When is an air unit, in the air?

[Guv’ner]

I am currently trying to diagnose outstanding combat bugs. One that I have come across is that when an air superiority needlejet engages a non-air-superiority needlejet in the air combat is not weapon-to-weapon as it should be.

However, this has opened up the issue of when is an air unit in the air. This is important because if an air unit is airborne it can only be attacked by units with the air superiority special ability. If an air superiority unit attacks another air unit, then combat will be weapon-to-weapon.

Current situation
The four chassis whose domain is defined as “air” are needlejets, copters, gravships, and missiles.

For the purposes of determining weapon-to-weapon combat this only occurs when the chassis is needlejet, copter, or gravship and both units have air superiority.

Only needlejets outside of bases, airbases, and carrier decks are defined as in air for the purposes of attack by non-air superiority units.

The Manual makes two clear statements (neither of which explicitly cover gravships) on page 101:

Any unit can attack a chopper.

To attack needlejets in flight (i.e., anywhere outside of a base or an airbase), a unit must have the Air Superiority special ability. Air units at bases and air-bases are considered to be “on the runway,” and can be attacked by any unit.

Proposed logic
Up in the air
Air units are on the ground if they are in a (air)base, or on a carrier-deck ability transport; unless they have air-superiority and are defending against an air unit. Copters are also on the ground when they finish their movement outside of a (air)base or carrier-deck. Units are always in air when scrambling.

Weapon-to-weapon combat
Weapon-to-weapon combat occurs when the attacking unit has an air chassis and air superiority and the defending unit has an air chassis and is not in an (air)base nor a copter that has finished its movement. It also occurs when both units have an air chassis and air-superiority. Scrambling air-superiority air units are the attacking unit for determining whether combat is weapon-to-weapon and whether combat is Psi or not.

Defending unit
If a unit with air-superiority attacks a stack of units that contains at least one gravship or needlejet that are not in an (air)base or on a carrier deck then they should engage with the strongest defence gravship or needlejet not the strongest defence unit overall.

If a unit without air-superiority attacks a stack of units that contains at least one gravship or needlejet that are not in an (air)base or on a carrier deck then they should engage with the strongest defence unit that is not a gravship or needlejet.

Collateral damage
When a land or sea unit in a stack of units that contains at least one gravship or needlejet and are not in an (air)base or on a carrier deck is destroyed it should cause collateral damage only to other land or sea units not to any gravships or needlejets. Destroyed gravships and and needlejets cause collateral damage as currently.

Result
The most notable changes that I perceive would result are:

• Gravships could only be attacked with air superiority
• Air units would no longer protect stacks against non-air superiority units
• Missiles would now defend against scrambling jets using their weapon

[TarMinyatur]

Good analysis.

A single SAM-equipped infantry can do enormous damage upon an enemy's mixed stack of needlejets/infantry. The collateral damage is surprisingly harsh.

I think the SAM infantry should attack a single needlejet by default. If that needlejet is destroyed, then perhaps collateral damage would occur as the mangled jet crashes into friendly units below. 

[Geo]

Just popping in to mention that the "missiles" wiki link in the OP doesn't work...

[Yitzi]

Good analysis.

A single SAM-equipped infantry can do enormous damage upon an enemy's mixed stack of needlejets/infantry. The collateral damage is surprisingly harsh.

I don't think it's any harsher than a non-SAM unit attacking infantry.  (Non-air unit SAM units don't get a bonus to attack air, just the ability to do so.)

[TarMinyatur]

Good analysis.

A single SAM-equipped infantry can do enormous damage upon an enemy's mixed stack of needlejets/infantry. The collateral damage is surprisingly harsh.

I don't think it's any harsher than a non-SAM unit attacking infantry.  (Non-air unit SAM units don't get a bonus to attack air, just the ability to do so.)

I'm confused. Are you referring to an artillery duel involving a stack containing airborne air units? The air units are immune to collateral damage, unless the artillery has the SAM ability. And a non-SAM, non-arty units lack the ability to attack a stack which includes an air unit, right?

My idea of "harsh" involves the extent of collateral damage caused by the destruction of a land unit which happens to have jets flying above it.

For example, let's say a SAM-equipped infantry attacks a stack of 5 jets. The infantry will probably destroy a single jet. OK. That seems right to me. No damage is dealt to the other 4 jets.

However, if we add a Synthmetal Garrison to that stack, the SAM infantry will attack the garrison and likely destroy it. Now things get harsh...The Synthmetal unit blows up and presumably sends shrapnel high into the skies, heavily damaging 5 jets! (The more powerful the SAM infantry's weapon, the greater the collateral damage.)

This seems like a lot of collateral damage caused by a non-artillery unit. 

[Geo]

However, if we add a Synthmetal Garrison to that stack, the SAM infantry will attack the garrison and likely destroy it. Now things get harsh...The Synthmetal unit blows up and presumably sends shrapnel high into the skies, heavily damaging 5 jets! (The more powerful the SAM infantry's weapon, the greater the collateral damage.)

This seems like a lot of collateral damage caused by a non-artillery unit.

Think of it as the SAM unit firing a volley on the air units, damaging some, and the debris falling out of the sky killing the synth defender, helped by some stray ammo from the initial volley. 

[Yitzi]

Good analysis.

A single SAM-equipped infantry can do enormous damage upon an enemy's mixed stack of needlejets/infantry. The collateral damage is surprisingly harsh.

I don't think it's any harsher than a non-SAM unit attacking infantry.  (Non-air unit SAM units don't get a bonus to attack air, just the ability to do so.)

I'm confused. Are you referring to an artillery duel involving a stack containing airborne air units? The air units are immune to collateral damage, unless the artillery has the SAM ability. And a non-SAM, non-arty units lack the ability to attack a stack which includes an air unit, right?

My idea of "harsh" involves the extent of collateral damage caused by the destruction of a land unit which happens to have jets flying above it.

For example, let's say a SAM-equipped infantry attacks a stack of 5 jets. The infantry will probably destroy a single jet. OK. That seems right to me. No damage is dealt to the other 4 jets.

However, if we add a Synthmetal Garrison to that stack, the SAM infantry will attack the garrison and likely destroy it. Now things get harsh...The Synthmetal unit blows up and presumably sends shrapnel high into the skies, heavily damaging 5 jets! (The more powerful the SAM infantry's weapon, the greater the collateral damage.)

This seems like a lot of collateral damage caused by a non-artillery unit.

I don't think it's any more than would be caused if the defenders were all land units.