Physics equations of the autopilot PX4

Hi, I would like to understand which equations of the motion are used when the drone is flying in Gazebo environment, regarding the simulation in the loop which equations are used? Euler equation or what?

All I know is that here are some of the Gazebo plugins (some of them are used) for SITL in Gazebo:

Thanks, I am gonna try to open this script and understand which equations are used.