The Aviation ruleset (github, forum thread), created and maintained by soundnfury, is focused on air warfare in the 20th Century. Unlike some other rulesets which merely add new units or mechanics to a basically Civ-like game, Aviation is close to being a total conversion. The ruleset is developed for freeciv 3.0 and also for's freeciv21 fork of 3.1.

As befitting the focus on air battles, land and sea forces have been heavily simplified: there are only nine different ground units and ten sea units — and most of the latter are aviation ships of one kind or another (aircraft carriers, seaplane tenders and helicopter ships). As for air units, there are over 100, covering not only a 60-year span of technology but also a wide variety of rôles.

Bombers, dive bombers, torpedo bombers and strike aircraft attack ground (or in some cases sea) units. Ground units can make airborne assaults either by parachute or by glider. Gliders are towed by bombers, and expended once dropped; paratroops jump from transport aircraft. Sea units can transport either carrier-capable aeroplanes, seaplanes or ground units. Airliners create trade routes between cities. Blimps and flying-boats patrol the seas, hunting submarines. Reconnaissance planes watch the enemy to find out what he's up to...

... and Fighters try to shoot down everything else!

Key Concepts[edit | edit source]

Mountains are impassable to all ground units!

Hit Points and FirePower[edit | edit source]

In standard freeciv rulesets there are generally two kinds of units: pre-gunpowder, with 10 HP (and 1 FP), and post-gunpowder with 20 (and sometimes 2 FP). Thus, most fights will take 10 or more hits to kill a unit, enough that randomness will mostly be smoothed out. Aviation is not like this. There are aircraft with every number of hitpoints from 6 to 16, plus a few outside of this range (from the four-hitpoint SA Armed Scout to the 24-hitpoint MJ Small Jet Bomber), and firepower goes up as high as 5. Most air units will take somewhere between four and eight hits from the types they're likely to be fighting, so even a small number of unlucky rolls can change the course of a fight.

Also, note that in many cases one unit's firepower won't divide evenly into the other's hitpoints, which causes all kinds of interesting effects — how strong a unit is depends to some extent on what it's fighting against. For example, having 10 HP instead of 9 is a big deal if you're fighting someone with 3 FP — they need a whole extra hit, so it's as though you had 12 HP — but makes no difference at all against an opponent with 2 FP (since either way they need the same five hits to bring you down).

Combat Rounds[edit | edit source]

Air combat is unlike the stand-up slugfest that usually constitutes fights in freeciv. Most importantly, it is not (necessarily) a battle to the death. Thematically, this is because once a bomber has dropped its bombs, it is empty; it can't just keep dropping bombs until it or the target is destroyed, it has to return home and re-arm. Similarly, if a squadron of fighters, having intercepted a bomber formation, find that they are losing the battle, they can use their superior speed to disengage, rather than fighting on until the last of them is shot down.

In Aviation this is achieved by the use of the Combat_Rounds feature which was added in 3.0: the battle will last for at most a number of rounds determined by the attacking unit type. In the case of bombers (for which attacking ends their turn), this limits how much damage they can deal, but also how much they can take from the defending unit — even the weakest of bombers will usually live to fight another day, as long as it doesn't get attacked by a fighter before it can get home.

A fighter's (or attacker's) Combat_Rounds have a slightly different effect: since the unit can keep on attacking as long as it has enough movement points, it will usually be limited more by hitpoints than by move. Instead, the CR determines the intervals at which the player can decide whether to disengage or keep fighting. However, there's another factor that comes into play when attacking a stack of units: after the first set of Combat_Rounds, when you re-engage you may be fighting a different unit, one which perhaps still has full hitpoints. Thus, a larger CR increases your chances to get kills without having to wear down the entire stack quite so far.

Targets/Unreachable[edit | edit source]

Every unit class — ground, sea and air — is considered unreachable-by-default in Aviation. With a few exceptions like units in cities (which all count as ground for this purpose) or bases, units can only be attacked by those which target them. Broadly speaking, bombers and attackers can target ground units, torpedo-bombers and some conventional bombers can target ships, and only fighters can target other aircraft. There are a few units that cross these categories, notably strike fighters and late-period attackers which combine the ground-attack and anti-air rôles, but in general each aircraft is built for a specific purpose and can't initiate combats outside of that category.

Speed and Fuel[edit | edit source]

As with the aircraft in the classic ruleset, air units have a limited supply of fuel, and must land on a city, base or carrier before the fuel runs out or else the unit will be lost. Generally aircraft can be divided into "fast" units which have 1 fuel and can attack multiple times per turn, and "slow" units which have 2 or more fuel but which end their turn on attacking. There are a few exceptions however: blimps, helicopters and escort-fighters can all multiattack, but have multiple fuel, allowing them to loiter on-task for various reasons.

Aircraft are much faster across the map than anything else; by the jet age, they can fight battles as much as 15 tiles away from their base. Since some aircraft can also deliver ground troops to capture cities, the 'front line' can be very deep — a poorly-defended city in the middle of your empire might suddenly fall to a long-range airborne assault.

Trade and Blockades[edit | edit source]

An important driver of the game's economy is the Merchant Ship, which travels to foreign cities and enters the marketplace there to be converted into gold and bulbs for both players. (You can also use it to trade between two of your own cities, but then you will only get gold, not bulbs.) Since this will (at least over decently long routes) yield rather more than building Export (i.e. Coinage, turning shields directly into gold at a 1:1 ratio), a trading civilisation can pull ahead in science and often not need gold tax at all.

However, Merchant Ships are quite vulnerable; with only 6 hitpoints, they can be sunk by a wide variety of units (submarines, torpedo-bombers, flying-boats, and some conventional bombers), meaning that a hostile power may be able to strangle your maritime trade routes. (Later in the tech tree there is the Catapult Armed Merchantman, which has triple defence against air attack, but it's still pretty weak.) Much of the importance of naval aviation in the game is to either protect your own merchants (Sea Control) or interdict the enemy's (Sea Denial), either directly or via submarines (which are themselves somewhat vulnerable to air attack).

Persistent trade routes between cities are also important; instead of the classic ruleset's Caravan and Freight, these are created with airliner units. Thanks to fuel, these have a limited range, so unless there are convenient allied cities or empty airbases to refuel at, you won't be able to create truly globe-girdling trade routes. Still, the routes you can create will earn plenty of trade for both ends. Beware, though, that airliners are completely defenceless, should some hostile power send in a fighter to catch them en route. Also, the number of trade routes a city can have depends on various buildings (and a wonder, ICAO); without any of them, the limit is 1.

Airborne Assault[edit | edit source]

Moving ground units around is slow. Most only have 1 move, and even the Landing Craft which can transport them across the sea only has 2 move. Roads don't speed them up at all, and even railways take half a movement point to traverse. If you want to fight a blitzkrieg, you need to deliver ground forces from the air. Without a friendly city or airbase to land at and unload, this can be difficult; there are three ways to do it: gliders, paras and helis.

Note that only Assault-class units can be transported; the Troops and Artillery units are too heavy to travel by air (or by boat), and are thus forever confined to the land-mass on which they were built.

Gliders[edit | edit source]

A glider is an air unit with zero move, which can carry a number of assault units, and can itself be 'carried' by certain aircraft (tugs), namely medium and heavy bombers from the 1920s through to the mid-’40s. The bomber tows the glider to the Drop Zone, then unloads it (it must be flat ground, i.e. not forest or jungle); next, the assault units unload from the glider and fight their ground battles. The glider is thus single-use (you may as well disband it afterwards), but that's okay because it's pretty cheap.

Parachutes[edit | edit source]

The Paratroops unit works a bit differently to classic freeciv. Instead of having a special Paradrop action, its distinguishing feature is that it can unload from a transport aircraft in flight. As well as dedicated military transports, some heavy bombers and even flying-boats can carry a small number of units. After unloading, the paras are immediately ready to fight. Though they avoid the complicated faff of discarding a glider, they aren't quite as good as gliderborne troops at holding on to their gains, and you can't paradrop artillery (the airlanding Assault Gun is a low-powered bombardment unit).

Helicopters[edit | edit source]

Once you develop gas-turbine-powered helicopters, you can use them to deliver units anywhere. Because a heli can land in a field without a prepared airbase, assault units can unload from it directly, without all that tedious mucking about with gliders. The main downside is the helicopter's short range.

Economy[edit | edit source]

At present, the ruleset's economy is rather underdeveloped. There are buildings to boost sci/tax/lux production (Aeronautical Library, Wind Tunnel, Commercial Airstrip, Balloon Rides, Airship Company, Air Tours, Hub Airport) as well as content-citizen buildings (Flying Club, Air Races) and the police-station-like War Memorial to mitigate military unhappiness. To limit corruption, the FAA Branch acts like a classic Courthouse. This is a much less multiplicative economy than the classic ruleset (with its three levels of Library/University/Research and Marketplace/Bank/Stocks); in Aviation the way to get rich is through foreign trade. This means that you need to (a) have at least some friendly neighbours, and (b) protect your merchant marine from any unfriendly neighbours.

Buildings like Crop Dusting (analogous to classic Supermarket), Waterbombers and Marshalling Yard increase tile output, while Lumber Yard, Engine Factory and Aircraft Factory boost shields (à la Factory and Mfg Plant). Tramways and Electrification combat pollution, broadly resembling the classic Mass Transit and Recycling Centre. Recruiting Office reduces unit upkeep (but only if your government pays in shields, not gold).

For supporting your military, the Barracks does what you'd expect, and Shipyard is like a Port Facility. For air units there are separate buildings for veterancy (Flying School) and fast HP recovery (Repair Sheds for landplanes, Aircraft Slipways for seaplanes). Flak Battery and SAM Battery give cities defensive bonuses against aircraft; Barrage Balloons protect specifically against dive-bombers.

Wonders are a bit of a grab-bag; there are some economic ones (Lloyd's of London, Kitty Hawk Monument, Aeronautical Institute, de Havilland, National Airline, Supersonic Wind Tunnel), happiness (Display Team, Human In Orbit) a leonardo (SBAC Airshow, halves upgrade prices), a tech-catchup great-library (Jane's All The World's Aircraft), and a couple of darwins (Schneider Trophy, Sound Barrier). Staff colleges give units increased chances of gaining veteran levels (War College for ground-troops, Naval College for ships, seaplanes and carrier aviation, RAF College Cranwell for landplanes).

Government[edit | edit source]

The available governments are rather different to classic freeciv. In particular, none of them have any tech requirements — by 1900 they've all been invented already.

Constitutional Monarchy[edit | edit source]

You start the game as a Monarchy. This government has moderate corruption, but pays upkeep in gold (rather than shields), and can use up to 2 units of martial law to keep citizens content. On the other hand, unhappiness due to empire size is something of a problem (base 10, step 9), and it also experiences unhappiness from aggressively deployed military units.

Democracy[edit | edit source]

Democracy has lower corruption (unaffected by distance from the capital), and gets +1 to tile trade; celebrating cities get another +1 on top of this. It suffers unhappiness from aggressively deployed military units, and has a Senate which may prevent you from declaring war. For farming your economy there's nothing to beat it, as long as you can keep everyone happy.

Communism[edit | edit source]

Corruption is lower than Monarchy but still varies with distance. There is also waste of shields, and Communists are bad at science (40% penalty) and produce more pollution (+50% to shield-based pollution). However, it gets two extra content citizens per city, and up to three units may impose martial law. Thus, it can be useful for militaristic rampages.

Fascism[edit | edit source]

The Fascists also like their militaristic rampages; they too get two extra content citizens per city and three units of martial law. They also get certain units upkeep-free (dive-bombers, Early Heavy Fighter, Paratroops, Assault Troops and the Assault Gun); for other units they pay upkeep in gold, but at double the rate. Corruption is severe. Fascism has the lowest unhappiness due to empire size (base 15, step 16). Can you conquer the world before your economy collapses?

Military[edit | edit source]

Ground units[edit | edit source]

There are not many of these. There is one main city defender, Troops, which lasts un-upgraded throughout the entire tech tree; it's unable to travel on transports. Nor is the Artillery, a reasonably powerful bombarder. If you have a hostile land border you might end up fighting trench warfare with lines of troops and arty (possibly with fortresses standing in for the trenches) but it'll be somewhere between 'stalemate' and 'meatgrinder'. If someone leaves a city undefended, you might be able to ship in some Marines to snatch it, but they're very weak in combat.

The main attacking units are the Assault Troops and Paratroops, both of which are designed to be delivered from the air in surprise attacks. There's also the Assault Gun, an airliftable bombarder that's quite handy for reducing big stacks (but isn't quite as strong as Artillery).

And of course there are the non-military Settlers and Seabees (workers), which have a very slight defensive ability.

Ships[edit | edit source]

The purpose of sea-power is found in the Merchant Ship (for trade) and the Landing Craft (a troop transport, good for amphibious invasions or for carrying settlers to colonise unoccupied islands). Everything else is either for sea denial — the Submersible, which can surface (convert unit) for extra speed, then submerge for stealth and greater attack strength — or sea control in the form of various aviation ships. The Seaplane Tender can refuel floatplanes, flying-boats and blimps, useful early on but then outclassed by carrier-borne aircraft. Those can fly from the Light Aircraft Carrier, Aircraft Carrier, Escort Carrier and Nuclear Aircraft Carrier; of these the CVL, CV and CVN form a progression of increasing capacity, speed and defence, while the CVE is a converted merchant ship which can cheaply supply a little air cover to a convoy.

Aircraft[edit | edit source]

There are so many of these that rather than listing them all here, I'll speak in generalities, and refer the reader to either the in-game help or the recognition chart for specifics.

On attaining the second veteran level (Ace), air units gain an extra point of speed.

Bombers[edit | edit source]

There are four main kinds of bombers: light, medium, heavy and dive. The heavy bombers deal a lot of damage, but are vulnerable to fighters; conversely, light bombers are robust (relative to their price) but only scratch at targets. Medium bombers are a balance between offence and defence. Dive bombers are an ultra-attacking option: they generally combine the offence of a medium and the cost of a light with defence weaker even than a heavy. Dive bombers and some light bombers are carrier-capable. While all bombers can attack ground units, some can also strike at ships. Most mediums can tow gliders, and some heavies can do the same or carry ground units directly (such as paratroops).

One very early bomber is the Zeppelin Bomber. It deals only a little damage and is totally defenceless against fighters, but if the enemy hasn't invented fighters yet it just might have a use.

Torpers[edit | edit source]

Built purely for attacking sea units, torpedo-bombers are hard-hitting but flimsy. The early floatplanes are soon overtaken by carrier-borne equivalents.

They can't bomb ships in port, only on the open seas. (This is thanks to a ruleset workaround for a game engine limitation.)

Flying-boats[edit | edit source]

These are mostly light or medium bombers, generally able to attack land or sea targets, but more expensive and less powerful than landplane equivalents. On the other hand, they are longer-ranged, especially if supported by tenders. Some of them can carry ground units.

The Jet Flying Boat is a cross between an attacker and a fighter; it's just all-round weird.

Blimps[edit | edit source]

Cheap and able to loiter (4 fuel), these can attack sea units, but not very powerfully — their primary purpose is hunting submarines.

Attackers[edit | edit source]

Ground-attack aircraft have multiattack, meaning they don't have to wait around for a turn and give enemy fighters a chance at them. However, they're typically short-ranged and not as powerful as bombers, making their use in battle more tactical than strategic. Near the end of the tech tree, some attackers gain the ability to target sea units; and there are also carrier-capable attackers.

Reconnaissance[edit | edit source]

Various aircraft from around the tech tree have the ability to Investigate City. Some are purpose-built for recon (including the low-tech Zeppelin Scout, which is long-ranged but slow), while others add it to other rôles (mostly light and later medium bombers).

Transports[edit | edit source]

For either shuttling units quickly between your cities, or delivering paratroops to their objectives. These aircraft have no combat capability, so beware of fighters. However, they can carry a lot more units than will fit in, say, a heavy bomber.

There's also the Helicopter, which can unload units in the field.

Fighters[edit | edit source]

Generally built for one purpose only: shooting down enemy aircraft. (There are occasional exceptions, like the Naval Strike Fighter, which combine fighter and attacker rôles, but these are generally less effective in air-to-air combat than dedicated fighters.) Besides the main progression of single-seat fighters (from WWI scouts through WWII monoplanes to postwar jets) there are a few side-options which have some (usually transient) advantages. Triplanes have a brief combat advantage but are a technological dead end, while two-seat fighters (later developing into turret fighters) are an idea that comes and goes, occasionally being stronger than single-seaters. Heavy fighters have 2 fuel, meaning they can stick around to escort bombers, but being less nimble, they are at a disadvantage in combat. The jet age brings the 'light fighter' concept, cheap to build but weaker than cutting-edge designs.

Seaplanes and flattops also get their own fighter families, generally weaker than the land-based equivalents (but then, the things they're likely to be fighting — other seaplanes, torpedo-bombers and dive-bombers — aren't that strong either).

Missiles[edit | edit source]

The Artillery Rocket is straightforward enough — effectively just a cheap bomber that's destroyed after attacking. But the Kamikaze, designed to attack ships, has a bunch of requirements: to build it you need to have a Fascist government, and have built the greatwonder Yasukuni Shrine. While it's cheap in shields, it also costs 1 population to build, so blowing up too many of these can gouge deep into your economy.

Civilian aircraft[edit | edit source]

Make embassies with the Ambassador. Establish trade routes with airliners — these need a Commercial Airstrip in the city that builds them, apart from the lighter-than-air Zeppelin Liner which instead needs a Mooring Mast. (Either of those buildings will unlock a city's second trade route slot.)

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