Structural Icing
The two basic environmental conditions required for structural icing to form on an airframe.
What are visible moisture and outside temperatures at or below freezing
This control redirects hot air around the engine into the carburetor to melt accumulated ice.
What is Carb Heat?
Fog that forms on clear, calm nights as the ground cools and warms up shortly after sunrise.
What is Radiation Fog?
Rain that falls from high clouds and evaporates before ever reaching the ground.
What is Virga?
An atmospheric condition where air temperature increases as altitude increases
What is a Temperature Inversion?
This type of ice forms from small supercooled water droplets, appears rough and opaque, and is brittle.
What is Rime Ice?
Carburetor icing can form even when the outside air temperature (OAT) is as high as this value.
What is 85 F?
Fog created when warm, moist air moves horizontally over a cooler surface; it can form even with strong winds and cloud cover.
What is Advection Fog?
A small, concentrated downdraft within a thunderstorm that is considered the most severe type of wind shear
What is a Microburst?
Temperature inversions are generally associated with this type of atmospheric stability.
What is a STABLE layer of air?
This type of ice has a smooth surface and forms when large supercooled water drops freeze slowly as they spread over the aircraft surface.
What is Clear Ice?
Structural ice that blocks the main engine air intake is called this.
What is Impact Ice / Engine Intake Ice?
Fog formed as moist air flows up rising terrain and cools adiabatically.
What is Upslope Fog?
The maximum size (diameter) threshold for a downdraft to be classified as a microburst.
What is 2 Nautical Miles (or 2.5 miles)?
The term for the visibility measured along a pilot's line of sight during approach or descent.
What is Slant Visibility/Range?
The specific precipitation type most likely to cause rapid clear ice accumulation.
What is Freezing Rain?
The flight deck control activated to bypass a blocked main air intake when engine intake icing occurs.
What is Alternate Air?
Also known as evaporation fog, this occurs in late spring or early fall when cold air moves over warm water.
What is Steam Fog?
Downdraft speeds within a microburst can reach up to this extreme rate of descent.
What is 6,000 feet per minute (fpm)?
How a temperature inversion affects pollutants, particles, fog, and smoke near the ground.
How does it act as a lid/blanket that stops vertical convection and traps particles in lower levels, causing poor visibility?
The ice type that consists of a combination of both rough, opaque ice and smooth, clear ice.
What is Mixed Ice?
Two heating/alternate systems used to protect flight instruments from icing failures.
What are Pitot Heat and Alternate Air (Static)?
Fog formed when rain falls through cold, dry air, evaporating and raising the dew point until saturation occurs.
What is Precipitation-Induced (or Frontal) Fog?
The duration of peak wind strength during a microburst, and the maximum wind speed it can exceed.
What is 2 to 4 minutes and 80 MPH?
Standing, lens-shaped clouds formed by mountain waves on the lee side of mountains that indicate extreme wind and turbulence.
What are Lenticular Clouds?