A remote pilot in command reviews a PIREP indicating 'occasional moderate turbulence' at 3,000 feet along a planned flight corridor near mountainous terrain. Based on standard PIREP turbulence intensity definitions, what should the pilot conclude about flying a lightweight sUAS in that area?
- AModerate turbulence causes noticeable changes in altitude/attitude and momentary loss of control; given the sUAS's low mass, the pilot should reconsider or delay the flight.
- BModerate turbulence causes only slight, erratic bumps; since sUAS rarely reach 3,000 feet, the flight can proceed without concern.
- CModerate turbulence reports apply only to turbine-powered aircraft and have no relevance to sUAS operating below 400 feet AGL.
- DModerate turbulence confirms the absence of convective activity, so the flight can proceed as planned without further evaluation.
Show answer & explanationAnswer & explanation
Correct answer: A. Moderate turbulence causes noticeable changes in altitude/attitude and momentary loss of control; given the sUAS's low mass, the pilot should reconsider or delay the flight.
By standard PIREP definitions, moderate turbulence produces noticeable variations in altitude/attitude and momentary loss of control, unlike the slight bumps of light turbulence. Lightweight sUAS are highly susceptible to turbulence and wind gradients that can extend down through the terrain-influenced airspace, so this report warrants delaying or rerouting the flight rather than proceeding as planned.
Why the other options are wrong
- B. Moderate turbulence is more significant than 'slight'; mountainous terrain can channel turbulence down to low altitudes.
- C. PIREPs and turbulence effects apply to all aircraft categories, including small UAS.
- D. Turbulence reports don't confirm absence of convective activity; they report observed conditions independently.
PIREP Turbulence Intensity Scale
Pilot reports (PIREPs) classify turbulence as light, moderate, severe, or extreme based on effects on aircraft control and occupant sensations; moderate turbulence causes noticeable altitude/attitude changes and momentary control loss.
- Light: slight, erratic changes in altitude/attitude
- Moderate: noticeable changes, momentary control loss
- Severe: large abrupt changes, possible momentary loss of control
- Extreme: aircraft violently tossed, structural damage possible
- sUAS are especially vulnerable due to low mass
Memory trick: Light bump, Moderate jolt, Severe slam, Extreme wreck.