17.5 - Propeller Ice Protection

Question 1

The 2 types of de-icing

Answer 1

Fluid and electrical

Question 2

Effects of ice

Answer 2

Distortion to aerofoil cross section
Vibration
Lower prop effieciency.

Question 3

Anti icing

Answer 3

Activated before formation of ice, does not remove ice.

Question 4

Fluid anti icing

Answer 4

Only piston engine a/c
U shaped slinger ring on each prop. Grooved rubber boots.
Weight of fluid. Does not remove ice already formed. Fluid level needs monitoring.
Isopropyl alcohol used.

Question 5

Electrical de - icing equipment.

Answer 5

Heating boots or mats bonded to inner 1/3rd of prop
Power transferred by slipper rings and carbon brushes.
To prevent overheating they work intermittently, cyclic heating to lessen load on electrical system and prevent run back.
On for 15-30 s
Complete cycle is 2 - 6 mins.

Question 6

2 speed cycling system for electronic de-icing.

Answer 6

Fast cycle
- 2 mins long.
- temps from +10 to -6 degrees C

Slow cycle
- 6 min cycle
- temps below -6 degrees C