Dive Bomber Comparison

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BombTaxi said:
I'm not arguing it was better or worse than anybody else's equipment, just that it wasn't as good as it could have been and that this failure cost the RN dearly throughout the early phases of the war
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The only thing that prevented the RN from covering their ships with far more HA guns, pom-poms and quad .5" was money...and the RN can't really be blamed for that! Sure they should have developed the 20mm and Bofors sooner, etc, but who was going to pay for it all? AFAIK, the RN outfitted their ships with the best AA in the world in 1939 despite the budget restraints.
 
guys, great debate, and very intersting, but we have strayed a lot off topic.......was the RN relatively successful or unsuccessful in fending off bomber, particulalry divebomber attacks.

I did a bit more scratching around, and found that the 2 pounders were a bit problematic, apparently the quality of the ammunition and the cleanliness of the gun were important. This produced patchy results. During the attacks by FKX in January 1941, the illustrious expended over 30000 rounds of ammunition without stoppage, and shot down and drove off, a largte number of attackers. Conversely, during the PoW, Repulse debacle, Repulse expereienced numerous stoppages, which was attributed to faulty ammunition in the post action enquiry. In many actions the Pom Pom proved effective and vital to fleet defence, but sometimes it failed, with disatrous consequences.


The RN estimated the Pom Pom to be about half as effective as the Bofors.

Returning to the Illustrious action, if she expended about 30000 rounds of ammunition defending against 30 aircraft, and destroyed 8 aircraft (a guess, based on the proportional numbers of a/c allocated to hit her....3/4 of 13 /c lost is 8-9, but estimate 1 or 2 shot down by the close escort) thyen she was expending about 3500 rounds per kill. Thats against Divebomber targets. Over germany at this time, the germans were expending around 8500 rounds per kill over germany at that time (based on figures by Westermann - Flak - German AA Defenses 1914-45) then even at this early date the vulnerability of Divebombers to flak was being exposed. By the end of the war, the USN estimated they were expending around 500-1000 rounds per kill, whilst the German flak defenses over Germany, after an improvement in 1942 (around 4500 rounds per kill, using highly trained crews and the best radar fc available to them had slumped to nearly 16000 rounds per kill, as a result of excessive barrel wear, relatively poorly trained crews (factory workers manninng flak guns part time are not as good as excperienced flak crews, and a shortage of rdf. even ammunitionthat was dubious at times. If Divebombers had been used over Germany in place of high altitude level bombers, the germans would have wiped the force off the map since the light flak units would have been able to engage as well, and the increased kill rates would have been disastrous.
 
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Hello RCAFson
Quote: "For a destroyer to engage aircraft, it has to have a FC system that can predict the aircraft movement and send the correct fuse timing to the guns…"

I know the FKC system and doubt that it was even as good as HACS, otherwise RN would have put it and not bigger HACS on bigger ships, and early version of HACS were flawed, later marks and upgrades made it better and last versions were IMHO good as I have wrote earlier. And I have read the chapter of HA fire in Gunnery Pocket Book, 1945 version, earlier. I put the Hodges' quote only to defend navweaps.com opinion because not being native English speaker to me "setting of HE time fuzes by hand" and using "manual Fuze-setting Machine Mk V for fuze-setting" is more or less same. To me by hand doesn't mean that one was turning fuze using a wrench, having seen many film and having read Hodges and Friedman, were the working of the Fuze-setting Machine Mk V is explained.

And again, if RN had thought that they had a passable DP system in their DDs they would never halved the torpedo-armament of their DDs just for to get ONE HA 3" or 4" gun onboard those DDs. OK in Tribals which had only a quad set anyway, they changed one twin 4.7" mount to one 4" mount. IMHO that reveal the state of AA defence of RN DDs, USN had only changed the mounts of their leaders which had had 5" LA mounts originally and IIRC some had both LA and HA 5" mounts during the war at least temporary.

Juha
 
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I can only say that FKC did work and it did shoot down aircraft and according to wikipedia FKC was used on cruisers and aircraft carriers:

It first appeared as the FKC Mk1 in destroyers of the 1938 Tribal class,[2] while later variants were used on sloops, frigates, destroyers, aircraft carriers and several cruisers.[3]
(3) Naval Weapons of WW2, Campbell, p. 19
Click to expand...
Fuze Keeping Clock - Wikipedia, the free encyclopedia

. Late in the war the USN was bypassing their 5" FC computers in favour of the Mk51 gyro system, so I guess the USN had some problems too. AFAIK, the fuze timing was sent to machine fuze setters which could very quickly set the fuse and allow the guns to be loaded quickly, and RCN 4" twin mounts could achieve 15 to 20 rounds per minute using them.


Lots of USN destroyers had 5" HA guns and/or torpedoes removed for more automatic AA:

Benham-class destroyers in World War II

Benson- and Gleaves-class destroyers — Four-gun modification

The fletcher class had 1/2 their torpedo tubes removed in favour of more AA:
Fletcher-class destroyers — 1945 anti-aircraft modification
 
Hello RCAFson
Quote:" Late in the war the USN was bypassing their 5" FC computers in favour of the Mk51 gyro system, so I guess the USN had some problems too"

IIRC not even US was able to produce enough high-precision analogue computers, their navy and army expanding so much so fast.

Quote:" AFAIK, the fuze timing was sent to machine fuze setters which could very quickly set the fuse and allow the guns to be loaded quickly"

There was usually nothing wrong with Fuze-setting Machine Mk V, occasional tuning problems, but nothing that would not be overcome with good training. As I wrote, I only took a notice on it because IMHO Hodges and navweaps.com are in principal agreement on it.

Quote:" The fletcher class had 1/2 their torpedo tubes removed in favour of more AA"

The most important point here is, when that happened. RN was forced to halve the torpedo-armament, which was DDs main anti-shipping weapon against heavier ships and sometimes also against enemy DDs, in 1941, when KM still was enlarging its surface fleet, Fletchers lost their second TT bank in 45, when most of IJN's surface fleet was sunk and in fact almost all what was left were floating at the harbours because of lack of oil. A big difference here.

Juha
 
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I am afraid that I missed this thread which is a shame as its a topic that interests me. I would argue that no navy understood the threat from the air before the war as well as the RN. They had a number of actions in place pre war, to deal with the threat that were not matched anywhere else and money was not the problem.

The actions I am thinking of were:-
i) The conversion of old WW1 cruisers to AA cruisers giving them a vital front line role which paid many dividends.
ii) The building of the first AA Dido class cruisers. Until the Atlanta class came along they were unique
iii) The conversion of some merchant vessels to AA ships. These were probably the most extensive and complete conversion of any merchant ship to a naval fighting vessel anywhere, with firepower equal to any cruiser in the AA role.
iv) A number of VW class destroyers were altered to 4 x 4in DP guns as an escort.
v) The Hunt class destroyers with more punch to the ton than you will find anywhere
vi) Escort such as the Black Swan equal to any AA escort you care to mention
vii) The early selection of the 2pd as a weapon of choice for defending warships. It may not be as effective as the 40mm but pre war you will have difficulty fining a better weapon. A quad mounting on a destroyer was an effective defence
viii) The 0.5 was an ineffective weapon but the same mistake was made by most navies and the RN did replace them with 20mm as quickly as possible

The only major and I admit it was a major mistake the RN made was the lack of DP guns on destroyers. That said I believe a case could be made for saying that this wasn't a massive probnlem until Proximity fuses were developed. Hiitting an aircraft with heavy AA fire was very difficult before this. I would always put forward the case that 6 x 4in DP would have been far more effective than 4 x 4.7 LA.

The difficulty that the RN had in increasing light AA fire wasn't in my view money or desire, it was space. People forget how much smaller RN destroyers were compared to other navies with the exception of the Italian navy.
The standard RN war built destroyer in standard tons was approx 30% smaller than the Fletcher, 20% smaller than the Yugumo and 40% smaller than the German destroyers.

To counteract this the RN tended to develop more sophisticated mountings to improve the effectiveness of the guns they carried. Twin 20mm were often in power operated mountings as were single 40mm guns and sighted using reflector sights. The twin Hazemeyer mounting was a step too far but being of a gyro stabalised mounting with built in radar direction and sight, it showed the lengths that they were trying to go to improve the situation.
All these developments cost money so I would suggest the limitation was on deck space not cost
 
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Hello Glider
I agree almost all of your analyze, but IMHO 5.25" wasn't too good as AA gun, being too slow in traverse and elevation and having too heavy shell for high ROF. 4.5" would have been better armament for an AA ship but I understand the RN's selection, they thought that 4.5" shell would have been too light for surface fire for a cruiser size ship.
I also think that especially Hunts and those AA cruiser conversions were very good decisions.

On heavy AA guns, IMHO the US system having one standard gun, 5"L/38 was better than that of RN's, still installing during the war 4", 4.5" and 5.25" heavy AA guns on their ships, partly because lack of production capacity for the newer guns, plus 4.7" for DDs, seems a bit like logistic nightmere.

IMHO the fact that RN emergency program DDs were smaller than those of most comtemporarys was a conscious decision to select quantity over quality, based on limited production facilities. And I agree with it, small DD was better than no DD. And those emergency DDs did well for ex. during the Battle of Barents Sea. But the fact remain that the Ts and Us of British Pacific Fleet were clearly weaker in AA and A/S weaponry than USN's Fletchers and Sumners, but as I wrote earlier RN had saw this and had Battles and Darings in pipeline.

Juha
 
Hello Juha
I totally agree that the 5.25 was a better anti shipping weapon and less effective as an AA gun but at the time it probably seemed a good design and showed that the RN were taking the AA threat seriously.

Re the emergency destroyer program the design was based on the JK destroyer hull which was the latest pre war design and larger than most inter war british designs. Looking at it from that position it wasn't I believe a decision to settle for a smaller design, more the current design. They were no match for the Fletcher class but they had a respectable AA fire (apart from the DP weapons). Most were equipped for the Pacific with either a quad 2pd or a twin 40mm Hazemeyer mounting backed up by other weapons such as 4 x 40mm in single mounts or 8 x 20mm whilst keeping her 8 x TT.
As we mentioned no match for the Fletcher but a fair comparison for the Benson class which was of a similar size.
 

The USN was using the Mk51 for close range AA work, with the 5"/38 even when the same ship had the Mk37 system installed. Apparently, the Mk37 computer, which was very advanced, was also quite slow in forming a "solution".

I think it really shows that the USN did not face the same intensity of air attack as the RN, until late in the war.
 
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Hello RCAFson
I'd say IJN attacks during the Battle of Coral Sea, Midway, Santa Cruz etc were intensive, USN lost Lexington and Hornet sunk by air attacks, Yorktown badly hit at both first ones and in the end sunk by IJN sub at the end of BoM, Enterprise damaged and Hornet sunk at Santa Cruz.

Juha
 

Elevation/traverse rates, deg/sec:

RN 5.25: 10/10 (most ships)
RN 5.25 RPC: 20/20 (Bellona class and Anson)
IJN 5": 6-12/4-6 (fixed angle loading so the gun had to be depressed and elevated again to load/fire.
IJN 5"/40 A1: 12/6-7 (Yamato and others mostly were A1, B1 very late war)
IJN 5"/40 b1: 16/16
RN 4.7" twin: 10/10
RN 4.5 twin: 10/15
RN 4.5 RPC: 20/20
KM 4.1" 10/8-8.5 (most common variants)
(data from navweaps.com)

so if the 5.25 was too slow in elevation and traverse, what does that say about axis AA guns?

However, the wikipedia article on the HACS states: "6 degrees per second... was sufficient to track a 360 knot crossing target at a range of 2000 yards." so it seems that 10 degs sec was adequate for most of the war.

There seems to be some disagreement about the ROF. The RN Pocket Gunnery Book says 10-12 rounds per minute per gun, which seems OK. The very long range and high MV would denote a flat trajectory which, along with the heavy shell should make it an effective AA gun. The USN, in 1945, began to introduce the 5"/54 which had a heavier shell and longer range than the 5"/38 and seems to be ballistically similar to the RN 5.25.
 

How many aircraft actually made it through the CAP to attack the USN carriers?


IJN attacking sorties:
K = kate, V=Val , HLB = high level

Coral Sea:18k,22v = about 40
Midway : 18v,(only 7 through CAP),10K(only 7 through CAP) = 14!
Santa Cruz: 22K, 18V (2-3 down by CAP) 12K, 20V, 9K, 4v 6HLB = about 90

so only Santa Cruz was a heavy attack, and it was split between two carrier groups

so three carrier battles = 144 IJN attack sorties, so about 1/2 of what the RN faced during Operation Pedestal alone, or PQ-18. alone.


data from Titans of the Seas, Belotte. This is pretty old, so newer books may be more accurate.
 
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A couple of things.
i) The HACS system was quite good for what it was intended for ie defending against high altitude bombers. However experience proved that this wasn't the most dangerous threat, dive bombers and torpedo planes were the greatest danger.
ii) 6 degrees per second may well be sufficient to track a target but first you have to get your gun to point at the target before you can track it. I don't know if you have done any clay shooting but the speed is required to get the gun on the target, tracking is a lot slower. When facing more than one target the ability to change from one to another is critical
iii) Air attacks can continue for long periods and you will note that the 10-12 rpm was a target not achieved due to the design of the turret and the effort required which could not be sustained.
 


10 degs/sec traverse was still better than most axis AA guns. It is only at very close ranges that traverse rates higher than a few degrees/sec are encountered, while closing targets on an attack course will have very low rates of elevation/traverse change. The RN was surprised sometimes, but they also had radar sooner than everybody else so that if an aircraft is detected at more than about 10000 yds the 5.25 would still have plenty of time to get on target.


The wikipedia article on the 5.25 has some things to say about ROF:
QF 5.25 inch Mark I naval gun - Wikipedia, the free encyclopedia


So it seems that 10 rounds per minute per gun was achieved in combat, which matches the 10-12 rounds per minute stated in the Pocket Gunnery Book.
 
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Found this on wikipedia:

Prince of Wales engaging TBs during Operation Halberd, with her 5.25in guns:
WITH THE NAVY - British Pathe
note the low angle of elevation of the 5.25" guns.

... Prince of Wales was credited with several 5.25 inch kills during Operation Halberd,[101] and damaged 10 of 16[102] high level bombers in two formations during her last engagement...
Click to expand...

(101)Allied Battleships in WW2, Garzke and Dulin, p. 191
(102) Garzke and Dulin. Allied Battleships in WW2. pp. 195, 206–207.

This is another video of a convoy battle, at about 1:03, watch the shells chase the TB:
MALTA CONVOY - FURTHER PICTURES - British Pathe
 
Hello RCAFson
Navweps says that for 5.25" 10-12 ROF was designed but 7-8 actual.
Now US 5"/38 had vastly superior rates and ROF and even US 5"/51 had better rates and ROF
Also 4.5" had better ROF, how much better difficult to say because AA cruisers would have had the same Mk III UD like WWII Ark Royal, my copy of Ark Royal book might have the answer but I don't have time to dig that out, same elevation but 50% better train rate.

Santa Cruz, the first attack, inside AA range: 16 dive-bombers, of which one was badly dam and 18 torpedo-planes, of which one badly dam. 2nd attack, 18 dive-bombers and 15 torpedo-bombers. 3rd attack 17 dive-bombers.

And from memory, Midway: 12-15 dive-bombers and 10 torpedo-bombers, Coral Sea more, probably even more than during the first two attack at Santa Cruz because the attackers came to same carriers which were bigger than Midway's Hiryu and USN fighter control had learned lessons from Coral Sea, Midway and Eastern Salomons.

Juha

ADDITION: On Midway, 10 VTs got inside AA-fire but some Wildcat followed them there, claimed 3 one Wildcat shot dowm/badly dam by own AA fire. Now fighter pilots claimed those 3 and said that AA fire was inaccurate, and guess what naval gunners said? Jap VBs at Midway, 7 might be right but that means to take more or less by face value of F4F pilots claims, the attack consisted 18VBs, 10VTs and 6 VFs(Zeros). And Japanese were more deadly than anybody else in 1941-42, the first 6 Vals that attacked Hornet got 3 hits. Also USN AA at Santa Cruz was deadly, especially that of TF 16.

2nd ADDITION, you are counting apples and oranges, At Coral Sea the first attack by Shohaku and Zuikaku, which instead of finding US carriers, found Naval oiler Neosho and DD Sims, both of which were sunk, 2nd attack was clearly smaller one, only most experienced VT crews, IIRC correctly 18 VTs , didn't found US carriers, dumped their torpedos and on return journey overflow US TF in the darkness and suffered losses. Next day the main attack, my First Team is in attick but according to Rohwer and Hummelchen consisted of 90 a/c. So IJN flew at least say 150 attack sorties during those 2 days.
CORRECTION: Contrary to my habits checked Wiki article on the Battle of Coral Sea, which seemed to be good, at least sources are good, so IJN carrier planes flew 78+27+69 attack sorties=174 attack sorties there.
 
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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.
 
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The 40mm gun made it's first appearance, in large numbers at Santa Cruz, but also the USN ships had a lot more 20mm guns by then as well, IIRC. IJN DBs might have been more accurate but Luftwaffe DBs were dropping 500kg bombs. Given equivalent numbs of ships, IMHO RN AA would have been more effective against IJN attacks at Coral Sea and Midway simply because there would have been a lot more barrels firing.
 
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
 
Hello RCAFson
on dive bombers, yes I agree that while in 41-42 IJN was unsurpassed in accuracy the Ju 87 could drop clearly more heavy bombs than Val. On the other hand also IJN carrier torpedo bomber crews were very good, much better than LW crews and better than Italians in spite of the very succesful attack on PQ 18 by KG 26, after all during that attack the merchantmen forgot evasive manoeuvres in the heat of battle, something that USN and RN ships didn't forgot even if PoW's first manouvre was a badly thought out and after that it could not manoeuvre much.

Juha
 
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