What is "wind shear" and why is it hazardous to sUAS operations?
Why →
Wind shear is a sudden change in wind velocity (direction or speed) over a short distance. Horizontally or vertically. In manned aviation, wind shear on final approach has caused accidents when airspeed suddenly dropped. For sUAS, a sudden reversal from headwind to tailwind or a large speed change can overwhelm flight controller compensation, causing altitude loss or loss of control. Thunderstorm outflows are the most common source of severe low-level wind shear.The trap →
Gradual wind increase with altitude (Choice A) is normal wind gradient, not shear. A daily speed difference between surface and 400 feet is a measurement, not a definition. Wind shear is specifically characterized by the sudden and localized nature of the change.SOURCE → PHAK Chapter 12, Weather TheoryCHECKED APR 21ACS III.A.K1MED