FAA Ground School Practice Test

In which environment is aircraft structural ice most likely to have the highest accumulation rate?

1. Snow showers

2. Freezing rain

3. Warm rain

4. Sleet

The correct answer is: Freezing rain

The environment where aircraft structural ice is most likely to have the highest accumulation rate is freezing rain. This phenomenon occurs when raindrops fall through a layer of cold air near the surface and become supercooled. Upon contact with the aircraft's surface, the supercooled droplets freeze instantly, leading to rapid ice accumulation. In freezing rain conditions, the droplets can be larger and contain more liquid than in other types of precipitation, allowing them to deposit a significant amount of ice very quickly. This contrasts with other options such as snow showers, where ice does not typically form from crystallized snowflakes as they are less likely to adhere and freeze upon impact. Warm rain does not present an ice hazard since the temperatures are above freezing, and sleet, while also involving frozen precipitation, generally falls as ice pellets that do not contribute to significant icing when compared to the effects of freezing rain. The characteristics of freezing rain, particularly its temperature dynamics and droplet size, make it a highly conducive environment for rapid ice accumulation on aircraft.