China Civil UAV Theory Questions — Questions 641–650

UAV-Q0641. When a UAV pilot flying level encounters a strong vertical updraft, to prevent exceeding load limits, the pilot should

Explanation

Reducing flight speed lowers dynamic pressure, reducing the extra force airflow exerts on the aircraft, avoiding over-limit load and maintaining a stable flight attitude.

UAV-Q0642. A fixed mass of gas has the following characteristic:

Explanation

Study note: density is directly proportional to pressure and inversely proportional to absolute temperature. According to the ideal gas law, at constant volume, pressure is directly proportional to temperature (Charles's law).

UAV-Q0643. The main factor affecting air viscous force is

Explanation

Air viscosity is the resistance from molecular friction as air flows, affecting flow properties. Temperature is a key factor in fluid viscosity, and liquids and gases trend oppositely with temperature: liquid viscosity falls as temperature rises, while gas viscosity rises as temperature rises. When temperature rises, the average distance between liquid molecules increases, reducing internal friction and viscosity; for gases, faster average molecular motion increases collision frequency, showing as higher viscosity. Air cleanliness: impurities or pollutants may affect flow properties, but cleanliness is not a direct main factor in viscosity, which relates more to air molecules' intrinsic properties. Relative humidity indicates water vapor content; humidity changes may affect some physical properties, but not significantly viscosity, which relates more to molecular structure and temperature.

UAV-Q0644. A fixed-wing civil UAV flying at full power in wind

Explanation

Airspeed is the aircraft's speed relative to the air. At full power, with power and attitude unchanged, airspeed is independent of wind direction and stays the same.

UAV-Q0645. Which is NOT a reason clouds adversely affect flight safety?

Explanation

Clouds impair visual observation and may cause icing, both adverse to safety; the drag clouds add is usually slight and not a main adverse cause.

UAV-Q0646. If an airport has only one runway, its runway direction should ensure aircraft can

Explanation

Runway direction design principle: a single airport runway's direction is usually set by local prevailing wind (the most frequent wind direction), ensuring aircraft can take off and land into the wind.

UAV-Q0647. Which type of meteorological UAV operation, with cost control, allows single use without recovery?

Explanation

Severe convective cloud detection environments are harsh and safe recovery is difficult, so single use without recovery is allowed to control costs.

UAV-Q0648. A cold front is ( )

Explanation

Study note: for a cold front, look for the cold air mass. A cold front is defined as a front formed when a cold air mass actively moves toward a warm air mass.

UAV-Q0649. When an air mass leaves its source region for an underlying surface of different properties, its physical properties gradually change. This process is called air mass modification. Generally:

Explanation

A cold air mass moving to a warm region absorbs heat fast and modifies fast; a warm air mass moving to a cold region loses heat slowly and modifies slowly.

UAV-Q0650. The same civil UAV undergoes ground checks at the same site in winter and summer. Which altitude changes?

Explanation

GPS altitude is based on a fixed Earth ellipsoid, so it does not change at a fixed site; field-relative height uses the ground as reference and is always 0 during ground checks; pressure altitude is affected by seasonal temperature and pressure changes and fluctuates.