Rotorama Flight termination system

Rotorama FTS is an independent safety switch for flight termination (Flight Termination System) that disconnects the main battery from the entire drone. It is connected in the negative line between the battery and the drone electronics. During normal flight, the switch is closed and the drone is powered normally; after a command from the transmitter, it opens and the motors stop immediately. It is used as a last resort in situations where the flight must be terminated immediately - in case of loss of control of the drone, leaving the permitted area, or if required by the operational authorization in the specific category of operation.

The board operates completely independently of the flight controller. It has its own microprocessor and its own receiver input, so termination works even if the flight controller freezes or fails. It is controlled by a two-position switch on channel 9 with a threshold of 1500µs, where a value above the threshold means termination and a value below it means normal flight. Firmware for other channels and other switching levels is available for download here and is uploaded via the service pads on the bottom side of the board. When the signal is lost, the switch holds the last state - the receiver failsafe settings therefore determine the final behavior, allowing either power retention and recovery via the flight controller or automatic termination after link loss.

The switch handles 50A continuous and up to 200A peak with stable airflow during flight, the resistance in the closed state is 1.3mOhm. Power supply is 4-6S LiPo. The integrated 5V/1A switching regulator powers the receiver, which the FTS requires to be separate from the rest of the drone electronics. The receiver connects via CRSF or S.BUS, and the board detects the protocol automatically, so an external inverter for S.BUS is not needed. The Anti-Spark circuit slowly pre-charges the drone capacitors through a resistor, so no spark or current spike occurs when the battery is connected. Three LEDs indicate board power, receiver link status, and switch status. The button on the board toggles the output during bench testing and is ignored once the board has a valid signal from the receiver.

The board dimensions are 36x36mm and the mounting spacing is 30,5x30,5mm with M4 holes (M3 with softmount), so it fits into a standard FPV stack. 

Important notice: the only allowed connection between the FTS and the rest of the drone is the power wiring. The receiver connected to the FTS must not be connected by any wire to the flight controller or any other drone electronics - such a connection bypasses the switching circuit, disables the FTS, and permanently damages the board. The board is not protected against reverse polarity, and all tests must be performed without propellers installed.