Icing Flashcards
Ice formation
Icing will occur when temps fall below 0 degrees
Low pressure can cause icing when temps are above 0 degrees
Types of icing and snow
- Rime ice, opaque white and granular ice.low temps in clouds of small water drops. brittle and easy to break off so not really an issue unless its prolonged flight
- Clear ice, transparrent dense and tough and adhesive. forms from mainly large super-cooled water. occur when rime happens but you can tell which is predominate
- Rain ice, Sub zero temps where rain occurs, rain is caught by a/c then freezes, occurs quickly because the airframe is below 0degrees c
- Packed snow, happens in wet snow or sleet because the airfram is not well streamlined, cover cover air intakes which is bad.
- Hoar frost, when a/c is below 0degreese c so thatr the air cooled below dew point, forms in early winter months, when a/c parked overnight on clear winter nights and quick descents.
- restricts view and increases stalling speed, which is critical in landing/take off.
Provision- sensitive to ice are as
- Aerofoil surface
- Engine intakes-
- Engine internal surfaces
- rotor blades and propellers
- Windscreens
- instrument probes and vanes
- control hinges and linkages
- weapons and weapon carriers
Aerodynamic Effects of ice formation
Aerofoil will not become aerodynamic increasing drag, decreasing lift and increase stalling speed. build up on moving parts can lead to serious control effect.
ice under the wing can cause change in performance of a/c
Weight and vibrations
Ice can cause weight issue which will lead to increase vibrations, especially on propellors. can also lead to fracturs within the airframe and changes in CoG
Effects on instruments
ice on external instruments (Pitot tubes) can cause a false reading inside cockpit.
effects on control surfaces
more risk on smaller a/c because the gap between the controls can build up ice jamming the controls and prevent them from being used properly., highly dependant on design rather than a/c size.
Misc effects
Ice on windscreens and canopys can cause decrease in vision, hoar frost causes this the most
communications and ice
ice can cause comm issues as the ice can reduce effectiveness, increase weight and vibrations
Undercarriage and ice
Undercarriage assemblies could be stopped by ice, landing gear etc,
Engines and ice
Engine intakes can be blocked by ice and snow hindering fuel and air flow
descending
Quick descent can cause fogging up of canopys and intruments inside, demisting devices should be used and at times the a/c should be allowed to heat up befire descent
icing on helicopters
Helicopter icing is critically bad, ice on rotor systems can interrupt laminar flow increasing drag nd reducing lift.
Ice on blades happens at tips because of water droplets, can change blade shape and blade imbalance
asymmetrical shed can be fatal as it will change the path of a blade causing violent vibrations and seriously effect a/c control. CoG of rotor disc changes moves away form the center of rotation.
icing on helicopters cont
ice can build rapidly in freezing fog conditions,
hovering causes build up of pack ice/snow over wet slushy surfaces
Rain ice is fatal, combination of loss of lift, increasing weight and engine icing forces it down
Groundcrew can be injured if shedding ice is flying around the joint
what to do in low temp environments
A/c should be positioned top ensure drift on wind driven snow dont form on the a/c where it shouldnt
monitor the effects of snow on upper services, effects on CoG
Fill fuel tanks in a heater hangar to allow for fuel expansion, reduces condensation in fuel tanks
fit protective covers where possible to stop the effects of ice and snow. use anti icing fluid where possible
