# Symmetry

The APM solver supports symmetry solutions across the x-z plane. When using the symmetry option the solver calculates the influence coefficients 2x faster and requires 2x less memory. To enable the symmetry option, set the `symmetry` option to 1 in the **.conf** file. Note that any motion that you prescribe (if performing an unsteady simulation) must honour the x-z symmetry requirements. This means no velocity components in the y-direction or non-zero sideslip angle! The image below shows the comparison of the wake between symmetric and non-symmetric solutions.

<figure><img src="https://81269019-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-MV8htLPXN-_fWc_anY_%2Fuploads%2Fhl1tYSjfEf6vqysZE50M%2Fsymmetric_solution_comparison.png?alt=media&#x26;token=9ffcccc7-12a5-400f-a0e3-66f71aee146c" alt=""><figcaption><p>Symmetric and non-symmetric (not assuming) symmetry of a fixed-wing UAV.</p></figcaption></figure>