While d20 Modern includes stats for modern aircraft, the vehicle combat system does little to accommodate them, focusing as it does on car chases and highway battles.
This is a collection of house rules for making the d20 Modern vehicle rules more accommodating to running air combats. It was originally devised for use with the Red Star campaign setting (and its abundance of military aircraft), but will function equally well with other campaigns.
The updates appear below, sorted by the section of the original rules they affect. Unchanged rules are not reprinted.
Scale
d20MAKS adds a third scale to the vehicle rules. If the scene involves only very fast moving vehicles, such as modern fighter aircraft, use tactical scale.
Tactical Scale: In tactical scale, each square of the grid represents 500 feet.
In tactical scale, most commonly encountered vehicles occupy only one square. (Some especially large vehicles, such as aircraft carriers or The Red Star’s sky furnaces, might occupy more than square.) More than one vehicle can occupy the same square. Vehicles in the same square are considered to be 200 feet apart for the purposes of determining range for attacks.
For other purposes, such as ramming, tactical scale is considered to be equivalent to chase scale.
Vehicle Speed
d20MAKS adds three additional speed categories, air cruise, supersonic, and hypersonic. The associated movement ranges and modifiers, along with the tactical scale values for the original five categories are listed in the table below.
| Speed Category | Character Scale Movement / Turn Number |
Chase Scale Movement / Turn Number |
Tactical Scale Movement / Turn Number |
Defense Modifier |
Check/Roll Modifier |
| Stationary | 0 / – | 0 / – | 0 / – | +0 | – |
| Alley speed | 1-20 / 1 | 1-2 / 1 | 0 / – | +0 | +0 |
| Street speed | 21-50 / 2 | 3-5 / 1 | 0 / – | +1 | -1 |
| Highway speed | 51-150 / 4 | 6-15 / 2 | 1 / 1 | +2 | -2 |
| All-out | 151-200 / 8 | 16-50 / 2 | 2-5 / 1 | +4 | -4 |
| Air cruise | 501-1000 / 16 | 51-100 / 4 | 6-10 / 2 | +6 | -6 |
| Supersonic | 1001-5000 / 32 | 101-500 / 4 | 11-50 / 2 | +10 | -10 |
| Hypersonic | 5001+ / 64 | 501+ / 8 | 51+ / 4 | +18 | -18 |
Moving
d20MAKS adds two additional optional aspects to the movement of vehicles, altitude and minimum airspeed. It is unnecessary to use these, but one or both of them can be added to the game to further differentiate air combats from combat scenes between ground vehicles.
Altitude: d20MAKS generally assumes that a two-dimensional grid continues to be used for combat. If you want to include altitude as a third dimension, it is suggested to track it in increments equal to the length of a square of the appropriate scale (i.e. in chase scale all changes to altitude will be tracked in 50 feet steps).
The current altitude of a vehicle should be noted down on a record sheet or with an appropriate token placed next to the vehicle on the grid.
Minimum Airspeed: Many aircraft are incapable of hovering in place and must maintain a certain minimum speed to remain airborne. This minimum speed is two speed categories lower than the aircraft’s top speed. An aircraft which is incapable of hovering and whose speed category at the end of its turn is below its minimum speed risks going out-of-control.
Piloting an Aircraft (Driving a Vehicle)
Instead of the Drive skill used with ground vehicles all relevant skill checks (e.g. for stunts or to avoid losing control) for aircraft are made using the Pilot skill.
Simple Maneuvers
d20MAKS adds the following simple maneuvers to those described in the basic vehicle rules.
Lining Up: A pilot might wish to maneuver his aircraft into a position which will make it easier to hit another aircraft with an attack. Typically this is achieved by moving behind the targeted aircraft.
Lining up may be performed whenever the target vehicle is in the front arc of the pilot’s vehicle, and the pilot’s vehicle is in the rear arc of the target vehicle. At chase or tactical scale a lining up maneuver may also be attempted, though the target vehicle can make a Reflex save (DC 15) to reduce the effects of the maneuver by half.
Lining up negates the speed penalty to attack rolls on the target vehicle for one round or until the target vehicle’s rear arc ceases to be in the attacker’s front arc (and vice versa), which ever happens first.
Lining up costs a number of squares of movement equal to the target vehicle’s turning number.
Change Altitude: If altitude is tracked (see Movement above) the 45-degree turn and sideslip simple maneuvers may also be executed in the third dimension (i.e. making a 45-degree turn up or down, or performing a “side”slip by moving 1 square forward and 1 altitude increment up or down).
Stunts
The Jump stunt is normally not used in d20MAKS.
d20MAKS adds the following stunts to thise described in the basic vehicle rules.
Landing: Landing allows an aircraft to safely land on a runaway or other surface.
To land the pilot must make a Pilot check with the DC determined by the type of landing strip.
On a failed check, the vehicle is still considered airborne (at a height of 1 altitude increment if tracking altitude). If the check failed by 5 or more, the vehicle crashed instead, colliding with the ground (see Collisions and Ramming).
| Landing Site | DC |
| Normal runaway | 10 |
| Short runaway | 15 |
| Highway | 15 |
| Normal road | 20 |
| Dirt strip | 25 |
| Carrier deck | 20 |
Take-Off: Take-off allows an aircraft currently on the ground to get airborne.
To take-off the pilot must make a Pilot check with the DC determined by the type of runaway. At the end of a successful take-off the vehicle is considered airborne (at a height of 1 altitude increment if tracking altitude).
On a failed check, the vehicle is still considered on the ground – this may result in the vehicle moving into a hazard at ground level, but is not dangerous otherwise.
| Runaway | DC |
| Normal runaway | 5 |
| Short runaway | 10 |
| Highway | 10 |
| Normal road | 15 |
| Dirt strip | 20 |
| Carrier deck | 15 |
Weapons Lock: Weapons lock allows a vehicle to employ guided weapons, such as air-to-air missiles, to greater effect.
To achieve weapons lock on a target vehicle, the pilot needs to succeed at a Pilot check with a DC equal to the target’s Defense.
If the stunt was successful, the attack penalty due to the attacker’s speed and the defense bonus due to target speed are both negated for attacks with guided weapons (e.g. missiles). This lasts until the end of the next turn.
On a failed check, nothing happens.
Change Altitude: If altitude is tracked (see Movement above) the hard turn stunt may also be executed in the third dimension (i.e. making a hard turn up or down).
Collisions and Ramming
Collisions and ramming are resolved as normal. The damage die types for the additional speed categories are listed below.
| Highest Speed | Damage Die Type |
| Air cruise | d20 |
| Supersonic | d3x10 |
| Hypersonic | d4x10 |
Collisions with the ground (crashes) are considered collisions with a colossal object.
Losing Control
Instead of the vehicle entering a roll, in d20MAKS a seriously out-of-control vehicle will crash.
Crash: The vehicle collides with the ground (see Collisions and Ramming above).
If altitude is tracked, the facing after a spin is determined using 1d12 instead of 1d8: 1, no change; 2, right 45 degrees; 3, right 90 degrees; 4, right 135 degrees; 5, left 135 degrees; 6, left 90 degrees; 7, left 45 degrees; 8, up 45 degrees; 9, up 90 degrees; 10, up 135 degrees; 11, down 90 degrees; 12, down 45 degrees.
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