I note the IJN has a TB max speed of 8600 yards while others are 4000 yards (per turn or air phase I assume - I've never played the tactical air rules). Don't know what that equates to in knots, but it seems what I had read above is covered.My question now is, how is this disparity addressed in Campaign Air Ops? The superiority of the IJN torpedo (not to mention the superior aircraft - until the US replaces the TBD with the TBF) and superior training of the crews - at least early in the war - is not accounted for.

#6 Jim O'Neil

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Posted 03 December 2007 - 10:05 PM

At Midway the US Devastators dropped Mk-13s from 50 feet at 110 knots.By late 1943 the Mk-13 could be dropped from 2400 feet at 410 knots... it was a case of putting similar (to the Japanese but better) in flight devices on the torpedo.The IJN did not have a categorically superior aircraft... in fact the Avenger was better in every respect. The Devastator was not, but had preceded it into service as the first monoplane torpedo plane, which was scheduled for replacement (it was no miracle that so many TBMs were available shortly after Midway). Despite its miserable performance at Midway, it had performed fairly well in previous operations (Tulagi, the strike over the Owen Stanley range to disrupt the Japanese invasion at Buna?) ... it was regrettably the wrong plane at the wrong place at Midway, as was every other Allied Torpedo attacker ... note that Kate's suffered ever more seriously as well.Japanese Torpedo pilots did enjoy some superiority in Torpedo training over their American foes early in the war ... this evaporated by the end of 1942 when trained Japanese aviators were few and far between.

#7 Lonnie Gill

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Posted 07 December 2007 - 06:28 PM

This question poses two core issues: 1) the effect of the aerial torpedo drop profile on the torpedo attack result and 2) the vulnerability effect of the drop profile on the launching torpedo bombers.1) The early war US Mk13 aerial torpedo did have a limited launch window with a maximum drop speed of 110 kts and max altitude of 50 feet, which required determination and increased the risk for USN torpedo bombers. Torpedoes launched within this low and slow profile generally ran satisfactorily without many of the problems that beset the Mk14 submarine torpedo [See my previous post.] Empirical tests showed that about a third of Mk13s would fail to run properly if this profile was exceeded. Historically, USN torpedo bomber squadrons made hits in carrier air strikes right from the early 1942 carrier raids, which suggests that a reasonable number of the US aircrews had the determination to fly the dangerous low, slow launch profile. The absence of significant observations of torpedo malfunctions in the action reports from 1942 is further evidence that the crews used the profile. Thus, there doesn’t seem to be evidence that the limited launch profile had a significant effect on aerial torpedo attack results.By 1943, modifications were being made to increase the launch profile. The solution was found in the wooden “pickle barrel” nose drag ring and box shaped wooden “ring tail” fitted to the Mk13 torpedo which increased the satisfactory drop speed to 300 kts and the drop height to 800 feet. The first major attacks using these were made in the Feb. 1944 raids on Truk. By the end of the war, further mods had improved the profile to 410 kts and 2,400 feet.Hence, there doesn’t appear to be a need add an adjustment to the Campaign TORPEDO BOMBER CRT. Both USN and IJN aircrews launched within their respective profiles. The early US profile was however more dangerous and difficult to fly. Thus, you might consider making a scenario rule to adjust for lower proficiency by “green” TB crews in specific situations.2) The tactical air rules in Section 2 already simulate the risks inherent in the low, slow US profile required until 1944 vs. the better IJN profile used by B5N Kates and the high speed, land based G3M and G4M Rikko. USN torpedo bombers are exposed to AA fire for more Air Phases and the low speed makes them more vulnerable to firing passes from Japanese fighters. The generally similar max launch movement for the various non-IJN torpedo bombers was averaged as 4,000 yds per one minute Air Phase beneath the Torpedo Bomber DROP table on Chart 17A. This corresponds to 120 kts (12,000 yds per three minute Game Turn). Specific max launch speeds for each navy are available on the bottom of the movement worksheet in the Design section of the on-line Bonus files elsewhere on the ODGW web site for those who want more detail. The IJN max drop movement of 8,600 yds per Air Phase corresponds to 258 kts.The issue of vulnerability of the TB during the launch is a thornier question at the campaign level, which is a higher-level abstraction of the whole aerial torpedo attack process. The US low, slow launch profile was certainly more dangerous than the IJN profile, but aside from the massacre of the TBDs at Midway, USN torpedo bombers did not suffer unusually heavy losses in 1942 or ‘43 air strikes. Midway was the result of a special set of circumstances in which the obsolescent TBDs attempted to penetrate the full IJN CAP alone, unsupported by fighter cover. Five out of six of the new TBFs were also lost in another attack. But, in earlier battles the TBDs were not shot out of the sky. Nor were the TBFs in post Midway battles. Further, the vulnerability of the early US launch profile is at least partially offset by the NST vulnerability of IJN torpedo bombers.In sum, you have a low, slow launch profile vs. weaker AA and less effective CAP contrasted with a better launch profile by NST bombers vs. strong AA and more efficient FDO and radar directed CAP. Therefore, I did not add a distinction at the campaign level. Do Forum members find this approach sufficient? I’d be interested in hearing your thoughts.LONNIE

#8 simanton



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Posted 20 March 2013 - 07:03 PM

If the wreck of Shoho is ever found, and it is in the right condition/attitude, the findings could be interesting. Both US and Japanese accounts indicate that she received multiple effective torpedo hits. In the right conditions (surprise/moderate to light AA/ineffective CAP) the TBD/Mk 13/First Team aircrew combo might have been pretty effective!

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