One problem with the defensive gunfire arcs' vertical limits, as given in the Fighting Wings rules, is that no allowance is made for changes to the aircraft's vertical arcs if the aircraft is in a climb or dive, nor if the aircraft is banked. This is not so important for "H" class aircraft, especially in fixed formation, as they rarely maneuver anyway. But for the rear gunner of a Me 110 or Blenheim, for example, it is necessary to make some allowance for the effects of maneuvering on their defensive gun coverage, as these aircraft did not fly in massed fixed formations but actively maneuvered in combat.
The following is a redefinition of the vertical gunfire arcs. They are based on those that exist already, but I have added rules for calculating altitude limits for other than level flight. These rules add a greater degree of "realism" by making the game more three-dimensional, but as with most attempts at realism, this adds complexity. They may be considered advanced and optional rules, to be used only with agreement of all parties. However, I recommend their use in the applicable situations, as they are not as difficult to use as they look, and they do take away the unreal situation of the mid-upper gunner on a diving aircraft firing at a fighter behind and below....
The following are the six standard vertical arcs.
These are the same arcs as used in the rules, but renamed to avoid confusion between the two. Their equivalents are:
Level: Combination of UL and LL.
High+ and Low +: UE and LE respectively.
High to Low: Combination of UE, UL, LL, and LE.
All High (AH) and All Low (AL): These cover the entire area covered by the three "Standard" vertical arcs for the same hemisphere, except the target must be at least one increment above/below the firing aircraft respectively, regardless of range.
A Steep dive is assumed to be about 15 degrees nose-down. In reality, this would only be so if at least one increment was lost per HFP expended. A "Steep Dive" can be anywhere from 5° to 30°, depending on how many increments were lost and how many HFP were used, but I will assume an angle of about 15° nose-down. Similarly, a Zoom Climb is about 15° nose-up.
Note that these dive/climb angles are the same that were used to calculate the vertical firing limits for Fixed Gunnery, so using them for Defensive gunnery is consistent with the rest of the gunnery rules.
Defensive guns can not fire in a Vertical Climb/Dive, even for those aircraft that can enter such a Flight Type voluntarily. However, it is necessary to define the Rear arc vertical limits for Vertical Climbing/Diving aircraft, as most (if not all) fighter aircraft are blind into some or all of their Rear arc. A climb/dive angle of 45° will be assumed - according to the Fixed Gunfire limits, this angle can actually be anywhere between 30° and 60°, and it would be 90° if all FP are expended as VFP. The effects of this are discussed below.
An aircraft which is banked also changes its defensive arcs altitude limits. For example, a TT on an aircraft in a left bank would now be able to see targets below to the left, but would only be able to see higher targets on the right. How far below/above would depend on the aircraft's angle of bank. Bank angle is also highly variable, and is also related to the severity of the turn being undertaken, harder turns requiring a higher bank angle. However, because aircraft that used a BT turn or harder cannot use defensive fire at all, a relatively shallow bank angle will be assumed of 15 degrees (the same angle as a Steep Dive/Zoom climb).
The attached table combines the effects of climbing, diving and banking on the vertical arc limits of defensive guns. These same tables can be used for determining blind arcs of Fighter aircraft as well, hence there is also a Vertical Climb/Dive table for the Rear arc only.
In some instances, a gun position that can fire vertically (either into the UV or LV arcs) will be able to fire into another arc entirely. This is due to the fact that when an aircraft rotates, its relative vertical rotates also. For example, when an aircraft dives, its upward vertical would now point into its Front arc, and its downward vertical would point into its Rear arc.
Therefore, these Vertical arcs can also see into a different Horizontal arc when an aircraft climbs/dives/banks, and the vertical limits for these are given in the format "a, X, b" in the upper/lower limits tables (explained fully later). To determine the new arc that can be seen by these Vertical arcs, refer to the following tables:
|Angle||Left Front||Front||Right Front||Left Rear||Rear||Right Rear|
|LEFT||-||Left Front||Front||-||Left Rear||Front|
|RIGHT||Front||Right Front||-||Rear||Right Rear||-|
|CLIMB||Left Rear||Rear||Right Rear||-||-||-|
|DIVE||-||-||-||Left Front||Front||Right Front|
|Angle||Left Front||Front||Right Front||Left Rear||Rear||Right Rear|
|LEFT||Front||Right Front||-||Rear||Right Rear||-|
|RIGHT||-||Left Front||Front||-||Left Rear||Front|
|CLIMB||-||-||-||Left Front||Front||Right Front|
|DIVE||Left Rear||Rear||Right Rear||-||-||-|
If an aircraft is both changing altitude and banked, then apply both changes separately, and then also combine both changes consecutively for a third result. To combine the changes, first find the change due to the climb/dive, then apply the banking change to this new arc. For example, assume a ventral turret can only fire on a lower target in the rear arc, but can also fire vertically downwards. The aircraft zoom climbs and banks left. The turret can now see into the Front arc (due to the climb), the Rear Right (due to the bank), and the Front Right Arc (the effect of the bank applied to the new arc that can be seen due to the climb). If this appears to give such a turret too great an area that can be covered, remember that the turret would only be able to fire into the first one or two hexes of the new arc - beyond that, and the target would be out of range due to the altitude difference. Also, most turrets that can fire vertically have 360° coverage anyway, but see the example below to see how this rule makes a difference to game play.
The left column is the combination of the aircraft's attitude and the gun's horizontal arc. Note that the table may have to be referenced twice in some circumstances, e.g. if steep diving in a left bank, two references would have to be made for an gun position attempting to fire on a target in the right rear arc, once due to the dive, and once due to the bank. Only if both conditions are satisfied is the target in arc. Cross-reference the target¹s horizontal range with the climb/dive/bank angle and allowed horizontal arc. If the result is in the format [a, b], then the difference in increments between the firer and target¹s altitude must be on or between these two figures tobe in that gun position¹s vertical arc. If "b" is given as "X" or "-X", that means there is no upper/lower limit on firing at that range.
If the format is [a, X, b] then "a" is again the lower/upper limit, and "X" (or "-X") still means there is no upper/lower limit. However, "b" is the lower/upper limit for the new horizontal arc that the gun can see into, or put another way, read this as [b,X] for the "opposite" arc. In most cases, this makes no difference, as most guns with vertical coverage were in a 360° mount and can already see into the other arc. However, it will make a difference if an attacker flies across the defending aircraft, as they may not be able to claim immunity for flying from one angle-off arc to the opposite arc (as per Rule 10.5, Acquisition Time Restrictions), as they would if the aircraft was flying level.
EXAMPLE: An FW 190 flies from 4 hexes behind a lone, Steep Diving B-17, to one hex directly in front. It is ten increments higher, and claims that it is immune to defensive fire from the B-17 as it has passed from the rear to the front angle-off arcs. However, the B-17 player checks the table, and discovers that the TT, which has "AH" vertical coverage, has a "rear" arc that extends into the "front" arc at one hex range as long as the target is at least 9 increments higher. The upper gunner merely elevates his guns fully and continues to poor shells upwards at the FW 190....
* For ranges beyond 7, use the following formulas, where R = horizontal
Climb, Rear: 3 x R, -X, -3 x R; Climb, Rear Low: -4.5 x R - 1 (drop fractions), -X, -3 x R.
Dive, Rear: -3 x R, X, 3 x R; Dive, Rear