The S3-A flight controller features comprehensive upgrades in software, hardware design and performance. It is equipped with a customized open-source APM firmware for the first time, delivering richer software functions. In terms of hardware, it adopts high-performance STM32H7 series main control chip as the core, which delivers powerful computing capacity for flight control. Its built- in IMU integrates BMI088 sensors with refined shock absorption optimization design. This enables stable and efficient attitude data acquisition even under complex flight conditions, greatly improving flight precision and reliability. Furthermore, screw mounting holes are specially added to the flight controller housing, which not only simplifies installation procedures but also guarantees assembly stability, building a solid safeguard for safe flight of the aircraft.