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Developer Diary | Plane Designer

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Hello, and welcome back to another Dev Diary for the upcoming By Blood Alone DLC and accompanying Patch 1.12! The team has returned from the summer vacation, and we are now back fixing bugs and tweaking the balancing of the new features and focus trees.

Today, we are taking a look at the Plane Designer. As always, any number value that you are going to see in this DD is subject to change.

The Plane Designer became a subject of discussion, both inside the team and in the community, almost as soon as we announced that No Step Back would feature a Tank Designer. We felt that it would mesh well with the rework of the Italian focus tree, not least because the Italian aviation industry was very well developed and produced some of the best combat airplanes of the war - hampered mostly, as Italy so often was, by lacking production capacity.

We also felt that a Plane Designer would help plug some gaps in the lineup of available aircraft. Over the years, many players have commented on the fact that many nations modified their fighters to also be able to carry bombs, or their tactical bombers to also carry torpedoes. One of the big goals of the Plane Designer was to allow for these types of multi-role aircraft.

At the same time, we didn’t want to make these multi-role planes too powerful. Instead, a plane design optimized for a single mission should still be more effective than a multi-role plane. Where multi-role planes offer flexibility, optimized designs offer top performance, if you can afford them.

The basics of the Plane Designer are probably not a surprise for anyone who is familiar with the Ship or Tank Designers. The base is called an airframe, which roughly corresponds to the hulls and the chassis of the ship and tank designers. The Airframes have a number of module slots, where you can put the modules that give the final design its actual stats. There are three different size classes of airframes: Small, Medium, and Large. Small planes also come in a carrier-capable variant of the airframe.

The types of module slots in the Plane Designer are slightly different from the Tank Designer. There are effectively only three types of slots: Engines, Weapons, and Special modules.

Engine modules are perhaps the most straightforward of them. Unlike tanks, where this slot dictates what type of engine the tank uses and a separate stat determines what its speed is, engine modules in the plane designer determine the number and power of the engines mounted on the aircraft. These engine modules produce a new stat called Thrust, while all other modules have another new stat called Weight. These two stats are effectively the limiting factor of what and how many modules you can put on the plane. A design is only legal if Weight does not exceed Thrust (some people might point out that the only planes with a Thrust/Weight ratio of 1 or better in reality are modern, high-performance fighter jets, but these people will be summarily ignored).

Any excess Thrust is converted into extra speed, which is intended to provide a reason not to fill every module slot.

One thing to note here is that jet engines (and rocket engines, for that matter) are part of these engine slots, which means that they are available for all types of planes. This, by necessity, means that Jet Fighters and other jet-powered airplanes are no longer their own unit type - they are now simply fighters with jet engines. Jet fighters will therefore reinforce regular fighter wings, and also that you can now effectively make jet carrier planes, jet CAS, jet heavy fighters etc.with the plane designer.
Or Rocket Naval Bombers, one supposes, if you really hate your pilots on a personal level.
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Weapon modules are also fairly self-explanatory. But beyond providing offensive stats like Air Attack, weapon modules fulfill two other major functions. The first is that the weapons define what type of plane a design ends up being. For this the designer has a Primary Weapon Slot. The module in this slot defines the role of the final design, i.e. Fighter, CAS, Naval Bomber etc.

This is relevant because the weapon modules also unlock what missions a design has available. That means that the strict separation of mission by type of aircraft will be gone. You can now create fighters that can provide ground support, or Strategic Bombers that can do naval strikes, depending on the modules you put on the plane. There are, of course, some restrictions - strat bombers can never mount the modules necessary to unlock air superiority missions, for example.

We still wanted to give you an easy way to classify your designs on a high level and it also makes it a lot easier to tell the AI what a design actually is and how it should be used. Without accounting for doctrines, there are no stat differences between, say, a fighter that has a set of 4 Heavy MGs in the Primary Weapon Slot and bombs in a secondary weapon slot, and a CAS that has the bombs in the primary weapon slot and the MGs in the secondary slot - but one goes into Fighter Airwings and the other goes into CAS Airwings.
CAS planes have a large variety of weapons available to them to attack ground targets.
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There is a full list of weapons, the missions they unlock, and what they classify a plane as if mounted in the primary weapon slot, below (stats omitted because balancing is still ongoing):

ModuleMissions UnlockedType
2x Light MGAir Superiority, InterceptFighter, Heavy Fighter
4x Light MGAir Superiority, InterceptFighter, Heavy Fighter
2x Heavy MGAir Superiority, InterceptFighter, Heavy Fighter
4x Heavy MGAir Superiority, InterceptFighter, Heavy Fighter
Cannon IAir Superiority, InterceptFighter, Heavy Fighter
2x Cannon IAir Superiority, InterceptFighter, Heavy Fighter
Cannon IIAir Superiority, InterceptFighter, Heavy Fighter
2x Cannon IIAir Superiority, InterceptFighter, Heavy Fighter
Rocket RailsClose Air Support, Logistics StrikeCAS
Bomb LocksClose Air Support, Naval Strike, Port StrikeCAS
Small Bomb BayClose Air Support, Logistics Strike, Port StrikeCAS
Tank Buster IClose Air Support, Logistics StrikeCAS
Tank Buster IIClose Air Support, Logistics StrikeCAS
Torpedo MountingNaval Strike, Port StrikeNaval Bomber/Maritime Patrol Plane
Guided Anti-Ship MissileNaval Strike, Port StrikeNaval Bomber/Maritime Patrol Plane
Fixed Explosive ChargeKamikaze StrikesSuicide Craft
Medium Bomb BayClose Air Support, Logistics Strike, Strategic BombingTactical Bomber
Large Bomb BayStrategic Bombing, Port StrikeStrategic Bomber

While some of these weapons are unlocked in the (reworked) Air Tech Tree, some of them are also found outside of it, in a similar manner as the tank weapons are found in various trees. I will note that the total number of techs in the Air tech tree has actually decreased.
A view of the Air Tech tree. It has a total of 28 techs, compared to the old tree’s 38 techs.
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One notable aspect is that a lot of these modules provide different stats only for specific missions. For true multi-role planes to make sense, we wanted to make sure that building a design with a mixed set of missions didn’t make the plane useless in some of them. Hanging bombs off a plane should make it less agile and slower, but a fighter that was able to do CAS missions shouldn’t be useless in air superiority missions. Thus, the weight and agility penalties only apply to the fighter if it is actually on a CAS mission, not if it is on an air superiority mission.

Modifiers only apply to certain missions. Here, the bombs the Stuka carries make it less agile, but the dive brakes give it better air defense
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Finally, we have the so-called “Special” module slots. These are effectively a catch-all term of various different items, a list of which you can find below:​

Armor Plate: Increased Air Defense, reduced range
Self-Sealing Fuel Tanks: increased Air Defense, costs Rubber
Drop Tanks: increased range (small airframes only)
Extra Fuel Tanks: increased range, reduced air defense
Dive Brakes: increased air defense, increased naval strike hit chance
Radio Navigation I: reduced night penalty, increased strat attack
Radio Navigation II: reduced night penalty, increased strat attack
Air/Ground Radar: reduced night penalty, increased strat attack, increased naval detection
Air/Ground Radar II: reduced night penalty, increased strat attack, increased naval detection
Air/Air Radar: reduced night penalty when on intercept mission
Air/Air Radar II: reduced night penalty when on intercept mission
Floatplane: increased naval spotting (small airframes only)
Flying Boat: increased naval spotting (medium+large airframes)
LMG Defensive Turret: increased Air attack, reduced agility
2x LMG Defensive Turret: increased Air attack, reduced agility
HMG Defense Turret: increased Air attack, reduced agility
2x HMG Defense Turret: increased Air attack, reduced agility
Cannon Defense Turret: increased Air attack, reduced agility
2x Cannon Defense Turret: increased Air attack, reduced agility
Recon Camera: unlocks recon mission (LaR only)
Demining Coil: unlocks demining mission (MtG only)
Bomb sights I: increased strat attack
Bomb Sights II: increased strat attack
Non-Strategic Materials: reduced Aluminum cost, reduced air defense

Special Modules are primarily intended to help optimize planes for various missions or give them different niches.

The eagle-eyed amongst you have already spotted that planes now have a surface and sub detection stat. Up until now, planes that were active in a sea zone always provided a flat bonus to the spotting speed of any navies active in the seazone. This will now change, with planes having dedicated spotting stats that determine how well they do with helping the navies spot. There are modules, like the Air-Ground Radar and the Flying Boat hull, which give bonuses to naval spotting.

Vanilla planes have those stats already baked in, with some being better than others - carrier planes are better than their land-based counterparts, naval bombers are better than fighters etc.

To further support this, we are adding two more things: Maritime Patrol Planes as a dedicated unit type and a special Naval Patrol mission for planes with the right modules.

Maritime Patrol Planes are built on the Large Airframe, giving them exceptional range. They are able to mount the whole array of naval bomber weapons, but naval strike is really not intended to be their primary role. Maritime Patrol Planes are meant to help with spotting raiders in the deep ocean, where smaller planes with shorter ranges struggle to provide much mission efficiency.
You can run naval patrol missions with many different types of planes.
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Finally, let’s talk a bit about art! While we already have a large amount of historical art for various plane types, we also wanted to give you more options to visually distinguish your designs, even if it is just to find the plane design more easily in the production menu. For the tank designer, we split up the existing art and recombined it into various combinations to quickly generate a large number of assets. We realized early on that this wouldn’t work for the plane designer. So instead, we decided to fill in some gaps in the existing art as well as add some art for a number of prototypes that flew but were historically passed over for mass-production.
Here is a partial list of new plane icons coming in BBA. Which one’s your favorite?
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We also decided that we wanted to add more 3d art. Much like the tank designer, you can select these assets when you design the plane. We are adding about 80 new 3d models for planes to the DLC, but more on that in the future!
Here is just a teaser of some of the new assets coming in the DLC:
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That is about it for this week. We hope that you will enjoy playing with the Plane Designer as much as we enjoyed making it. To end this DevDiary on a personal note: The Plane Designer will be my final contribution to Hearts of Iron 4. After close to 6 years on the project, all the way from the early days on Together for Victory, the time has come for me to leave the company and move on to greener pastures. It has certainly been an eventful and productive couple of years, and there are many things that I am very proud of (and a few that I regret - like adding Austria-Hungary as a joke and then finding out that people love monarchism). Working on the Hearts of Iron series has always been a dream for me, since the day I launched Hearts of Iron 1, almost 20 years ago now. Few people can say that they had an impact on a piece of entertainment that has had a similar impact on themselves. But the thing I am most proud of is the team we have built. Hearts of Iron is in very good hands, and there are years of content still to be released. I’m looking forward to it - but, once again, as a player.​

Weird designs that QA came up with:
This single plane outguns an entire tank platoon, unfortunately it can’t ever turn:
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And then we restricted the number of bomb bays you can have on a plane:
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6 engines, 8 cannons, 4 cannons in turrets, and a production cost 50% higher than a strategic bomber. Needless to say, this combo is no longer possible:
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When you look at the Spitfire Mark I’s armament and wonder: but what if…more guns?
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How would this become extremely powerful? They can be balanced with great agility, weight, speed, bomb load and HP deductions to a point that flying boat/ floating plane can be destroyed by any previous tier fighter, ground AA and ship AA so that they can only do sea rescue, recon mission and hunt down submarine and unescorted convoys.
The weight/thrust mechanic can also limit the floatplane universality. Giving a high weight to floats can limit number of other modules
 
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My pet suggestion would be, for various radars, guide bombs and the like, to introduce shall we say the ''rich man production line'' of electronics. Game changing weapons on paper, that require a staggering investment to be worth it
If only game supported that. Engines would be great piece of equipment too. Hate how countries like China can just turn up with latest greatest air force over night.
 
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The weight/thrust mechanic can also limit the floatplane universality. Giving a high weight to floats can limit number of other modules
Yes, floats are a good example of a 'module' that doesn't really add much weight, but does add a considerable amount of drag (and off-line-of-thrust drag, at that). The absence of a mass-drag dichotomy is going to be problematic in general, I think.
 
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Generally speaking, hydroplanes relative usefulness in HOI IV would be related to one of their main use in real life : ASW (floatplanes carried by cruisers and battleships are harder to present in game, since, after all, it was at best a few dozen aircraft per nation)

As submarines are a very relative threat and one that can be dealt with energetically with even the crudest land bomber....(I mean, imagine they give a buff to hydroplanes to fight submarines-the later are going to explode more than TIE fighters...)
 
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As submarines are a very relative threat and one that can be dealt with energetically with even the crudest land bomber....(I mean, imagine they give a buff to hydroplanes to fight submarines-the later are going to explode more than TIE fighters...)
I read the fact that they have split off sub detection from general naval detection for aircraft to mean that subs will be a lot harder to detect than they are at present by aircraft. The buffs to detection will then become relevant as getting to a reasonable detection chance will be harder.

Edit: at least, I hope that this will be what happens. There might even be moddable detection multipliers for sub spotting and for ship spotting from the air.
 
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The best would be to reflect drag as weight since both affect speed
Weight affects acceleration, wing loading (and therefore drag indirectly, to a degree) and climb rate, but doesn't really affect maximum speed directly. Drag affects maximum speed, but isn't a big effect on agility, climb rate (except via limiting speed) and so on. Ideally, you would have wings that generate lift for drag, engines that generate thrust for weight and drag, and then limit weight to the lift at takeoff speed, maximum speed by thrust over total drag and agility by the weight under lift at maximum speed (plus a few special mods for elements off the line of thrust, maybe).
 
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Weight affects acceleration, wing loading (and therefore drag indirectly, to a degree) and climb rate, but doesn't really affect maximum speed directly. Drag affects maximum speed, but isn't a big effect on agility, climb rate (except via limiting speed) and so on. Ideally, you would have wings that generate lift for drag, engines that generate thrust for weight and drag, and then limit weight to the lift at takeoff speed, maximum speed by thrust over total drag and agility by the weight under lift at maximum speed (plus a few special mods for elements off the line of thrust, maybe).
So just 3 new values for aircraft modules
  1. drag(negative thrust) for every external modules
  2. Max speed limit (don't want to see a float plane that can fly with jet engine 600 km/h, beside those modules would break off if the plane fly too fast) for every external modules
  3. Wing area(wingload =weight/area) for different wing modules
To allow play to have more max speed, climb rate and agility customisable plane?
 
So just 3 new values for aircraft modules
Not quite - I think it's actually only two:
  1. drag(negative thrust) for every external modules
Drag is negative thrust that is generalted by speed; you need a factor and that combines with the thrust to give maximum speed.
  1. Max speed limit (don't want to see a float plane that can fly with jet engine 600 km/h, beside those modules would break off if the plane fly too fast) for every external modules
I'm not convinced this would be necessary. Floats can be assumed to be designed strongly enough, but they fight against the whole point of jets because they create a lot of drag moment, and the drag increases with speed - meaning that a jet floatplane won't be that much faster then a non-jet floatplane, so what would be the point?
  1. Wing area(wingload =weight/area) for different wing modules
It's not just wing area, but quotients for lift and drag for wings - both of which are factored up by speed - yes.
To allow play to have more max speed, climb rate and agility customisable plane?
Climb rate I take to be part of "agility", but the result would be customised Max.Speed and Agility, yes.

The extra factors for each module are drag and (for wings) lift quotients. Weight is still important, and engines still produce thrust.
 
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My pet suggestion would be, for various radars, guide bombs and the like, to introduce shall we say the ''rich man production line'' of electronics. Game changing weapons on paper, that require a staggering investment to be worth it
I think it would be difficult to make this happen in practice. If those weapons are powerful enough to change the game, they'll probably be worth the costs. But if they have the cost of 1000 planes while only having the impact of 500 planes... people are going to be inclined to just build the 1000 planes.

We can see examples with how battleships, despite their stats, are hardly ever built. Or stuff like the tank engines other than gas or diesel practically never being chosen.
 
We can see examples with how battleships, despite their stats, are hardly ever built. Or stuff like the tank engines other than gas or diesel practically never being chosen.
In part I think that's because of the lack of any "slipways" limitation. When there are only so many (big) ships you can build at once, building real beasts looks more enticing. If you can build unlimited numbers, cheap and plentiful looks better.
 
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In part I think that's because of the lack of any "slipways" limitation. When there are only so many (big) ships you can build at once, building real beasts looks more enticing. If you can build unlimited numbers, cheap and plentiful looks better.
I think there's a factor you're missing here, and that is how much time the different ships would occupy the 'slipway' and prevent it from being used by another ship. We could take 100 dockyards and put them on 100 separate orders for a ship, each with a single dockyard building it. And that would theoretically need 100 slipways. But we could also take those 100 dockyards and put them on 10 parallel orders of 10 ships sequentially, which would in aggregate produce ships at the same rate while only consuming a supposed 10 slipways for the same period of time.
 
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I think there's a factor you're missing here, and that is how much time the different ships would occupy the 'slipway' and prevent it from being used by another ship. We could take 100 dockyards and put them on 100 separate orders for a ship, each with a single dockyard building it. And that would theoretically need 100 slipways. But we could also take those 100 dockyards and put them on 10 parallel orders of 10 ships sequentially, which would in aggregate produce ships at the same rate while only consuming a supposed 10 slipways for the same period of time.
Yep, you're right - there should be a set-up time for a build on a slipway. Making fewer big ships should be more efficient than making hordes of little ones on a big slipway. Actually, you should arguably be able to use more dockyards on a bigger ship than on a smaller one, but the smaller one doesn't need a big slipway. Then, building destroyers on a big slipway would be a waste, whereas building cruisers would just be less efficient than building battleships (with the caveat that the BB might not be ready in time for the war!)
 
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Max speed limit (don't want to see a float plane that can fly with jet engine 600 km/h, beside those modules would break off if the plane fly too fast) for every external modules
Umm, you do realize that there have been Jet Powered Float and Seaplanes in real life? One (the Convair F2Y Sea Dart) was even supersonic. Most were seaplanes, but most also had wingtip floats.
 
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In any case, knowing the AI tendancies to produce dozens of types of divisions that cross the spectrum between ''horrible'' and ''awful'' and/or fill them with 10 variations of ''1936 light tank'', I can't wait to see what kind of aircraft will come out. Cause the AI imagination can't match reality...

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Jet powered hydroplane fighter. With jetskis.


The best thing ever since tyranosaurus flying F-15. Thank you Calvin.
 
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Umm, you do realize that there have been Jet Powered Float and Seaplanes in real life? One (the Convair F2Y Sea Dart) was even supersonic. Most were seaplanes, but most also had wingtip floats.
Sorry I was thinking old sea planes with fixed floats like A6M2-N or Ar196 when I was typing that post. Even Wingtip floats are deemed too OP by dev and won’t put into the next DLC, it would still be modable, if the dev put a switch/feature that would allow planes to land on sea/ navy base
 
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Sorry for the delay - was travelling. The main one I remembered was the Bell FM-1 Airacuda, but that was actually front-facing MGs, in pusher engine nacelles, in an interceptor... But Bristol Blenheim bombers, Petlyakov Pe-8s, Heinkel He-115 seaplanes and Focke-Wulf Fw-191s all had at least the option of rear-firing machineguns in the engine nacelles. So, to answer your question, no specific plane, but several examples.

Maybe just Bristol Blenheim IV and He-115 have fixed rear firing MGs.
Fw 191 ones were remote control and Pe-8 ones were manned turret.

For both Bristol Blenheim IV and He-115, I can only find articles description for such modifications but not any old pictures or blueprint. However, as every plane you mentioned has at least one designated rear gunner, how can you tell those guns would be controlled by the pilot instead of the rear gunners, hence those rear pointing guns should not be count as turret, as in your previous post?
 
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Not quite - I think it's actually only two:

Drag is negative thrust that is generalted by speed; you need a factor and that combines with the thrust to give maximum speed.
Thrust in the next DLC surely is not the thrust IRL. I would be amused if the thrust of a pistol engine in game would decrease with the flying speed of the plane as IRL. So as the drag it surely won’t be speed dependent. As making thrust and drag speed dependent would be more complicated than putting altitude zones mechanism into the game.

I'm not convinced this would be necessary. Floats can be assumed to be designed strongly enough, but they fight against the whole point of jets because they create a lot of drag moment, and the drag increases with speed - meaning that a jet floatplane won't be that much faster then a non-jet floatplane, so what would be the point?
Therefore, the “drag barrier” of any modules should be break very easily with advance engine, or else every non-jet float plane would have negative thrust. Therefore, a module max speed is need to ensure some modules can only work in certain speed range. Like you cannot put a fix floats/gear on a Rocket Plane and fly 1000 km/h .

In coding perspective it would be a hard stop for exploit you are not going to able to balance without recoding a large portion of the code.

It's not just wing area, but quotients for lift and drag for wings - both of which are factored up by speed - yes.

It is needed to be simple and referable. If the states was set too abstract, Dev or Modder would need more time and effort to mod and balance the game for each new change. If the new variable can “workablely” anchored to specifications, like wing area, to plane IRL. It would save a lot of time for everyone in the future.

Climb rate I take to be part of "agility", but the result would be customised Max.Speed and Agility, yes.

Climb rate is not agility, How fast you climb doesn’t mean how tight you turn. Hawker Tempest V has good climb rate but bad agility, while Fokker Dr.I has good agility but bad climb rate. Those two things cannot really mix together and call it a day