General Knowledge of Rotorcraft and Remotely Piloted Aircraft Systems
System architecture
An RPA system comprises the aircraft, the control station, the command and control link, and any support equipment. Candidates must understand the main rotor system, the tail rotor or anti-torque device, the powerplant, the flight controller, the inertial sensors, the GNSS receiver, and the payload. Know the function of the flight controller in stabilising the aircraft and in interpreting pilot inputs, and understand the difference between manual, assisted and automatic flight modes.
Concepts to master
Understand how a multirotor achieves control: varying rotor speeds produces thrust changes and moments about the three axes. Know the role of the accelerometer, gyroscope, magnetometer and barometer, and what happens when each fails or is disturbed. Learn battery chemistry and management: cell voltage, capacity, discharge rate, temperature effects and the risks of deep discharge. Understand link budget basics, antenna placement, frequency bands and the causes of loss of command and control link. Know the failsafe behaviour programmed for link loss, low battery and loss of GNSS.
Common traps
Questions often confuse the sensor that measures orientation with the sensor that measures acceleration, or assume GNSS provides altitude with high precision. Another trap is treating a compass error as a motor failure. Be careful with the difference between a system that is redundant and one that is merely duplicated.
Rule of thumb
Before flight, confirm the failsafe configuration and the battery state. Worked example: if a multirotor loses its command and control link, the programmed failsafe normally commands a hold, a return to home or a landing; the pilot must know which one is set before take-off, because the aircraft will not ask.