Frost & Ice

Question 1

Frost

Answer 1

Frost is different than ice in that rather than large frozen droplets of water that make up ice, frost is just small ice crystals that form on the ground or the surface of your aircraft. All of the planes surfaces need to be defrosted before any flight. Frost forms near the surface primarily in clear, stable, low wind conditions when the temperature of the collecting surface is at or below the dew point of the adjacent air and that dew point is below freezing.

Question 2

The surfaces of an aircraft are designed to be as smooth as possible to keep the air

Answer 2

Attached to the surface and flow over the wing as smooth as possible. Frost causes the surface to be rough, and the roughness can spoil the smooth air over the surface. The air becomes detached and turbulent. This increases the drag and reduces lift capabilities of the wing. A heavy layer of frost over the wings can increase the stall speed by 5 to 10%.

Question 3

Ice

Answer 3

In order for structural icing to occur the air temperature needs to be 0 degrees Celsius or colder and in the presence of visible moisture in the form of supercooled liquid water droplets or freezing rain (wet snowflakes). However, if the air temperature is above 0 degrees celsius, but the surface of the aircraft remains below the freezing point, then icing is still possible.

Question 4

Freezing rain presents the most likely scenario for….

Answer 4

Structural icing because of its low temperature and large size of droplets. The larger the droplets, the greater the “catch rate” of the droplets onto the aircraft surface.

Question 5

What are the first surfaces on an aircraft to collect ice?

Answer 5

Thin leading edges on antennas, horizontal stabilizers, and landing gear struts. Wings are usually one of the last places structural icing will form.

Question 6

Icing on the propellor is indicated by….

Answer 6

A slow loss of power and engine roughness. Enough ice forming unevenly on the blades, can cause massive vibrations caused by the imbalance that may lead to engine failure. If the propellor is seeing ice, then the wings are likely seeing ice as well.

Question 7

Wing ice is even more dangerous, because…

Answer 7

it changes the aerodynamic shape of the wing, which completely changes the lifting capabilities of the aircraft.

Question 8

What are the effects of icing?

Answer 8

Increases drag
Decreases lift
Reduces thrust
Increases weight