PLT493: The Dynamics of Frost
What code PLT493 covers, why the FAA tests it, and how to study The Dynamics of Frost before your checkride.
Recall the dynamics of frost / ice / snow formation on an aircraft
What this means for your checkride
Frost, ice, and snow change the wing before you ever leave the ground. Frost forms when a surface cools below the dewpoint and below freezing, roughening the wing enough to disrupt airflow; ice and wet snow add weight and drag. All of it must be removed, because even a thin, rough layer can prevent the wing from producing enough lift to fly.
Contamination on the wing has caused takeoff accidents, so the FAA tests how it forms and the absolute requirement to remove all of it before flight.
Pilots believe a thin coat of frost is harmless if it looks smooth. Frost's roughness, not its weight, is the problem: it disrupts the boundary layer and can raise stall speed enough to prevent a safe takeoff, so it must be removed, not left in place.
Where to study it
A code on your test report is an area of deficiency. An authorized instructor must review it with you and endorse that review before you take the practical test, and the examiner may revisit it during the oral. Study it until you can explain it out loud, not just recognize the answer.