Japanese shipborne flak

[Yaab]

I had this brilliant idea of how to convert Japanese ships into viable anti-air platforms. Since level bombing does not pose much danger to ships, I thought I could create pure mid-AA TFs to shoot dive-bombers and torpedo bombers who release their bombs and torpedoes in the 200-3000 feet range. Basically, stuff the TF with as many 25mm AA guns as possible instead of 8-12.7cm DP guns.

Well, that did not work. I created an APD TF that matched the above criteria and used it in the Guadalcanal scenario. I parked the TF near the Allied CV TF and waited. Soon Alied dive-bombers came and sank all four APDs. I noticed on average maybe one flak burst per combat animation. I ran the test maybe ten times.

On the other hand, a Jap CA TF parked nearby defended itself splendidly on every occasion, producing lots of flak bursts and damaging some planes.

That got me thinking. I started the Coral Sea scenario as Japs and ran it on auto-pilot noticing AA effects. Here is what I have found.

At the end of scenario, most of the 12.7cm ammo on the CVs and CAs was expended during several Allied air attacks. The 25mm ammo went from 36 to 30-31, the 13mm ammo went from 36 to 35. Seems that the heavy DP guns with their long range had MORE chances to fire at incoming aircraft. The small AA guns barely fire at all. It seems that a dive bomber, travelling at 10,000 feet before the dive attacks, goes through MORE flak from 12.7cm DPs then when diving from 10,000 to 3,000 feet. In the 7,000-3,000 feet range it should go through 25mm fire and, even if it does, the effect on aircraft's disruption or damage is non-existent.

It seems also that the 3,000-1,000 feet range is just too short timewise for 13mm to actually fire at the aircraft.

The whole thing is somewhat counter-intuitive. One would think that 25mm-13mm would fire more than 12.7cm DPs, but it isn't so.

It seems that if want your TF to survive, you need to stuff it with as many 12.7cm DP guns as you can. Other than CVs, the only powerful ships are late Japanese Maya CA class ships, which sport 12 x 12.7cm DP guns. Best Japanese DDs get 6 such guns, most CA have 8 such guns.

It is also ironic, that several classes dump their 12.7cm DP guns later in the war for more 25mm AA guns, CVs included.

[witpqs]

It's not counter-intuitive, it's about the amount of time that the plane can be engaged by the various guns. The Allied 20 mm and Japanese 25 mm were sometimes referred to as "revenge weapons" because their limited range meant that they could only engage attacking planes when those planes were already close enough (or just about close enough) to deliver their own weapons.

The larger guns, even though they fire more slowly, have a longer range and can both shoot at aircraft over a longer period of time and can hit an attacking aircraft before it is in range to drop bombs or torpedoes. And of course the damage from the larger guns is more likely to disable or destroy an aircraft than is the damage from a 20 or 25 mm gun. Also, guns with longer range can fire on aircraft attacking other ships, increasing mutual defense.

[Yaab]

You are right about the mutual defence part.

In the Coral Sea scenario, the Japanese amphib TF bound for Port Moresby was attacked by Wirraways which level-bombed from 18,000 feet. The aircraft attacked two xAKs whose AA weapons had the maximum ceiling of just 12,000 feet. Yet, during the combat animation, there were flak bursts. The bursts could only come from the heavy AA weapons of the two combat ships in the TF. So yes, heavy DP guns extend coverage to other ships. But what is the threshold for this mutual defence? Did my APDs mutually supported each other? Can 25mm fire from ship A help ship B defend itself? It is hard to deduct from combat animations where the treshold is.

As for rate of fire of the big DP guns. What stat in Tracker/game database should I look for? Is gun's ROF lumped into i.e.the Accuracy stat?

Anyway, heavy DP guns are the only way to go. Seems the late war Japanese AA upgrades are completely misguided.

[Yaab]

BTW, if the above observations are true, then a dedicated late-war Japanese CLAA should have 24 x 12.7cmDP guns with 72 ammo. Even better would be 36 or 48 guns, but then the CLAA would have to be followed by an AE ship providing underway ammo replenishment.

[obvert]

ORIGINAL: Yaab

BTW, if the above observations are true, then a dedicated late-war Japanese CLAA should have 24 x 12.7cmDP guns with 72 ammo. Even better would be 36 or 48 guns, but then the CLAA would have to be followed by an AE ship providing underway ammo replenishment.

Well, not really![;)]

The key point is that Japanese flak sucked because it relied on the 25mm gun too heavily, which had other practical problems in reality. They didn't emphasize the mid-range guns like the 40mm Bofors that were so effective for the Allies. They did have some good platforms, but there is no way to get good flak for the IJN. It's decent, but nothing like what the Allies could field.

The Akitsuki class, the Taiho and the Oyodo class get Type 98 10cm flak guns that are rapid fire and the best IJN AA guns of the war. It fired 15-21 rounds per minute! [X(]

http://www.navweaps.com/Weapons/WNJAP_39-65_t98.htm

There are several IJN 12.7cm DP guns used on a variety of ships. The effective ceiling for these guns was lower than that of the 10cm Type 98 due to lower muzzle velocity. The 3rd year type used on most IJN DDs had some problems as an AA platform in WWII.

[font="Trebuchet MS"]The very slow training speeds and lack of power ramming made these mountings almost useless against the fast-moving aircraft of World War II.[/font]
http://www.navweaps.com/Weapons/WNJAP_5-50_3ns.htm

The Type 88/89 used on CVs, BBs and CA/CL were better AA platforms.

http://www.navweaps.com/Weapons/WNJAP_5-40_t89.htm

Many of the older cruisers and DDs and many Es, DMS and other escorts carried some kind of 12cm gun with an effective rate of fire of 5-8/minute, but some were able to get to 10-11 for short periods.

http://www.navweaps.com/Weapons/WNJAP_47-45_10ns.htm
http://www.navweaps.com/Weapons/WNJAP_47-45_11ns.htm

All of these types are used in shore based batteries as well.

The 25mm AA gun used on virtually all Japanese ships was too small and not well suited to faster, heavier, more well armored aircraft of the mid-late war. They never employed a 40mm system on ships.

http://www.navweaps.com/Weapons/WNJAP_25mm-60_mg.htm

[LoBaron]

In game terms shipborne AAA works the following way:

There are 3 phases of AA fire: Inbound, attack run, outbound.

On the inbound and outbound leg the AA weapons fire against the set strike alt. So if the raid is incoming at 12k, only weapons 12k+ ceiling can fire at the a/c. BUT, in these phases all AA weapons of a TF may contribute to the defense (with certain penalties tied to TF size).

On attack run the planes drop to weapon release alt (200ft for TB, 1-4k for DB, level bombers obviously stay at the set alt) and in case the alt is lower than the weapons´ max ceiling can also be engaged by the shorter range point defense weapons. But in this phase only the AA weapons of the ship under direct attack fire at the planes.


The above is the main reason why DP high caliber guns expend more ammo. They a) usually fire in three phases instead of one, and b) also fire against a/c attacking other ships in a TF.

[Yaab]

LoBaron, many thanks for the explanation of the AA routine. Great food for thought.

obvert, thanks for the short lecture. I guess maybe the Japanese went with more 25mm guns because the 10-12mm ammo was bulkier and more space-consuming, and the 25mm guns didn't require turrets. Just keep adding more 25mm mounts like in the case of the Yamato upgrades and everything will be hunky-dory.

[Czert]

ORIGINAL: Yaab

You are right about the mutual defence part.

In the Coral Sea scenario, the Japanese amphib TF bound for Port Moresby was attacked by Wirraways which level-bombed from 18,000 feet. The aircraft attacked two xAKs whose AA weapons had the maximum ceiling of just 12,000 feet. Yet, during the combat animation, there were flak bursts. The bursts could only come from the heavy AA weapons of the two combat ships in the TF. So yes, heavy DP guns extend coverage to other ships. But what is the threshold for this mutual defence? Did my APDs mutually supported each other? Can 25mm fire from ship A help ship B defend itself? It is hard to deduct from combat animations where the treshold is.

As for rate of fire of the big DP guns. What stat in Tracker/game database should I look for? Is gun's ROF lumped into i.e.the Accuracy stat?

Anyway, heavy DP guns are the only way to go. Seems the late war Japanese AA upgrades are completely misguided.

Well, game model and reality differs . In reality most planes were shot down by 40/30/25/20/13mm guns than by dp big calibers. And as no propably in game only few hits (1-3) from 20mm+ were manytimes enought to shot down most planes, except 4e heavy bombers (for these were 30mm+ ).
And in theory these short legs (25mm) could defend another ship, but that will need that ship will be close enough to recive it, and im not completly sure if ships in aa defence formation were close enought that thier firing circles were overlaping another ship, or were just overlaping with some end before geting to close to another ship to prevent acidental friendly hits.

[obvert]

ORIGINAL: Yaab

LoBaron, many thanks for the explanation of the AA routine. Great food for thought.

obvert, thanks for the short lecture. I guess maybe the Japanese went with more 25mm guns because the 10-12mm ammo was bulkier and more space-consuming, and the 25mm guns didn't require turrets. Just keep adding more 25mm mounts like in the case of the Yamato upgrades and everything will be hunky-dory.

Questions like yours always teach me something, because I realize I don't know the answer completely, and I need to go look it all up.

One piece of IJN AA I didn't know much about at all are the AA rockets installed late war on CVs. I had assumed they were longer range weapons, but it turns out they were extremely short range, apparently, and almost useless.

http://www.navweaps.com/Weapons/WNJAP_12cm_AA_Rocket.htm

When I searched this with Google an AE thread was one of the top choices! [:D]

http://www.matrixgames.com/forums/tm.asp?m=2811663

All of this info begs the questions if the late war AA 'upgrades' are worth it even with the added radar.

[LoBaron]

ORIGINAL: czert2
Well, game model and reality differs .

No, not by much. Have you seen late war IJN attacks torn apart by Bofors and Oerlikons late war?

In reality most planes were shot down by 40/30/25/20/13mm guns than by dp big calibers.

This depends very much on the context. Strategic bombers? Naval attack? Strafe? Throughout the whole war I doubt that significantly more planes were brought down by small caliber AA than by large caliber flak. Even if it turns out correct you´d have to take into account the aircraft type and mission type for a conclusive statement.

And in theory these short legs (25mm) could defend another ship, but that will need that ship will be close enough to recive it, and im not completly sure if ships in aa defence formation were close enought that thier firing circles were overlaping another ship, or were just overlaping with some end before geting to close to another ship to prevent acidental friendly hits.

The problem with mutually supporting point defense was the high lead angles and the chance of friendly fire. Even if the formations were close enough, until very late war short range high deflection AA was more dangerous to own ships than to the enemy a/c. The target usually had the best chance to hit an incoming a/c due to small lead angles. The model reflects that OK(ish).

[decaro]

ORIGINAL: witpqs

It's not counter-intuitive, it's about the amount of time that the plane can be engaged by the various guns. The Allied 20 mm and Japanese 25 mm were sometimes referred to as "revenge weapons" because their limited range meant that they could only engage attacking planes when those planes were already close enough (or just about close enough) to deliver their own weapons.

The larger guns, even though they fire more slowly, have a longer range and can both shoot at aircraft over a longer period of time and can hit an attacking aircraft before it is in range to drop bombs or torpedoes ...

Also, when the planes get closer, the ship maneuvers more violently to avoid them, putting the shorter range flak crews at a distinct disadvantage.

[Czert]

ORIGINAL: LoBaron

ORIGINAL: czert2
Well, game model and reality differs .

No, not by much. Have you seen late war IJN attacks torn apart by Bofors and Oerlikons late war?

In reality most planes were shot down by 40/30/25/20/13mm guns than by dp big calibers.

This depends very much on the context. Strategic bombers? Naval attack? Strafe? Throughout the whole war I doubt that significantly more planes were brought down by small caliber AA than by large caliber flak. Even if it turns out correct you´d have to take into account the aircraft type and mission type for a conclusive statement.

And in theory these short legs (25mm) could defend another ship, but that will need that ship will be close enough to recive it, and im not completly sure if ships in aa defence formation were close enought that thier firing circles were overlaping another ship, or were just overlaping with some end before geting to close to another ship to prevent acidental friendly hits.

The problem with mutually supporting point defense was the high lead angles and the chance of friendly fire. Even if the formations were close enough, until very late war short range high deflection AA was more dangerous to own ships than to the enemy a/c. The target usually had the best chance to hit an incoming a/c due to small lead angles. The model reflects that OK(ish).

1. yes, i know that oerlikons were japanese killers, that why i stated that short/medium range wepons were doom of planes, and long range - dp - didnt get much scores. I have no numbers, but i base it on knowlege from redings and mathematick - after all the more lead you pump to air, the bigger chance it willl hit somethind, and 40mm bofors have much nicer rof thah 100mm+ .
But in this game dp got 3 chances to fire, while AAA basicaly only one. With results that dp are biger plane killers (at least for japanese).

2. true, my fault, my statement was about naval attacks (since op question), you dont use much ships in stategick area defence right .
and as sidenote - during raids againts germany by "mighty 8" cca 1/4 of loses were due to flak, rest due to fighters + ops. And on "funny side" price of ammo consumed to show down one 4e bomber was nearing price of fighter plane (but this statement ignores many other planes damaged or crashed due to damage, as jerrys didnt have tools to count this).

3. im little confused here, so you are confriming that ships were outside or inside range of own AAA with chance of friendly fire.

[Spidery]

But in this game dp got 3 chances to fire, while AAA basicaly only one. With results that dp are biger plane killers (at least for japanese).

Is this true for larger raids? Or is there one in and one out bound attack against the full strike and one attack phase attack against each 4 plane packet but only by its intended target? In the later game there are larger strikes so maybe the balance of value differs from that in Coral Sea?

Also, I would hope there is much less chance of hits during the in/out bound phase against dive and torpedo bombers since they do not need to fly predictable paths.

There is also the point, and I don't know if the game reflects it, that heavy AA may shoot planes down but it won't interfere with the attack. Light AA may have little success at shooting aircraft down but may be they reduce the attack effectiveness?

[Yaab]

czert2, in my test, the 12,7cm DP guns were not actually aircraft killers. They did produce lots of flak bursts in combat animations and I reckon this translated into more disruption for the attacking aircraft.On average, my 5 CAs with DP guns got attacked by by 45-60 aircraft and damaged on average 3 aircraft, and destroyed none.

As I said, the APDs sunk producing on average just ONE flak burst, without damaging a single plane.

LoBaron is also right in his analysis of AA phases. Basically, in combat animation you can see two messages i.e "aircraft A approaching" (accompanied by flak bursts) and "aircraft A attacking ( accompanied by another flak burst). DPs give you flak burst and disruption, but they do not rack up kills. As with the B-17s bombing bases, disruption is everything - disrupt the bomber and its bombs miss the target, and you live to see another day.

[Yaab]

There is also one WITP:AE database thing which I do not understand.

25mm Type 96 AA gun is device 1682
13.2mm Type 93 AAMG is device 1683.

When you have a ship with both guns mounted, the guns are marked with * sign, meaning the gun is a double-purpose gun. Now, the ship info says:

25mm has range of 4,000 feet
13.2mm has range of 3,000 feet

If you now go to the WITP:AE database or Tracker you will see that:

25mm has ceiling of 7,000 feet
13.2mm has ceiling of 3,600 feet

In rough terms, 3,600 feet equals 3,000 feet. By why is 25mm ceiling of 7,000 feet truncated to 4,000 range on the ship info screen? If a shipborne 25mm fires at an aircraft, does is use ceiling (7,000 feet) or range (4,000 feet)?

[crsutton]

ORIGINAL: czert2

ORIGINAL: Yaab

You are right about the mutual defence part.

In the Coral Sea scenario, the Japanese amphib TF bound for Port Moresby was attacked by Wirraways which level-bombed from 18,000 feet. The aircraft attacked two xAKs whose AA weapons had the maximum ceiling of just 12,000 feet. Yet, during the combat animation, there were flak bursts. The bursts could only come from the heavy AA weapons of the two combat ships in the TF. So yes, heavy DP guns extend coverage to other ships. But what is the threshold for this mutual defence? Did my APDs mutually supported each other? Can 25mm fire from ship A help ship B defend itself? It is hard to deduct from combat animations where the treshold is.

As for rate of fire of the big DP guns. What stat in Tracker/game database should I look for? Is gun's ROF lumped into i.e.the Accuracy stat?

Anyway, heavy DP guns are the only way to go. Seems the late war Japanese AA upgrades are completely misguided.

Well, game model and reality differs . In reality most planes were shot down by 40/30/25/20/13mm guns than by dp big calibers. And as no propably in game only few hits (1-3) from 20mm+ were manytimes enought to shot down most planes, except 4e heavy bombers (for these were 30mm+ ).
And in theory these short legs (25mm) could defend another ship, but that will need that ship will be close enough to recive it, and im not completly sure if ships in aa defence formation were close enought that thier firing circles were overlaping another ship, or were just overlaping with some end before geting to close to another ship to prevent acidental friendly hits.

I would like to know your sources on this? I caution you about dumping lesser caliber guns into the same group with the excellent 40mm gun, which may have been the best all around AA gun produced in the war. Plus, the introduction of the Allied proximity fuse and radar fire control undoubtedly changed the kill rate for larger guns as the war progressed. (At least for the Allies) So, you may be too general in your comment, not only about the types of light AA guns but also the nationality and time frame. I myself am no authority on this.

One thing I have learned from a post action report that someone posted her years ago is that the ship with the best chance to shoot down an attacking aircraft is the ship being attacked. All other ships no matter how equipped are firing at a greater range and having to deal with deflection. I doubt that the game system reflects this but who knows...[;)]

[LoBaron]

ORIGINAL: czert2
1. yes, i know that oerlikons were japanese killers, that why i stated that short/medium range wepons were doom of planes, and long range - dp - didnt get much scores. I have no numbers, but i base it on knowlege from redings and mathematick - after all the more lead you pump to air, the bigger chance it willl hit somethind, and 40mm bofors have much nicer rof thah 100mm+ .
But in this game dp got 3 chances to fire, while AAA basicaly only one. With results that dp are biger plane killers (at least for japanese).

I was trying hint that a significant percentage of strike missions flown in WWII did not get in range of point defense guns. This probably includes 99% of all heavy bomber missions flown against strategic targets. I doubt that the higher kill probability of point defense guns when in range would be able to mitigate the simple fact that they had much less opportunity to fire at a target.

3. im little confused here, so you are confriming that ships were outside or inside range of own AAA with chance of friendly fire.

No, I just said that as long as a ship was not the target it faced problems when trying to engage aircraft with point defense weapons.

crsutton said it much better than me, basically I was just stating the same:

One thing I have learned from a post action report that someone posted her years ago is that the ship with the best chance to shoot down an attacking aircraft is the ship being attacked. All other ships no matter how equipped are firing at a greater range and having to deal with deflection.

And high deflection often could mean that a friendly target (e.g. a ship) moves into the arc of fire unnoticed.

[LoBaron]

ORIGINAL: Spidery

But in this game dp got 3 chances to fire, while AAA basicaly only one. With results that dp are biger plane killers (at least for japanese).

Is this true for larger raids? Or is there one in and one out bound attack against the full strike and one attack phase attack against each 4 plane packet but only by its intended target? In the later game there are larger strikes so maybe the balance of value differs from that in Coral Sea?

Point defense in general is much more deadly than large caliber AA in game, at least mid-late war. The effect of AAA is much greater for the Allies, but applies to the IJN as well.

Also, I would hope there is much less chance of hits during the in/out bound phase against dive and torpedo bombers since they do not need to fly predictable paths.

Only in an abstracted way, as high caliber guns have a lower accuracy and ROF.

There is also the point, and I don't know if the game reflects it, that heavy AA may shoot planes down but it won't interfere with the attack. Light AA may have little success at shooting aircraft down but may be they reduce the attack effectiveness?

Also as an abstraction. The game simulates the effect of AA and plane damage on pilot fatigue.

[Theages]

ORIGINAL: LoBaron
On attack run the planes drop to weapon release alt (200ft for TB, 1-4k for DB, level bombers obviously stay at the set alt) and in case the alt is lower than the weapons´ max ceiling can also be engaged by the shorter range point defense weapons. But in this phase only the AA weapons of the ship under direct attack fire at the planes.

CLAA are said to contribute to flak defense for attacked ships also "on attack run" phase.

[witpqs]

Regarding friendly fire, remember that the targets aircraft and the friendly fire victims are ships. The effective range and altitude of AA weapons is less than the maximum range that the weapon can launch the projectiles to at a given altitude. This the was discussed extensively in the past in the mod sub-forum.

Friendly fire is different. First of all the range of friendly fire danger is not limited by a notion of 'effective' range where the weapon is accurate. Second, the ships are on the surface and so the danger extends to a greater range as the shells com back to earth. And of course ships are much bigger targets than aircraft.

I've read accounts where ceasing fire for a time due to danger to own ships was quite common, and I've read of friendly fire hits on own ships by AA weapons.