FAA Private Pilot Helicopter (PRH)WeatherMedium
A pilot reviewing forecast winds and temperatures aloft notes the freezing level is forecast at 6,000 feet MSL along a mountainous route. What is the significance of this information for the flight?
- ADensity altitude will be at its lowest value at 6,000 feet
- BVFR flight is prohibited above the freezing level altitude
- CStructural icing becomes possible in visible moisture at or above 6,000 feet
- DWind shear is guaranteed to occur at that altitude
Show answer & explanationAnswer & explanation
Correct answer: C. Structural icing becomes possible in visible moisture at or above 6,000 feet
The freezing level marks the altitude at which the outside air temperature reaches 0°C. Above this altitude, any visible moisture (clouds, rain) can result in structural icing on the helicopter, which is a significant hazard requiring the pilot to plan accordingly.
Why the other options are wrong
- A. Freezing level relates to temperature, not directly to density altitude values.
- B. There is no regulatory prohibition on VFR flight above the freezing level; icing is a hazard to manage, not a flight restriction.
- D. Wind shear can occur at any altitude and is not guaranteed simply by reaching the freezing level.
Freezing Level
The lowest altitude at which the air temperature reaches 0°C, above which structural icing becomes a hazard in visible moisture.
- Found in Area Forecasts and Winds/Temperatures Aloft forecasts
- Icing risk exists above freezing level in clouds or precipitation
- Freezing level can vary geographically and with terrain
Memory trick: Freezing level = the invisible ice line pilots must respect