Tribal class dd

[dunmunro]

As far as I know, no-one mentioned the L-class except you. I was talking about the Tribal class, which is the topic. I mentioned replacing the 4.7"/45 with 4"/45 because the latter were better AA weapons, and you said you doubted the 4"/45 were better AA weapons than the 4.7"/50. As far as I can see, that is not relevant because 4.7"/50 guns were not installed on Tribal class destroyers.

With respect to the 4.7"/45 guns installed on the Tribals, they could traverse at only 10 degrees per second. If you are being attacked by aircraft, your ship is usually maneuvering radically. I don't know the turn rate of a Tribal, but I suspect it is high enough to make tracking aircraft problematic when you have a gun which traverses so slowly. This is particularly problematic when a weapon gets wooded due to a turn and has to re-engage on the other side, but just tracking an aircraft in a turn could also be a big problem. That is why DP guns normally were given a high traverse rate on the order of two times that of the 4.7"/45 or more.

As an aside, the USN's 5"/51 gun was not considered for AA use because it was too heavy and it's traverse and elevation rate was too slow. They went to a 5"25 cal gun for AA use, but in practice it was being used to engage surface targets where it's ballistics weren't really up to the task, and my understanding is that that is why the 5"/38 was introduced ... a compromise between the two conflicting requirements.

Finally, I can understand if you have credible information which conflicts with the navweaps site, but why exactly should I believe you over them in this case? As far as I know, they are capable of doing the same sort of research as you are.

You stated above:

"A couple of the later ships of the class had 8x4""

And I pointed out that the only war built destroyers to mount 8 x 4in were the 4 x L class.

The info on the Abdiel class comes from the Warship profile and it quotes some the design documents to illustrate that the original design armament was 2 x twin 4in/45, and it discusses the ensuing debate that saw them fitted with 6 x 4in.

The 4.7in twin was a powered mount. The early 4in twin (as fitted to the Tribals) was entirely hand powered.

No WW2 warship that was manoeuvring radically (including battleships) could maintain an AA FC solution.

Even land based systems based on SCR-584 could not track close range targets where the tracking rate exceeded about 5 degrees/sec or so.

[Steve Crandell]

No WW2 warship that was manoeuvring radically (including battleships) could maintain an AA FC solution.

Why do you think that?

Why do you think the trend in medium DP guns was to increase the rate of elevation and traverse?

[dunmunro]

No WW2 warship that was manoeuvring radically (including battleships) could maintain an AA FC solution.

Why do you think that?

Why do you think the trend in medium DP guns was to increase the rate of elevation and traverse?

I've read enough USN battleship, cruiser and destroyer action reports to know that they couldn't; a prime example being South Dakota's AR at Santa Cruz. Even though the specs say that they could, there was enough inertia and lag in the servos that the 5in guns couldn't track accurately while the ship manoeuvred.

Another example was a USN 6in cruiser covering the Doolittle raid, that expended nearly a 1000 rnds of 6in ammo to sink a fishing boat, because the RPC couldn't keep the FC solution against a heavy swell and resultant roll.

Theoretically, increases in tracking rates are needed to provide tracking at high elevation and to compensate for roll and cross-roll but WW2 technology couldn't quite make it happen because the computing power wasn't there yet and because there was still too much lag in the servos.

[Steve Crandell]

No WW2 warship that was manoeuvring radically (including battleships) could maintain an AA FC solution.

Why do you think that?

Why do you think the trend in medium DP guns was to increase the rate of elevation and traverse?

I've read enough USN battleship, cruiser and destroyer action reports to know that they couldn't; a prime example being South Dakota's AR at Santa Cruz. Even though the specs say that they could, there was enough inertia and lag in the servos that the 5in guns couldn't track accurately while the ship manoeuvred.

Another example was a USN 6in cruiser covering the Doolittle raid, that expended nearly a 1000 rnds of 6in ammo to sink a fishing boat, because the RPC couldn't keep the FC solution against a heavy swell and resultant roll.

Theoretically, increases in tracking rates are needed to provide tracking at high elevation and to compensate for roll and cross-roll but WW2 technology couldn't quite make it happen because the computing power wasn't there yet and because there was still too much lag in the servos.

Can you give me a link to the South Dakota AAR which said the 5" guns couldn't track accurately while she maneuvered? I know I've seen several accounts which said the main battery could, so that seems somewhat surprising to me.

The performance of that cruiser at the Doolittle raid has been described as terrible shooting, and I can't imagine taking an example of six inch guns in a bad swell as representative of per performance of 5" rpc or even rpc in general. You take one example of a ship's really bad shooting as an indictment of rpc in general?

According to your logic it was impossible to shoot down aircraft while a ship was maneuvering, but it must have been accomplished because maneuvering was the rule for ships under air attack. RPC was used for 40mm weapons as well as 5", for example.

[dunmunro]

Why do you think that?

Why do you think the trend in medium DP guns was to increase the rate of elevation and traverse?

I've read enough USN battleship, cruiser and destroyer action reports to know that they couldn't; a prime example being South Dakota's AR at Santa Cruz. Even though the specs say that they could, there was enough inertia and lag in the servos that the 5in guns couldn't track accurately while the ship manoeuvred.

Another example was a USN 6in cruiser covering the Doolittle raid, that expended nearly a 1000 rnds of 6in ammo to sink a fishing boat, because the RPC couldn't keep the FC solution against a heavy swell and resultant roll.

Theoretically, increases in tracking rates are needed to provide tracking at high elevation and to compensate for roll and cross-roll but WW2 technology couldn't quite make it happen because the computing power wasn't there yet and because there was still too much lag in the servos.[/quote]

Can you give me a link to the South Dakota AAR which said the 5" guns couldn't track accurately while she maneuvered? I know I've seen several accounts which said the main battery could, so that seems somewhat surprising to me.

The performance of that cruiser at the Doolittle raid has been described as terrible shooting, and I can't imagine taking an example of six inch guns in a bad swell as representative of per performance of 5" rpc or even rpc in general. You take one example of a ship's really bad shooting as an indictment of rpc in general?

According to your logic it was impossible to shoot down aircraft while a ship was manoeuvring, but it must have been accomplished because maneuvering was the rule for ships under air attack. RPC was used for 40mm weapons as well as 5", for example.[/quote]

Here's a quote from Captain Gatch's report:

...The 5" battery was in general handicapped by inability to track planes due to low clouds, the short ranges at which planes first appeared, and by the extremely rapid manoeuvring of this ship. The 40 mm. and 1.1 quads were similarly effected but to a lessor degree. Some planes are reported to have been shot down by these batteries. It is, of course, impossible to accurately to estimate the number of planes destroyed by each battery when so many guns were firing on the same plane. Rough effectiveness estimates during this particular engagement would be:

20mm -- 65 percent

40 and 1.1in -- 30 percent.

5inch -- 5 percent ...

Manoeuvring was the rule while the bombs were falling, but not while the aircraft were approaching.

[Steve Crandell]

Manoeuvring was the rule while the bombs were falling, but not while the aircraft were approaching.

Is that just your opinion? If South Dakota wasn't maneuvering until bombs were dropped, it seems to me that wouldn't be a huge problem for her AA.

The fact that South Dakota had problems getting their AA guns on target while maneuvering doesn't mean the servos couldn't keep up. There are other explanations for that, including the relative inexperience of her fire control team. For example, knowing when to switch a 5" gun mount from one director to another would be a difficult problem for an inexperienced team.

Obviously short range would be a problem for heavy AA especially early in the war when they didn't have good close range fire control.

[alecsandros]

Manoeuvring was the rule while the bombs were falling, but not while the aircraft were approaching.

Is that just your opinion? If South Dakota wasn't maneuvering until bombs were dropped, it seems to me that wouldn't be a huge problem for her AA.

The fact that South Dakota had problems getting their AA guns on target while maneuvering doesn't mean the servos couldn't keep up. There are other explanations for that, including the relative inexperience of her fire control team. For example, knowing when to switch a 5" gun mount from one director to another would be a difficult problem for an inexperienced team.

Obviously short range would be a problem for heavy AA especially early in the war when they didn't have good close range fire control.

... For what it's worth, several years ago, while doing research for a program, I read the manual of USN late-war AA training.
In the amount that I understood it, practical training was focused on aircraft traveling at ~ 200kts (360km/h), attempting to torpedo or to dive bomb the ship. Thus several aircraft trajectories were expected and learned.

USN fast battleship AA battery performance in a normal battle, that is, against conventionaly flying aircraft, attempting torpedo or bomb attacks, was very good. Problems appeared against un-conventionaly flying aircraft, such as kamikazes, which were using unconventional trajectories. Also, from the kamikazes that actualy hit their targets, most were modern , very fast aircraft, flying in excess of 550km/h.

[Francis Marliere]

Can you give me a link to the South Dakota AAR which said the 5" guns couldn't track accurately while she maneuvered? I know I've seen several accounts which said the main battery could, so that seems somewhat surprising to me.

(...)

According to your logic it was impossible to shoot down aircraft while a ship was maneuvering, but it must have been accomplished because maneuvering was the rule for ships under air attack. RPC was used for 40mm weapons as well as 5", for example.

According to Norman Friedman latest book (Naval Antiaircraft Guns and Gunnery), South Dakota had difficulties to aim accurately 5" guns while steering evasively. It was much less a problem for 20 mm and 40 mm guns.

[Steve Crandell]

Can you give me a link to the South Dakota AAR which said the 5" guns couldn't track accurately while she maneuvered? I know I've seen several accounts which said the main battery could, so that seems somewhat surprising to me.

(...)

According to your logic it was impossible to shoot down aircraft while a ship was maneuvering, but it must have been accomplished because maneuvering was the rule for ships under air attack. RPC was used for 40mm weapons as well as 5", for example.

According to Norman Friedman latest book (Naval Antiaircraft Guns and Gunnery), South Dakota had difficulties to aim accurately 5" guns while steering evasively. It was much less a problem for 20 mm and 40 mm guns.

Yes, I responded above to dunmunro's post about that. Does it explain why?

[dunmunro]

Can you give me a link to the South Dakota AAR which said the 5" guns couldn't track accurately while she maneuvered? I know I've seen several accounts which said the main battery could, so that seems somewhat surprising to me.

(...)

According to your logic it was impossible to shoot down aircraft while a ship was maneuvering, but it must have been accomplished because maneuvering was the rule for ships under air attack. RPC was used for 40mm weapons as well as 5", for example.

According to Norman Friedman latest book (Naval Antiaircraft Guns and Gunnery), South Dakota had difficulties to aim accurately 5" guns while steering evasively. It was much less a problem for 20 mm and 40 mm guns.

Yes, I responded above to dunmunro's post about that. Does it explain why?

I've already explained why. WW2 technology was not yet able to overcome the inherent lags in servos, computers and other control mechanisms.

If you have a system where the DCT layer/trainer merely have to keep their sights on the target, then the RPC mechanisms/computers/stable elements should produce accurate gunfire within the inherent error limits of the system because there is minimal human input (which is whole point!). There should be no such things as "poor shooting"...but there was because the GFCS as a whole simply couldn't cope when the ship was not steering reasonable steady courses in reasonably calm conditions.

The fact that we are even having this discussion is due to the fact that the USN widely published essentially falsified AA kill claims in 1942, as anyone who reads Lundstrom and other modern accounts of 1942 Pacific engagements (where IJN data is used to verify AA kill claims) knows. USN RPC systems simply couldn't do what was claimed for them.

[alecsandros]

The fact that we are even having this discussion is due to the fact that the USN widely published essentially falsified AA kill claims in 1942, as anyone who reads Lundstrom and other modern accounts of 1942 Pacific engagements (where IJN data is used to verify AA kill claims) knows. USN RPC systems simply couldn't do what was claimed for them.

... That seems a bit harsh Duncan,

US battleships performed very well in 1942 and all other war years, in the AA department.

The performance of North Carolina or South Dakota in 1942 was well observed from multiple ships and it gave high praise to both battleships. Perhaps South DAkota did not destroy 26 IJN planes that day, but overclaiming was an almost natural part of the war. (As you know, IJN aviators returning from the strikes on USS Yorktown reported "2 sunk carriers", when in fact they had sunk 0. At Santa Cruz they reported 3 carriers sunk, when they had realy crippled 1). That doesn't rob her of the fact that she gave a tremendous AA umbrella to her squadron and most likely saved USS Enterprise from annihilation. 20km farther, USS Hornet was not so fortunate to have a heavy, fast battleship to cover her, and was destroyed by the end of the day...

[Steve Crandell]

I've already explained why. WW2 technology was not yet able to overcome the inherent lags in servos, computers and other control mechanisms.

If you have a system where the DCT layer/trainer merely have to keep their sights on the target, then the RPC mechanisms/computers/stable elements should produce accurate gunfire within the inherent error limits of the system because there is minimal human input (which is whole point!). There should be no such things as "poor shooting"...but there was because the GFCS as a whole simply couldn't cope when the ship was not steering reasonable steady courses in reasonably calm conditions.

The fact that we are even having this discussion is due to the fact that the USN widely published essentially falsified AA kill claims in 1942, as anyone who reads Lundstrom and other modern accounts of 1942 Pacific engagements (where IJN data is used to verify AA kill claims) knows. USN RPC systems simply couldn't do what was claimed for them.

You haven't explained why, if this system was not able to keep up, that the 40mm guns weren't affected as much. They also used rpc, with about the same traverse and elevation rate as the 5".

It's interesting how you defend the Tribal's 5"/45 guns with their 40 degree elevation and 10 deg/sec traverse rate by explaining that it was good enough because no other system was capable of using higher elevation or traverse rates. You defend one system by attacking a better one.

[dunmunro]

I've already explained why. WW2 technology was not yet able to overcome the inherent lags in servos, computers and other control mechanisms.

If you have a system where the DCT layer/trainer merely have to keep their sights on the target, then the RPC mechanisms/computers/stable elements should produce accurate gunfire within the inherent error limits of the system because there is minimal human input (which is whole point!). There should be no such things as "poor shooting"...but there was because the GFCS as a whole simply couldn't cope when the ship was not steering reasonable steady courses in reasonably calm conditions.

The fact that we are even having this discussion is due to the fact that the USN widely published essentially falsified AA kill claims in 1942, as anyone who reads Lundstrom and other modern accounts of 1942 Pacific engagements (where IJN data is used to verify AA kill claims) knows. USN RPC systems simply couldn't do what was claimed for them.

You haven't explained why, if this system was not able to keep up, that the 40mm guns weren't affected as much. They also used rpc, with about the same traverse and elevation rate as the 5".

It's interesting how you defend the Tribal's 5"/45 guns with their 40 degree elevation and 10 deg/sec traverse rate by explaining that it was good enough because no other system was capable of using higher elevation or traverse rates. You defend one system by attacking a better one.

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 - each with it's own servo lags) 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.

I do defend the Tribals because there is a lot of misconception of what was and wasn't possible using WW2 technology. The 10 deg/sec training rate of a Tribal class was still higher than than the FC system could utilize in 1939, and even in 1945 with RPC, the amount of time that the system would utilize rates higher than 10deg/sec would be vanishing small.

[Steve Crandell]

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.

[dunmunro]

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.