China Civil UAV Theory Questions — Questions 276–285

UAV-Q0276. For a ground wire, when the number of broken strands reaches (number of layers − 1) (except single-layer)

Explanation

Study note: with two parentheses, choose “major”. This is a power-line worker exam question. Note: online question banks often misprint option C as “urgent”; if “major” is not among the options, choose “urgent”.

UAV-Q0277. Which of the following is NOT a function of the ESC?

Explanation

By elimination: the ESC's function is to change motor speed according to the control signal, so A is an ESC function — eliminate it. A multirotor's power supply is DC, which must be converted to AC by the ESC to drive the three-phase AC brushless motors used on UAVs, so B is an ESC function — eliminate it. Motor speed depends on the kV value; the ESC regulates speed mainly by changing output voltage or the PWM waveform, not by changing current magnitude. So C is not an ESC function.

UAV-Q0278. The thickest red and black wires on an ESC are used to connect

Explanation

The thickest 2 red/black wires connect to the battery, the medium 2–3 wires connect to the motor, and the thinnest 3 wires connect to the flight controller.

UAV-Q0279. The ESC is one of the most important components of a multirotor UAV. Which of the following is NOT a function of the aircraft ESC?

Explanation

From the forward/reverse control circuit and its principle: to reverse a motor, just swap any two of the three-phase power lines feeding the motor. That has nothing to do with ESC function.

UAV-Q0280. The English abbreviation for electronic speed controller is

Explanation

The full name of the ESC is electronic speed controller (Electronic Speed Control), abbreviated ESC. Depending on the drive motor, ESCs are brushed or brushless. The ESC regulates motor speed according to the control signal.

UAV-Q0281. For a multi-axis aircraft

Explanation

A multi-axis aircraft relies on its rotors for lift, and adjusts lift on different axes by changing rotor speeds to achieve pitch and roll, and adjusts torque by changing rotor speeds to achieve yaw.

UAV-Q0282. For charging a multi-axis aircraft power battery, which charging method is wrong?

Explanation

A Li-polymer battery's full-charge voltage is 4.2V per cell. Charging to 4.6V is overcharging.

UAV-Q0283. For a mixed-fuel engine, how should the winter fuel-to-oil mixture ratio be adjusted compared to summer?

Explanation

Increasing the fuel-to-oil ratio means increasing the fuel proportion. In winter, lower temperatures reduce fuel volatility and increase oil viscosity. Increasing the fuel proportion improves fuel volatility so it ignites more easily, keeping the engine starting and running normally. An appropriate fuel proportion also helps offset the effects of thicker oil and keeps the engine lubricated.

UAV-Q0284. The rotor rotation direction of a multirotor aircraft is generally

Explanation

An alternating adjacent layout cancels reaction torque. (Translator note: the source stem and option A are partly garbled; option A appears to read “clockwise rotors viewed from above the multirotor”.)

UAV-Q0285. For a multirotor aircraft, if any 2 of the 3 single-color wires connecting the ESC and motor are swapped, the result is

Explanation

Swapping any two of the three wires connecting the ESC to the motor reverses the motor.