FCU multicopter hybrid
A Flight Control Unit, or FCU, is the flight control computer of a hybrid multicopter. In this type of aircraft, energy comes from a piston engine feeding a distributed propulsion architecture with fixed-pitch vertical-thrust propellers. The FCU translates pilot commands into safe, stable, and efficient flight behavior. It distributes power between the rotors, keeps the aircraft balanced, continuously monitors onboard sensors, corrects deviations caused by wind or system anomalies, and manages warnings as well as emergency procedures. Unlike a conventional helicopter, where the pilot directly manages much of the aircraft response, or a fully electric VTOL focused mainly on battery management, the FCU of a hybrid multicopter must simultaneously stabilize flight and coordinate a more complex propulsion system.
10 Operating Cases, from the Simplest to the Most Complex
For clarity, vertical climb and vertical descent are presented here as two separate cases, even though they are grouped together in the original FCU requirements document.
1. Progressive takeoff When the pilot increases throttle, the FCU distributes power across the rotors so the aircraft lifts vertically while remaining level, limiting climb rate and preventing motor saturation.
2. Stabilized hover When hover mode is requested, the FCU uses sensor data to maintain position and altitude, even in the presence of wind or drift.
3. Vertical climb The FCU adjusts thrust so the aircraft climbs along its vertical axis while preserving trajectory control, stability, and motor availability.
4. Vertical descent The same principle applies during descent: the FCU regulates power to keep the aircraft stable and on a controlled vertical path down to the target altitude.
5. Yaw rotation on the spot When the pilot commands rotation about the vertical axis, the FCU modulates rotor power to produce accurate yaw motion without excessive drift or loss of control.
6. Straight forward flight When a forward command is given, the FCU generates a pitch command and adapts rotor power so the aircraft moves ahead in a stable, controlled way.
7. Turning while moving forward The FCU combines roll, yaw, and power management to perform a coordinated right or left turn during forward flight.
8. Turning while climbing In a more complex maneuver, the FCU must manage the turn, altitude increase, and reinforced sensor monitoring at the same time to maintain safety and stability.
9. In-flight emergency stop with parachute deployment In a critical failure, the FCU detects the emergency, confirms parachute deployment logic, stops or manages the rotors as required, continues monitoring critical systems, and issues the alerts needed to secure descent.
10. Final shutdown on the ground After landing, when the pilot commands shutdown, the FCU confirms the instruction, prepares the aircraft for a safe stop, and cuts the motors according to a controlled sequence.
Why it Matters
The FCU is a core technology for the missions targeted by a hybrid multicopter, including light air ambulance operations, tourism, and pilot training. Without it, distributed propulsion would be difficult to operate safely and reliably. With it, the aircraft can take off, hover, move forward, turn, handle emergencies, and shut down in a controlled way while maintaining a high level of operational safety.