Kevin Reeder

Ground School Quiz - Checking Question Answer

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I am enrolled in the Part 107 Ground School.  After completing the Weather & Micro-meteorology section in the Quiz section question 10 /25.  Why is frost considered hazardous to sUAS operations.  Options are 1) Frost decrease lift capacity by changing the aerodynamic shape of the propellers. 2) Frost decreases lift capacity by spoiling the smooth air over the propellers. 3) Frost increases control effectiveness by slowing the airflow.  The Quiz marks #2 as the correct answer.  I went with #1

According to your lecture in section on icing on page 23 there is the following paragraph (half way through) "In the same way that frost can change the aerodynamic qualities of the propellers, ice can do the same thing"

Can you point me to the section in the lecture that provides the explanation for #2 being the correct answer?.

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Just took FAA test, cats test today. Course very helpful in my getting a great score.  Think your question is indicative of some of the tricky ones on the actual test.  I believe the difference in the two answers you question is: one addresses the frost on the surface and its effects.   The other actually claims the frost has somehow changed the properties of the propeller, or wing.   Good luck!

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Hey @Kevin Reeder, pardon the delayed response! In the future, please email us directly at support@dronepilotgroundschool.com

You're referring to this practice question:

Why is frost considered hazardous to sUAS operations?

A) Frost decreases lift capacity by changing the aerodynamic shape of the propellers.    
B) Frost decreases lift capacity by spoiling the smooth flow of air over the propellers.    
C) Frost increases control effectiveness by slowing the airflow.

Page 301 of the Pilot Handbook of Aeronautical Knowledge:

Quote

While dew poses no threat to an aircraft, frost poses a definite flight safety hazard. Frost disrupts the flow of air over the wing and can drastically reduce the production of lift. It also increases drag, which, when combined with lowered lift production, can adversely affect the ability to take off. An aircraft must be thoroughly cleaned and free of frost prior to beginning a flight.

So B is the right answer. And while you might think A is the right answer, frost does not change the basic aerodynamic shape of the propeller, but the roughness of its surface spoils the smooth flow of air, thus causing a slowing of the airflow.

Hope that helps!

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