FAA Part 107 Remote Pilot (UAG)WeatherHard
A remote pilot is planning small UA operations over an open field with dark, dry soil on a clear day with light surface wind. Which condition would create the greatest risk of convective turbulence from thermals during the flight?
- AFlying during overcast conditions with a stable air mass
- BOperating over the field during peak afternoon heating
- CAn early morning launch with cool surface temperatures
- DOperating over a large body of water during the flight
Show answer & explanationAnswer & explanation
Correct answer: B. Operating over the field during peak afternoon heating
Convective turbulence from thermals is strongest when surface heating is at its maximum, typically in the early-to-mid afternoon, especially over dark, dry surfaces that absorb solar radiation efficiently and generate strong rising air currents. Morning launches, water surfaces, and stable overcast conditions all produce far less thermal activity.
Why the other options are wrong
- A. Overcast, stable conditions suppress convection, resulting in little to no thermal turbulence.
- C. Early morning has minimal surface heating, so thermal activity and associated turbulence are weak.
- D. Water surfaces heat much more slowly than land, producing far fewer and weaker thermals.
Convective Turbulence
Turbulence caused by rising thermal currents from uneven surface heating, typically strongest over dark, dry surfaces during peak afternoon heating in unstable air.
- Peaks in early-to-mid afternoon when solar heating is greatest
- Dark, dry surfaces (asphalt, plowed fields) generate stronger thermals than light or wet surfaces
- Suppressed by cloud cover, stable air, or over large bodies of water
Memory trick: 'Afternoon = the surface stove reaching max heat between 2 and 4 PM.'