During a pretakeoff contamination check, which surfaces must be free from frost, ice, or snow?

• A. Non-structural panels
• B. Cockpit instruments
• C. Critical surfaces of the aircraft
• D. Air data sensors

Answer: (C)

The key idea is that frost, ice, or snow must be cleared from surfaces that directly affect the airplane’s aerodynamic performance and controllability. Those are the critical surfaces of the aircraft—the wings and tail surfaces, along with their control surfaces. Ice or snow on the leading edges or on any part that changes lift, stall characteristics, or control effectiveness can dramatically reduce performance or make the aircraft hard to control during takeoff and initial climb. Clearing these surfaces ensures the airplane can rotate properly, climb as expected, and maintain stable control.

Non-structural panels and cockpit instruments aren’t part of the aerodynamics that determine takeoff safety, so contamination there doesn’t carry the same immediate risk to flight performance. Air data sensors can be affected by contamination, but the primary concern of the pretakeoff check is the surfaces that generate lift and provide control authority. That’s why the critical surfaces are the focus.