17.5 De icing equipment

Question 1

what can happen as a result of ice build up?

Answer 1

distortion to the aerofoil section, vibrations and lower propeller efficiency.

Question 2

what regions are most at risk for ice build up?

Answer 2

blades
spinner
engine air intake

Question 3

what are the two most common anti ice protections for propellors?

Answer 3

fluid anti ice
electrical de ice

Question 4

where is fluid anti ice typically used and why?

Answer 4

piston engine as the fluid can damage compressor blades

Question 5

what is the most common and problem free fluid anti ice used?

Answer 5

iso-propyl alcohol

Question 6

where is anti ice fluid stored?

Answer 6

reservoir in the airframe

Question 7

how is anti ice fluid speed of distribution controlled?

Answer 7

with a rheostat

Question 8

what does the pump for anti ice fluid do?

Answer 8

it injects filtered fluid through a fixed nozzle on each engine into a U shaped slinger ring on each propellor
fluid centrifugally enters grooved rubber de icing boots

Question 9

what are the disadvantages of fluid anti icing?

Answer 9

-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 10

what makes up electrical de icing systems?

Answer 10

-electrical energy
-resistance heating element
-system controls
-wiring

Question 11

where are electrical heating elements mounted?

Answer 11

internally or externally on the propeller spinner and blades

Question 12

where are Heating boots/mats containing electrical elements bonded?

Answer 12

inner third of each propellor blade

Question 13

how is electrical power transferred from the aircraft system to the rotating propellor hubs?

Answer 13

by spring loaded carbon brushes rubbing against copper slip rings

Question 14

how can the heater element be attached to the de icing boot/mat?

Answer 14

single, or segmented into two parts. A single element boot/mat has two electrical leads while a twin element has three leads (2 live and 1 earth).

Question 15

when is the propellor de icing system only operated to reduce the risk of overheat?

Answer 15

when moving or shortly for testing

Question 16

what is run back?

Answer 16

more than that required for melting just the inner ice face, but insufficient to evaporate all the water formed, water will run back over the unheated surface and freeze

Question 17

what is done to limit the risk of run back and to limit the load on electrical systems?

Answer 17

cyclic heating

Question 18

what is secondary effect of cyclic heating?

Answer 18

allowing a small amount of ice to form on the heater mat which when temperature rapidly rises causes ice to disperse centrifugally

Question 19

what is done on propellors with an equal number of blades to prevent imbalance?

Answer 19

opposite blades are heated together

Question 20

what controls the cyclic heating function?

Answer 20

cyclic timer

Question 21

what is the timing cycle for a heating system?

Answer 21

15-30 seconds a complete cycle being 2-6 mins

Question 22

what is usually used to accommodate propellor and spinner requirements in terms of cyclic heating?

Answer 22

a two speed cycling system

Question 23

how long and what temperatures are a fast cycle used for?

Answer 23

2 mins
10 degrees to -6 degrees

Question 24

what are the temperatures and timings of a slow cycle?

Answer 24

6 mins
below -6 degrees