# Simulation errors of MIT NREL TLP (Test 23)

**URL:** <https://forums.nlr.gov/t/simulation-errors-of-mit-nrel-tlp-test-23/2264>\
**Category:** Structural Analysis\
**Created:** [June 4, 2020, 8:28pm UTC](https://forums.nlr.gov/t/simulation-errors-of-mit-nrel-tlp-test-23/2264 "2020-06-04T20:28:51Z")\
**Posts on this page:** 1\
**Showing post:** 2

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**Author:** ![Jason.Jonkman](https://dub1.discourse-cdn.com/nrel/user_avatar/forums.nlr.gov/jason.jonkman/32/3086_2.png) [@Jason.Jonkman](https://forums.nlr.gov/u/Jason.Jonkman)\
**Post date:** [June 4, 2020, 9:47pm UTC](https://forums.nlr.gov/t/simulation-errors-of-mit-nrel-tlp-test-23/2264/2 "2020-06-04T21:47:28Z")

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Dear Yajun,

Increasing the time step to DT=0.25 s is likely leading to a numerical instability in the FAST solution. While you have disabled structural DOFs, one or more of the remaining 6 DOFs platform frequencies is likely high enough that a smaller time step is required. My rule of thumb for selecting the time step for the structural module is given in the following forum topic: [FAST Integrator, step size & precision - #3 by Jason.Jonkman](http://forums.nlr.gov/t/fast-integrator-step-size-precision/247/3).

Best regards,

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