# 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](https://81269019-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-MV8htLPXN-_fWc_anY_%2F-MVXbpsu2CSjcnspTuoq%2F-MVXd0gDAks75NgLvkRC%2Factuator_disk.png?alt=media\&token=a2c4bbfd-8204-46a1-bbdb-68fb2b956778)

{% 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](https://81269019-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-MV8htLPXN-_fWc_anY_%2F-MVX355erRsTpmfpbtjk%2F-MVX3yFeZJdJY41Yua4R%2Fnaca4412_actuator_disk.png?alt=media\&token=a75c9e6e-11ae-41e1-b9e3-8763ca54554e)

![Fixed-wing UAV with two actuator disks](https://81269019-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-MV8htLPXN-_fWc_anY_%2F-MVX355erRsTpmfpbtjk%2F-MVX47yCGt0-XI0lSoZW%2Fcruiser_uav_actuator_disk.png?alt=media\&token=74dbe08a-0672-4441-9424-d0a47faa64d6)