FAA Aerodynamics of sUAS 2

Question 1

What is 'pitch' as it relates to sUAS propeller blades?

Accepted Answer

The theoretical distance a propeller would advance through the air in one complete revolution

Answer

The rotational speed of the motor in RPM

Answer

The total diameter of the propeller arc

Answer

The weight distribution along the length of the blade

Question 2

Why do most multirotor sUAS use counter-rotating propellers on opposite arms?

Accepted Answer

They cancel out the reactive torque effect, preventing the aircraft body from spinning

Answer

Counter-rotating propellers generate more total lift per unit of power

Answer

They reduce electrical interference between adjacent motors

Answer

Counter-rotating propellers are significantly quieter than same-direction propellers

Question 3

What aerodynamic principle allows a multirotor sUAS to accelerate into forward flight from a hover?

Accepted Answer

Tilting the aircraft forward converts a portion of rotor thrust from vertical lift into horizontal propulsion

Answer

Differential thrust between front and rear rotors pushes air backward

Answer

Increased motor speed creates a low-pressure zone that pulls the aircraft forward

Answer

The landing gear extends to create a rearward aerodynamic drag surface

Question 4

How does increased payload weight primarily affect the hover efficiency of a multirotor sUAS?

Accepted Answer

It reduces hover efficiency by requiring higher RPMs, increasing power consumption and reducing flight time

Answer

It improves hover efficiency by stabilizing the aircraft

Answer

It has no effect on hover efficiency below maximum takeoff weight

Answer

It reduces power consumption because added weight pushes air down more effectively

Question 5

What is 'translational lift' and when does it occur in sUAS operations?

Accepted Answer

Improved rotor efficiency that occurs as the sUAS transitions from hover into forward flight, entering undisturbed air

Answer

Lift generated by horizontal tail surfaces during forward flight

Answer

A sudden loss of lift when crossing between two different air masses

Answer

Lift generated by the aircraft fuselage shape during high-speed forward flight

Question 6

What is the aerodynamic effect of propeller blade damage such as chips, cracks, or nicks on sUAS flight?

Accepted Answer

Blade damage causes vibration, reduces thrust efficiency, and can lead to catastrophic failure mid-flight

Answer

Minor blade damage has no measurable effect on flight performance

Answer

Damaged blades only affect operations above 200 feet AGL

Answer

Blade damage causes increased lift due to additional disturbed airflow patterns

Question 7

What role does the flight controller's IMU (Inertial Measurement Unit) play in maintaining aerodynamic stability?

Accepted Answer

It measures acceleration and angular rates, enabling the flight controller to adjust individual rotor speeds to correct attitude deviations

Answer

It adjusts rotor blade pitch to compensate for wind gusts

Answer

It measures air pressure to maintain a constant barometric altitude

Answer

It controls the camera gimbal to compensate for aircraft movement