# Creating actuator disks

{% hint style="warning" %}
This is still an experimental feature! Use with caution.
{% endhint %}

The APM Solver has the ability to simulate propellers by using the actuator disk model. To create an actuator disk add the following lines to the end of the **.conf** file:

```
[actuator_disk]
x = 0
y = 0
z = 0
nx = 0
ny = 0 
nz = 0
R = 0
CT = 0
```

The `x`,`y`,`z` variables specify the centre of the actuator disk. The `nx`, `ny`, `nz` specify the unit normal vector of the actuator disk and the R and CT variables specify the radius and the thrust coefficient. The image below shows the centre of the actuator disk, its radius and its unit normal vector.

![Definition of an actuator disk](/files/-MVXd0gDAks75NgLvkRC)

{% hint style="info" %}
The unit normal vector should point in the direction of the thrust vector.
{% endhint %}

The images below show some examples of actuator disks.

![NACAA 4412 Wing with actuator disk](/files/-MVX3yFeZJdJY41Yua4R)

![Fixed-wing UAV with two actuator disks](/files/-MVX47yCGt0-XI0lSoZW)


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