Glossary
Flight controller
The small circuit board with sensors and firmware that reads pilot input and stabilizes an FPV drone in flight.
The flight controller is effectively the brain of an FPV drone. It reads input from the radio receiver, combines that with data from its onboard gyroscope and accelerometer, and sends rapid correction signals to the electronic speed controllers many times per second to keep the aircraft stable and responsive.
Flight controllers run firmware, most commonly Betaflight on freestyle and racing builds, which handles the tuning parameters that decide how twitchy or smooth the drone feels to fly. The board's physical size and mounting pattern need to match the frame, and its processor and gyro quality affect how cleanly it handles fast, aggressive flying.
Many flight controllers today are sold stacked together with the ESC as a single unit, which simplifies wiring for a first build. A common early mistake is ignoring the voltage rating printed on the board and pairing a 4S-rated flight controller with a 6S battery, which can damage the board on the very first power-up.