Module 17.5 Propeller ice protection Flashcards
What are the two main ice protection methods?
- Fluid anti-icing system
- Electrical de-icing
When is the anti-ice system activated?
Before formation, after ice has formed it is ineffective
What fluid is used to prevent ice formation?
Isopropyl alcohol
In the fluid anti-ice how is the pump speed controlled?
By a rheostat
How is the fluid injected to the sleeve shoes?
Through a fixed nozzle on each engine into a ‘u’ shaped slinger ring on each propeller
How is electrical power supplied to the heating boots?
Spring loaded carbon brushes rubbing against copper slip rings
Where are the copper slip rings?
Back of the rotating propeller hub
Why do we have cyclic heating?
To prevent run back and reduce the load on the aircraft electrical system
What is run back?
Melted ice travels to the trailing edge of the blade and freezes on the unprotected section
The period for which the heating elements remain energised is dependent on timer selection and can be how long?
15 to 30 seconds period for one complete cycle of 2 to 6 minutes
When would a fast cycle be used?
Higher air temperatures
How long is a fast cycle?
2 minutes
What temperatures would the fast cycle be used?
+10℃ down to -6℃
What temperatures would a slow cycle be used?
Temperatures below -6℃
How long is a slow cycle period?
6 minutes
What do controls for the propeller electrical de-icing systems include?
- On-off switches
- Ammeters to indicate current in the circuits
- Protective devices, such as current limiters or circuit breakers
How is fluid forced onto the grooved anti-icing rubber boots?
Centrifugal force
Where is the fluid anti-icing system mainly used?
Piston engine
Why can’t the fluid system be used on turbine aircraft?
It can contaminate compressor blades
In the electrical system what can the heating element be?
Single or segmented into two parts
How many wires does a single element boot/mat have?
Two electrical leads
How many wires does a twin element boot/mat have?
3 leads
