Icing Flashcards
In which temperature range can the greatest concentration of SCWD be found in a cloud?
0°C to -10°C.
What are the hazards of flying in icing conditions?
The accumulation of ice on the aircraft can lead to:
» increased aircraft mass and drag
» disruption of airflow over aerofoils
» classic piston engines: carburettor icing
» turbine engines: reduction in the air intake diameter
» jamming of the control surfaces
» windscreen icing
When does hoar frost form?
If the aircraft is flown from cold air to warm air of high humidity (deposition).
It can also accumulate overnight on the ground.
Define: freezing rain.
Rain that freezes as it falls.
It forms in an inversion of temperature where it falls from a level above 0°C to a level below 0°C.
What affects the size of SCWD?
Vertical depth of ascending air in a cloud (more collisions = larger droplets).
Describe: rime ice.
Opaque and brittle. Forms quickly.
How can we estimate ram rise with a formula?
RR = (TAS/100)2
Which service provides information on likelihood of carburettor icing on a given day?
No service provides such information. Pilots must use their knowledge and experience to assess the risk.
What’s the relationship between temperature and dew point?
The closer the temperature and dew point, the higher the relative humidity.
On which days will chances of carburettor icing be higher:
(a) on cold and dry winter days
(b) on warm and humid summer days
?
On warm and humid summer days, because of the higher water vapour content of the air.
When can airframe icing be experienced?
Whenever an aircraft flies through clouds or precipitation at negative temperatures.
Before flight, if we want to assess the possibility of carburettor icing, we need information on RH (from dew point). What if such information is not available to us?
We assume a high RH.
By which processes may ice form on the aircraft?
Deposition and freezing.
Should encounters with icing conditions be reported to ATS?
Yes.
Are engines with fuel injection system prone to carburettor icing?
No, because fuel is delivered to cylinders directly.
Define: ram rise.
Heating of the airframe due to airflow compression and friction.
What is another name for intake ice?
Impact ice.
Describe: hoar frost.
Light and brittle.
In which conditions will ice form in turbine engine intakes?
In the same conditions that produce airframe icing, and additionally at high power settings at low speeds.
Why is freezing rain particularly dangerous?
Because it can fall onto all the exposed upper surfaces of the airframe, not just the leading edges.
List the icing intensity criteria for reporting.
Trace: perceptible but not hazardous
Light: not hazardous unless present for more than an hour, occasional AI/DI prevents any problems
Moderate: potentially hazardous, AI/DI is necessary
Severe: hazardous, AI/DI is of no use
Can clear ice occur on the airframe if the water droplet temperature is above 0°C?
If the airframe temperature is below 0°C, yes.
When can impact ice form?
In clouds or precipitation when the temperature of the aircraft or the precipitation is below 0°C.
What’s a common cause of carburettor icing?
A combination of the reduced temperature and pressure caused by low power settings in conditions of high humidity.
