Cold weather operations Flashcards
What is aquaplanning (hydroplanning)?
Tires of the aircraft are seperated from the runway surface by a thin fluid film.
What is contamination? 4
All forms of frozen or semi-frozen moisture such as frost, snow, slush or ice.
What is contamination check?
When you check the aircraft to establish the need for de-icing.
De-icing is applied?
Heated to ensure maximum efficiency.
What is dew point?
Temperature at which water vapor starts to condense.
What is friction coefficient?
Normal force depends on?
Friction coefficient is the relationship between the friction force acting on the wheel and the normal
force on the wheel.
The normal force depends on the weight of the aircraft and the lift of the wings.
The start of the holdover time is?
From beginning of the anti-icing treatment.
What is post-treatment check?
External check of the aircraft after de-icing and or anti-icing to ensure that the aircraft is free from any frost, ice, snow or slush.
Icing conditions generally occur from?
Slightly positive temperature down to -40 and are most likely around FL100.
When rapid icing is encountered in a stratiform cloud
Moderate change of altitude will significantly reduce the rate.
If icing conditions prevail on the approach, what should we do?
Keep speed as high as permitted, delay flap extension as much as possible and do not retract flaps after landing.
Which ice is not visually detected?
Clear-ice.
If aircraft is not clean we need to de-ice to remove everything. When do we use anti-icing?
When outside conditions may lead to an accumulation of percipitation before take-off = holdover time.
Published tables for hold-over times should be used as?
Guidance only, parameters like severe weather, high wind velocity, jet blast etc may AFFECT it.
How does RWYCC work?
Reporting process begines with evaluation of the runway by human observation and are then transffered to ATC and we use it to calculate our performance. We should also use our own observation after landing if it´s more poor than the reported condition.
How does the ground spoilers brakes the aircraft?
Increases the drag and improves the brake efficiency by adding load on the wheels.
How does the thrust reversers brake the aircraft?
It is very important on?
Thrust reversers decelerate the aircraft by creating a force opposite to the aircraft’s motion regardless of the runway’s condition.
The use of thrust reversers is essential on contaminated runways.
Hard contaminants are?
Fluid contaminants are?
Compacted snow and ice and reduce the friction forces.
Water, slush and loose snow = reduce the friction forces and created an additional drag and may lead to aquaplanning.
In crosswind conditions the pilot may have to choose between?
Braking and controlling the aircraft.
Taxi, take-off, and landing operations in X conditions are prohibited
LESS THAN POOR
GOOD TO MEDIUM REPORTED, maximum crosswind and RWYCC?
RWYCC 4, 20kt.
MEDIUM reported, maximum crosswind and RWYCC?
RWYCC 3, 15kt.
MEDIUM TO POOR reported, maximum crosswind and RWYCC?
RWYCC 2, 10kt.
Take-off and landing is permitted only when reported RWYCC is equal to X or higher.
RWYCC 3. For
performance calculations and crosswind limitations maximum RWYCC 3 may be used.
When runway is reported DAMP, crew can use runway condition
WET instead of Slippery Wet,
unless the airport publishes lower RWYCC.
The presence of a contaminant on the runway leads to an increased accelerate-stop distance, as well
as an increased accelerate-go distance (due to the precipitation drag). This results in?
If this limitation occur, what can we do?
A lower take-off
weight which can be significantly impacted when the runway is short.
Higher than standard flap setting and take-off speeds can be used. Results in better runway performance since both the accelerate-stop and accelerate-go distances are reduced.
On short and contaminated runway, it normally calls for? Bear in mind?
Higher flap setting (2 instead of 1) = ASDA is reduced = we climb before. Bear in mind that if you have obstacle during climb-put requires lower flaps setting as it provides better climb performance.
V1, VR and V2 also have a significant impact on the take-off performance.
Contaminated runway calls for?
High speeds generate good climb performance but we spend long time on runway = take-off distances are increased. Not recommended on contaminated runways.
For lower speeds. Presence of an obstacle may limit the speed reduction and right balance must be found.
Maximum freezing point for JET A?
Maximum -40 degrees.
Temperature below ISA?
Aircraft true altitude below indicated altitude.
Basic mechanism for aircraft icing?
Supercooled droplets?
Water at negative Celsius temperature may remain liquid = supercooled (unstable). They can freeze all of a sudden if they are bit by an object expecially if the object is at negative temperature.
On ground, when does the airframe may get covered with frost?
Overnight, if the sky is clear and temperature gets around 0 degrees or below.
CB clouds are a special threat, why?
Because icing conditions can be met outside of the cloudy body for example under the anvil, generates freezing drizzle or freezing rain = lead to severe ice.
Speed as an effect on several characteristics of ice which accretes. Best known as? Temperature recovery?
Kinetic heating (KH) which is difference between TAT and SAT. KH is sometimes called temperature recovery because it naturally heats the leading edge relative to the rest of the airframe = naturally heats leading edge protects from icing as long as the OAT is above -10 degrees.
At 250kt, the kinectic heating KH is about?
+ 10 degrees = temperature increase by 10 degrees of the leading edge = good.
Why can we not expect icing when SAT it 40 degrees or below?
Because no supercooled water may be present at colder temperatures.
Increase of the speed does what?
Decreases the amount of ice accreted because of the kinetic heating KH.
If rapid ice accretion is met, what can we do?
Moderate change of altitue is normally enough to decrease or stop the ice to accrete. ATC must accept such a pilot request.
Aircraft designers do their best to ensure airframes have smooth surfaces (wind leading edge, upper surface). WHY?
Smoothness in these areas produces best lift force. Any type of ice accretion is an obstacle to smooth airflow. Any obstacle will slow the airflow down and introduce turbulence and will degrade the lifting performance of the wing.
Aircrafts are not certified for sustained icing in configurations?
With slats and flaps out. Delay them. Aircraft wouldn´t stay long enough in icing conditions with slats/flaps extended.
How do we protect the engines and leading edges from icing on air?
We switch anti/wing ice on before ice accretes. All Airbus wing and nacalle (engine intake) ice protection systems use hot bleed air type anti-icing from the compressors HP.
Engine intake: In certain flight conditions, the temperature may drop by several degrees inside the intake (“sucking” effect). Therefore?
Therefore, inside icing may occur at
slightly positive outside air temperatures, whilst the wing itself wouldn’t. We should use the engine anti-ice.
What is covered by electrical heating on Airbus?
Sensors, static ports, pitot tubes, TAT and AOA probes, flight compartment windows are electrically anti-iced.
When does icing condition exists? 2
What must we immediatly to if we see these conditions?
OAT on ground or TAT in flight is AT or below 10 degrees and visible moisture in any form is present (clouds, fog, rain, snow etc).
OAT on ground and for take off is AT or below 10 degrees and operating in ramps, taxiways or runways where surface snow, standing water or slush may be ingested by the engines or freeze on engines, nacalles or engine sensor probes.
Turn on the engine anti-ice.
When SAT is below 40 degrees engine anti ice must be on only when?
When entering CB clouds.
Why should we avoid to fly in icing conditions with slats and flaps extended?
Accreted ice may block the retraction of the high lift devices causing mechanical damage to the slat/flap system.
