In this guide I will cover everything you need to know about how to make a working piston aircraft powerplant in Flyout. This includes explanations for every slider and box in an engine, gearbox, and propeller to make sure that after reading this you can confidently make your own powerplants. Please leave any suggestions for improvements down in the comments and I hope you all enjoy, :)

For engines, I will be be discussing engine concepts, real life examples, and general knowledge concerning internal combustion engines. I will tell you how to make your engines as realistic " or unrealistic" as you can in Flyout.

For propellers I will be going over things like prop twist, prop size, and prop speed, In order to maximize the performance of your aircraft for whatever you want it to do.


Special thanks to JagJeg and Wanderer for sharing very helpful information that was used in this guide

The biggest visual choice you are going to have to make regarding your piston engine is going to be its layout. In Flyout currently there are 3 engine layouts, to include 1. Inline, 2. V-Type, and finally Radials. These engines are practically identical in terms of function, the only real difference will be in the appearance "and sometimes drag" of your aircraft.

Below, you can see each engine type along with its respective air and liquid cooled variation.
Air cooled engines can be identified by the rows of fins wrapping around each cylinder. These are the heatsinks which allow for better air cooling.
Liquid cooled engines have the tops of the pistons covered in a black housing with an intake and exhaust port on opposing sides. These ports are non functional and are purely visual.

Engines that rely on air cooling have different requirements than a liquid cooled engine and vice versa. An air cooled engine is cooled by air passing over it, while liquid cooled engines rely on separate radiators for their cooling. In the real world, air cooled engines have the advantage of being lighter and less complex. However air cooling is almost exclusively used on radial engines due to the large frontal area for cooling, The main drawback of radials is that the large area for cooling also creates a lot of drag. Liquid cooled engines have the advantage of a smaller frontal area which allows for a pointed nose, with the disadvantage of being heavier and more complex due to it needing a radiator system, this style of cooling is mainly used for V-type and Inline engines.

Here is an example of a radial powered P-47 vs the V-Type P-51. You can clearly see how much of a difference your engine can have on the overall looks of your aircraft.

Radiators are a part that can be found in the power category directly underneath the engine itself, and are placed like any other part. Once placed select your radiator, you will notice that it is not connected to an engine and it also is functioning as an inter-cooler. In order to make your radiator work as intended, click the engine drop-down and select the engine that is the correct distance away from the radiator. Then select the function tab and click "Radiator".


The radiator part functions by cooling the assigned engine based off of the volume of the radiator, this means you can have radiators be any dimension that you like, because they will provide the same cooling as long as their internal volume is the same.

For example, these radiators provide the same cooling despite looking very different

Keep in mind that a radiator will only work when your engine is Liquid Cooled, and will not do anything other then add drag when connected to an air cooled engine.


Intercoolers are used for cooling off air in your super/turbocharging system. The cooler air allows for better high altitude performance by condensing the air even more before it enters your engine. Just like the standard radiator, the amount of cooling you get is proportional to how large your intercooler is. The intercooler also works with air cooled engines because it is cooling your intake air and not your engine itself.

Bore is the diameter of your pistons. The larger your bore is, the more fuel and air can be ignited in every combustion cycle of your engine. While stroke is the distance that your piston travels while reciprocating in your engine.





All engines have a Bore/Stroke ratio, it shows how much bore an engine has relative to its stroke. For example, an engine with 100mm of bore and 50mm of stroke would have a ratio of 2 and be considered oversquare, while an engine with 50mm of bore and 100mm of stroke would have a ratio of 0.5 and be undersquare. And finally and engine with 100mm of stroke and 100mm of bore would have a ratio of 1 and be a perfectly square engine.

Engines with a bore stroke ratio of more than 1 tend to be more performance oriented at the cost of reliability, while engines with a ratio of under 1 are more efficient at the cost of power. Formula 1 engines have a bore/stroke of just over 1.5 while a standard semi-truck engine has a ratio of around 0.8. keep this in mind when determining what your engine is being used for.

If you are making a WW2 inspired aircraft, keep in mind that almost all of the popular engines being used during that period were either square or undersquare for reliability.

In Flyout your compression ratio is the number displayed, to 1. So if your compression ratio says 10 in Flyout, just pretend like it is 10:1 for clarity.

Your compression ratio determines how much air is compressed during each piston stroke. For example, if an engine has a compression ratio of 10, and your cylinder has 100 cm³ of volume. Then your engine will compress the air down to 10 cm³ before ignition.


More compression in an engine can make it more powerful and more efficient, but you have to be careful in how you do this, because doing it wrong can result in pre-ignition. This means that your fuel is igniting to early and results in a loss of power. You can look for pre-ignition by testing your aircraft,
and clicking the circle icon in the bottom left side of your screen that displays temperature. At the bottom of this menu, pre-ignition will be displayed in red text along with the percentage.

Note that in this screenshot the engine is making negative power due to there being no propeller or gearbox attached yet.




Your compression ratio can vary a lot depending on whether you have an engine with a turbo/supercharger or if it is naturally aspirated. Naturally aspirated engines tend to have higher compression due to them not having already compressed air available to them and need to compress it themselves. A good rule of thumb is around 6-8 for forced induction engines, and 8-12 for naturally aspirated engines.

WW2 engines often used a compression ratio of between 6:1 and 8.5:1. This might seem low, but for forced induction engines this is pretty standard. Turbos and superchargers can provide more power to engines with a lower compression, so the boost from your turbo/supercharger should more than make up for the loss of power that you get from lowering your compression ratio.

Your valves are what allow air to flow in and out of your engine. The larger your valve area, the more air you are able to utilize during combustion. A 4 valve engine allows more air flow through the cylinder due to more of the cylinder area being dedicated to breathing.


Inline and V-Type engines have either 2 or 4 valves depending on the performance requirements or technology available. Radial engines however almost exclusively use 2 valves, due to the complexity of having 2 cams on each separate cylinder, instead of on a single set of shafts covering multiple cylinders, like can be achieved on Inline and V-type engines.

Hera is a 2 valve Radial compared to a 4 valve V-type engine

Superchargers and turbochargers are vital tools for increasing power at higher altitudes. They work by compressing outside air before it enters the engine. and as you already know, the more air, the better.


Your overall boost in Flyout is a measure of your engines boost across both your supercharger and turbocharger in addition to atmospheric pressure. So if your engine displays 1 bar of boost, then at sea level you get 2 bar of pressure. meaning you get twice as much air compared to a naturally aspirated engine.

Your max pressure shows how much of that boost is actually getting to your combustion chamber. So if your engine makes 2 bar of boost, and your max pressure is set to 1.5, that extra 0.5 will be expelled. This allows you to maintain your desired boost pressure up to higher altitudes without stressing your engine. For example if your engines overall boost is 4 bar and your max pressure is 1.5, your engine will maintain 1.5 bar far longer than an engine with only 2 bar of overall boost.


A supercharger works by being driven by a belt or chain connected to the crankshaft on an engine and is tied directly to your engine rpm. Superchargers are generally cheaper then turbochargers which is why they were more prevalent on WW2 aircraft engines.


Superchargers can also have up to 2 speeds. meaning you can have different boost levels for different altitudes. This is useful for optimizing engines at different heights, and was done on a lot of WW2 engines. Single speed superchargers are simpler and cheaper than a dual speed, but you might run the risk of bogging down your engine at lower altitudes. Below is a chart for top speed for the BF-109, which uses a two speed supercharger.



Turbochargers are driven by your engines exhaust and can run independently from your engines rpm. Your engines high pressure exhaust is used to drive a turbine, this turbine is connected to another turbine via a fixed shaft. This second shaft is the one that actually compresses the air before it enters your engine.

There is a turbocharger part in the power menu, this part is purely visual and all that happens when this part is connected to an engine, is the turbine on the turbocharger spins when throttle is applied.

Turbochargers are generally more efficient than superchargers due to them being not taking power from the engine itself, and instead using the energy already in the exhaust. However they are more complicated and expensive, as well as being more difficult to mount to an existing engine.

Idle throttle is exactly what is sounds like. it controls how much throttle is applied to your engine while you have throttle set to zero. An idle throttle of 0.1 means that while you are idle and your throttle is at zero, your engine is actually at 10% throttle in order to keep it running. Engines that are being pushed closer to their limits require a higher idle throttle to run.

Your mixture is the air to fuel ratio "AFR" that your engine uses. A mixture of 15 in Flyout would be 15 parts air, and 1 part fuel. Engines that run a lower ratio are considered "rich" while higher ratios are considered "lean". Richer mixtures increase power and decrease the odds for pre-ignition at the cost of being very fuel demanding. Lean engines can be very fuel efficient, but tend to have less power.

Here is a pretty good chart for good AFR


In order to find your RPM limit you should look to see your engines Performance curve. This button is directly under the "Flywheel" option and will bring up a graph showing your engines power and torque. Here you will see a vertical line for maximum power in green and maximum torque in yellow. A general rule of thumb is to make your max rpm about 300-500 higher than the green line. In this picture it would be where the white line is.

Exhaust is a very often overlooked aspect of engine design. It can provide a lot of your thrust at high altitude due to it not being dependent on air pressure and speed like your prop. The exhaust part also allows you to add more exhaust pipes, this is a purely visual change.

Notice how nearly 20% of my total thrust is coming from my exhaust.


Exhaust thrust can be increased in multiple different ways. All of these ways either increase exhaust temperature, or increase airflow. For example, a turbo or supercharger will increase exhaust thrust because more air passes through the engine as well as making the combustion hotter. Increasing compression also can improve thrust because it makes temperatures higher along with adding more air.

The two main fuels you will be using for piston engines are going to be "Iso-octane" and "AVGAS 115". These fuels are similar, but have different uses. Iso-octane is around 100 octane and represents a fuel used for lower power applications, or older generation fuel. AVGAS 115 is a 115 octane leaded fuel used in more advanced engines like the ones used in WW2 on the frontlines.

When you place down a fuel tank, it will default to JET-A. Piston engines really don't like that and will pre-ignite like crazy until you switch the fuel type.




Priority group tell your engines which tank to pull fuel from, and in what order. Tanks with a higher priority group will have fuel drawn from them first. So a tank with a group of 10 will have its fuel drained before a fuel tank with group 9 priority starts getting drained.

This section will go over a couple of things that don't really fit into the other categories, but i still think that they are useful.


The performance graph can be updated by clicking the "Plot" button in the bottom right of the window. This allows you to see what impact the change you made has on your engine without having to load up a test flight. The Performance graph also allows you to show how your engine will perform an any given altitude.



Did you know that you can test you whole power-plant without ever having to leave the ground? Simply place a cube below your engine and shape it into a platform, spawn in your craft, go down to the bottom right of your screen, click the up arrow and select environment. Now that you have that window open, change your wind direction to match your heading "which is found on the left side of your screen", then simply change wind speed to whatever you want to test your powerplant at.



You can make your own custom V-Type engines using 2 inline engines connected to the same gearbox. This can be useful if you want an engine that has a slimmer profile in order to fit into certain slimmer spaces.

Your gearbox is the link between your engine and propeller. It controls how fast your propeller turns in relation to your engine rpm. If your engine is spinning at 3000 rpm and your gear ratio is set to 1, in theory your propeller will be spinning at 3000 rpm.


A gearbox can have up to 9 gears, and each gear should have a lower ratio number than the one before it, as seen in the picture. However you will most likely only be using 1 or 2 gears for your plane since having more than that doesn't really improve performance.

The higher your ratio, the more torque your engine will have on your propeller, however this comes at the cost of propeller speeds. Generally your gear ratio will be between 1 and 2, but if it is a little more or less don't worry.




In order to find your gear ratio you need to first find out how fast you want your propeller to spin. This is the easiest to do with a "Target RPM" propeller. Place down a propeller and select the drop down menu underneath "Constant Speed Mode".

Your propellers target rpm should be different depending on the size of your propeller. A general rule is to keep your "Max Mach" around 0.7-0.8 for standard operation and between 0.8-0.9 for high speed. You usually do not want your propeller to reach near, or over Mach 1, this causes inefficiency and could cause damage in a real propeller. Below is an example of a good prop rpm and one that is too fast.


Actually getting your gear ratio is quite simple once you've figured out your prop rpm. You simply divide your engine rpm, by your prop rpm and that number is your gear ratio. For example if your engine runs at 3000 rpm and your prop runs at 2200. You take 3000 divided by 2200 and get a 1.36 gear ratio.

In Flyout there are 5 types of propellers, each perform differently then one another and are not just for looks.

"The following is a summary of what is said in Wanderer's Piston and Propeller Tutorial video"

Blade type 0 is an elliptical blade that performs decently well in all conditions
Blade type 1 is a parabolic blade which is marginally less efficient at making thrust
Blade type 2 is a cutlass or scimitar blade, it is more efficient and performs much better at high tip mach due to the swept tips.
Blade type 3 has a squared off tip and is generally more efficient than the elliptical
Blade type 4 is a tapered blade, it can be more efficient, however it needs to be larger and heavier than the elliptical to do so.


The number of blades your propeller has depends on a number of factors. Generally less blades are more efficient but cannot utilize as much power. While the opposite is true for more blades. More blades can also be used to reduce propeller diameter while still keeping the same propeller area.


Contra-rotating propellers are useful for eliminating prop torque in a single direction. They also can the increase efficiency of your propellers. They can be created by placing duplicating your propeller, placing it close in front or behind and changing the direction of one of them to counter clockwise.

In order to make maximum thrust, propellers have twisted blades. The twist allows for the air to strike the propeller at the optimal angle for generating thrust while using least amount of energy. Propellers move slower at the root and need more extreme twist the closer to the hub, this allows them to catch the same amount of air while moving slower.

There are a variety of things that you need to keep in mind when figuring out your prop twist. This image was made by JagJeg on the official Flyout discord and is the best graphic i've seen for how propeller twist works.



Propellers generally fit into one of two groups. Long and thin, or short and stubby. Both have advantages and disadvantages.


Longer thinner blades are more efficient but rotate slower and take up much more room. While shorter blades take up less space and can have a higher rpm while worrying less about tip mach.


There is also an excellent tool online for calculating your prop twist using Desmos. It allows you to enter all of your propellers characteristics, and it outputs your prop twist. Below is how to use this tool.

https://www.desmos.com/calculator/2uc5lmji6d

1. This is your angle of attack for your blades. 5 is the default and is just fine for most propellers
2. This is your props diameter in meters. you can find this right above constant speed mode, and below blade twist.
3. This is the airspeed that your prop will be optimized for. This is measured in meters per second, so remember to convert your speed units before entering it into this calculator.
4. This is your props rpm, just input the number you used to calculate your gear ratio.
5. All this slider does is move the graph up and down to prevent negative blade twist.
6. Now that all the data is in, just move your mouse over 0.1 for your blade root, 0.5 for your mid and 1 for your tip, then just input that into your propeller twist in flyout.

There are 3 constant speed modes that you can choose from along with a fixed pitch option for simpler propellers. Fixed pitch is the simplest option with only one variable to choose from. All you need to decide on is what pitch you want your propeller to stay at throughout the flight.


Target RPM is exactly what it sounds like. it adjusts the angle of your blade depending on how fast your propellers rpm is. When your prop angle increases it is able to produce more thrust at the cost of a higher power requirement. It will do this until the propeller is at a stable rpm that it can maintain.


The centrifugal response increases blade pitch the faster your prop spins. The responsiveness number controls how aggressively your blade will pitch at any given speed. The higher this number is, the more aggressive the pitch.

The power number is a measure of how linear the response is. A higher value will make your propellers have less pitch at lower speeds and helps to reduce stalls. Generally a higher power requires a higher responsiveness value in order to maintain effectiveness at all speeds.


A mach response changes your prop pitch based off of the tip mach of your blades. When your blades get closer to mach 1, the propeller will increase in pitch in order to slow the propeller down and increase thrust.

Changing the mach response number will change how aggressively your propeller will pitch the closer it gets to mach 1. A higher number means a more aggressive pitch, while a lower number will have a less aggressive pitch.


Your pitch range minimum and maximum determine the hard limits of your propellers pitch. This does not affect propeller feathering which always takes your propellers to 90 degrees

Pre-ignition is when the fuel in your combustion chamber ignites before your piston is fully compressed. This will fight the engine and reduce power and efficiency greatly. This is a pretty common problem if you don't know exactly what goes into making a good engine. These are some reasons why your engine might be pre-igniting.


Compression is a major cause of pre-ignition problems, it can be tempting to crank the slider to 15 once you see increased power and efficiency, but compression should be at most around 12 in a naturally aspirated high performance engine. In a forced induction engine that number should be even lower, somewhere at 10 or below is good for most engines.


The more boost you have the the hotter your combustion chamber gets. you can see this right below your overall boost and anything past around 1200K can start to cause problems. Try reducing your max pressure to less than 2 and your overall boost to around 3-6 bar to mitigate this issue.

Inter-coolers can also help reduce pre-ignition because they cool the air and by proxy, the combustion chamber.


A lean fuel mixture is great for decreasing fuel consumption but can sometimes lead to pre-ignition problems. Anything near or above a mixture of 20 can start to greatly hinder your engine not just from pre-ignition, but also by not providing enough fuel to run to its full potential. Try reducing your mixture to somewhere between 13-17.


Every time you make a wing tank or place down a fuel tank part, the game makes it Jet-A by default. Piston engines do not run well on Jet-A and can completely ruin your engine from pre-ignition. Always remember to change your fuel type to either AVGAS 115 or Iso-octane.

Have you ever wanted to make a V24 engine? or perhaps a 630 cylinder radial capable of powering a small town? Well your in luck, because file editing lets you do just that!

First you are going to want to find your Flyout folder. Go into your file explorer and in the top filepath bar type in only %AppData%. This will bring you to appdata/roaming. back out of the roaming tab so you are in the appdata folder with just "Local", "Locallow", and "Roaming" and select "Locallow". Scroll down until you find "Stonext games" and click on it.


Now you are going to select the "Craft" folder, this stores all of your Flyout creations. Find your craft you want to edit the file too and go into it. Then you want to click on your crafts "Data" file and open it with notepad.


Finally you want to Ctrl+F and search for "Engine". this will bring you too your engine which you can now feel free to change the highlighted values.

Cyl_type can be 1 or 0, and changes between air cooled and liquid cooled
Cyl_count and Banks are how many cylinders are in each row and how many rows of cylinders there are.