Icing Flashcards
Drizzle definition
Fairly uniform precipitation composed exclusively to fine drops - diameter less than 0.5mm - very close together
Fog definition
Vis aggregate of very minute water droplets in the air reducing the horizontal vis to less than 1000m
Frost definition
Also know as hoar frost
Deposit of ice having a crystalline appearance - assuming the form of scales, needles and fans
Rain definition
Precipitation of liquid water particles - either in the form of more than 0.5mm in diameter or small drops - widely separated
Slush definition
Saturated snow - has a heel and toe slap down motion against the ground and will be displaced with a splatter
Snow definition
Ice crystals mostly branched in the form of 6 pointed stars
Dry snow - temp below freezing
Wet snow - temp is at/near or above freezing
Rime ice
Opaque low density - similar to frost
Rain ice
Cold a/c structure flying through a shallow rain front - can be quite severe
Icing effects statistics
Increasing stall by 5% - reduces angle by 3*
Reduced lift by 30%
Drag increases by 40%
Ice on the intake of the engine power information will cause
EPR will over-read
The clean a/c concept
Critical surfaces must be completely clear of ice before t/o
Frost may be allowed on the underside of the wing - depth doesn’t exceed 3mm
Amount of hoar frost acceptable on the fuselage
Up to 3mm provided a/c markings can still be seen
Ultimate responsibility when de icing
Rests with the commander using the clean a/c concept
Hold over time beings
When the deicing starts
Can you brush the ice off
Acceptable but not safe
Type 1 deicing fluid
Hold over time is short and fluid failure occurs rapidly
Old - clear colour
New = orange
Type 2 deicing fluid
Mixed with a thickening agent - makes it more viscous - more chance of it staying on the a/c
Usually straw coloured
Type 3 deicing fluid
A/c with low rotation speeds - as thickening agent
Holdover times are less than type 2 but longer than type 1
No assigned colour
Type 4 deicing fluid
Uses more advanced thickening agent - longest hold over time
Req a high airspeed
Usually coloured green
Steps of deicing and anti icing
1 step - heated anti ice fluid - remains on the a/c structure to provide anti ice
2 step - 1st step = deicing - 2nd step = anti ice as a separate fluid application
Fluid limitations
LOUT - lowest operational temp - past this then the fluid will not work
Repeated use of thickening agent can cause build up in the aerodynamically quiet areas - designed for the air to take it off - type 4 is the worst
Control restrictions
Hold over time depends on
Dilution of fluid
Met conditions
Type of fluid
Following deicing the pilot is given
Fluid type used and brand name
Fluid/water ratio
Date and start time of the final deicing application - UTC
Confirmation the a/c is compliant with the clean a/c concept
