# Announcement: Fix for AdvancedLiftDrag Pitching Moment Computation

**URL:** <https://discourse.openrobotics.org/t/announcement-fix-for-advancedliftdrag-pitching-moment-computation/57364>\
**Category:** Gazebo General\
**Created:** [August 13, 2026, 3:02am UTC](https://discourse.openrobotics.org/t/announcement-fix-for-advancedliftdrag-pitching-moment-computation/57364 "2026-08-13T03:02:08Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![arjo129](https://sea2.discourse-cdn.com/flex022/user_avatar/discourse.openrobotics.org/arjo129/32/6316_2.png) [@arjo129](https://discourse.openrobotics.org/u/arjo129)\
**Post date:** [August 13, 2026, 3:02am UTC](https://discourse.openrobotics.org/t/announcement-fix-for-advancedliftdrag-pitching-moment-computation/57364/1 "2026-08-13T03:02:08Z")

</div>

Hello Gazebo Community,

We want to highlight an important bug fix and subsequent behavior change in the `AdvancedLiftDrag` system, recently addressed in [Issue #3695](https://github.com/gazebosim/gz-sim/issues/3695).

### What was the issue?

Previously, when computing the pitching moment coefficient (`Cem`) in `AdvancedLiftDrag.cc`, the alpha-based pitching moment (derived from `Cem0`, `Cema`, and `CemaStall`) was unintentionally being overwritten by the sideslip contribution.

Because the code used an assignment instead of an accumulation, the previously computed alpha-based pitching moment was discarded entirely. As a result, parameters like `Cem0` and `Cema` configured in your SDF files were having no effect on the final aerodynamic calculations.

### What has changed?

This behavior has been corrected. The sideslip contribution is now correctly added to the existing alpha-based pitching moment, matching the intended coefficient build-up method:

```cpp
// Previous unintended behavior
Cem = this->Cemb \* this->beta;

// New corrected behavior
Cem += this->Cemb \* this->beta;

```

### Fixed Versions

This fix is available starting in the following `gz-sim` releases:

- **gz-sim 10.5.0**

- **gz-sim 9.6.0**

- **gz-sim 8.15.0**

### Action Required

If you use the `AdvancedLiftDrag` plugin, we highly recommend updating to one of these versions.

**Important Note:** Because `Cem0`, `Cema`, and `Cema_stall` are now correctly contributing to the simulation, **you may notice changes in the aerodynamic behavior of your existing models** if they unknowingly relied on the broken state. We recommend re-testing your aircraft and aerodynamic models to ensure they perform as expected now that the proper physics are being applied.

A special thank you to **@lyw426457** for reporting this issue, and to **@Jaeyoung-Lim** for providing the fix!

If you run into any issues or have questions regarding this change, please feel free to reply to this thread.