Anti-Aircraft Fire

Revision as of 20:34, 4 January 2020

Nearly every ship in World of Warships mounts anti-aircraft guns in order to defend themselves from hostile planes. These mounts can range from small-caliber machine guns all the way up through anti-aircraft artillery; some ships are even capable of utilizing their main battery weapons to provide anti-aircraft fire. Each weapon and caliber is grouped into set range bands in order to defend a ship from incoming aerial attacks.

Like ships, every plane in World of Warships possesses a certain number of hit or health points (HP). (Carrier-based aircraft HP ranges roughly 1500-2400.) In order to shoot down a plane, this health pool must be reduced to zero. A surface ship can do that with its AA guns and, in some cases, with its fighters. We'll start with how AA guns are implemented.

Anti-Aircraft Guns

Guns that are useful against attacking aircraft are generally grouped into three classes by range and effect, both functions of caliber.^[1]

Short Range Guns

30mm or smaller caliber. Essentially, these are machine guns. Small, light, fast-firing guns that usually throw solid shells (with a few tracer rounds mixed in). The small shells aren't able to retain enough energy to be effective (or aimable) beyond 2km. But the high volume of fire can make them dangerous within that range. Small caliber AA guns can be single-mounted nearly anywhere on the ship or they can be clustered in mounts with up to 8 barrels and relatively sophisticated aiming mechanisms. An example of the single mount is the ubiquitous ".50 Cal" Browning machine gun. (12.7mm caliber)

Medium Range Guns

30.1 to 85mm caliber (1.1" to 3.5"). These are serious guns, with shell weights from 1 to 9kg. These calibers are perfect for the anti-air role as they have good range, respectable rates of fire, and hits do significant damage even against relatively large aircraft. The larger guns can fire proximity fused shells; the smaller are light enough to mount on nearly any ship. An example of the medium range AA gun is the 40mm Bofors, often quad-mounted, which is considered to be the most effective anti-air weapon of WWII.

Long Range Guns

Greater than 85mm caliber (3.5" and up). Large calibers with much slower rates of fire than the smaller classes, but with long effective range and altitude and a large warhead. These guns are similar to - and often were - secondary anti-surface, or dual-purpose guns. Especially later in WWII, even main batteries were modified to perform as dual-purpose weapons, e.g. 155mm (6") and 203mm (8")^[2] USN cruiser mounts. More common in the AA role were the USN's 127mm (5") twin mounts.

For AA use, the shells often carry explosive warheads designed to throw out a sphere of deadly shrapnel so that just getting a shell close to an aircraft might kill it.

Anti-Aircraft Auras

Anti-aircraft auras

Unlike anti-ship artillery or torpedo armament, World of Warships does not plot fields of fire or calculate trajectories for anti-aircraft guns. With the large number of AA guns and high rates of fire, doing so would place an unacceptable load on the servers. Instead, anti-aircraft armament is collected into three zones of effect — auras — divided by the three gun classes described above. The auras overlap and reinforce each other.

Auras start at 100m from the ship. The depth of each aura is defined by the types of guns that form it: a ship with X type gun may have an aura with maximum range (depth) 2.5km, while on a ship with Y type gun the depth of the same aura may be only 1.9km. The auras do have minimum depths.

The three auras are short range - guns up to and including calibers of 30mm, depth >1.5km; medium range - guns of caliber 30.1 to 85mm, depth >2.5km; long range - the big rifles over 85mm, depth >4km.^[3]

Like secondary batteries, AA guns begin a battle unloaded and start to load as soon as an enemy plane enters the outer aura. Thus, for the very first air attack on your ship, AA may not inflict damage immediately. (This mechanic may change in the future.)

Continuous Damage

Every AA mount can do damage to attacking planes. Grouped by gun class into auras, this damage is applied as continuous damage. Within an aura, continuous damage has two components: a maximum damage done, and a rate at which that damage is done. The maximum damage is determined by the number and types of guns comprising the aura. The hit rate captures the effect of the ship's AA fire control systems. The same gun with a better fire control will have the same maximum damage but a higher hit rate. The hit rate generally increases with tier.

For example, a short range aura that can do 100 maximum damage with a hit rate of 90%: Each second that an airplane or squadron remains within that aura, the system applies the average, (100 * 90%) or 90, damage to it.^[4]

But the squadron doesn't get off that easily. In the case of the short range aura, both the medium and long range auras overlap it. Continuous damage from all three auras is applied independently to a squadron within ~2 km of the ship.

If several planes or squadrons are within an aura, continuous damage at full current strength is applied to each of them. If a plane or squadron occupies auras from more than one ship, each aura operates independently at full current strength.^[5]

Continuous damage is applied to the last plane in the squadron.^[6]

For instantaneous damage, see Sector Reinforcement below.

Flak

Long-range guns^[7] cover a flak zone between the maximum range of the big guns and 3.5 km from the ship. Into this zone they can throw shells that explode in deadly bursts of shrapnel. These explosions are modeled as flak bursts or flak clouds. If an aircraft flies into a flak cloud, the shrapnel does a large amount of damage (roughly 1000-2000 HP per second).^[8] Few carrier-based aircraft can enter two clouds and survive. However, since these clouds only damage those planes that fly through them, they are ineffective against skilled pilots who manage to dodge.

The number of flak bursts depends on the guns, AA fire control (for the hit rate), and modifications.^[9] The size or radius of a burst scales with the gun caliber. For example, flak bursts from a Massachusetts, which are generated by 127mm guns, are larger than those of a Roma, which relies on 90mm guns. Flak guns reload and throw up new flak clouds every 2 seconds. (By the time they appear older clouds have dissipated.)

Flak is aimed at A but might end up in B.

The air defense fire directors try to place shells in the path of the incoming squadron. From the speed and current course of the squadron, they calculate a target zone (zone A in the accompanying illustration). The depths of zone (marked x1 and x2) depend on the speed of the aircraft, and are smaller for slower planes. Most of the flak bursts will appear in the target zone, but some shells will miss and explode nearby (zone B).

From a single ship against a single squadron, 80% of the shells, to a maximum of six, explode in zone A, the rest in zone B. If there are multiple squadrons in the flak zone (and thus more than one target zone A), the guns generate the same number of bursts, and the bursts are distributed among the A zones.

When more than one ship engages the squadron, the number of flak clouds in the target zone can nearly double. In this event, the most powerful flak bursts are prioritized to appear in Zone A.^[10]

Damage from flak is not applied at the squadron level, but to the individual plane that enters the volume of a burst. A single large burst might damage multiple planes. Flak bursts do not overlap.

Note that not all ships have long range AA guns. These ships have no long range aura and cannot generate flak.

An Example - Prinz Eugen

Here we illustrate air defense operations using the characteristics of the German Tier 8 Premium Cruiser Prinz Eugen.

Short Range Aura

Details of Prinz Eugen's short range air defenses

Prinz Eugen carries 28x 20 mm Flakzwilling 38 barrels in dual and quad mounts. Her short range aura has effect at ranges between 0.1 and 2km. Within that hemisphere, the short-range 20mm guns may deal up to 95 damage to aircraft every second. The hit percentage is 85%. This means that every second nearly 81 damage is done to the intruder.

Note that the medium- and long-range auras overlap the short-range aura, so within it the overall damage per second in much higher — just short of 300 HP per second.

Medium Range Aura

Details of Prinz Eugen's medium range air defenses

Prinz Eugen's medium range aura is active out to 3.5km. There is a 90% chance every second that each of her eighteen 40 mm L/56 Flak 28 mounts (242 max. HP/sec) will hit, doing aggregate 218 damage.^[7]

Long Range Aura and Flak

Details of Prinz Eugen's long range air defenses. Note that the AA Mod 1 upgrade is mounted.

Prinz Eugen's long-range artillery is 6x2 105 mm L/65 Dop. L. C/31. These are effective out to 5.2km. The big 105mm guns can do 123 continuous damage with a hit rate of 90% (~111 HP average).

In addition, they throw up eight flak bursts every two seconds in front of an attacking squadron. (Normally six bursts, but our example ship has the AA Modification 1 upgrade.) A plane that flies into a cloud must absorb 1400 damage per second - almost enough to kill a smaller carrier plane. The flak tracks inward until the attacking squadron gets closer than 3.5km to the ship.

Sector Reinforcement

Every ship with an anti-aircraft capability can focus its AA firepower on one side of the ship, while correspondingly weakening the other side. Pointing the camera to one side of the ship's mid-line and pressing the '~' (tilde) or letter 'O' key activates a priority AA sector on that side of the ship (preferably the side where aircraft are attacking).

The phases of sector reinforcement

Activating a priority sector has two effects: First, an amount of damage is immediately applied to all enemy squadrons within the ship's air defense aura. Second, the continuous damage from the auras gradually increases on the priority side and correspondingly decreases on the other side.^[11] Sector reinforcement has no effect on flak bursts.

Sector Reinforcement and other AA boosts such as the Defensive AA Fire consumable stack additively for continuous damage. E.g. An aura with base 100 HP/sec might increase to 135 with Sector Reinforcement (+35%) and to 185 with simultaneous Defensive AA Fire (+50%). (Actual effects depend on the ship.)

Instantaneous damage

Instantaneous damage, expressed as a percent of the entire squadron's HP,^[12] is applied to the squadron immediately on activation of a priority sector. (Prinz Eugen, as a cruiser, applies base 3.5%.) That amount is applied to the last plane(s) in the squadron.^[6] If there is no squadron within an AA aura when sector reinforcement is activated, no instantaneous damage is done.^[13]

Continuous damage shift

Each ship type has a duration over which the continuous damage is shifted toward the incoming attacker. In the case of a cruiser, the shift takes approximately half the 10 second reinforcement duration. The maximum effect is a 150% increase in continuous damage. Then the effect returns to normal and there is a base 10 second cooldown period (preparation time) before sector reinforcement can be activated again.

The table below shows how priority sector action varies by ship type. Max. and Min. are the effects on the reinforced and depleted sides respectively, at full effect, as mulitipliers. Reenable Time is the total time until a sector can be reinforced again.

Massive AA Fire

The Massive AA Fire commander skill has a pronounced effect on a reinforced sector, doubling instantaneous damage while removing any boost to continuous damage.^[13] Since there is no reinforcement period, cooldown starts immediately. Thus while cooldown time is 50% longer, the time between reinforcements is decreased significantly.

If a ship has no anti-aircraft capability, then this skill does nothing.

An Example

Using cruiser Prinz Eugen as an example again: An enemy plane approaches from the starboard side. At 5.2 km the long-range guns open up, doing 111 continuous damage and generating an average of eight flak clouds, each potentially dealing 1400 dps. Sector reinforcement is available so the ship commander (who does not have the Massive AA Fire skill) quickly orders his AA gunners to reinforce the starboard side. The plane instantly takes 3.5% damage. As it approaches, the ship's long-range continuous damage increases to 166 (111*150%) dps. Then as the plane, having somehow survived, leaves the flak zone at 3.5 km range it enters the mid- then short-range auras which are reinforced up to 493 (166+327) and 614 (166+327+121) dps respectively. Crossing over the ship, the dps decreases to 204 (40+109+55), then 149 (109+55), then 55 (111*50%) with no flak to dodge.

The cockpit — all that remains of the now-shredded plane — drops into the sea. After a 10 second cooldown, the ship again is ready to make enemy pilots regret an attack.

(This example does not consider the speed of the plane and thus where the plane would be when reinforcement reaches maximum or expires. It is considered to be within the auras for the full duration of reinforcement.)

Attrition

Shells and other ordnance can destroy AA mounts that may be critically important to protect the ship. Destroyed mounts cannot fire so the continuous damage of the related aura is reduced. Losing long-range guns may also reduce the number of flak clouds that can be generated.

The location of a destroyed AA mount does not matter as each gun is considered to cover all directions. This also means that sector reinforcement remains unaffected aside from the reduced continuous damage. Once all AA mounts that contribute to an aura are destroyed, no more damage (continuous or flak) will be generated in this range band. However, as longer range AA auras overlap the shorter range auras, continuous damage may still occur at the destroyed aura's ranges.

(Unlike main armament, AA and secondary mounts cannot be damaged and repaired — only destroyed.)

Enhancing Anti-Aircraft Fire

Upgrades

Auxiliary Armaments Modification 1 (Slot 1) increases the survivability of AA mounts by 100%.

AA Guns Modification 1 (Slot 3) increases by 2 the number of flak bursts produced by long-range AA guns.^[15]

AA Guns Modification 2 (Slot 6) increases all continuous damage by 15%. Increases the damage from flak bursts by 15%.

The special upgrade Defensive AA Fire Modification 1 (Slot 2) increases the duration of the Defensive AA Fire consumable by 20%.

The Legendary Upgrade Enhanced Countermeasures (Slot 5) for Worcester increases the duration of the Defensive AA Fire consumable by 20%.

Defensive AA Fire Consumable

The Defensive AA Fire I and II consumables, available on higher-tier cruisers and destroyers, give a major boost to the effectiveness of AA defenses. For 30-60 seconds, all continuous damage is increased 50%^[16] and the damage caused by flak clouds is tripled.

While Defensive AA Fire  is active, flak bursts will appear with a reddish hue, whereas normally flak burst animations will appear more orange. An aircraft carrier commander should take note of the color, as this is the only visual cue that Defensive AA Fire  is active.

Activating the Defensive AA Fire consumable will also immediately activate AA fire without the need to press the 'P' key.

Deactivating the Defensive AA Fire consumable (tap the button again) immediately terminates the action of the consumable and begins its cooldown. This can shave a few seconds off the next charge becoming ready.

Combat Signals

November Echo Settoseven () increases both continuous and flak damage by 5%.

Commander Skills

Several Commander skills directly affect the performance of anti-air defenses.

Basic Firing Training (BFT) increases continuous damage within all auras.

Advanced Firing Training (AFT) increases the damage per second (dps) of flak clouds.

Massive AA Fire^[17] Doubles instantaneous damage and speeds sector reinforcement action at the cost of continuous damage boost. See details above.

Direction Center for Fighters adds an additional fighter to a Catapult Fighter  squadron.

Fighters

Main article: Ship:Aircraft

Some ships carry fighters that can be launched from catapults. These take the form of the Catapult Fighter  consumables (standard and premium) that deploy a squadron of one to four^[18] fighter aircraft. These fighters orbit their home ship at a radius of about 3.25 kilometers for 60 seconds. The squadron functions automatically, and other than launching cannot be controlled by the player.

If an enemy aircraft squadron comes within range, the defending squadron will attempt to shoot it down. (The range depends on the relative speeds of the squadrons.) The attacking squadron may summon a Patrol Fighter  squadron to assist it. Launched at the right time, catapult fighters can be very effective.

Maneuvering

There are actions the captain can take independent of his AA defenses. Notably, maneuver the ship (sometimes known as WASD hacks) to make attacks as difficult as possible for aircraft. Here is advice on what to do against certain types of attackers.

• Attack planes deal the least amount of damage, but they are very fast, agile, and relatively easy to aim. The dispersion of their rockets is different per game nation. You should not expose broadside to USN attack planes. Try to avoid going bow or aft against IJN and RN planes.

• Dive bombers are usually slower and it's hard for them to adjust their aim while in the attack run. That means quick maneuvering is the key, and, as their dispersion pattern is usually long, they deal the most damage with bow or aft attack runs.

• Torpedo bombers have different attack run patterns per nation, but they have one thing in common — they always try to catch you broadside to maximize the number of hits. USN torpedo bombers usually carry more torpedoes per attack, but they have more challenging aiming, so evasive maneuvers in advance will make their life much more difficult. IJN torpedo bombers usually carry torpedoes with relatively long range, so beware of long drops and pay attention even if they do something on the edge of your visibility.

Smaller agile ships may find that use of the throttle is as effective as use of the rudder.

Hiding

Smoke

Ships hidden in smoke cannot be detected by aircraft. However, the ships' AA guns do still operate. A ship in smoke that is detected by other means can be attacked by aircraft.

Smoke is a temporary reprieve against air attack, at best, and the smart squadron leader simply will avoid the area until the smoke dissipates.

Suppressing AA fire

On some ships, the range of AA and secondary batteries can exceed the ship's air detectability range. Firing those guns can reveal the ship to nearby aircraft. In attempting to remain as stealthy as possible the captain can turn off the ship's AA and secondary batteries by pressing the P key.

When AA and secondary batteries are suppressed the symbol appears next to the main battery ammunition icons along the bottom of the battle screen. Tap the P key again to turn the batteries back on.

Notes

Other Resources

LittleWhiteMouse has an interesting article on AA mechanics. It's a bit out of date now, but some of the observations are quite thought provoking : Link

A Feb.2019 Dev Blog post that explains how AA defense changed for the 0.8.0 carrier rework : Link and largely repeated here. Parts have been modified since, but still largely applicable.

Footnotes

1. ↑ List of anti-aircraft guns.
2. ↑ Although advertised by the Navy as dual purpose, the 203/55 Mk.16 mount was rarely if ever employed in the AA role. It is not AA-capable in World of Warships.
3. ↑ Dev Blog post.
4. ↑ While damage is expressed in HP per second, damage is actually applied several times per second (time slices). E.g. an average of 90/10 or 9 damage may be applied every 1/10 second. See Update 0.8.6.
5. ↑ At one time, overlapping auras were devalued. That is no longer the case. Forum announcement.
6. ↑ ^{6.0 6.1} See Update 0.8.5 for how damage to aircraft is applied. If a packet of damage results in the destruction of the last plane, for continuous damage the balance of that damage is lost. For instantaneous damage, the remaining damage is applied to the next 'last plane'. (Note that a continuous damage packet is much smaller than an instantaneous damage packet, so little is lost.)
7. ↑ ^{7.0 7.1} As of Update 0.8.7 medium range guns do not produce flak clouds. See the News article for full illustrations.
8. ↑ The amount of flak damage appears to vary by gun size, type, and ship tier. For instance, VIII Cleveland, VIII Baltimore, IX Buffalo. and X Salem all have the same batteries: 6x2 127/38 Mk.32s. However, the flak increases by tier.
9. ↑ From the Feb. 2019 Dev Blog post, paraphrasing: "[The number of flak bursts is the base flak burst parameter (the number displayed in the game client)] multiplied with Hit chance. Normal (Gauss) distribution is applied, and the minimal burst [count] is symmetrical to the maximum. That means that with 10 base burst[s] and 70% hit chance, it will mostly be 7 bursts, 10 is maximum number and 4 is minimum."
10. ↑ While the ships may have slightly different Zones A, the zones are amalgamated for display.
11. ↑ With the Massive AA Fire commander skill, there is no increase in continuous damages.
12. ↑ The squadron's HP is defined as the original health of the planes in the squadron at the time of activation. The pool, and thus the % damage done, decreases as planes are lost.
13. ↑ ^{13.0 13.1} From a Dev Blog post about the new sector reinforcement mechanism.
14. ↑ See Update 0.8.7 for the recent changes to sector reinforcement.
15. ↑ As of Update 0.8.10 it is not possible to mount the AA Guns Mod 1 upgrade on a ship without long-range AA guns.
16. ↑ On Stalingrad, the increase is 25%.
17. ↑ Previously Manual Fire Control of AA (MFCAA).
18. ↑ This squadron size is increased by one by the Direction Center for Fighters skill.