17.5 Propeller Ice Control

Question 1

What does ice formation on propeller cause?

Answer 1

Vibrations and lower propeller efficiency

Question 2

What are the places most at risk for ice build up?

Answer 2

Propeller blades, spinner and engine air intake

Question 3

What are the two main ice protection methods from icing?

Answer 3

Fluid anti icing and electrical de icing

Question 4

When is anti icing activated ?

Answer 4

Anti-icing systems are activated before the formation of ice on the propeller. Once ice builds on the propeller, this system is largely ineffective in removing ice

Question 5

how long can the electric de-icing system run for ?

Answer 5

Electric de-icing systems can provide ice protection for the entire duration of the flight, if necessary

Question 6

what is a major disadvantage of using a fluid based anti ice system?

Answer 6

The fluid that is used can contaminate the compressor blades of gas turbine engines and is therefore not suitable for turboprop aircraft

Question 7

What fluid is used in a fluid based anti icing?

Answer 7

using an alcohol-based fluid Iso-Propyl-Alcohol

Question 8

Where is Iso-Propyl-Alcohol stored?

Answer 8

Fluid is stored in a reservoir housed within the airframe

Question 9

How does the fluid anti icing system work?

Answer 9

injects filtered fluid through a fixed nozzle on each engine into a ‘U’ shaped slinger ring on each propeller. From there the fluid is forced by centrifugal force onto grooved anti-icing rubber boots

Question 10

What are the disadvantages of the fluid system?

Answer 10

The weight of the fluid to be carried.
The amount of fluid must be constantly monitored.
The system must be operated before icing occurs.
It is not able to remove impacted ice once it has formed.

Question 11

What does a propeller electric de icing system consist of?

Answer 11

A propeller electric de-icing system consists of an electrical energy source, a resistance heating element, system controls, and necessary wiring

Question 12

How do you transfer heat from the aircraft to the boots?

Answer 12

Through the propeller hub with electrical leads

Question 13

Electrical supply from the aircraft how is this transferred from the engines?

Answer 13

By spring loaded carbon brushes rubbing against copper slip rings attached to the back of the rotating propeller hub

Question 14

How many wires does a single element/boot mat have?

Answer 14

Two electrical leads

Question 15

How many leads does a twin element have?

Answer 15

3 wires 2 live 1 earth

Question 16

What do controls for propeller electrical de icing systems include?

Answer 16

on-off switches, ammeters (load meters) to indicate current in the circuits, and protective devices, such as current limiters or circuit breakers

Question 17

what could the propeller de icing system be used for on ground ?

Answer 17

When the propellers are rotating and for short test periods of time during the take-off check list or system inspection

Question 18

What is run back?

Answer 18

Build up of water when the heating elements is left on and then the water builds up

Question 19

What does cyclic heating allow?

Answer 19

allows a thin layer of ice to form on the heater mat

Question 20

What is used to accommodate the propeller and spinner requirements?

Answer 20

A two speed cycling system

Question 21

how long is the fast cycle operated and under what conditions?

Answer 21

Approximately 2 minutes. Used for atmospheric temperatures of +10 °C (50 °F) down to -6 °C (21.2 °F)

Question 22

how long is the slow cycle and under what conditions is it applied ?

Answer 22

Approximately 6 minutes. Used for atmospheric temperatures below -6 °C (21.2 °F)