FAA Instrument Rating Airplane (IRA)Weather and Weather ServicesHard
During a preflight briefing, a pilot is told the freezing level is forecast at 4,000 feet MSL along the route, with tops of stratiform clouds at 8,000 feet MSL. The planned cruise altitude is 6,000 feet MSL. Which statement best describes the icing risk assessment for this flight?
- AThe aircraft will be flying above the freezing level within visible moisture, creating a significant icing risk
- BNo icing risk exists because the cruise altitude is below the cloud tops
- CIcing risk only exists if the aircraft climbs above the cloud tops into clear air
- DSince the freezing level is below cruise altitude, the air will be too cold to support supercooled water droplets
Show answer & explanationAnswer & explanation
Correct answer: A. The aircraft will be flying above the freezing level within visible moisture, creating a significant icing risk
At 6,000 feet, the aircraft is 2,000 feet above the 4,000-foot freezing level, meaning temperatures are below freezing. Since the aircraft is also within the stratiform cloud layer (base below 6,000, tops at 8,000), it will be flying through visible moisture at subfreezing temperatures — the classic recipe for structural icing.
Why the other options are wrong
- B. Being below the cloud tops does not eliminate icing; the aircraft is still within the cloud layer where moisture and subfreezing temps combine.
- C. Icing risk exists within the cloud layer, not just above the tops in clear air.
- D. Supercooled water droplets exist at temperatures below freezing and are actually more prevalent, not absent, in this range.
Icing Risk Assessment
Structural icing requires both visible moisture (clouds, precipitation) and temperatures at or below freezing; comparing freezing level to cloud layers and cruise altitude identifies risk.
- Icing needs subfreezing temps AND visible moisture together
- Compare freezing level, cloud base/tops, and planned altitude
- Supercooled water droplets exist in clouds well below freezing
Memory trick: Cold plus cloud equals ice—check both before you fly.