What was the most effective naval anti-aircraft gun of WW2?

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Re: What was the most effective naval anti-aircraft gun of W

Postby Keith Enge » Mon Dec 03, 2012 6:26 pm

The 20mm was still downing planes at the end of the war. The problem was that it was basically a revenge weapon. Many of the times, perhaps most, it killed planes after they had dropped their ordnance, particularly divebombers when they were vulnerable pulling out of their dive. A weapon that kills planes after it has dropped its ordnance has a major problem when that plane is a kamikaze. Even if you killed the pilot, the plane continued on in its ballistic trajectory.

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Re: What was the most effective naval anti-aircraft gun of W

Postby Dave Saxton » Mon Dec 03, 2012 8:33 pm

alecsandros wrote:
Dave Saxton wrote:
Neoconshooter wrote:IIRC, they dropped 18-19 Tallboys and got one hit and 1-2 near misses? One of the bombs landed over a mile away, again IIRC. If only those three planes would have been shot down, the Tirpitz would have been unscathed?
The ability of Radar directed medium caliber guns shooting proximity fused shell at target less than 20,000'/6,096M during WW-II is very well documented earlier in this very thread. The possibility that such a system could have saved Tirpitz is beyond question


It matters little what type of gun is used, it IS the fire control system that makes the big difference!


Tirpitz had a Wuerzburg mounted to a M42 director and firecontrol system.


But hiting the Lancasters at 7km altitude was a very difficult task...

Exactly, even with the best radar and FC system available. I think we tend to over estimate the effectiveness of ship board flak during WWII.
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Re: What was the most effective naval anti-aircraft gun of W

Postby Dave Saxton » Mon Dec 03, 2012 9:04 pm

The 1st Lancaster attack on Sept 15 1944 was with Tirpitz still in Kaa Fjord. The attack consisted of 27 Lancasters. German radar detected the attack in plenty of time, but requests for fighters amounted to nothing. Becauase the attack was detected so early, by the time the bombers got close enough to sight Tirpitz, it was already completely shrouded by 10/10 smoke screen. The British couldn't even see the target. The must have bombed using H2X or H2S, and the accuracy was actually terrible. Most bombs missed by up to mile. Only the 1st group to release bombs came close and one scored a hit through the bow with the bomb exploding underneath the bow after passing through it. In other words pure luck!

The light flak wasn't used if I recall correctly. Tirpitz's heavy AA was forced to fire blind, and as with the carrier strikes with complete smoke screen, it was only through the use of radar that it was able to fire at the bombers. The bombers did their run in at 16,000 feet and released their bombs at 12,000 feet. There were up to 98 AA guns around about the anchorage but most of these were light flak and they were mounted mainly around the outer portions of the fjord where the destroyers tied up.
Entering a night sea battle is an awesome business.The enveloping darkness, hiding the enemy's.. seems a living thing, malignant and oppressive.Swishing water at the bow and stern mark an inexorable advance toward an unknown destiny.

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Re: What was the most effective naval anti-aircraft gun of W

Postby Neoconshooter » Tue Dec 04, 2012 2:18 am

alecsandros wrote:
Dave Saxton wrote:
Neoconshooter wrote:IIRC, they dropped 18-19 Tallboys and got one hit and 1-2 near misses? One of the bombs landed over a mile away, again IIRC. If only those three planes would have been shot down, the Tirpitz would have been unscathed?
The ability of Radar directed medium caliber guns shooting proximity fused shell at target less than 20,000'/6,096M during WW-II is very well documented earlier in this very thread. The possibility that such a system could have saved Tirpitz is beyond question


It matters little what type of gun is used, it IS the fire control system that makes the big difference!


Tirpitz had a Wuerzburg mounted to a M42 director and firecontrol system.


But hiting the Lancasters at 7km altitude was a very difficult task...

The Lancs were at <5,500 to <5,800 M altitude! Not 7,000M. The typical operational ceiling of the Lancaster was well under 20,000' when laden, and even after bomb drop, Lancs at long range have so much fuel still on board that they can not climb above 20,000'
Do you think Wurzburg/M-42 is equal to any of the later American AA FCSs?

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Re: What was the most effective naval anti-aircraft gun of W

Postby Neoconshooter » Tue Dec 04, 2012 2:31 am

Dave Saxton wrote:The 1st Lancaster attack on Sept 15 1944 was with Tirpitz still in Kaa Fjord. The attack consisted of 27 Lancasters. German radar detected the attack in plenty of time, but requests for fighters amounted to nothing. Becauase the attack was detected so early, by the time the bombers got close enough to sight Tirpitz, it was already completely shrouded by 10/10 smoke screen. The British couldn't even see the target. The must have bombed using H2X or H2S, and the accuracy was actually terrible. Most bombs missed by up to mile. Only the 1st group to release bombs came close and one scored a hit through the bow with the bomb exploding underneath the bow after passing through it. In other words pure luck!

The light flak wasn't used if I recall correctly. Tirpitz's heavy AA was forced to fire blind, and as with the carrier strikes with complete smoke screen, it was only through the use of radar that it was able to fire at the bombers. The bombers did their run in at 16,000 feet and released their bombs at 12,000 feet. There were up to 98 AA guns around about the anchorage but most of these were light flak and they were mounted mainly around the outer portions of the fjord where the destroyers tied up.

This is new to me. I thought the smoke screen was ineffective because of wind direction. Also, I thought they dropped from 18-19,000'? From 12,000' is the first time I've ever herd of dropping Tallboys form so low! Much was made of them going supersonic before impact, but that is impossible even in a vacuume from altitudes the loaded Lanc can reach.
But on what, according to you above, must have been the second attack, the Tirpitz was clearly visible in the film shot at the time and they missed by a mile on at least one occasion and by very large distances with more than half the bombs. You can see some of those huge misses in the film on U-Tube!

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Re: What was the most effective naval anti-aircraft gun of W

Postby Neoconshooter » Tue Dec 04, 2012 2:49 am

delcyros wrote:
dunmunro wrote:
I wonder how these shells maintained structural integrity against the accelerations required for such high MVs?


In all applications I know of for the M-Geschoss they never cut down the mv. Rather contrary, in smaller guns (f.e.20mm and 30mm range) the adoption of the M-Geschoss, which was a bit lighter than a normal HEI/HET-thanks to different density figures for high explosive and steel, respectively- significantly increased the muzzle velocity. Still, the sectional density was lower, hence a poorer ballistic coefficient and worse energy retention of these rounds.
Downrange striking velocity wasn´t considered as important as blast effect againt aircraft targets.

But I am not very enthusiastic about the reliability of these rounds structurally. Probably not a problem during firing these weapons (no such safety records to the best of my knowledge) but what RobertsonN meantioned above as "berstfrei" represents a dud by impacting strong surfaces. They would also desintigrate hitting armourplates in airplanes with greatly reduced effect.

I was also wondering why the US didn´t adopt the M-round for it´s light AAA in the Pacific (and else). I understand that the principle was adopted in the 50´s and 60´s, though.

The united States never adopted a "M-Geschloss" type round for any weapon! The post war M-50 series of 20 MM shell was considerably smaller and held much less explosive than the German WW-II shell. ( 9-10 Grams of much denser HE, compared to 17 for the German shell.) It took us forever to adopt the British L-15 projectile for 155 MM Howitzers. We wanted a stronger shell to perforate some targets before detonation.

Our philosophy was that the shell had to perforate the target intact before detonation, something that could not be guaranteed with the German shell, even against the very thin aircraft skins of WW-II! Any even cursory examination of damage pics from then would show many partial detonations, or failures to detonate at all.

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Re: What was the most effective naval anti-aircraft gun of W

Postby Neoconshooter » Tue Dec 04, 2012 3:13 am

dunmunro wrote:
Neoconshooter wrote:It matters little what type of gun is used, it IS the fire control system that makes the big difference!
Search for pictures of 20 MM guns. Some have huge bulky sighting systems and other have a ring and bead. Look at 40 mm quads, some have radar dishes and others do not. Which type do you think will be more effective. You see it is the stuff you can not see, or do not notice, like the large boxes housing FC Computers beside, or behind the mounts that makes the largest differences.
The second most important ingredient in the mix is the type of ammo used. Proximity fused shell from larger caliber cannon are the clear winners here, far out pacing any other munition. The larger gun with the highest rate of fire easily out ranges the smaller and each has a band where it will be most effective. The farther out you engage the enemy, the least likely he is able to damage you.

So, to summarize, 5/38 Calibre gun, with either on mount, or remote mount Radar and FC Computer, shooting proximity fused ammo is the king of WW-II guns.

While the British invented the computer controlled firing predictor, it was the Americans who perfected it in mid/late WW-II to the point it could be used to shoot down aircraft. Regardless of tech sharing, no other nation or Navy implemented such a system during the war.


All the major navies had AA FC systems that could shoot down aircraft.They were just not nearly as effective as those on American ships late in the war. The introduction of radar ranging by the RN in 1939/40Which set/system was this and which ships was it installed on in 1939? radically improved the effectiveness of AA systems against straight line targets but no WW2 era long range AAFC system could reliably shoot down manoeuvring aircraft,This is not true! Many maneuvering aircraft were shot down, even at longer ranges when using VT ammo. IE >5-6,000M! except at close range, with VT ammo, when the ToF became very short.

How did the system you mention above couple the range as found by the Radar to the FCS?

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Re: What was the most effective naval anti-aircraft gun of W

Postby Dave Saxton » Tue Dec 04, 2012 3:17 am

Neoconshooter wrote:This is new to me. I thought the smoke screen was ineffective because of wind direction. Also, I thought they dropped from 18-19,000'? From 12,000' is the first time I've ever herd of dropping Tallboys form so low! Much was made of them going supersonic before impact, but that is impossible even in a vacuume from altitudes the loaded Lanc can reach.
But on what, according to you above, must have been the second attack, the Tirpitz was clearly visible in the film shot at the time and they missed by a mile on at least one occasion and by very large distances with more than half the bombs. You can see some of those huge misses in the film on U-Tube!


The smoke screen was ineffective during the strikes at Tromso, but not the one at Kaa Fjord. During the Oct. strike the wind changed direction. During the final strike the smoke generators on the ship wre unoperable and those placed around the anchorage were incomplete.
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Re: What was the most effective naval anti-aircraft gun of W

Postby tommy303 » Tue Dec 04, 2012 5:22 am

Our philosophy was that the shell had to perforate the target intact before detonation, something that could not be guaranteed with the German shell, even against the very thin aircraft skins of WW-II! Any even cursory examination of damage pics from then would show many partial detonations, or failures to detonate at all.


Considering the normal mix in cannon ammunition was M-shell, HEI, HE, and AP, I should think it would be difficult to tell the difference between the impact points as a simple hole punched in the skin of a plane could be an AP round and an HE or HEI might appear to be a partial detonation compared to an M-Geschoss.

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Re: What was the most effective naval anti-aircraft gun of W

Postby Dave Saxton » Tue Dec 04, 2012 6:09 am

"All the major navies had AA FC systems that could shoot down aircraft."They were just not nearly as effective as those on American ships late in the war.


Be careful to not overstate your case. Note:

While the Army was beginning to demonstrate excellent AA fire, the Navy’s performance with FD radar with the mechanical-analog predictor, although greatly improved with the introduction of the proximity fuse, was failing all to often. …attacks often came in very low, evading air warning radar until late and making it impossible for the 40cm FD to determine height accurately. When air attacks began to come from kamikazes the deficiencies of air defense became serious. The proximity fuse was of no avail, if the shell was not placed within 20 meters of the target…Bell also took to design a replacement for the FD, the mark 12, using the same basic structure but on 33cm and with automatic tracking for range; automatic tracking in direction was to follow with a later modification. This still left the mark 12 with manual tracking, not suited to the agile attackers and still followed by a slow mechanical predictor, and most ships retained the mark 4 (FD). No mark 57 directors appeared until early 1945. Once the kamikazes were within range, the non radar 40 and 20 mm guns had to save the ship and often did.

This situation seemed nothing short of scandalous to Ivan Getting, who had been working on a Navy 3 cm fire-direction radar, the mark 35, and a compatible and highly advanced director, the mark 56. When there was no evident move by April 1945 to place this system into service, he wrote a sharp letter to the Navy Department, pointing out the superiority of the Army radar, thinking that tweaking the inter-service rivalry would suffice to bring about the desired conversion from 40cm manual to 3cm automatic. Given the size of the US fleet by the end of 1944 and the time required for conversion compared to the expected length of the war; it is hardly surprising that this suggestion was rejected, which with afterthought Getting conceded to have been the right decision.
( L Brown, Technical and Military Imperatives A Radar History of WWII, page 415-416)

At this time the Royal Navy was introducing Type 275, and the German Navy had already deployed FuMO213 with a highly advanced director, and would be deploying Euklid with a highly advanced director had the overall war developed more to their favor.
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Re: What was the most effective naval anti-aircraft gun of W

Postby dunmunro » Tue Dec 04, 2012 11:59 am

Neoconshooter wrote:
How did the system you mention above couple the range as found by the Radar to the FCS?


Type 280 and type 279 both had a precision ranging panel which transmitted the radar range AND range rate directly to the HACS table (computer) via magslips (syncro motors) with power follow-up for the range rate (radar operator would match the range rate to the target and that rate would continue to be transmitted to the table as long as the target maintained a steady course.

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Re: What was the most effective naval anti-aircraft gun of W

Postby Neoconshooter » Wed Dec 05, 2012 5:39 pm

tommy303 wrote:
Our philosophy was that the shell had to perforate the target intact before detonation, something that could not be guaranteed with the German shell, even against the very thin aircraft skins of WW-II! Any even cursory examination of damage pics from then would show many partial detonations, or failures to detonate at all.


Considering the normal mix in cannon ammunition was M-shell, HEI, HE, and AP, I should think it would be difficult to tell the difference between the impact points as a simple hole punched in the skin of a plane could be an AP round and an HE or HEI might appear to be a partial detonation compared to an M-Geschoss.

That is a good point, but not relevant. Because of the huge differences in type of construction, it is easy to tell the differences between the types of shell when they burst. The conventional thick walled shell burst in to few, but large fragments that make holes far from the detonation point and the size of the tear in the skin from the expanding explosive products is very small. The M-Shell with it's very thin walls had few, if any large fragments and even partial detonations of damaged shells made large tears in the skin, but almost no fragment holes larger than a fingernail clipping. It is the absence of large fragment holes and presence of numerous very small holes close to the burst point that are easy to identify which type of shell made which hole. Partial dets can be judged by the size of the torn area and absence of larger holes from conventional shell bodies in the skin next to the detonation. In pictures of the inside, the presence of large fragments that make holes far from the point of detonation indicate conventional shell types. A conventional shell might make exit holes on the far side of the fuse, away from the point of impact Most of the fragments from the M-Shell would fail to perforate the skin of the plane more than a foot or so from the point of detonation and show up in the pictures as many small dents with some partial perforations. The absence of fragmentation near the impact point proves the type as AP. While 20 mm AP had little trouble perforating ALL armor on any plane, HE/HEI/HE-T and their respective fragments would not perforate any armor at any point, usually owing to fuse initiation on the plan's skin at any distance before the armor plate. Things like the outer case of Radios, air bottles and instrument panel plates would stop all fragments from small caliber bursting munitions. That is why post war, the VERY thin wall M-Shell construction type was eventually abandoned by every one. The closest imitator is, IIRC, the British Mk-Z(50) 30 mm shell for the Aden Revolver gun and the shell body walls are more than twice as thick as the German war time M-Shell bodies. IIRC, the Mk-Z was discontinued in the mid to late sixties?

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Re: What was the most effective naval anti-aircraft gun of W

Postby Neoconshooter » Wed Dec 05, 2012 5:53 pm

Dave Saxton wrote:
"All the major navies had AA FC systems that could shoot down aircraft."They were just not nearly as effective as those on American ships late in the war.


Be careful to not overstate your case. Note:

While the Army was beginning to demonstrate excellent AA fire, the Navy’s performance with FD radar with the mechanical-analog predictor, although greatly improved with the introduction of the proximity fuse, was failing all to often. …attacks often came in very low, evading air warning radar until late and making it impossible for the 40cm FD to determine height accurately. When air attacks began to come from kamikazes the deficiencies of air defense became serious. The proximity fuse was of no avail, if the shell was not placed within 20 meters of the target…Bell also took to design a replacement for the FD, the mark 12, using the same basic structure but on 33cm and with automatic tracking for range; automatic tracking in direction was to follow with a later modification. This still left the mark 12 with manual tracking, not suited to the agile attackers and still followed by a slow mechanical predictor, and most ships retained the mark 4 (FD). No mark 57 directors appeared until early 1945. Once the kamikazes were within range, the non radar 40 and 20 mm guns had to save the ship and often did.

This situation seemed nothing short of scandalous to Ivan Getting, who had been working on a Navy 3 cm fire-direction radar, the mark 35, and a compatible and highly advanced director, the mark 56. When there was no evident move by April 1945 to place this system into service, he wrote a sharp letter to the Navy Department, pointing out the superiority of the Army radar, thinking that tweaking the inter-service rivalry would suffice to bring about the desired conversion from 40cm manual to 3cm automatic. Given the size of the US fleet by the end of 1944 and the time required for conversion compared to the expected length of the war; it is hardly surprising that this suggestion was rejected, which with afterthought Getting conceded to have been the right decision.
( L Brown, Technical and Military Imperatives A Radar History of WWII, page 415-416)

At this time the Royal Navy was introducing Type 275, and the German Navy had already deployed FuMO213 with a highly advanced director, and would be deploying Euklid with a highly advanced director had the overall war developed more to their favor.

All good points!
My point, hyperbolic as it was, is that none of those other new art systems were deployed, if at all, in significant numbers by any other Navy. It is not the cutting edge that counts, but that installed on the majority of ships. Did any of those new systems ever actually down any significant number of planes? I think not. Limited as my current knowledge, coming from pre-internet books as it does, can not remember any single instance of any of those newest systems downing a single plane. While I might, probably am, wrong in that assumption, one or even a few does not count when compared to the THOUSANDS of planes downed by the USN in the last stages of the war. ALL things considered, no other system came close!
Last edited by Neoconshooter on Wed Dec 05, 2012 7:38 pm, edited 1 time in total.

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Re: What was the most effective naval anti-aircraft gun of W

Postby Neoconshooter » Wed Dec 05, 2012 6:47 pm

dunmunro wrote:
Neoconshooter wrote:
How did the system you mention above couple the range as found by the Radar to the FCS?


Type 280 and type 279 both had a precision ranging panel which transmitted the radar range AND range rate directly to the HACS table (computer) via magslips (syncro motors) with power follow-up for the range rate (radar operator would match the range rate to the target and that rate would continue to be transmitted to the table as long as the target maintained a steady course.

I guess we have different ideas about what the word precision means? Also, how timely was the transmission of the Plotting Table info, originally intended to control surface fire against ships, sent to the AA guns? When compared to late war USN equipment in wide spread use, just how effective were these two types?
Did they save PoW and Repulse? Not actually a fair question. How many planes did those two ships down before they were sunk? A better question would be how many planes did the Royal Navy shoot down in the entire war using either of those systems?
My point is that conversion of a surface FCS into a AA-FCS is very much harder than it looks from the internet of hind sight. See Frieden's tome "Principles of Naval Weapons Systems" from the Naval Institute Press, 1985.

http://en.wikipedia.org/wiki/HMS_Prince_of_Wales_(1939)
Sensors and processing systems:
Type 279 radar added
Type 284 radar added.
Radars added in May 1941.
4 x Type 282 and Type 285 radars added.
Radar added between June–July 1941.
Type 271 radar added.

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Re: What was the most effective naval anti-aircraft gun of W

Postby Thorsten Wahl » Wed Dec 05, 2012 8:22 pm

Neoconshooter wrote:, one or even a few does not count when compared to the THOUSANDS of planes downed by the USN in the last stages of the war. !


Do you have an official account or even a educated guess onkills of japanese aircraft by USN AA-Fire?

Compared to the US maritime campaign on the Pacific the air war against shipping at the european theater was much more a secondary theater. So pure counts on attacks and kills wer not comparable.
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