FAA Part 107 Remote Pilot (UAG)OperationsEasy
A remote pilot is preparing to land a multirotor sUAS on a small rooftop pad. During the final few feet of descent, the pilot notices increased lift and a change in handling characteristics as the aircraft nears the surface. This is an example of which aerodynamic phenomenon?
- ADissymmetry of lift
- BGround effect
- CVortex ring state
- DWake turbulence
Show answer & explanationAnswer & explanation
Correct answer: B. Ground effect
Ground effect occurs when a rotorcraft operates very close to a surface, causing the rotor downwash to be compressed between the aircraft and the ground, resulting in increased lift and altered control response.
Why the other options are wrong
- A. Dissymmetry of lift relates to forward flight airflow differences on rotor blades, not surface proximity.
- C. Vortex ring state occurs during steep descents through the aircraft's own downwash, not near the ground.
- D. Wake turbulence comes from another aircraft's wingtip vortices, not surface proximity.
Ground Effect
An aerodynamic phenomenon where a rotorcraft near the surface experiences increased lift efficiency due to compressed rotor downwash, altering handling during takeoff and landing.
- Occurs within roughly one rotor diameter of the surface
- Increases lift and can mask underpowered conditions
- Can cause unexpected handling changes on takeoff/landing
Memory trick: Ground effect = the ground gives you a lift boost, like a trampoline of air.