Tribal class dd

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Steve Crandell
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Re: Tribal class dd

Post by Steve Crandell » Wed Sep 24, 2014 2:15 pm

dunmunro wrote:The Tribal class were introduced in 1938/39. A Tribal had 8 x 4.7in guns all of which could engage aerial targets to the limits of their elevation. A Tribal had a quad 40mm pom-pom and two quad .5in MGs. USN Leaders had 8 x 5", none of which could engage aerial targets beyond a simple barrage fired with fixed fuze timing. The Tribals had better AA potential than any other destroyer on the planet in 1939, when engaging targets within it's engagement envelope. The USN and IJN were the only navies to build destroyers with larger AA engagement envelopes, but the IJN destroyers were severely limited by using guns with fixed loading angles, and in having little in the way of an AA fire control system. Only the USN's destroyers had a larger engagement envelope than a Tribal while utilizing guns with loading trays and an advanced AA GFCS. Unfortunately, while impressive on paper, the Mk 33 GFCS was a near complete failure as a AA GFCS. The lack of a viable CIWS meant that Mk 33 equipped destroyers had far less actual AA potential than their RN counter parts ( Tribal and later) and the same was probably true for MK 37 in many cases as well. Mk 37 was better but not in service until 1940 and then hamstrung by it's very complex and heavy servo systems, which were considerably overweight and far less capable than the USN hoped for. I would suggest reading David Mindell's book: Between Human and Machine: Feedback, Control, and Computing before Cybernetics for a look at the limitations of RPC in ~1940.
I agree with much of what you say in this paragraph. What I don't agree with is that the Tribals were satisfactory AA platforms compared with later systems. That is what you imply when you say that rate of train is not important nor is elevation. If you think those things are important, then the Tribal is not a very good AA platform. I wouldn't ague at all that the USN leaders were good AA platforms, or that the Tribals had better potential than any other destroyer in 1939. My problem is with your implication that their 5"/45 guns were just fine for AA use as installed. That was the question in the original post.

Matrose71
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Re: Tribal class dd

Post by Matrose71 » Wed Sep 24, 2014 5:37 pm

dunmunro wrote:
Steve Crandell wrote:
dunmunro wrote:
The system wasn't able to keep up. 40mm guns are much less effected because there is a direct connection from the lightweight Mk 51 director (versus a 15 ton DCT with multiple stabilized sights to the 40mm mount. The 40mm mount is much lighter than a 5in turret so it has much less lag in the servo system and there is no fuze setting involved.
The 5" also has a more powerful traversing motor. The traversing rate is about the same for the two weapons. Fuse setting isn't really relevant because it was part of the hoist, so it really didn't matter what the mount was doing. In any case, VT fuses would eventually make the fuse setting delay less critical, but that isn't really relevant to the difference between turns and steady course.

We aren't going to agree on this. You apparently think the weapons on the Tribals were as good as they could get for AA use. For some reason, British destroyer guns tended to get higher traversing rates and greater elevation as the war progressed, but I guess that was just because they felt like it and not because of any perceived need. I don't think there is any way I'm going to convince you otherwise, and it's really a waste of time.
The Tribal class were introduced in 1938/39. A Tribal had 8 x 4.7in guns all of which could engage aerial targets to the limits of their elevation. A Tribal had a quad 40mm pom-pom and two quad .5in MGs. USN Leaders had 8 x 5", none of which could engage aerial targets beyond a simple barrage fired with fixed fuze timing. The Tribals had better AA potential than any other destroyer on the planet in 1939, when engaging targets within it's engagement envelope. The USN and IJN were the only navies to build destroyers with larger AA engagement envelopes, but the IJN destroyers were severely limited by using guns with fixed loading angles, and in having little in the way of an AA fire control system. Only the USN's destroyers had a larger engagement envelope than a Tribal while utilizing guns with loading trays and an advanced AA GFCS. Unfortunately, while impressive on paper, the Mk 33 GFCS was a near complete failure as a AA GFCS. The lack of a viable CIWS meant that Mk 33 equipped destroyers had far less actual AA potential than their RN counter parts ( Tribal and later) and the same was probably true for MK 37 in many cases as well. Mk 37 was better but not in service until 1940 and then hamstrung by it's very complex and heavy servo systems, which were considerably overweight and far less capable than the USN hoped for. I would suggest reading David Mindell's book: Between Human and Machine: Feedback, Control, and Computing before Cybernetics for a look at the limitations of RPC in ~1940.
You want to kidding us?
For example the german destroyer had also 40 degree elevation, a AA firecontrol computer and zone munition and nobody would claim they were good AA platforms. The 4.7 inch guns in twin mountings and 40 degree elevation are worse to mention for good AA capacity. I thought I'm here at a naval forum and not at a history myths forum.
Every USN destroyer with a 5/38 and Mark 25 mountings is the much much better AA plattform, because they had an elevations of 85 degree and also AA computers.The Sims class will beat the Tribals in AA capacity any time.

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Re: Tribal class dd

Post by dunmunro » Wed Sep 24, 2014 8:07 pm

Matrose71 wrote:
You want to kidding us?
For example the german destroyer had also 40 degree elevation, a AA firecontrol computer and zone munition and nobody would claim they were good AA platforms. The 4.7 inch guns in twin mountings and 40 degree elevation are worse to mention for good AA capacity. I thought I'm here at a naval forum and not at a history myths forum.
Every USN destroyer with a 5/38 and Mark 25 mountings is the much much better AA plattform, because they had an elevations of 85 degree and also AA computers.The Sims class will beat the Tribals in AA capacity any time.
What you are saying is that German destroyers had the ability to fire a fixed range barrage but no ability to continuously track and engage individual aircraft with "controlled fire" as it was called in the RN. The German destroyers had no on-mount fuze setters. Their 12.7cm and 15cm single mount guns had a max 30 deg elevation. Only the rather rare 15cm twin mount could elevate to 65degrees but again it had no AA FC, and no on mount fuze setters.

The Sims class had 4 x 5in guns (one removed due to topweight issues largely due to Mk 37 being overweight) and four .5in MGs. Under 40 degs target elevation the Tribals had far more AA firepower. Over 40 degs the Tribals still had a quad 40mm pom-pom, so the Sims only advantage was engaging aircraft at high elevation/high angles of sight, and while this may have conferred an advantage in some situations, the overall advantage would still rest with the Tribal. Tribals began to be fitted with a 4in twin mount in lieu of "X" 4.7in mount just as the Sims class were commissioning.

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Re: Tribal class dd

Post by Francis Marliere » Thu Sep 25, 2014 10:07 am

Steve Crandell wrote:Yes, I responded above to dunmunro's post about that. Does it explain why?
Steeve, sorry, I could not answer sooner. I don't have the book at hand and relies just on my poor memory.
What I understand is that violents maneuvers made aiming of the large guns difficult because they fired at longer range than smaller ones and their fire controls took much more time to elaborate a solution. With a 20 mm, the gunner just points the gun toward the target with small corrections for elevation and deflection. When the ship turns,what the gunner has to do is a slight change in aiming. Changing a solution for 5" guns is much more complicated.

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Re: Tribal class dd

Post by Francis Marliere » Thu Sep 25, 2014 10:43 am

dunmunro wrote:The Tribal class were introduced in 1938/39. A Tribal had 8 x 4.7in guns all of which could engage aerial targets to the limits of their elevation. A Tribal had a quad 40mm pom-pom and two quad .5in MGs. USN Leaders had 8 x 5", none of which could engage aerial targets beyond a simple barrage fired with fixed fuze timing. The Tribals had better AA potential than any other destroyer on the planet in 1939, when engaging targets within it's engagement envelope. The USN and IJN were the only navies to build destroyers with larger AA engagement envelopes, but the IJN destroyers were severely limited by using guns with fixed loading angles, and in having little in the way of an AA fire control system. Only the USN's destroyers had a larger engagement envelope than a Tribal while utilizing guns with loading trays and an advanced AA GFCS. Unfortunately, while impressive on paper, the Mk 33 GFCS was a near complete failure as a AA GFCS. The lack of a viable CIWS meant that Mk 33 equipped destroyers had far less actual AA potential than their RN counter parts ( Tribal and later) and the same was probably true for MK 37 in many cases as well. Mk 37 was better but not in service until 1940 and then hamstrung by it's very complex and heavy servo systems, which were considerably overweight and far less capable than the USN hoped for. I would suggest reading David Mindell's book: Between Human and Machine: Feedback, Control, and Computing before Cybernetics for a look at the limitations of RPC in ~1940.
Dunmunro, I agree that the quad 2 pdr gave British DD a better short range AA than their US counterparts (untill they got 20 mm then 40 mm guns). You're right that the early US directors were not sucessfull. I would however note that, according to Friedman, the director of Tribal and later DDs was quite worse. The 5"/38 guns had a higher elevation, hence a longer engagement enveloppe than the 4.7"/45, and a higher rate of fire (10-12 rpm for 4.7", 15-20 for 5"). Please consider that Tribal class DDs carried only 50 HE rounds per guns (according to http://navweaps.com/Weapons/WNBR_47-45_mk9.htm). Hence IMHO, Tribal class DDs had good AA for self defense early in the war, but were not good AA escorts. USN DDs in the other hand became very effective AA platforms when they got some more light AA and better directors, fire controls, radars and proximity fuzes later in the war.

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Re: Tribal class dd

Post by Steve Crandell » Thu Sep 25, 2014 12:48 pm

Francis Marliere wrote:
Steve Crandell wrote:Yes, I responded above to dunmunro's post about that. Does it explain why?
Steeve, sorry, I could not answer sooner. I don't have the book at hand and relies just on my poor memory.
What I understand is that violents maneuvers made aiming of the large guns difficult because they fired at longer range than smaller ones and their fire controls took much more time to elaborate a solution. With a 20 mm, the gunner just points the gun toward the target with small corrections for elevation and deflection. When the ship turns,what the gunner has to do is a slight change in aiming. Changing a solution for 5" guns is much more complicated.
I agree that changing 5" gun solution is much more complicated. However, that should not be a problem if the same fire control computer is being used throughout, even if the ship is maneuvering. I think the problem is confusion when there are multiple attacks coming from more than one direction and the AA fire control officer has to change gun tasking and director tasking on the fly. That is always a problem, and much more so with a new ship who's fire control team is inexperienced. I think that probably affected South Dakota at Santa Cruz. I do agree that maneuvering is going to affect 5" guns more than 20mm or 1.1" or 40mm because those are all locally controlled. I really doubt it's related to rate of train though unless I see something that specifically addresses that. I do know that the 5" battery experienced some trouble early on with "hunting", where the mount would oscillate under rpc. The main battery didn't have that problem because of the much greater inertia of the turrets.

Also, a destroyer wouldn't have the 5" director problem under maneuver because it has only one and the guns keep firing until they are "wooded". However, it would take a 5"/38 much less time to switch sides after being wooded than the 5"/45 on the Tribals. For a 150 degree shift it would take a tribal battery about 15 seconds, where it would only take a 5"/38 battery about six.

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Re: Tribal class dd

Post by dunmunro » Thu Sep 25, 2014 4:35 pm

Francis Marliere wrote:

Dunmunro, I agree that the quad 2 pdr gave British DD a better short range AA than their US counterparts (untill they got 20 mm then 40 mm guns). You're right that the early US directors were not sucessfull. I would however note that, according to Friedman, the director of Tribal and later DDs was quite worse. The 5"/38 guns had a higher elevation, hence a longer engagement enveloppe than the 4.7"/45, and a higher rate of fire (10-12 rpm for 4.7", 15-20 for 5"). Please consider that Tribal class DDs carried only 50 HE rounds per guns (according to http://navweaps.com/Weapons/WNBR_47-45_mk9.htm). Hence IMHO, Tribal class DDs had good AA for self defense early in the war, but were not good AA escorts. USN DDs in the other hand became very effective AA platforms when they got some more light AA and better directors, fire controls, radars and proximity fuzes later in the war.
RN CIWS was improved during the war as well, but the key point is that the RN decided upon a strong CIWS from the very beginning and to get a strong CIWS they decided to keep the 4.7in/45 twin elevation at 40 degrees to reduce it's weight. This allowed for 8 x 4.7in guns with AA capability in the Tribals, 6 x 4.7in/50 (50 deg elevation) in the L-M class and 6 x 4.7in in the J-K-Ms versus no 5in AA capability in the USN leaders and only 4 x 5in with AA capability guns in the smaller destroyer classes that were equivalent to the J-K-M class.

Which of Friedman's books are you referring to? I disagree that the Tribal's AA director was worse. It was a very lightweight director that could track targets easily versus Mk 33 which was a nightmare to use against aircraft:
...A study of the results of antiaircraft firings by the ships of the Fleet, from July 1, 1938 to June 30, 1940, gave little cause for cheer or hope for solution in this area. This study showed that in 307 firing runs by 1.1", 3", and 5" antiaircraft guns against high-altitude, horizontal-bombing drone aircraft, dive-bombing drone aircraft, and low-atitude, horizontal bombing drone aircraft, only 5% of the drone target aircraft had been hit seriously enough to stop the bombing attack and only 17% hit at all.(10) Increased numbers of guns on the ships of the Fleet, and putting increased skill into using them would undoubtedly improve results, but it did not appear this action would provide the protection sought..."

(10) '"Defense of the Fleet Against Attack by Aircraft, General Board No. 420-11, serial 1952-A of 12 June 1940, GB Files, NHD, p. 1; CNO, serial 085323 of 12 June 1940, letter. " Commander Carrier Division One, Feb. 1940, letter to CINCUS.
Richardson, On the Treadmill to Pearl harbor, p224.

From the “Sham battles” we had with our own carrier planes, it became clear that in war we would be subjected to attacks which broke very quickly, seldom with any warning. When an incoming plane was sighted, we would struggle to get our director’s sights on target, measure the rapidly closing range, adjust the Mk-10 to a solution and simulate opening fire before the attacker could complete his attack. Frequently we’d still be “slewing” the director to get on target when he roared overhead, attack completed. We held tracking drills at every opportunity to improve our ability to acquire targets quickly, but we had no mechanism to point out the target to the men on the director’s telescopes—the control officer had to coax them on by voice. I became seriously concerned that we couldn’t handle incoming dive or strafing attacks.
Crenshaw, Crest of a wave
Warren Armstrong, standing on the control officer’s platform with his head out of his hatch, tried to coach the Mk-33 around to the diving planes. Jaworski and Serwitz would slew the director frantically by eye with their handwheels until, with Canaday’s advice, they thought they were “on target,” then would drop down to try to catch the plunging planes in their optics. It was an impossible task! At the rangekeeper, Copeland and I watched Warren’s feet and lower torso expectantly as he squirmed about, hoping he’d get the director “locked on” to something so we could shoot. The attack was coming in from high over our section of the screen. The enemy planes were passing over our heads as they bore in on Enterprise. We’d whirl the director to try to get our sights on a Jap, but it takes a big arc of train to make even a small change near the zenith. They’d be over the top and out the other side before we could settle on them. Jaworski on the Pointer’s scope reported “On Target” a couple of times, but he couldn’t follow the fast motion as the attackers dove in. We never got a shot off!
Crenshaw, Crest of a wave

The 5in/38 twin mounts in the USN leaders had only 35 deg elevation and no AA capability. The 5in single mount did have a higher elevation than the 4.7in but at least in 1942 it did not much, if any, advantage in rate of fire:
A total of 362 rounds were fired, 74 at the shore battery, 20 in the first engagement, and 268 in the second destroyer engagement, of which it is estimated that 200 rounds were fired at the first destroyer and 68 at the second. All firing was director-controlled, rapid, continuous fire. The average gun range for the first firing was 9,500 yards, for the second 14,000 yards, and for the third 12,500 yards...

...It is particularly pleasing that the guns maintained a sustained rapid fire of 268 rounds (average 68 rounds per gun) at an estimated rate of at least 12 shots per gun per minute without casualty.United States Navy, AntiAircraft Action Summary, July 1942 to Dec 1942 (Information Bulletin No. 22), p.161-163
"Salvoes roared out at five-second intervals." Crenshaw, Crest of a wave.
Crenshaw also notes a number of problems with the 5in guns themselves, especially premature bore enlargement.

The Tribal class ammo load-out could be, and was, varied depending upon the expected mission and I have no doubt that the RN soon increased the HE load out while reducing the number of 4.7in SAP carried.

I have no doubt that USN and RN destroyers increased their AA effectiveness later in the war, but in 1939 the Tribals were superior, IMHO. The Tribals gave good service as AA escorts, as long as they themselves were not the primary target.

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Re: Tribal class dd

Post by dunmunro » Thu Sep 25, 2014 5:11 pm

Steve Crandell wrote:
I agree that changing 5" gun solution is much more complicated. However, that should not be a problem if the same fire control computer is being used throughout, even if the ship is maneuvering. I think the problem is confusion when there are multiple attacks coming from more than one direction and the AA fire control officer has to change gun tasking and director tasking on the fly. That is always a problem, and much more so with a new ship who's fire control team is inexperienced. I think that probably affected South Dakota at Santa Cruz. I do agree that maneuvering is going to affect 5" guns more than 20mm or 1.1" or 40mm because those are all locally controlled. I really doubt it's related to rate of train though unless I see something that specifically addresses that. I do know that the 5" battery experienced some trouble early on with "hunting", where the mount would oscillate under rpc. The main battery didn't have that problem because of the much greater inertia of the turrets.

Also, a destroyer wouldn't have the 5" director problem under maneuver because it has only one and the guns keep firing until they are "wooded". However, it would take a 5"/38 much less time to switch sides after being wooded than the 5"/45 on the Tribals. For a 150 degree shift it would take a tribal battery about 15 seconds, where it would only take a 5"/38 battery about six.
3. There is evidence of poor director training so that bursts oscillate in deflection. Radical maneuvering to avoid bombs is a factor in disrupting rangekeeper solution and accuracy of director laying, especially on destroyers.
http://www.ibiblio.org/hyperwar/USN/rep ... index.html
Even the task of correcting estimates of course and speed, which Ford originally left to the gunnery officers, now returned to the machine. Belowdecks the Mark 1 computer converged on a solution and commanded servos to move the entire director and its scopes to track the target. With a feature called “automatic rate control” the telescope operators watched the motorized tracking, adjusting the rate of motion to keep the targets centered while the computer converged on a solution. The director and the computer formed what one user manual called a “regenerative group,” a feedback loop that eased the job of tracking fast-moving targets. (111) However useful and innovative, this feature exceeded the limits of BuOrd’s or its contractors’ technical knowledge. The feedback loop on the Mark 37,“a previously untried closed-circuit servo,” had a stability problem: the output of the computer moved the director, which in turn affected the input to the computer. Both the computer and the power drives had time lags, so the two could push and pull each other and make the system oscillate. How these loops interacted and fed back on each other was poorly understood and caused severe problems in operations. added in 1940, The stability problem in the Mark become unstable.“It is well known, that the guns, because of their enormous inertia, do not respond instantaneously to a signal from the director . . . for similar reasons the guns tend to swing too far when coming to alignment with the director after such motion, giving rise to ‘hunting’ or oscillations” .(112) When radar was the noisy, often erratic signals instigated a complete breakdown. But the equipment was already in production, and the navy was preparing for war. was the most prominent example of a complication arising throughout naval fire control. Wherever sensitive instruments and intricate computers drove powerful servos on heavy gun mounts the systems could 1937 report read, that “the guns, because of their enormous inertia, do not respond instantaneously to a signal from the director . . . for similar reasons the guns tend to swing too far when coming to alignment with the director after such motion, giving rise to ‘hunting’ or oscillations.” (113) Adjustments could make these systems stable, but only at the cost of unacceptably degraded performance. A series of tests identified an “inherent weakness”in the Ford system of control and in the hydraulic speed gear with which it was used. BuOrd’s precious machines suffered from “insufficient ‘stiffness’ or ‘rigidity’ or a lack of prompt response to the director system.” (114) Naval fire control systems, for all their precision, ruggedness, and sophistication, had run up against a problem the engineering culture could not solve: how to make a feedback loop move a large mass at high speed without making it unstable. Solving this problem required more theoretical analysis than the engineering culture of fire control could provide, so the navy turned to institutions that had developed different types of knowledge about feedback, including Bell Labs and MIT.

111. U.S. Navy, Bureau of Naval Personnel, Naval Ordnance and Gunnery,
112. U.S. Navy, Administrative History, 79:148.
113. “Type Tests— 6Љ/47 Caliber Triple Mount— Determination of the Accuracy of the Transmission and Operation of the Automatic Control,” 1 August 1937, RG S-71, box
114. Ibid., 19.

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Re: Tribal class dd

Post by Steve Crandell » Thu Sep 25, 2014 8:40 pm

If we were to take those examples as indicative of what happened most of the time, it shows it was impossible for a 5"/38 to shoot down aircraft at all. And yet these weapons shot down a lot of aircraft. If you look at IJN comments, they describe USN flak as heavy and accurate. How do you think that happened? You make it look like it wouldn't even come close.

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Re: Tribal class dd

Post by dunmunro » Fri Sep 26, 2014 12:38 am

Steve Crandell wrote:If we were to take those examples as indicative of what happened most of the time, it shows it was impossible for a 5"/38 to shoot down aircraft at all. And yet these weapons shot down a lot of aircraft. If you look at IJN comments, they describe USN flak as heavy and accurate. How do you think that happened? You make it look like it wouldn't even come close.
According to Lundstrom ( Lundstrom has stated to me and to others that his book Black Shoe Carrier Admiral contains his most accurate analysis) USN AA successes were very limited until Santa Cruz, and then the vast majority of AA kills were made by the CIWS. If USN 5in guns couldn't shoot down slow and non-manoeuvring drones in large numbers, it seems reasonable that they would have even less ability to shoot down higher speed, manoeuvring targets, and the numbers from Lundstrom support this:

At Coral Sea they claimed 37 AA kills by the USN carrier force but Lundstrom assessed only 3.
At Midway the USN claimed 20 AA kills and got 3.
At Eastern Solomons the USN claimed 30 and got 4.
At Santa Cruz the USN claimed 127 and got ~25. Gatch assessed that only 5% were downed by 5in AA and the rest by the CIWS.

For the first 3 actions the USN claimed 87 but Lundstrom assessed only 10 AA kills. ( for all AA weapons including 5in and CIWS)

5in kills were very rare in 1942. In 1943 and later the 5in guns benefited greatly due to the availability of VT ammo. AA successes by 5in fire was probably one aircraft per several thousand rounds of 5in gunfire, which was probably the same or even worse than the kill rate achieved by RN medium calibre AA. 5in AA kills were probably achieved through simple volume of fire rather than accuracy of control. In the Deadly Fuze, Baldwin (an NDRC scientist who worked on VT development) the author states that the actual 5in kill rate during ww2 was very low:
With mechanical time fuzes, the sky around a target was often spotted with shell burst smoke, but the chances of bringing a plane down were low. It was estimated that it took about twenty-four hundred rounds of five-inch time fuzed ammunition to bring down a single plane. (p.24)
Of course officially, the USN was claiming one kill per 114 rounds fired in 1942 (USN AA summary June -Dec 1942), but later revised that to ~250 per kill. 2400 rounds per 5in kill tallies very closely to Lundstrom's (and Gatch's) numbers.

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Re: Tribal class dd

Post by Steve Crandell » Fri Sep 26, 2014 4:17 am

How could you possibly get a kill with a VT fuse if the fire control system is unable to get the round close enough to the target?

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Re: Tribal class dd

Post by dunmunro » Fri Sep 26, 2014 4:53 am

Steve Crandell wrote:How could you possibly get a kill with a VT fuse if the fire control system is unable to get the round close enough to the target?
According to Baldwin, average MT fuze error on 50% of fuzes was .1 sec, with 50% having greater errors and all errors increased in proportion to the ToF. Even a perfectly aimed and timed shell would be expected to detonate several hundred feet from the target, unless it actually struck the target. Another weakness in the USN system was that deadtime varied between gun crews as there was no load lamp, as used in the RN AA FCS, to ensure that each gun was loaded with identical deadtimes, and this also increased the AA burst pattern size (MPI per salvo)

A VT fuze would trigger if it approached to within ~100 ft from the target. This reduced the theoretical rounds per kill by about a factor of about 10 since it eliminated MT fuze errors and deadtime loading errors.

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Re: Tribal class dd

Post by Steve Crandell » Fri Sep 26, 2014 5:30 am

It's interesting how you convert the integral hoist/fuse setter into a disadvantage because the USN doesn't have to wait for a "load lamp".

Every advantage of the Mark 37 system you try to turn into a disadvantage. Too bad Vanguard was hobbled with that horrible kluge.

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Re: Tribal class dd

Post by alecsandros » Fri Sep 26, 2014 7:17 am

dunmunro wrote:
Steve Crandell wrote:How could you possibly get a kill with a VT fuse if the fire control system is unable to get the round close enough to the target?
According to Baldwin, average MT fuze error on 50% of fuzes was .1 sec, with 50% having greater errors and all errors increased in proportion to the ToF. Even a perfectly aimed and timed shell would be expected to detonate several hundred feet from the target, unless it actually struck the target. Another weakness in the USN system was that deadtime varied between gun crews as there was no load lamp, as used in the RN AA FCS, to ensure that each gun was loaded with identical deadtimes, and this also increased the AA burst pattern size (MPI per salvo)

A VT fuze would trigger if it approached to within ~100 ft from the target. This reduced the theoretical rounds per kill by about a factor of about 10 since it eliminated MT fuze errors and deadtime loading errors.

http://www.history.navy.mil/library/onl ... wii.htm#IV
pg 19
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Re: Tribal class dd

Post by dunmunro » Fri Sep 26, 2014 7:35 am

Steve Crandell wrote:It's interesting how you convert the integral hoist/fuse setter into a disadvantage because the USN doesn't have to wait for a "load lamp".

Every advantage of the Mark 37 system you try to turn into a disadvantage. Too bad Vanguard was hobbled with that horrible kluge.

Here's the deadtime calculation done by the Mk 1 computer:

http://www.hnsa.org/doc/computermk1/pg288.htm

It's pretty obvious that loading variations between gun crews will increase pattern size. By the time Vanguard appeared, VT ammo was the norm and deadtime no longer mattered so much, although without a metadyne fuze setter manual and the manual for the RN modded Mk1 computer, there's no way to know if the RN modded the Mk1 to include a load lamp.

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