China Civil UAV Theory Questions — Questions 446–455

Payload capacity is affected by many factors, including motor performance, rotor count, rotor size, and battery capacity. Although more axes increase stability and hovering ability, they also increase the aircraft's weight and complexity. So more axes does not necessarily increase payload capacity.

A multi-axis aircraft's mechanical structure is relatively simple, and its propellers generally spin at high speed, controlling flight direction by changing rotor tilt angles. This design consumes more energy to overcome air resistance during flight, reducing aerodynamic efficiency.

The Black Hawk is a helicopter, not a multi-axis aircraft. The UH-60 is a helicopter.

Helicopters use variable-pitch propellers and mainly change blade pitch; multi-axis aircraft use fixed-pitch propellers and mainly change rotor speed.

The landing gear is not used during hover, so it does not affect hover stability. Wind is a significant environmental factor directly affecting hover stability: wind causes drift, attitude changes, and position instability, so the flight controller must constantly adjust to maintain hover. Ground effect refers to increased lift and stability changes when the aircraft is close to the ground because the ground affects airflow. In hover, if the aircraft is near the ground, ground effect may affect its stability.

When shooting sunrises and sunsets, light color temperature is low, showing warm tones. To get accurate color under such lighting, the camera needs white balance adjustment. High color temperature values are generally used in high-color-temperature environments, such as midday sunlight on a clear day. Low color temperature values suit low-color-temperature environments such as sunrises and sunsets. Flash mode is generally used indoors or in low-light environments when the flash is the main light source for white balance adjustment.

Failsafe return-to-home is a multi-axis safety protection mechanism: when the aircraft loses signal or battery power is too low, it automatically returns to the takeoff point. During this process, the flight controller automatically controls flight along a preset return path. To regain control, switch from GPS mode to manual mode to interrupt the flight controller's automatic control. Gimbal status switching mainly controls gimbal attitude and angle, and heading lock switching mainly locks the aircraft's heading angle, so neither can interrupt the flight controller's automatic control.

Helicopters use variable-pitch propellers, controlling lift changes by changing total rotor pitch to climb and descend; multi-axis aircraft use fixed-pitch propellers, controlling lift by changing rotor speed to climb and descend.

Study note: the side you move toward slows down; the opposite side speeds up. Moving left requires the rotor plane to tilt left so lift gains a leftward component. Therefore the right propellers speed up and the left propellers slow down.

Dihedral changes airflow direction, making the aircraft more stable under crosswinds or disturbances. Dihedral improves stability but does not directly increase maneuverability, which depends more on the power and control systems. (Translator note: the source explanation repeats the power-loss paragraph from the dihedral question #144, which does not address option C.)