ATPL Meteorology - Class 9: Icing.

Summary

In this meteorology class, Grant discusses aircraft icing, a significant hazard affecting flight dynamics. Icing occurs when aircraft encounter liquid water below freezing temperatures, leading to various ice types like hoarfrost, rime, and clear ice, each with distinct formation processes. These ice formations increase aircraft weight, alter aerodynamics, and can cause engine issues, impacting lift and power. The video outlines the conditions for icing, its effects on aircraft performance, and the importance of anti-icing measures.

Takeaways

• ✈️ Icing significantly impacts aircraft performance by adding weight and disrupting airflow over aerodynamic surfaces.
• ❄️ There are three main types of airframe icing: hoarfrost, rime ice, and clear ice, each formed under slightly different conditions.
• 🌀 Hoarfrost forms when water vapor sublimates directly to ice on the cold aircraft surface, similar to frost on a car window.
• ❄️ Rime ice occurs when small supercooled water droplets rapidly freeze on the aircraft's leading edges, creating a brittle structure.
• 🌟 Clear ice forms from larger supercooled water droplets that slowly freeze and spread, leading to a heavier and more uniform ice structure.
• 📈 Icing can cause an aircraft to become imbalanced due to the added weight, potentially leading to a loss of lift if the aircraft is near its maximum load.
• 🔧 Engine icing, including carburetor and intake icing, can restrict airflow and lead to a rich fuel mixture, reducing engine power output.
• 🌡️ Icing conditions typically occur below 10 degrees Celsius with visible moisture, and the type of icing can vary with temperature ranges.
• ☁️ In temperatures between 0 and -20 degrees Celsius, both large and small supercooled water droplets can cause a mix of rime and clear ice.
• ❄️ Below -40 degrees Celsius, supercooled water droplets are less likely to cause icing as they tend to freeze into solid particles that don't adhere well to the aircraft.
• 🛠️ Pilots should activate anti-icing systems when entering clouds at temperatures below 10 degrees Celsius and may turn them off below -40 degrees Celsius when icing conditions are less likely.

Q & A

What are the main challenges aircraft face due to icing?

Aircraft face challenges due to added weight from ice and changes in the shape of aerodynamic surfaces, leading to disruption in airflow and potentially a loss of lift.

What is the difference between rime ice and clear ice?

Rime ice forms from small supercooled water droplets and is brittle with many air bubbles, while clear ice forms from larger supercooled water droplets, is more uniform, and is heavier and harder to remove.

How does carburetor icing occur in piston engines?

Carburetor icing occurs when fuel vaporization in the carburetor causes a temperature drop, leading to ice formation on the venturi tube walls, which restricts airflow and affects the fuel-to-air mixture.

What is the role of temperature in the formation of different types of ice on an aircraft?

Temperature plays a critical role in determining the type of ice formed; rime ice is more common in warmer sub-zero temperatures, while clear ice is more likely in colder conditions.

How does the presence of ice affect an aircraft's lift and weight balance?

Ice adds weight to the aircraft, requiring more lift to maintain balance. If the aircraft is near its maximum load, it might not be able to produce enough lift to counteract the added weight from ice.

What is the significance of the temperature range between -20 and -40 degrees Celsius for icing conditions?

In this temperature range, there is a higher likelihood of encountering rime ice due to the predominance of small supercooled water droplets, which are more likely to freeze and form rime ice.

Why is it important for pilots to be aware of icing conditions when flying through clouds?

Pilots need to be aware of icing conditions to manage the aircraft's anti-icing systems effectively, as clouds can contain supercooled water droplets that can lead to ice formation on the aircraft.

What is the impact of engine intake icing on jet engines?

Engine intake icing can restrict the airflow into the engine, leading to an imbalance in the fuel-to-air mixture and a reduction in engine power output.

How does the sublimation of water vapor contribute to icing on an aircraft?

Sublimation of water vapor directly to ice on the aircraft's surface can lead to hoarfrost, which is a type of icing that forms when the aircraft transitions from cold air to warmer, humid air.

What are the typical conditions for the formation of hoarfrost on an aircraft?

Hoarfrost forms when an aircraft flies from a cold air mass into an area of warmer, higher humidity air, causing water vapor to sublimate directly onto the cold airframe.

How do the principles of flight relate to the problems caused by icing on an aircraft?

The principles of flight, particularly the generation of lift and the balance of forces on an aircraft, are disrupted by icing, which alters the shape of the wings and other surfaces, leading to a loss of lift and an increase in drag.

Outlines

00:00

🛩 Introduction to Aircraft Icing

Grant introduces the ninth class in the meteorology series, focusing on the hazards of aircraft icing. Icing poses a significant threat to aviation as it adds substantial weight to the aircraft and alters the aerodynamic surfaces, disrupting airflow. The video builds upon the principles of contamination from the principles of flight series. Icing occurs when an aircraft encounters liquid water below freezing temperatures or when precipitation contacts a cold airframe. There are several types of icing, including hoarfrost, rime ice, and clear ice, each formed under slightly different conditions. Hoarfrost forms when water vapor sublimates directly onto the cold surface of the aircraft, similar to frost on a car. Rime ice forms when small supercooled water droplets rapidly freeze upon contact with the airframe, while clear ice forms from larger droplets that freeze more slowly, creating a denser and heavier structure. These ice types are more common in specific cloud types and temperature ranges.

05:01

🌡️ Types and Effects of Icing

This section delves into the various types of icing and their specific conditions. Hoarfrost forms when an aircraft transitions from cold air to warmer, more humid air, causing water vapor to sublimate onto the airframe. Rime ice is common in clouds with small supercooled water droplets, while clear ice is more prevalent in clouds with larger droplets, such as cumulonimbus clouds. The presence of ice on an aircraft leads to increased weight and altered aerodynamics, which can be critical if the aircraft is near its maximum load capacity. Engine icing is also discussed, with two main forms: carburetor icing and intake icing. Carburetor icing occurs when fuel vaporization in the carburetor causes a temperature drop, leading to ice formation that restricts airflow and affects the fuel-to-air mixture, reducing engine power. Intake icing affects both piston and jet engines, where ice restricts air intake and leads to an imbalance in the combustion process, also decreasing power output. The video explains the conditions under which these icing scenarios are likely to occur, such as temperatures and the presence of moisture in the air.

10:04

❄️ Icing Conditions and Anti-Icing Measures

The final paragraph discusses the operational considerations for pilots when encountering icing conditions. Icing is a concern below 10 degrees Celsius with visible moisture, as the aircraft's surfaces can cool significantly in flight, leading to ice formation. Between 0 and -20 degrees Celsius, both large and small supercooled water droplets can cause rime and clear ice, respectively. Below -20 degrees Celsius, the likelihood of rime ice increases as larger droplets have already frozen. At temperatures below -40 degrees Celsius, icing conditions are considered unlikely due to the formation of solid ice particles that are less likely to adhere to the aircraft. The video concludes with advice on when to activate anti-icing systems, suggesting that they should be turned on when entering clouds at temperatures of 10 degrees Celsius or lower and can be turned off once the temperature drops below -40 degrees Celsius. The summary underscores the importance of understanding and managing the risks associated with aircraft icing.

Keywords

💡Icing

Icing refers to the accumulation of ice on an aircraft's surfaces, particularly the wings and engine inlets, which can significantly impact flight performance and safety. In the video, icing is the central theme, with detailed discussions on how it forms and its effects on aircraft, including increased weight and altered aerodynamics. The script mentions different types of icing and their specific impacts, making it a critical concept for understanding the video's message.

💡Aerodynamic surfaces

Aerodynamic surfaces are parts of an aircraft, such as wings and tail fins, designed to generate lift and control the aircraft's movement through the air. The video explains how icing can alter these surfaces' shapes, leading to disrupted airflow and reduced lift. This concept is crucial for understanding how icing affects flight dynamics and the importance of de-icing measures.

💡Horfrost

Horfrost is a type of ice that forms when water vapor in the air sublimates directly onto an aircraft's surface. It is likened to the frost that forms on a car's windshield. In the video, horfrost is one of the three main types of icing discussed, highlighting its formation process and its relatively thin and easy-to-remove characteristics.

💡Rime ice

Rime ice is formed when small supercooled water droplets come into contact with the aircraft's surface, leading to rapid ice formation with many air bubbles. The video describes rime ice as being brittle and easy to remove, contrasting it with clear ice. It is a significant type of icing that occurs within clouds and is crucial for pilots to manage during flight.

💡Clear ice

Clear ice forms when larger supercooled water droplets contact the aircraft, resulting in a slower freezing process that covers a larger area and is heavier. The video explains that clear ice is harder to remove due to its uniform structure and lack of air pockets, making it a more challenging type of icing for pilots to deal with.

💡Lift

Lift is the force that opposes the weight of an aircraft and keeps it airborne. The video discusses how icing adds weight to the aircraft and changes the shape of its aerodynamic surfaces, leading to a reduction in lift. Understanding lift is essential for grasping the impact of icing on flight performance and the need for de-icing systems.

💡Engine icing

Engine icing refers to the formation of ice within an aircraft's engine components, such as the carburetor or intakes, which can restrict airflow and lead to a reduction in power. The video explains two forms of engine icing: carburetor icing and intake icing, both of which can be hazardous if not managed properly.

💡Carburetor icing

Carburetor icing occurs when fuel vaporization in a piston engine's carburetor causes a temperature drop, leading to ice formation that can restrict airflow. The video provides an example of this phenomenon, explaining how it can lead to an incorrect fuel-to-air mixture and reduced engine power, emphasizing the need for pilots to be aware of and manage such conditions.

💡Temperature bands

The video discusses specific temperature bands that are conducive to different types of icing. For instance, between 0 and -20 degrees Celsius, both large and small supercooled water droplets can be present, leading to a mix of rime and clear ice. Understanding these temperature bands helps pilots anticipate and prepare for icing conditions.

💡Anti-icing systems

Anti-icing systems are mechanisms used on aircraft to prevent the formation of ice. The video mentions that these systems are typically activated when entering clouds with temperatures below 10 degrees Celsius. These systems are crucial for maintaining flight safety in icing conditions by preventing the accumulation of ice on critical surfaces.

Highlights

Icing adds significant weight to aircraft, disrupting balance and airflow.

Airframe icing occurs below zero degrees Celsius with liquid water or precipitation.

Horfrost forms when water vapor sublimates on cold airframes, similar to car frost.

Rime ice forms from small supercooled water droplets, creating brittle and easily removable ice.

Clear ice forms from larger supercooled droplets, leading to a heavier and harder ice to remove.

Icing can cause weight imbalance, necessitating more lift to maintain flight.

Engine icing occurs in carburetors and intakes, reducing engine power due to restricted airflow.

Carburetor icing happens when fuel vaporization drops temperature, potentially freezing the venturi tube.

Intake icing in jet engines restricts air intake, affecting combustion and power.

Icing conditions are prevalent below 10 degrees Celsius with visible moisture.

Between 0 and -20 degrees Celsius, aircraft may encounter both rime and clear ice.

Below -20 degrees Celsius, rime ice is more likely due to a higher proportion of small supercooled droplets.

Anti-icing systems should be activated at temperatures of 10 degrees Celsius or lower in clouds.

Anti-icing can be deactivated below -40 degrees Celsius as ice adhesion becomes unlikely.

Three main types of icing are identified: frost, rime ice, and clear ice, each with distinct formation processes.

The transcript provides a comprehensive guide to understanding and managing aircraft icing.

Transcripts

ice ice baby

stop collaborate and listen

maybe that's an intro

yeah

[Music]

hi i'm grant and welcome to the ninth

class in the meteorology series all

about icing

ice adds a lot of weight to the aircraft

that we then have to lift through the

air with us it also changes the shape of

aerodynamic surfaces leading to

disruption in the airflow

previously i've done a class called

contamination in the principles of

flight series which can add a bit more

information to this video should you

need it to help build a nice picture of

why icing is such a big problem for

aircraft airframe icing can occur

whenever an aircraft flies through

liquid water at temperatures below zero

degrees celsius

or if it flies through precipitation

that falls onto a cold below zero

degrees celsius airframe and it forms

ice on contact

there are few types of airframe icing

caused by slightly different conditions

the first one is horfrost

this happens when water vapor in the air

sublimates

directly to ice on the surface of the

aircraft

this is the kind of frost you would get

on your car overnight and you have to

defrost your car in the morning

it can occur in flight when flying from

an area of cold air

which has cooled the airframe

into an area of warmer

higher humidity air

and that means that the saturation water

vapor pressure reduces near the cold

airframe

and the water vapor sublimates directly

out onto

the airframe in the form of hor frost

second type of icing is known as rhyme

ice it is formed when small

supercooled water droplets come into

contact with the airframe

the impurity of the

aircraft and the airframe

gives something for the ice crystals to

form around this ice forms almost

instantaneously on the leading edges of

the airframe and the rapid freezing

process

leads to air bubbles being trapped

within the ice structure itself and this

means that right mice is quite brittle

and easy to get rid of using

de-icing systems

this type of icing is typical within

clouds themselves

as the suspended water droplets are

still small

as they have not yet grown large enough

to fall as precipitation

also it will be common in more

stratiform clouds

because the lower levels of rising air

means that the water droplets are

smaller

clear ice is rhyme ice's older brother

it is formed when large supercooled

water droplets come into contact with

the airframe rather than small

supercooled water droplets

because the droplets are larger they

take a bit longer to freeze so when the

aircraft gives something for the ice

crust to form around

they begin to freeze but keep flowing

backwards over the length of the wing

due to the airflow

and they slowly freeze as they go

this slow freezing process means that

there are a lot fewer air pockets i mean

that clear ice is

has a much more uniform structure

and it covers a large area as it's

slowly freezing and it's working its way

back

this means that it's heavier and harder

to get rid of

and as this type of ice is formed by

large super cooled water droplets in

it's more common in clouds with higher

levels of rising air and therefore

bigger droplets such as cumuloform

clouds or cumulonimbus clouds for

example you could also encounter a

mixture of both small

and large supercooled water droplets

and when you're in one cloud and then

you would have a mixture of rhyme ice

and clear ice

so why is icing even an issue then

firstly the ice that forms on the

airframe will add weight to the aircraft

so normally an aircraft is in perfect

balance if it's flying straight and

level the weight and the left are equal

to each other

and therefore if we add a bit more

weight in the form of ice

we then don't have enough lift to

balance out

this

added weight

so we're therefore going to have to

produce more lift in order to counteract

this increase in weight

if the aircraft is already carrying up

to close of its maximum load

then it might not be able to maintain

flight

if the ice build up gets too

extreme so it just simply can't produce

the correct amount of lift for this

added weight

the second problem with icing kind of

adds to this problem

so the ice on the aerodynamic surfaces

mainly the wing

will change the shape of them it'll make

them more rough at the surface what this

means in practice is you get a reduction

in lift an increase in weight which is

not a very good combo because you want

to be increasing your lift because

you've got more weight

in terms of

engine icing there's two main forms you

get carburetor and intake icing

so in a piston engine a device called a

carburetor sucks in air to the engine

using a venturi tube

and inside the venturi fuel is added in

vapor form and this fuel vaporization

causes a drop in temperature

this sudden drop in temperature can

cause ice to form and freeze to the

walls of the venturi tube as long as the

amount of water in the air

is high enough as long as there's enough

water vapor in the air

the temperature doesn't necessarily have

to be low for this to happen as the fuel

vaporization

can cause a temperature drop of around

20 degrees so if you're at 15 degrees

celsius you drop by 20 you're obviously

below freezing at that point but it's

going to be

more

obvious and more of a problem when the

temperature is already cold

so this ice that forms in the inside of

the venturi tube restricts the amount of

air that is able to flow through it and

it will lead to an incorrect ratio of

fuel to air going to the engine normally

what happens is the mixture sent to the

engine will be too rich in fuel and the

ignition of the fuel will be worse

because it's not got enough oxygen to

burn

this will lead to less power output from

the engine

and a similar thing can happen if we go

upstream of the carburetor if you think

about the vents that are actually

allowing the air in

if they become restricted with ice

less air can flow in

and leads to problems downstream with

the mixture

and a reduction in power as well so

that's a form of intake icing and you

also get intake icing on jet engines so

jet engines have large intakes where the

airframe icing occurs

and it restricts

the hole

that the air can get

to the engine basically

and it's the same sort of thing that's

happening

on the intakes of the piston engine

you're just not allowing a big enough

space for the air to flow in and it

means that downstream in the combustion

chamber

and you've got too much fuel not enough

oxygen

unless

good burn

a less good explosion in the engine

basically and a reduction in power

because of that

so icing conditions occur

whenever we are below 10 degrees celsius

and there's visible moisture in the air

10 degrees celsius is obviously not

below freezing point but when we are

moving through the air the wind on the

aircraft can basically cool it down

significantly

and if it reaches below freezing

then air moisture can freeze onto the

surface of the aircraft or the engine

intakes

when we are below zero degrees celsius

until about minus 20 degrees celsius

then we are in the band to basically

experience

large and small super cooled water

droplets in clouds

and therefore we're going to encounter

both rhyme and clay writing

when we go slightly colder and we look

between -20 and

40

there is more chance for there to be

smaller supercooled water droplets

this is because large water droplets

whilst freezing slower and more

gradually tend to form ice at a warmer

temperature than the small water

droplets

so as it gets colder there's a larger

proportion of small supercooled water

droplets than there is large super cold

water droplets

which means we're more likely to

experience rhyme ice

when we're at temperatures below 40

degrees celsius

most of these super cold water droplets

will have frozen into solid ice

and we would consider it very unlikely

for the ice particles to stick to the

aircraft and we'd say that we are no

longer within icing conditions below 40

degrees celsius

so when we're flying around we would

switch on the anti-icing whenever we

enter cloud and the temperature is 10

degrees

or lower

up until we reach about -40 and then we

can switch the anti-icing back off

to summarize then you've got three main

types of icing you've got frost

you've got rhyme ice and you've got

clear ice

core frost is when the

water vapor in the air sublimates

directly on into ice

and on the surface of the aircraft it's

very thin very easy to get rid of it's

the kind of ice you get on your

windscreen of your car

after a cold night

rime ice is formed when small super

cooled water droplets freeze

instantaneously on the leading edges of

the airframe and because this freezing

process takes place so quickly it leads

to a lot of impurities in the ice a lot

of air bubbles air pockets and therefore

rhyme ice is quite brittle and easy to

get rid of

clear ice is formed when larger super

cooled water droplets freeze on the

surface

and the leading edges of the aircraft

and because they're larger they freeze a

bit slower and they have time to

spread out over the length of the

airframe

and it's a lot more pure in its form a

lot fewer air bubbles and therefore it's

heavier and harder to get rid of

the issues with icing mainly come from

adding weight

which then needs to be balanced out by

more lift and if you're close to your

maximum amount of

uh your maximum load if you're close to

your maximum takeoff weight or landing

weight for instance

then

you might not have enough

aerodynamic lift to counteract this

added weight

and that problem is

enhanced by the fact that the ice

forming on the wings and any aerodynamic

surfaces such as the tail or the fin

will change the shape of the surface

and that means that the air flow doesn't

flow in its predicted pattern and it

disrupts the formation of these forces

and leads to in practice a loss of lift

which you add to your increase in weight

so you're getting even smaller amount of

lift and a larger amount of weight

um which adds to the problem in terms of

enginizing you get carburetor writing or

engine intake icing

carburetor icing is formed by the fuel

injection

into the carburetor

causing a reduction in temperature it

doesn't necessarily have to be below

zero degrees for this to happen but when

it's below zero degrees is easier for

this to happen

and what happens is

the venturi tube that is being used to

suck engine suck air into the engine

becomes restricted and it means that

there's less air flowing and

with a larger proportion being fuel

that means there's less oxygen to help

with the burn and the explosion in the

pistons

so

you get less power output and the same

sort of thing is happening with engine

intake icing

so normally you've got a big disk of air

coming in when you've got icing you're

restricting

the amount of air that can flow in and

it means that there's less oxygen in the

fuel to air mixture

to burn to explode in the engine and to

create that power

so you get a reduction in power if

you've got either carburetor rising or

engine intake icing

icing conditions we would consider

anything below 10 degrees celsius with

moisture in the air

with visible moisture in the air so

basically clouds or precipitation

and when you're between 0 and -20 you're

likely to get both large and small super

cooled water droplets so you're getting

both

uh clear ice and rye mice large and

small super cooled droplets

when you're between minus 20 and minus

40 you're far more likely to get rye

mice because the clear

um

the large super cooled water droplets

have already frozen into solid particles

by the time we get to these temperatures

and you're more likely to get the small

ones and therefore more likely to get

right mice

and then when we're temperatures below

minus 40

and even the rye mice will have frozen

into solid particles

and it's very unlikely for these solid

ice particles to stick to the aircraft

and therefore you would be considered as

no longer being in icing conditions so

you'd switch your anti-icing on at 10

degrees and you could switch it back off

again if you get

colder than minus 40.