FAA Part 107 Remote Pilot (UAG)OperationsEasy
During a preflight inspection on a cold winter morning, a remote pilot notices a thin layer of frost covering the propellers and top surfaces of the sUAS. What is the primary concern with launching the aircraft in this condition?
- AFrost only adds negligible weight and has no aerodynamic effect
- BFrost disrupts smooth airflow over lifting and control surfaces, reducing lift and increasing drag
- CFrost improves battery performance in cold temperatures
- DFrost has no effect since small UAS do not rely on lift generated by wings
Show answer & explanationAnswer & explanation
Correct answer: B. Frost disrupts smooth airflow over lifting and control surfaces, reducing lift and increasing drag
Even a thin layer of frost roughens surfaces and disrupts smooth airflow, which can significantly reduce lift and increase drag on rotor blades or airfoils. This principle applies to sUAS just as it does to manned aircraft, and frost should always be removed before flight.
Why the other options are wrong
- A. Frost's aerodynamic effect is far more significant than its added weight.
- C. Cold temperatures generally reduce, not improve, LiPo battery performance.
- D. Multirotor sUAS rotors act as airfoils and are affected by frost similarly to fixed wings.
Frost Effects on Aerodynamics
Frost roughens the surface of airfoils and rotor blades, disrupting smooth airflow, reducing lift, and increasing drag, which can degrade flight performance.
- Even thin frost layers affect airflow
- Should be fully removed before flight
- Applies to rotor blades as well as fixed wings
Memory trick: 'Frosty blades = Failing Lift'