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Turbulence from ground obstructions

Remote Pilot (Part 107) practice question 10 of 25 on Weather / Effects on Performance. ACS element UA.III.B.K1b · difficulty: recall. Want to answer it in a timed quiz? Use the Remote Pilot (Part 107) practice mode.

Question bank updated 2026-09-22

QUESTIONThe intensity of the turbulence created by ground obstructions such as hangars, bluffs or canyons depends on

  1. Athe air temperature and the relative humidity near the obstacle
  2. Bthe height of the obstacle above sea level and the time of day
  3. Cthe size of the obstacle and the primary velocity of the wind
Show the answer and explanation

Correct answer: C. the size of the obstacle and the primary velocity of the wind

  • A — incorrect Temperature and humidity affect air density, not the mechanical turbulence produced when wind flows around an obstacle.
  • B — incorrect Elevation above sea level and time of day are not the factors named; the obstacle's size and the wind speed determine the turbulence.
  • C — correct The study guide states that the intensity of turbulence associated with ground obstructions depends on the size of the obstacle and the primary velocity of the wind.

BACKGROUND

Obstructions on the ground affect the flow of wind and can be an unseen danger. Ground topography and large buildings break up the flow of the wind and create gusts that change rapidly in direction and speed. Obstructions range from man-made structures such as hangars to large natural features such as mountains, bluffs or canyons. The intensity of the resulting turbulence depends on the size of the obstacle and the primary velocity of the wind, and it can present a very serious hazard to any aircraft.

STUDY TIP

When you see a large obstacle upwind of the operating area on a windy day, expect gusts that change rapidly in speed and direction.

KEY POINTS

  • Ground obstructions break up wind flow and create rapidly changing gusts.
  • Turbulence intensity depends on obstacle size and wind velocity.
  • Obstructions include hangars, buildings, mountains, bluffs and canyons.

SOURCES

  • remote_pilot_study_guide.txt ch3b "Effect of Obstructions on Wind"
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SkyDrill is not affiliated with the FAA. This is an original practice item based on 14 CFR part 107, 14 CFR part 89, and the FAA Remote Pilot – Small UAS Study Guide (FAA-G-8082-22). Regulations and handbooks are revised; confirm details against the current edition.