FAA Sport Pilot Airplane (SPA)WeatherHard
A pilot receives a PIREP reporting moderate rime icing between 6,000 and 8,000 feet MSL. The briefer states the current freezing level is 5,500 feet MSL. To avoid the icing conditions while remaining clear of clouds, which action would most likely help the pilot?
- AClimb to 9,000 feet MSL, where temperatures are colder
- BIncrease airspeed to prevent further ice accumulation
- CMaintain the current altitude within the reported icing layer since rime ice is not hazardous
- DDescend to 4,500 feet MSL, which is below the freezing level
Show answer & explanationAnswer & explanation
Correct answer: D. Descend to 4,500 feet MSL, which is below the freezing level
Since the icing occurs at and above the freezing level (5,500 feet), descending to an altitude below the freezing level, such as 4,500 feet MSL, places the aircraft in air warm enough that visible moisture will not form structural ice.
Why the other options are wrong
- A. Climbing higher stays within or above the icing layer, worsening exposure to supercooled moisture.
- B. Airspeed changes do not eliminate the temperature/moisture conditions causing structural icing.
- C. Rime ice can still be hazardous, disrupting airflow and adding weight and drag.
Freezing Level and Icing Avoidance
The freezing level is the altitude where the outside air temperature reaches 0°C; structural icing typically occurs at or above this altitude in visible moisture.
- Icing requires visible moisture and temperatures at or below 0°C
- Descending below the freezing level is a common icing avoidance strategy
- PIREPs provide real-time confirmation of icing altitudes and severity
Memory trick: Below freezing level = 'melt zone' — descend to escape the ice.