17.5 Propeller Ice Control Flashcards
What does ice formation on propeller cause?
Vibrations and lower propeller efficiency
What are the places most at risk for ice build up?
Propeller blades, spinner and engine air intake
What are the two main ice protection methods from icing?
Fluid anti icing and electrical de icing
When is anti icing activated ?
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
how long can the electric de-icing system run for ?
Electric de-icing systems can provide ice protection for the entire duration of the flight, if necessary
what is a major disadvantage of using a fluid based anti ice system?
The fluid that is used can contaminate the compressor blades of gas turbine engines and is therefore not suitable for turboprop aircraft
What fluid is used in a fluid based anti icing?
using an alcohol-based fluid Iso-Propyl-Alcohol
Where is Iso-Propyl-Alcohol stored?
Fluid is stored in a reservoir housed within the airframe
How does the fluid anti icing system work?
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
What are the disadvantages of the fluid system?
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.
What does a propeller electric de icing system consist of?
A propeller electric de-icing system consists of an electrical energy source, a resistance heating element, system controls, and necessary wiring
How do you transfer heat from the aircraft to the boots?
Through the propeller hub with electrical leads
Electrical supply from the aircraft how is this transferred from the engines?
By spring loaded carbon brushes rubbing against copper slip rings attached to the back of the rotating propeller hub
How many wires does a single element/boot mat have?
Two electrical leads
How many leads does a twin element have?
3 wires 2 live 1 earth
What do controls for propeller electrical de icing systems include?
on-off switches, ammeters (load meters) to indicate current in the circuits, and protective devices, such as current limiters or circuit breakers
what could the propeller de icing system be used for on ground ?
When the propellers are rotating and for short test periods of time during the take-off check list or system inspection
What is run back?
Build up of water when the heating elements is left on and then the water builds up
What does cyclic heating allow?
allows a thin layer of ice to form on the heater mat
What is used to accommodate the propeller and spinner requirements?
A two speed cycling system
how long is the fast cycle operated and under what conditions?
Approximately 2 minutes. Used for atmospheric temperatures of +10 °C (50 °F) down to -6 °C (21.2 °F)
how long is the slow cycle and under what conditions is it applied ?
Approximately 6 minutes. Used for atmospheric temperatures below -6 °C (21.2 °F)
