Anti-Aircraft Fire

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.

N.b that some details shown in the How It Works video are out of date, particularly with regard to how AA defenses operate. The pictures and basic concepts are still good. Read the text below for up to date information.

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.

Short Range Guns

28mm 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

28.1 to 85mm caliber (1.1" to 3.5"). These are serious guns, with shell weights from 1 to 9kg.

An example is the 40mm Bofors gun, 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") 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 in World of Warships, anti-aircraft guns do not calculate trajectories or have limited fields of fire. Due to 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 maximum range 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 28mm, depth >1.5km; medium range - guns of caliber 28.1 to 85mm, depth >2.5km; long range - the big rifles over 85mm, depth >4km.

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 range into an aura, this damage is applied as continuous damage. Continuous damage has two parts: a maximum damage done, and a percent chance that it is done. (The maximum damage and hit rate are determined by the numbers and types of guns comprising the aura.) For example, a short range aura can do 100 damage with a to-hit rate of 90%. Each second that an airplane remains within the aura, the system applies, on average, (100 * 90%) or 90 damage to it.

Note: While continuous damage is expressed in HP per second, damage is actually applied several times per second. In the example above, an average of 90/4 or 22.5 damage may be applied every 1/4 second.

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 the auras from two or more ships overlap, the resulting continuous damage is not the sum of them, but a lesser amount using an unspecified formula.

Continuous damage is applied to the last plane in the squadron.

Need a reference for the following :

[ The expressed hit % reduces both the continuous dps and the number of FlaK bursts that a ship is going to generate. Huh?? ]

For instantaneous damage, see Sector Reinforcement below.

Flak

Long-range guns also throw shells that explode in deadly bursts of shrapnel. This is modeled as flak bursts or flak clouds that appear in front of incoming aircraft between 3.5 km from the ship and the full range of the big guns. If the squadron flies into a cloud, it must absorb a large amount of damage (base 1400) per second. Few carrier-based aircraft can do that twice and survive. However, since these clouds only damage those planes that fly through them, they are ineffective against skillful pilots that manage to dodge.

The number of flak bursts depends on the guns and modifications. Typically it is 6 bursts every two seconds, distributed in front of and to either side of the path of an incoming squadron beginning at maximum range and ending at 3.5km from the ship. The size or radius of a burst scales up with caliber. For example, the flak bursts from a Massachusetts, which are generated by 127mm guns, are larger than those of a Roma, which relies on 90mm guns. In terms of damage applied by flak bursts, it's a case of either being within the blast radius or not, and no transition zone exists. The damage is only applied to those planes within the blast radius, so if only one plane if a squadron flies into a burst, it is the only plane to be affected by it. Flak bursts do not overlap.

The reload of the flak clouds is set at two seconds, after which the cloud will be spawned again. The way these clouds spawn is dependent on a few factors. In general, there are two possible zones in which a flak cloud will spawn: either directly ahead of the squadron's direction of travel, or in a zone shifted to the left and right. The size of the central area is dependent on the speed of the aircraft, and will become smaller the slower the plane is. The amount of flak clouds in the central area are limited depending on if the squadron is being engaged by one ship or several. In the case of one ship firing, the long range AA can generate up to six. If more flak clouds can be generated, they will be placed in front of other squadrons in the AA aura. In case no other squadrons can be engaged, the clouds will instead spawn in the outer areas. When more than one ship engages the squadron, the number of flak clouds increases up to twelve, depending on the contributing guns. In this event, the most powerful flak bursts are prioritized to appear directly in front of the aircraft rather than to the left or right.

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

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. This damage is not guaranteed; the hit percentage is 85%. This means that every second there is an 85% chance that 95 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 — up to 460 HP.

Medium Range Aura

Details of Prinz Eugen's medium range air defenses

Prinz Eugen's medium range aura is active out to 3.5km. As with the short range aura, there is a 90% chance every second that her eighteen 40 mm L/56 Flak 28 mounts will do 242 damage.

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% (110 HP average).

In addition, they throw up eight flak bursts every two seconds in front of the 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 has the ability to focus the AA firepower on one side of the ship, which correspondingly weakens the other side. Pointing the camera toward the incoming planes and pressing '~' or the 'O' key, or clicking on the desired sector in the compass rose, activates a priority AA sector on either the port or the starboard side of the ship (preferably the side that 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 sector. Second, the continuous damage from the auras gradually increases on the priority side and correspondingly decreases on the other side. Sector reinforcement has no effect on flak bursts.

Instantaneous damage

Instantaneous damage, expressed as a percent of the entire squadron's HP, 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. If there is no squadron when a priority sector is activated, no instantaneous damage is done.

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.

There is a level of skill in timing the use of sector reinforcement. Activate it too early - while the attacker is outside the outer aura - and no instantaneous damage will be done. Activate it too late and the squadron may get its attack off and escape before the continuous damage can increase significantly. The faster the attacker, the more important this timing becomes.

The table below shows how its action varies by ship type.

Normal AA Sector Reinforcement Values

Ship Type	Instant. Dmg	Ramp-up time	Max. Reinforcement	Reinforce Time	Cooldown
Destroyer	5%	~5 sec	135%	10 sec	10 sec
Cruiser	3.5%	~5 sec	150%	10 sec	10 sec
Battleship	3.5%	~5 sec	135%	15 sec	15 sec
Aircraft Carrier	3.0%	~5 sec	135%	15 sec	5 sec

Massive AA Fire

The Massive AA Fire commander skill has a pronounced effect on a reinforced sector, doubling instantaneous damage while stretching out the cooldown time. It also makes an important changes to how the sector reinforcement operates: there is no gradual ramp-up of continuous damage on the selected side; that damage goes immediately to its 'fully reinforced' level. Conversely the opposite side goes immediately to its weakened level.

AA Sector Reinforcement Values with the "Massive AA Fire" commander skill

Ship Type	Instant. Dmg	Ramp-up time	Max. Reinforcement	Reinforce Time	Cooldown
Destroyer	10%	0 sec	135%	10 sec	15 sec
Cruiser	7%	0 sec	150%	10 sec	15 sec
Battleship	7%	0 sec	135%	15 sec	22.5 sec
Aircraft Carrier	6%	0 sec	135%	15 sec	7.5 sec

An Example

Using Prinz Eugen as an example again. Sector reinforcement is available. A plane approaches from the starboard side. At 5.2 km the long-range guns open up, doing 123/90% continuous and generating eight flak clouds, each potentially dealing 1400 dps. The ship commander now assigns the starboard side as the reinforced sector. The plane immediately takes 3.5% damage. Over about 5 seconds the ship's long-range continuous damage increases to 184 dps (with no change to the flak). Then as the approaching plane leaves the flak zone it enters the mid- then short-range auras which are reinforced to 547 and 690 dps respectively. Then crossing the ship, the dps decreases to 230, then 182, then 61 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 is again ready to make enemy planes regret an attack.

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. Note that a number of ships can mount this upgrade, but have no such guns. Without long-range AA guns it does nothing.

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% and the damage caused by flak clouds is tripled.

While Defensive AA Fire  is active, flak bursts will appear with a more 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 Doubles instantaneous damage and provides an immediate burst of stronger continuous damage. See details above.

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

Fighters

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 two to four 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.

Notes

Other Resources

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

A Dev Blog post that explains how AA defense changed for the 0.8.0 carrier rework : Link and largely repeated here.