Principles of Flight (Rotorcraft)
How a rotor generates lift
Candidates must understand that a rotor produces lift by accelerating air downward, and that the lift depends on air density, blade angle of attack, rotor speed and blade area. Know the terms: angle of attack, pitch, induced drag, profile drag, parasite drag, translational lift and effective translational lift. Understand that a hovering rotor recirculates its own downwash and that forward motion through undisturbed air improves efficiency.
Concepts to master
Learn how a multirotor controls its attitude by differential thrust, and how an increase in collective or rotor speed increases lift and also increases the torque reaction and power required. Understand ground effect, vortex ring state, retreating blade stall and dissymmetry of lift in the context of conventional helicopters. Know the power curve and why a hover out of ground effect requires more power than a hover in ground effect.
Common traps
Questions often confuse angle of attack with pitch angle, or assume that increasing rotor speed always improves performance regardless of power limits. Another trap is forgetting that induced drag decreases with speed while parasite drag increases.
Rule of thumb
Hovering in ground effect saves power; transition to forward flight saves more. Worked example: an aircraft that hovers at 80 percent power out of ground effect may hover at 70 percent in ground effect at one rotor diameter, and requires still less once effective translational lift is reached in forward flight.
Communications and Radio Telephony
Radio communication essentials
Candidates must understand the standard phraseology used for RPA operations and the structure of a radio call: who is called, who is calling, position, altitude, intention and any request. Know the phonetic alphabet, the pronunciation of numbers, and the standard words such as roger, wilco, affirm, negative, standby and say again. Understand the difference between a distress call and an urgency call, and the frequencies and procedures associated with each.
Concepts to master
Learn to read back clearances and to use standard readback for instructions that affect safety. Understand the role of the remote pilot in maintaining a listening watch, and the requirement to announce intentions before entering or leaving an area. Know the emergency phrase MAYDAY for distress and PAN-PAN for urgency, and know that the distress message includes identification, position, nature of the problem, altitude and intentions.
Common traps
Questions often test whether the candidate knows that MAYDAY is repeated three times and that it takes priority over all other traffic. Another trap is confusing 'roger' with 'wilco': roger means received, wilco means received and will comply.
Rule of thumb
Speak slowly, use standard phraseology, and read back safety-related instructions. Worked example: an RPA pilot with a failing battery should transmit 'MAYDAY, MAYDAY, MAYDAY' followed by identification, position, the nature of the emergency and the intended landing area, then comply with any instructions from the controlling station.