Icing

Question 1

Drizzle definition

Answer 1

Fairly uniform precipitation composed exclusively to fine drops - diameter less than 0.5mm - very close together

Question 2

Fog definition

Answer 2

Vis aggregate of very minute water droplets in the air reducing the horizontal vis to less than 1000m

Question 3

Frost definition

Answer 3

Also know as hoar frost

Deposit of ice having a crystalline appearance - assuming the form of scales, needles and fans

Question 4

Rain definition

Answer 4

Precipitation of liquid water particles - either in the form of more than 0.5mm in diameter or small drops - widely separated

Question 5

Slush definition

Answer 5

Saturated snow - has a heel and toe slap down motion against the ground and will be displaced with a splatter

Question 6

Snow definition

Answer 6

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

Question 7

Rime ice

Answer 7

Opaque low density - similar to frost

Question 8

Rain ice

Answer 8

Cold a/c structure flying through a shallow rain front - can be quite severe

Question 9

Icing effects statistics

Answer 9

Increasing stall by 5% - reduces angle by 3*
Reduced lift by 30%
Drag increases by 40%

Question 10

Ice on the intake of the engine power information will cause

Answer 10

EPR will over-read

Question 11

The clean a/c concept

Answer 11

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

Question 12

Amount of hoar frost acceptable on the fuselage

Answer 12

Up to 3mm provided a/c markings can still be seen

Question 13

Ultimate responsibility when de icing

Answer 13

Rests with the commander using the clean a/c concept

Question 14

Hold over time beings

Answer 14

When the deicing starts

Question 15

Can you brush the ice off

Answer 15

Acceptable but not safe

Question 16

Type 1 deicing fluid

Answer 16

Hold over time is short and fluid failure occurs rapidly

Old - clear colour

New = orange

Question 17

Type 2 deicing fluid

Answer 17

Mixed with a thickening agent - makes it more viscous - more chance of it staying on the a/c

Usually straw coloured

Question 18

Type 3 deicing fluid

Answer 18

A/c with low rotation speeds - as thickening agent

Holdover times are less than type 2 but longer than type 1

No assigned colour

Question 19

Type 4 deicing fluid

Answer 19

Uses more advanced thickening agent - longest hold over time

Req a high airspeed

Usually coloured green

Question 20

Steps of deicing and anti icing

Answer 20

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

Question 21

Fluid limitations

Answer 21

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

Question 22

Hold over time depends on

Answer 22

Dilution of fluid

Met conditions

Type of fluid

Question 23

Following deicing the pilot is given

Answer 23

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