Dive Bomber Comparison

[Juha]

Hello
checked from Lundstrom, at Midway one of Hiryu's 10 VTs was shot down before AA opened fire, 2 F4Fs were shot down inside the escort screen, one by a Zero and one was claimed by a Kate gunner but the US pilot thought that he was shot down by naval AA, and F4Fs got 11 Vals before they dived according to Lunstrom, my old source says 10.

 

[RCAFson]

Hello RCAFson
I have no opinion on Coral Sea and on Midway (not time to check comparable real results) but Lundstrom's The First Team and the Guadalcanal Campaing says that at Santa Cruz USN AA shot down 25 japanese planes and USN a/c 29. IMHO at that time US AA was more effective than RN AA

Juha

I decided to compare the AA of USN and RN ships in Oct 1942, using actual USN ships in 1942 at santa Cruz and equivalent RN ships, in Oct 1942:

According to US Battleships, (googlebooks) South D. had 4 x quad 40mm, 4 x quad 1.1", and about 50 20mm.
Enterprise had 8 x 5", 4 quad 40mm, 1 quad 1.1", 44 20mm
Hornet had 8 x 5" 5 x quad 1.1", 32 20mm

In October 1942 Howe or Anson would have had 16 x 5.25, 6 x octuple pom-pom, 18 x 20mm.
Indomitable or Victorious would have had 16 x 4.5", 6 x octuple pom-pom and 10-12 20mm.

Capital ships:

RN: 16 x 5.25in, 32 x 4.5" 18 x octuple pom-pom, 40 20mm = 48 x DP guns, 144 40mm pom-pom, 40 20mm = 48 x DP and 184 AAA

USN: 24 x 5", 8 x quad 40mm, 10 x quad 1.1" 126 20mm = 24 DP guns, 72 40/1.1", 126 x 20mm = 32 x DP and 196 AAA

3 x Atlanta ckass cruisers: 16 x 5"/38 2 x quad 1.1" 8 x 20mm = 48 x DP and 48 AAA
3 x Dido class 10 x 5.25", 2 x quad pom-pom, 4 or 5 x 20mm = 30 x DP and 38 AAA



2 x USN heavy cruisers with 4x 5", 12 x 20mm (?) can't find exact info on Northampton and Pensacola
1 with 8 x 5" 4 x quad 1.1" 12 x 20mm = 16 x DP and 52 AAA

typical RN heavy cruiser:
2 with 4 x twin 4", 2 octuple pom-pom 5 20mm
1 with 4 x twin 4", 2 x quad pom-pom, 5 20mm = 24 DP and 55 AAA

USN Destoyers 7 with 5 x 5"/38 and 4 x 20mm
7 with 4 x 5", 1 quad 1.1" 4 x 20mm (typical mix) = 63 DP, 115 AAA

RN Destroyers:
6 with 6 x 4.7" 1 x 4" HA, 1 quad pom-pom, 4 x 20mm
6 with 4 x 4.7" 1 quad pom-pom, 6 x 20mm.
2 with 5 x 4", 1 quad pom-pom, 6 x 20mm = 76 DP, 118 AAA

Various websites for data.

RN Totals = 178 DP and 395 AAA of which 268 are 40mm pom-pom

USN totals = 159 DP and 411 AAA of which 32 are 40mm bofors.

I would say that the RN was still ahead of the USN in Oct 1942.

 

[Glider]

The RN states 5.25 ROF of 10-12 and a first hand account from an RN gunner states 10 rounds/minute. Navweaps states 12 RPM for 4.5in. Maybe Navweaps data is out of date?

Your figures for attacks seem to match mine pretty closely and I edited my post to include the numbers of attacks, and the total for all 3 actions was about 145.

I think that you are being a little selective over your quotes from Navweapons. On the 5.25 it also states:-

Unfortunately, the design of the gunhouse was cramped and the heavy projectile and cartridge cases resulted in a lower rate of fire than expected. In addition, the slow elevating and training speeds of the mounts were found to be inadequate for engaging modern high-speed aircraft.

1) As designed, the expected rate of fire for these guns was 10 - 12 rpm. However, the heavy weight of the projectile and cartridge case plus the semi-automated fuze setting mechanism meant that this round required much crew handling before it could be rammed into the breach. The tight design of the gunhouse also interfered with the smooth crew operation necessary to achieve high rates of fire.

The mountings used on the King George V and Dido classes were very cramped and difficult to maintain. They were also difficult to train in the non-powered mode using the hand mechanisms. Their rather slow training speeds meant that they could not track fast-moving aircraft. These last two problems were highlighted during the Japanese attacks on HMS Prince of Wales. When she took up a 10-11 degree list as a result of damage received, it was found that some of the mounts could not be trained to engage the succeeding attacks
Remember my comments on the ability to switch targets being critical?

On training speeds the question that should be asked is 'If 10 deg/sec is sufficient why did the RN modify the 4.5in mounts to increase change rates from 10 to 20 deg/sec

Also I don't understand your comparison figures in the previous posting. Can you tell me how you calculated them.
Thanks

 

[RCAFson]

I think that you are being a little selective over your quotes from Navweapons. On the 5.25 it also states:-

1) Unfortunately, the design of the gunhouse was cramped and the heavy projectile and cartridge cases resulted in a lower rate of fire than expected. In addition, the slow elevating and training speeds of the mounts were found to be inadequate for engaging modern high-speed aircraft.

2)1) As designed, the expected rate of fire for these guns was 10 - 12 rpm. However, the heavy weight of the projectile and cartridge case plus the semi-automated fuze setting mechanism meant that this round required much crew handling before it could be rammed into the breach. The tight design of the gunhouse also interfered with the smooth crew operation necessary to achieve high rates of fire.

3)The mountings used on the King George V and Dido classes were very cramped and difficult to maintain. They were also difficult to train in the non-powered mode using the hand mechanisms. Their rather slow training speeds meant that they could not track fast-moving aircraft. These last two problems were highlighted during the Japanese attacks on HMS Prince of Wales. When she took up a 10-11 degree list as a result of damage received, it was found that some of the mounts could not be trained to engage the succeeding attacks
Remember my comments on the ability to switch targets being critical?

4)On training speeds the question that should be asked is 'If 10 deg/sec is sufficient why did the RN modify the 4.5in mounts to increase change rates from 10 to 20 deg/sec

5) Also I don't understand your comparison figures in the previous posting. Can you tell me how you calculated them.
Thanks

1) As I said previously, the RN and an RN 5.25iin gunner states that the 5.25in ROF is 10-12 rounds/minute/gun:
QF 5.25 inch Mark I naval gun - Wikipedia, the free encyclopedia Navweaps or the RN...guess who I believe more?

10deg/sec training rate is sufficient to track WW2 era aircraft. This is a simple fact and easy to verify with a protractor and some paper. The 5.25 is a long range AA gun and at 5000 yards, a 270 knot target will have maximum rate of bearing change of 1.7 degs/sec.

2)The 5.25 round weighed 80 lbs and used the same fuse setters as the 4.5 and 4" guns. The 4.5 twin (also a very cramped turret by the look of it) had a ROF of 12 r/m and the 4in 15-20 r/m. Who ever wrote the navweaps article is being illogical, as the crew handling is really no different than other RN DP weapons. The shell is placed in a fuze setter and then into the loading tray, exactly the same as the 4.7in and 4.5 twin turrets.

3) The ability of the 5.25 turret to operate without power and with a 10-11 degree list is not relevant. Would any turret operate under such conditions?

4) Sure higher is better, but for the vast majority of cases 10 degs/sec is sufficient. If it wasn't sufficient then I guess no Axis navy had any DP AA capability. Think about that for second. Also with VT ammo 20degs/sec might prove useful for very high speed, close range targets that didn't exist in 1940.

5) The USN had 1 battleship, 2 carriers, 3 heavy cruisers. 3 AA cruisers and 14 destroyers at Santa Cruz. I calculated the number of guns of each calibre for these ships and for an equal number of equivalent RN ships from the same time frame (Oct 1942).

 

[Juha]

Hello RCAFson
on 4.5" on NavWeaps.com, Mk III UP might well had higher ROF than that of Mk II BD because being with openbacked shield there should have had a bit more room for the crew to work.

On Force Z, IMHO 5.25" didn't do especially well, they didn't succeed broke the tight formations of IJNAF level bombers which got one hit on Repulse during the first attack and didn't hinder IJNAF torpedo bombers, which got 1-2 hits on PoW during their first attack, after which part of 5.25" were knocked out and PoW was practically out of fight, waiting for coup de grace. IIRC IJNAF lost only 3 planes during the attacks, 2 of which were allocated to pom-pom on the B-turret of Repulse during the last attack. Now AA of one BB + One BC + 3 DDs shoot down 3 planes and the planes got some 9-11 torpedo hits and 2 bomb hits on 2 RN capital ships.

Compare to on 9 March 1942 Tirpitz was attacked by the strike force of 12 torpedo-carrying Albacores under the command of Lieutenant-Commander W. J. Lucas from the aircraft carrier Victorious. The attack failed and 2 Albacores was shot down. Tirpitz was escorted by 4 DDs. Now Albacore was a different plane than Nell or Betty and numbers are different and Tirpitz had aircover by one of its Ar 196 float planes but after all one of Repulse's Walrus was also around Force Z but didn't try to interfere like the Arado crew did. Apples and oranges but still IMHO German naval AA did better than that of Force Z. Only conclusion one can draw on those 2 combats IMHO is that KM's AA wasn't hopeless.

On your comparison on AA, first of all, USN carrier defence was based on fighters, RN's originally on AA. So US carriers carried more fighters, RN carriers more AA and newest one had armoured flight decks. So it rather odd to give heavy weight to carriers AA and leave fighters off, unless one wants to give some advantage to RN and to the idea that carrier's best defence is its AA not its planes.

On heavy cruisers, standard USN treaty cruiser AA suit was at the beginning of the Pacific War 8 single 5"/25s, Pensacolas and Northamptons had had the number of their 5"s increased to 8 in late 30s. All New Orleans, Pensacolas and Portlands had 4 quad 1.1" plus up to 12 20mm already in Aug 42. Also Northamptons had some quad 1.1"s and some 20mm.

And after all even RN thought than twin Bofors was better than quad pom-pom, now obviously USN thought that twin Bofors was better than quad 1.1" but how to compare quad pom-pom to quad 1.1", especially when opinions differed widely on quad 1.1", but generally it wasn't liked.
And on heavy AA, here the quality of predictors was crucial, so counting the barrels is rather meaningless.

 

[Shortround6]

1) As I said previously, the RN and an RN 5.25iin gunner states that the 5.25in ROF is 10-12 rounds/minute/gun:
QF 5.25 inch Mark I naval gun - Wikipedia, the free encyclopedia Navweaps or the RN...guess who I believe more?

Lets see, the HMS Euryalus manages to demonstrate 10rpm while firing with zero change in elevation,zero change in training and zero change in range when fresh out of harbor and in calm seas in view of shore.
What happened to the 12 rounds per minute?
What happens when the turret is moving in train, the guns are changing elevation, the fuse settings keep changing and the deck is rolling and pitching? rate of fire speeds up

2)The 5.25 round weighed 80 lbs and used the same fuse setters as the 4.5 and 4" guns. The 4.5 twin (also a very cramped turret by the look of it) had a ROF of 12 r/m and the 4in 15-20 r/m. Who ever wrote the navweaps article is being illogical, as the crew handling is really no different than other RN DP weapons. The shell is placed in a fuze setter and then into the loading tray, exactly the same as the 4.7in and 4.5 twin turrets.

the round did not weigh 80lbs, the projectile weighed 80lbs. + the 41lbs of charge and cartridge case.
the 4.5 weighed 55lbs plus 38.5lbs of charge and cartridge case. the early mountings used a fixed round that combined both weights together. By the way the early twin mounts in the big ships did not have ammunition hoists that came into the mounts. the ammunition hoists/conveyors were outside the mounts and crew men took the rounds from the hoists/conveyors and placed them in two scuttles on the rear of the mount. distance the rounds had to moved from the hoist to the scuttles changed as the mount rotated.
the 4" used only a fixed round that weighed 63.5lbs.

5) The USN had 1 battleship, 2 carriers, 3 heavy cruisers. 3 AA cruisers and 14 destroyers at Santa Cruz. I calculated the number of guns of each calibre for these ships and for an equal number of equivalent RN ships from the same time frame (Oct 1942).

Except you made a few mistakes and/or fudged a few things.

you left out the South Dakotas 20 5in guns or only counted them as 8 guns?
Hornet CV 8the one at Santa Cruz had eight 5 in guns.
Enterprise had eight also.
total is 36 not 24.

Both US cruisers had had their 5"/25s (not really dual purpose but dedicated AA guns) doubled to 8 per ship after being built but pre war.
16 guns instead of 8.
so US total for heavy cruisers is 24, same as the British.

No argument with the AA cruisers.

As for the 76 DP guns on the British destroyers, I think you are being more than a bit optimistic.
The twin 4.7 had the elevation problem of 40 degrees, why don't you get out your pencil and paper and protractor or better yet some trig tables.
of from the Wiki page on the 5.25" gun.
" Hodges, Tribal Class Destroyers, p32: Diagram of High Level Bomber Attack: A 240mph target, at 12 thousand feet altitude could expect to be under for fire about 75 seconds, from the time it enters the effective range of the HACS until it flies to within the minimum range of a 5.25 gun elevated to 70 degrees. A Tribal class destroyer would be able to engage the same target for about 37 seconds."
Please note that the minimum range for the 4.7 would be at a much longer distance than the 5.25". In fact (if I have done the math right) the 240mph target at 12,000ft would be safe from a 4.7in armed destroyer once it got within 4768yds of it.
The J class (and follow ups) had inferior AA fire control to the Tribals for the 4.7s.
As for the 4in gun that replace the bank of torpedo tubes, it wasn't connected to anything. It depended on the gun captain's squinty eye for range, speed , altitude and course. It also depended on his wetted finger held up for atmospheric conditions data (doesn't work to well on a moving destroyer). And depended on the aimer and trainers cartwheel sights for final aiming.
The 4.7s on the Os and Ps (those that had them) were hand worked and not power worked.
The were fitted with 4 single 20m as completed and were later changed (in most) to 2 singles and 2 twins for 6 barrels.
The Q and R classes did get the better "tribal" AA director set up but the guns were essentially unchanged from the H class if not earlier.

Of course if your really want to disagree with my assessment of the 4.7" guns as dual purpose you could always claim that the the 8" guns on the British cruisers were dual purpose because of their 70 degree elevation, of course they have that fixed loading angle down at 10 degrees that you complain about with the Japanese ships.
The Japanese also provided AA shells even for battleship guns but that doesn't really make them true AA guns or dual purpose does it?

The British early 4.7s may have been called dual purpose but they weren't even really fooling themselves about it.

 

[Glider]

1) As I said previously, the RN and an RN 5.25iin gunner states that the 5.25in ROF is 10-12 rounds/minute/gun:
QF 5.25 inch Mark I naval gun - Wikipedia, the free encyclopedia Navweaps or the RN...guess who I believe more?

I think shorthounds posting covers this point.

10deg/sec training rate is sufficient to track WW2 era aircraft. This is a simple fact and easy to verify with a protractor and some paper. The 5.25 is a long range AA gun and at 5000 yards, a 270 knot target will have maximum rate of bearing change of 1.7 degs/sec.

Something I have never disagreed with. What I have said is that switching from one target to another is critical. A point you have not adressed

2)The 5.25 round weighed 80 lbs and used the same fuse setters as the 4.5 and 4" guns. The 4.5 twin (also a very cramped turret by the look of it) had a ROF of 12 r/m and the 4in 15-20 r/m. Who ever wrote the navweaps article is being illogical, as the crew handling is really no different than other RN DP weapons. The shell is placed in a fuze setter and then into the loading tray, exactly the same as the 4.7in and 4.5 twin turrets.

Now I must ask who do I prefer to believe. An article written by an organisation that specialises in this topic, or yourself who has written the article off as being illogical without any evidence. Who would you prefer?

3) The ability of the 5.25 turret to operate without power and with a 10-11 degree list is not relevant. Would any turret operate under such conditions?

Because ships get damaged and power can fail in combat.

4) Sure higher is better, but for the vast majority of cases 10 degs/sec is sufficient. If it wasn't sufficient then I guess no Axis navy had any DP AA capability. Think about that for second. Also with VT ammo 20degs/sec might prove useful for very high speed, close range targets that didn't exist in 1940.

I didn't ask if higher is better, I asked WHY would they make the change. After all it would involve slowing production, taking design experts from other areas of development. You don;t do this in a war without a very good reason. The questions stands Why did the RN make the change.
Of course the Japanese had DP guns no one is saying they didn't and the comment about close range targets didn't exist in 1940 I take to be a joke, you are kidding right?

5) The USN had 1 battleship, 2 carriers, 3 heavy cruisers. 3 AA cruisers and 14 destroyers at Santa Cruz. I calculated the number of guns of each calibre for these ships and for an equal number of equivalent RN ships from the same time frame (Oct 1942).

Thanks for this, as others have pointed out you have made some errors on this.

 

[Nikademus]

Hello
checked from Lundstrom, at Midway one of Hiryu's 10 VTs was shot down before AA opened fire, 2 F4Fs were shot down inside the escort screen, one by a Zero and one was claimed by a Kate gunner but the US pilot thought that he was shot down by naval AA, and F4Fs got 11 Vals before they dived according to Lunstrom, my old source says 10.

Hi Juha,

Here's what i garnered from Lundstrom:

Ok. here's the AA breakdown:

Coral Sea

Over Shoho:

none

Over Shok and Zuik

1 x SBD

Failed Dusk attack near USN TF 5/7/42

1 x D3A

Over Lex and York

2 x B5N
1 x D3A

Over Neosho and Simms

1 x D3A

Midway

Over Kido Butai

1 x A6M (friendly fire)
possibly 1 x B-26
1 x SBD

Over Tanikaze

1 x SBD

Over Mikuma/Mogami

2 x SBD

Over Yorktown

2 x D3A
2 x B5N

Eastern Solomons

Over Ryujo

zip

Over Enterprise

1 x F4F (friendly fire)
4 x D3A

(no B5N's attacked)

Santa Cruz

Over Shok and Chukuma

possibly 1 x SBD (Lundstrom is unclear here)

Over USN TF's

14 x D3A
11 x B5N

These figures represent immediate losses directly attributed to AA. They do not include damaged planes that ditched or were written off. It should also be noted that AA may have contributed in the loss of some Japanese bombers scored by USN fighters.

As mentioned, prior to Santa Cruz, USN AA wasn't really more effective vs. aircraft than the typical RN experience when it came to outright losses. The differential begins at Santa Cruz and can be directly attributable to the upgrading to large numbers of 20/40mm mounts. King Board AA upgrades helped but war experience showed way more and better AA was needed.

The Force Z experience must take into account the early crippling of PoW by a hit in the worst place imaginable which also took out the majority of her powered AA and imparied her speed and maneuverability. The biggest lesson the RN drew from the experience (besides the confirmation that aircraft were not the dominant weapon...capable of sinking even a modern capital ship...manned and at sea, ready for attack), was the need for redundant power and auxillery power backup.

 

[Glider]

I think its worth mentioning that the HACS worked to some degree over Force Z despite the problems. If I remember correctly a high proportion of the high level bombers were damaged and had to abandon the original plan for them to attack twice.
Could be wrong on this but its something that I recall

 

[parsifal]

HACs did work, but the AA effort over Pow Repulse was not one of the better AA moments for the RN. There were continual stoppages in the 2 pdrs, and the 5.25s had problems as previously alluded to. I dont think ther was any impedeiment to the Japanese preparing a second strike. 3 aircraft were lost, and 9 damaged to varying degrees.

There were times when RN AA produced some very fine results, such as over the Illustrious in 1941 and Fijis effort off Crete (though she was sunk after running out of ammunition) but the PoW and Repulse episode is not one of those Kodak moments

 

[RCAFson]

Hello RCAFson
on 4.5" on NavWeaps.com, Mk III UP might well had higher ROF than that of Mk II BD because being with openbacked shield there should have had a bit more room for the crew to work.

On Force Z, IMHO 5.25" didn't do especially well, they didn't succeed broke the tight formations of IJNAF level bombers which got one hit on Repulse during the first attack and didn't hinder IJNAF torpedo bombers, which got 1-2 hits on PoW during their first attack, after which part of 5.25" were knocked out and PoW was practically out of fight, waiting for coup de grace. IIRC IJNAF lost only 3 planes during the attacks, 2 of which were allocated to pom-pom on the B-turret of Repulse during the last attack. Now AA of one BB + One BC + 3 DDs shoot down 3 planes and the planes got some 9-11 torpedo hits and 2 bomb hits on 2 RN capital ships.

Compare to on 9 March 1942 Tirpitz was attacked by the strike force of 12 torpedo-carrying Albacores under the command of Lieutenant-Commander W. J. Lucas from the aircraft carrier Victorious. The attack failed and 2 Albacores was shot down. Tirpitz was escorted by 4 DDs. Now Albacore was a different plane than Nell or Betty and numbers are different and Tirpitz had aircover by one of its Ar 196 float planes but after all one of Repulse's Walrus was also around Force Z but didn't try to interfere like the Arado crew did. Apples and oranges but still IMHO German naval AA did better than that of Force Z. Only conclusion one can draw on those 2 combats IMHO is that KM's AA wasn't hopeless.

On your comparison on AA, first of all, USN carrier defence was based on fighters, RN's originally on AA. So US carriers carried more fighters, RN carriers more AA and newest one had armoured flight decks. So it rather odd to give heavy weight to carriers AA and leave fighters off, unless one wants to give some advantage to RN and to the idea that carrier's best defence is its AA not its planes.

On heavy cruisers, standard USN treaty cruiser AA suit was at the beginning of the Pacific War 8 single 5"/25s, Pensacolas and Northamptons had had the number of their 5"s increased to 8 in late 30s. All New Orleans, Pensacolas and Portlands had 4 quad 1.1" plus up to 12 20mm already in Aug 42. Also Northamptons had some quad 1.1"s and some 20mm.

And after all even RN thought than twin Bofors was better than quad pom-pom, now obviously USN thought that twin Bofors was better than quad 1.1" but how to compare quad pom-pom to quad 1.1", especially when opinions differed widely on quad 1.1", but generally it wasn't liked.
And on heavy AA, here the quality of predictors was crucial, so counting the barrels is rather meaningless.

The RN 4.5 BD turret could maintain 12 r/m for long periods:

# QF Mark III: same as Mark I, except for firing mechanism. Was fitted in twin mountings BD Mark II, BD Mark II** and BD Mark IV. HMS Illustrious fired about 3000 rounds of 4.5" ammunition, at an average of 12 rounds per gun per minute, during one prolonged action in January 1941.[3]
(3)Naval Weapons of WW2, Campbell, p17

QF 4.5 inch Mk I ? V naval gun - Wikipedia, the free encyclopedia

The 5.25 forced two bombers to abort and damaged 10 of 16, even though they were the only effective HA guns in Force Z. Repulse had a total of 4 x 4" and none of the destroyers had an AA FC system.

I don't understand, you are arguing that KM AA wasn't hopeless, yet Tirpitz's 4.1in guns had a slower traverse than the RN 5.25in.

This discussion is about AA capability. So agree that RN was ahead in AA capability in Oct 1942?

I could find any info on two of the older heavy cruisers, but even if we increase the AA as per your post above, it really doesn't change the over all picture.

All the RN capital units had the latest versions of HACS and tachymertic pom-pom directors with radar. I doubt there is any difference in FC, and for the AAA the RN is probably ahead.

 

[RCAFson]

Hi Juha,

Here's what i garnered from Lundstrom:

Ok. here's the AA breakdown:

Coral Sea

Over Shoho:

none

Over Shok and Zuik

1 x SBD

Failed Dusk attack near USN TF 5/7/42

1 x D3A

Over Lex and York

2 x B5N
1 x D3A

Over Neosho and Simms

1 x D3A

Midway

Over Kido Butai

1 x A6M (friendly fire)
possibly 1 x B-26
1 x SBD

Over Tanikaze

1 x SBD

Over Mikuma/Mogami

2 x SBD

Over Yorktown

2 x D3A
2 x B5N

Eastern Solomons

Over Ryujo

zip

Over Enterprise

1 x F4F (friendly fire)
4 x D3A

(no B5N's attacked)

Santa Cruz

Over Shok and Chukuma

possibly 1 x SBD (Lundstrom is unclear here)

Over USN TF's

14 x D3A
11 x B5N

These figures represent immediate losses directly attributed to AA. They do not include damaged planes that ditched or were written off. It should also be noted that AA may have contributed in the loss of some Japanese bombers scored by USN fighters.

As mentioned, prior to Santa Cruz, USN AA was really more effective vs. aircraft than the typical RN experience. The differential begins at Santa Cruz and can be directly attributable to the upgrading to large numbers of 20/40mm mounts. King Board AA upgrades helped but war experience showed way more and better AA was needed.

The Force Z experience must take into account the early crippling of PoW by a hit in the worst place imaginable which also took out the majority of her powered AA and imparied her speed and maneuverability. The biggest lesson the RN drew from the experience (besides the confirmation that aircraft were not the dominant weapon...capable of sinking even a modern capital ship...manned and at sea, ready for attack), was the need for redundant power and auxillery power backup.

Thanks for the AA totals but how did you conclude that RN AA was less effective? Force Z really only had one effective modern ship with minimal capability in Repulse and still did as well as the entire USN force at Midway or Coral Sea. If Force Z had had 3 modern destroyers and a modern ship like Renown, it would have done much better, as the RN was doing while defending convoys such as PQ-18.

I think there is every probability that an equivalent RN force could have matched or bettered the USN AA kills at Santa Cruz, simply because they would have more 40mm calibre AA combined with effective radar equipped tachymetric directors.

 

[Juha]

Hello Nikademus
thanks for you analyze, all that I can add that also at Santa Cruz USN had first time a BB screening a CV but I agree that that was only one of the factors that contributed to dramatic improvement in AA rffectiveness. Also IMHO in the Fist Team Lundstrom underestimate the effectiveness of US AA, accepting too easily pilots' opinion. In The First Team and The Guadalcanal Campaign he is more objective in pilots' claim vs AA claims question. But any way at most one could add one Val and 3-4 Kates to Midway AA kills around Yorktown.

Hello Gilder
On Force Z, IMHO the number of lightly damaged a/c isn't important, what counts is how many had to abort the attack. I cannot remember reliable info on that. For the plus side IMHO one can add a fourth plane to AA kills, that was the plane which was badly damaged and crashed on landing at Saigon. On the minus side, IIRC, it is decades ago when I read this, that 2 of the 3 kills around the ships were allocated to the pom-pom on the B-turret of Repulse, and that because its crew, as did the Captain Tennant, felt during the last torpedo attack that "This is it" ie felt that Jap VTs had got them cornered and didn't move fire to other targets when a target plane dropped its torpedo but kept firing at incoming VT until it was torched, only after that took the next nearest VT under fire. So their tactic wasn't anymore to try to save their ship but to make Japanese to pay max prise for sinking their ship.

Juha

 

[RCAFson]

Lets see, the HMS Euryalus manages to demonstrate 10rpm while firing with zero change in elevation,zero change in training and zero change in range when fresh out of harbor and in calm seas in view of shore.
What happened to the 12 rounds per minute?
What happens when the turret is moving in train, the guns are changing elevation, the fuse settings keep changing and the deck is rolling and pitching? rate of fire speeds up

HA guns are actually hardest to load at low elevation, as per the example stated. The RN states 10-12 r/m in the gunnery pocket book, and 10 r/m is within that range.

the round did not weigh 80lbs, the projectile weighed 80lbs. + the 41lbs of charge and cartridge case.
the 4.5 weighed 55lbs plus 38.5lbs of charge and cartridge case. the early mountings used a fixed round that combined both weights together. By the way the early twin mounts in the big ships did not have ammunition hoists that came into the mounts. the ammunition hoists/conveyors were outside the mounts and crew men took the rounds from the hoists/conveyors and placed them in two scuttles on the rear of the mount. distance the rounds had to moved from the hoist to the scuttles changed as the mount rotated.
the 4" used only a fixed round that weighed 63.5lbs.

The 4.5in BD mount fired a 93lb fixed round then, and was able to do so at 12r/m for long periods of time, and it used the same fuse setter and loading tray as the 5.25. The RN/RCN 4" didn't even have a loading tray and the entire round had to be pushed up into the breech with one hand, yet they could still fuse and load it at better than 15 r/m. I think we will have to agree to disagree regarding the 5.25 ROF as I think the evidence is pretty strong that it could fire at 10 r/m in combat.

Except you made a few mistakes and/or fudged a few things.

you left out the South Dakotas 20 5in guns or only counted them as 8 guns?
Hornet CV 8the one at Santa Cruz had eight 5 in guns.
Enterprise had eight also.
total is 36 not 24.

South Dakota had 16 x 5" and was the only new USN battleship with 16 5" guns. I actually added it up correctly as I made a subtotal for each class of ship and I used the correct numbers in the subtotal.

Both US cruisers had had their 5"/25s (not really dual purpose but dedicated AA guns) doubled to 8 per ship after being built but pre war.
16 guns instead of 8.
so US total for heavy cruisers is 24, same as the British.

I'll take your word for that as I can't find specifics on two of those ships.

As for the 76 DP guns on the British destroyers, I think you are being more than a bit optimistic.
The twin 4.7 had the elevation problem of 40 degrees, why don't you get out your pencil and paper and protractor or better yet some trig tables.
of from the Wiki page on the 5.25" gun.
" Hodges, Tribal Class Destroyers, p32: Diagram of High Level Bomber Attack: A 240mph target, at 12 thousand feet altitude could expect to be under for fire about 75 seconds, from the time it enters the effective range of the HACS until it flies to within the minimum range of a 5.25 gun elevated to 70 degrees. A Tribal class destroyer would be able to engage the same target for about 37 seconds."
Please note that the minimum range for the 4.7 would be at a much longer distance than the 5.25". In fact (if I have done the math right) the 240mph target at 12,000ft would be safe from a 4.7in armed destroyer once it got within 4768yds of it.

If the IJN focused their attacks on USN destroyers at Coral Sea, Midway and Santa Cruz, I would agree that 40deg elevation was a serious handicap, but they didn't, did they? The RN chose 40deg elevation because it still allowed the destroyers to provide AA coverage to capital ships within the destroyer screen, which was typically about 5-6000 yards from the screening destroyers. Your example actually proves that 40deg elevation DP guns can provide effective AA defense for capital ships, just as the RN worked out pre-war.

The J class (and follow ups) had inferior AA fire control to the Tribals for the 4.7s.
As for the 4in gun that replace the bank of torpedo tubes, it wasn't connected to anything. It depended on the gun captain's squinty eye for range, speed , altitude and course. It also depended on his wetted finger held up for atmospheric conditions data (doesn't work to well on a moving destroyer). And depended on the aimer and trainers cartwheel sights for final aiming.

As per wikipedia, the J-k-n class had their AA FC upgraded to match the Tribal class. The 4in gun could still receive AA direction from then main FC via phones and could still provide a long range barrage, and close range defence by eye sights, but I agree that another quad pom-pom would be better.

The 4.7s on the Os and Ps (those that had them) were hand worked and not power worked.
The were fitted with 4 single 20m as completed and were later changed (in most) to 2 singles and 2 twins for 6 barrels.
The Q and R classes did get the better "tribal" AA director set up but the guns were essentially unchanged from the H class if not earlier.

If you are firing at long range aircraft, even hand worked guns can keep up. Doubtless their are minor variations in the close range fit, but it doesn't make much difference.

Of course if your really want to disagree with my assessment of the 4.7" guns as dual purpose you could always claim that the the 8" guns on the British cruisers were dual purpose because of their 70 degree elevation, of course they have that fixed loading angle down at 10 degrees that you complain about with the Japanese ships.
The Japanese also provided AA shells even for battleship guns but that doesn't really make them true AA guns or dual purpose does it?

The RN actually provided a radar ranging system for non AA FC controlled guns called the Auto Barrage Unit:

The Auto Barrage Unit or ABU, was a specialized gunnery computer and radar ranging system that used Type 283 radar. It was developed to provide computer prediction and radar anti-aircraft fire control to main and secondary armament guns that did not have inherent anti-aircraft capability. The ABU was designed to allow the guns to be pre-loaded with time fused ammunition, and it then tracked incoming enemy aircraft, aimed the guns continuously to track the aircraft, and then fired the guns automatically when the predicted aircraft position reached the preset fuse range of the previously loaded shells.[32] The ABU was also used with guns that were nominally controlled by the HACS to provide a limited blind fire capability.[33]

 

[renrich]

Post # 117. Nik I stronly question the tonnage numbers. It shows the US sank in surface battles 33900 tons. The Kirishima was around that tonnage figure and sunk at Guadalcanal. The Furutaka was at least 7500 tons and the IJN DDs at Guadalcanal had substantial losses. I am doing this from memory but that 33900 figure looks fishy to me. Pun intended.

 

[Juha]

Hello RCAFson
Quote:"The 5.25 forced two bombers to abort..."

Thanks for that info, IMHO that was an achievement, not that of damaging lightly x planes. IMHO the badly damaged plane, if it was one of those damaged in this occasion, was an achievement.

Quote:"I don't understand, you are arguing that KM AA wasn't hopeless, yet Tirpitz's 4.1in guns had a slower traverse than the RN 5.25in."

Simply because to me the real results are what counts, so 2 out of 12 and effectively prevent accurate torpedodropping was a good achievement.

Quote:"So agree that RN was ahead in AA capability in Oct 1942?"

No, unless you can show that RN AA did better than what USN AA achieved at Santa Cruz

BTW Repulse had 6 4" AA guns and 3x 8 pom-poms IIRC and might well has been able to use it 9-12 x 4" LA guns against VTs

Juha

 

[RCAFson]

Something I have never disagreed with. What I have said is that switching from one target to another is critical. A point you have not adressed


Now I must ask who do I prefer to believe. An article written by an organisation that specialises in this topic, or yourself who has written the article off as being illogical without any evidence. Who would you prefer?

I did address it. But a 10 deg/sec traverse gun can swing 90 degs in the time it takes a 205 knots aircraft to fly about 1000 yds. This is hardly a serious handicap, and again 10degs/sec is better than most Axis AA guns.

The RN was an "an organisation that specialises in this topic" and they say 10-12 r/m and I believe them.

Because ships get damaged and power can fail in combat.

Fine, can a USN battleship 5" twin turret function without power at a 10-11 degree list? As I asked earlier can any turret function under those conditions?

I didn't ask if higher is better, I asked WHY would they make the change. After all it would involve slowing production, taking design experts from other areas of development. You don;t do this in a war without a very good reason. The questions stands Why did the RN make the change.
Of course the Japanese had DP guns no one is saying they didn't and the comment about close range targets didn't exist in 1940 I take to be a joke, you are kidding right?

It was becoming apparent by 1942 that the Luftwaffe would be introducing high speed guided missiles while very high speed fighter bombers were also appearing. These trends were not evident when the 5.25in gun was designed, nor was VT ammo, and a 20deg/sec 5.25 mount with VT ammo would be better able to engage very close range, very high speed targets.

 

[Juha]

Hello RCAFson
on that 40deg, now the plan was during the Pedestal that appr 3 DDs were 2000ys out of the heavy ships, other DDs 4000-6000y out. But when ships manouvered wildy under air attacks the distanced changed and sometimes even the outer DDs were much nearer to heavy ships than 4000y. And the 85 deg elevation of US DDs allowed that USN's anti-aircraft formation was that DDs were around heavy ships 2000y out. AND if you look pictures of RN Pacific Fleet under air attack in 1945 you can see that for some reasons the DDs (Ts and Us) were much nearer than 6000y from carriers. Why, for some reason when 55 deg elevation allowed it, also RN DDs operated much closer to carriers than that 4000-6000y.

Juha

 

[Nikademus]

Thanks for the AA totals but how did you conclude that RN AA was less effective? .

I didn't. My fumble fingers however are known Anglophobs!

I have corrected the post to what i really meant to say and have sentenced my fingers to holding a cup of Tea for an hour in public.

 

[Nikademus]

Post # 117. Nik I stronly question the tonnage numbers. It shows the US sank in surface battles 33900 tons. The Kirishima was around that tonnage figure and sunk at Guadalcanal. The Furutaka was at least 7500 tons and the IJN DDs at Guadalcanal had substantial losses. I am doing this from memory but that 33900 figure looks fishy to me. Pun intended.

The figures were for the Med Theater.