iAirCombatLimit controls how much damage an air unit can do to another unit. 50 = it will cause damage up to 50% of the target unit's strength, 70 = it will cause damage up to 70% of the unit's strength, 100 = it can damage the unit until it dies.
Changing this value does not affect how much damage the attacking unit does per strike; that is calculated during combat resolution and is based on many factors, the major ones being the attacking unit's combat value vs. the target's unit's value.