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Air units bombing mechanics in the open


May 22, 2020
How do aircrafts target stacks of units out in the open? Do they lethally target air units in the stack first or is it a random thing where they alternate between land units and air units?

I'd like to test making catapult to howitzer line being air units to get rid of the smart aiming. Ballista to ATGMs can be traditional artillery with the ability to defensively bombard and smart targeting units in cities but their ROF of 1 means their overall firepower will be less than the former.

I can give the air unit artillery pieces stealth ability and set interception of stealth units to 0%. But does stealth prevent them from being shot down by units and improvements with anti air value? I notice stealth aircrafts have received defensive values in the C3C. Does that mean that if stealth aircrafts got intercepted in vanilla they're surely doomed because their def value was 0?
I'm digging - right now I have the AA formula:
  • The real strength of each AA unit is 1/10th of the value shown in the editor. So Flak has a strength of 0.2.
  • Each AA unit in the tile being bombarded takes a shot against the defense of the bombarding air unit. The chance of shooting down the air unit is A/(A+D), as with all other forms of combat in Civ3. Remember, A is 10 times less than what is in the editor for the AA unit.
  • The maximum number of AA units that are given a chance to shoot down the plane is 4. Any AA units above 4 are ignored.
So, for example, if you want the formula for the probability of N units with a strength of A shooting down a plane with defense of D, here it is:

1 - (D / (D+A))^min(N,4)

You can find a discussion HERE.
I'm digging - right now I have the AA formula:
  • The real strength of each AA unit is 1/10th of the value shown in the editor. So Flak has a strength of 0.2.
  • Each AA unit in the tile being bombarded takes a shot against the defense of the bombarding air unit. The chance of shooting down the air unit is A/(A+D), as with all other forms of combat in Civ3. Remember, A is 10 times less than what is in the editor for the AA unit.
  • The maximum number of AA units that are given a chance to shoot down the plane is 4. Any AA units above 4 are ignored.
So, for example, if you want the formula for the probability of N units with a strength of A shooting down a plane with defense of D, here it is:

1 - (D / (D+A))^min(N,4)

You can find a discussion HERE.

That means by giving these air unit artillery pieces the max defense value the editor allows would minimize the odds of them being shot down when they shell tiles with AA units/improvements. By setting interception chance to 0% with stealth they won't shoot down fighters. They can still be bombing sponges though that with that high defense because air units can still lethally target them regardless of what ground unit guarding them (like aircrafts on an airfield/city). But with -4 HP I think it could be fair. Artillery pieces could get destroyed by airpower.

An air unit artillery piece with a defense strength of 50 and -4 HP would have a 3.2% chance of being shot down by a cluster of 4 Mobile SAMs with the AA value of 4 (0.4 entered into the combat calculator).

And a 7.4% chance of being shot down by a SAM Battery with Interception percentage set at 50%.

And a 28.8% chance of of being destroyed by a bomber with a bombard strength of 12 ROF:3 in the open where the bomber will target air units half of the time.

I'll start testing with these values. Even against the strongest concentration of AA the game could offer, there is a less than 10% chance of you losing the artillery piece while still allowing for bombers to hit and destroy them. They do cover the regular aircrafts from bombing runs though.

I still don't like how squishy the regular aircrafts are to being bombed. It's like air combat doesn't matter as much as trying to wipe them out on the ground. A bomber with 12 bombard strength, ROF:3 has a big chance of wiping out its grounded counter part/fighter with a defense value of 2 and 4 HPs.
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More on air combat (with apologies:these were in my "General Notes" folder, and so - sadly - lack both authors & thread names.) Nonetheless:

Spoiler "Chance to Intercept Enemy Air Missions" :

In the process of experimentation for a mod I'm working on, I did some testing to try to "fix" air combat. I thought the results might be of interest to modders. Some of this is in the Civ 3 FAQ, but some of it isn't.

First, the "Chance to Intercept Enemy Air Missions" percentage in the "general settings" tab of the editor controls only the probability that aircraft assigned to air superiority in the region will engage the attacker in combat. This means two very important things. Firstly, this percentage does not affect surface based anti-aircraft (that is, a land\sea unit with an "air defense str"). Secondly, if the interceptor's numbers come up and succeeds in intercepting the enemy, it does not automatically mean success.

As far as I can tell, only bombing and precision bombing can be intercepted (but I have not tested this!). When an intercept occurs, the outcome is decided by comparing the interceptor's attack with the bomber's defense. As far as I can tell, the procedure is the same as for any other kind of combat between two units in that one aircraft will be destroyed and the other may take damage in the fight. An aircraft going into a fight without full health will suffer the same penalties as a land or sea unit would.

From the FAQ:

If an aircraft is intercepted it will always fail to bomb the target even if it wins the air battle.
A defending (air superiority) aircraft can't intercept more than once per turn (even if it wins).
Interceptors will only attack aircraft that target squares inside the interceptor's radius of operation. In other words: it does not matter if an aircraft tries to bomb a square lying outside the intercept radius of any fighter if there is no route to the target square that doesn't pass through intercept regions - for all intents and purposes we can assume Civ 3 doesn't consider routes for air missions.

So... what happens if we turn the intercept probability up to 100%? We get a scenario that looks a bit closer to reality (well, WW2 era at least (afaik)). One of the tasks of fighter aircraft is to protect friendly bombers by attacking enemy fighter aircraft which may try to intercept the bombers - either to shoot down the enemy aircraft or to simply draw them off and away so that the bombers can do their job. Further, initial bombing raids against Germany by the USAF showed quite dramatically that sending unescorted bombers is little short of suicide, as the defending fighters will cut them to pieces.

If we change the intercept probability to 100%, this is exactly what can happen. Say we play with the numbers so that fighters have an equal attack and defense value, with bombers having a lower defense than the fighters' attack (note that it doesn't matter what the bomber's attack rating is since it can't perform air superiority). The result is that bombers will usually lose if they attack alone, and even if they win they won't be able to bomb the target. However, the attacker can "escort" the bomber by ordering fighter aircraft to bomb the target first. The defending fighters will always engage the attackers, and a fight will take place. In this way, the attacking force can try to achieve control of the skies before sending vulnerable bombers. Even if the attacking fighters fail to destroy the defenders they will have kept them busy, reducing the number of defending aircraft available to intercept bombers.

There's one major catch: I doubt the AI will take advantage of this when attacking. For the fighters to be able to conduct "escort" missions they need the "bombing" ability, and for that they need at least one point of bombard strength; the closest applicable AI strategy is obviously "air bombard", and I would assume that the AI chooses what aircraft to use for bombing based on whichever has the highest bombard strength (ie, the vulnerable bomber). My assumption is pure conjecture - I have no evidence either way and I haven't read anything on the topic.

Spoiler Evidence Suggests That Combat Against Surface Units Works Differently. " ] Evidence suggests that combat against surface units works differently. It seems that the bombarding aircraft's defense value is compared with the target's air defense value to determine the probability that the aircraft is shot down outright (not damaged and\or driven off!). I'm pretty sure surface AA only works on bombardment targeting the square which the surface AA unit is on (I think there's no radius involved as there is with air interception). The only actual impact of the "stealth" flag for aircraft is that the "Chance to Intercept Enemy Stealth Missions" is used instead. Everything else about air combat seems to work the same way (if you so desired, you could swap the probabilities around completely with no other effects). I have not tested the impact of terrain, radar towers, fortresses or barracks on air combat. (I knew there was something more! ) [/SPOILER] [SPOILER="Naval Air Defense Versus Bombers - Amended (Appended?) :

I thought I'd do some testing and try to figure out why a certain ship in a stack is picked out first when the fleet is bombed and what role Air Defense values play in this. In the editor, I took a Destroyer and Aegis cruiser and assigned them equal values to have a base. I then adjusted a single value at a time on the control ship. Here are my findings.

First off, the Air Defense value. This works like regular combat. When a bomber goes to bombard a ship, the ships Air Defense value acts like an attack value, and is checked against the bombers defense. So, the standard combat formula applies, Attackers Attack Value[ship's Air Defense Strength] divided by (Attackers Attack Strength+Defenders Defense Strength). If the bomber makes it through the Air Defense of the target ship, then the Bomber's Bombardment Value is checked against the Ship's Defensive Strength. Again, the standard combat formula applies. If the bombardment ROF is 4, then I'm assuming each volley is checked against the ships Defensive Strentgh to see if each volley makes it through or not.

Now regarding vessels. Two scenarios apply. One is where the ships are stacked, and the other is where the ships are side by side or close together. In the case of the stacked ships, the HP Bonus and Defense Strength are the factors. If one ship has one point more than another ship with 2 greater points of defense strength, the HP bonus is the deciding factor and the ship with the HP bonus is hit first. But, if the other ship's defense value is high enough, it overides the HP bonus on the other ship, and the ship with the greatest defense strength gets hit first. The game apparently has some sort of ratio parameters here. HP bonus seems to trump defensive strength until the defensive strength reaches a certain ratio against the HP bonus. EXAMPLE: one ship has 2 HP bonus, but another ship's defensive strength is say, 10 points higher than the ship with the HP bonus.

The other scenario where ships aren't stacked but are close to each other. In this intsance the defense value and the cost of the ship are the factors. I tested this out. I had the destroyer and cruiser at equal values across the board, but I made the destroyer cost 1 shield above the cruiser. The destroyer was hit first. I then bumped up the destroyer's defense values quite a bit. This resulted in the cruiser being hit first. So, when ships are close to each other and not stacked, the bombers will go after the ship with the lowest defensive value and the highest build cost. Again, I believe the game has some sort of ratio parameters it follows here.

One thing I did notice about stacked ships. If you have a ship that has the most hit points and highest defense, but it's marked as a king unit. All the other ships will take the hits and sink before your "king" ship is hit. I noticed this while playing El Justo's TCW scenario. I marked some unbuildable ships as king units so they could be upgraded later with newer technolgies. This aspect is somewhat realstic. The capital ship (Carrier or Battleship) is usually escorted by smaller ships. In an air attack, the smallers ships(especially modern ones) would be the vanguards for air-defense and presumably receive the first hits.

Spoiler Anti Air Defense Combat :

This has probably been discussed before, but I thought I would post some observations I had while conducting some tests. It appears that the chance of air interception percentage in the editor has no impact on ships or ground units with anti air defense. This would make sense since air interception is a flag that only works with air units. (before C3C, I did flag an Aegis cruiser with air interception, and had flying cruisers).
To back up my claim, I had one Aegis cruiser with an air defense of 100, and had 20 bombers with defense of only one, I wanted to get sure kills to form a basis. I adjusted the air interception chance from 0, then 25, then 50 and finally 100. I ran each test twice. The results were pretty much the same. On 0, 25, and 100 percent chance air interception the results were 90% of the aircraft killed. With 50 percent chance air interception the results were 95% of the aircraft killed. Where I saw differences were not in the interception chance, but in the anti air defense strength of the defending ship or ground unit. What appears to effect whether or not the ship or ground units shoots down the attacking aircraft is the ship/ground unit's air defense strength and the attacking aircraft's defense strength. The lower the anti air defense and the higher the defense of the attacking aircraft, the less chance of the plane being shot down.

So, in conclusion, when an aircraft attempts to bomb a ship or ground unit with anti air capabilities, the ship or ground unit's anit air defense strength really equates to an attack strength and is applied to the combat system. So, a ship with an anti air defense of 10, is being bombed with a bomber of a defense of 4, the typical combat system is used. 10/ (10)+(4)= 71.4% chance of bomber being shot down. If the bomber succeeds at defeating the anti air defense, which in this case would be a 28.6% chance. Then it goes on to bomb the target, and the bombing strength would be checked against the defenders defense ? I never looked into how the bombard/bombing combat is resolved.

... To undoubtedly be continued :borg:

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Be advised that air units' interception range is half of their general operational range (which is available for other missions).
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