A study of quadcopter flight dynamics is conducted using a test bench that allows modeling quadcopter reactions to control actions and external disturbances (frame geometry, moment of inertia, and engines’ synchronization). It was found that even minor changes in frame geometry or moments of inertia can significantly affect flight dynamics. Non-synchronous operation of the motors, even within 2–3%, leads to an imbalance of the moments of forces, which causes deviations from the specified trajectory and requires constant adjustments by the control system. The used test bench minimizes the influence of external factors such as wind or air resistance, allowing focus on studying the internal characteristics of the quadcopter. Experiments demonstrated that increasing the moment of inertia by more than 5% leads to a significant decrease in angular velocity and an increase in control response time. Asymmetric frame designs and inconsistencies in the characteristics of motors enhance the effects of instability and increase the amplitude of oscillations, which requires the development of more advanced stabilization algorithms.