Answers - Ice and Rain Protection

Fill in the Blanks

1. airfoils and air inlets
2. moisture, freezing temperatures
3. lighter, of little
4. rime, clear
5. icing, performance, deteriorate
6. thermal, electrical, and chemical anti‐icing systems
7. turbine compressor, engine exhaust heat exchangers, combustion heater
8. computers
9. electric thermal
10. weeping wing
11. pneumatic de‐icing system, leading edge
12. vacuum, suction
13. engine‐driven air pump (vacuum pump), gas turbine compressors
14. electrical boots or chemical de‐ice
15. ice, fog
16. resistance wire, conductive coating
17. ice detector sensors


1. true
2. true
3. true
4. true
5. true
6. false
7. false
8. true
9. false
10. true
11. false
12. true
13. false
14. true
15. true

Knowledge Application

1. clear and rime ice

2. a) malformation of the airfoil which could decrease the amount of lift; b) additional weight and unequal formation of the ice which could cause un‐balancing of the aircraft.

3. surge, vibration, and complete thrust loss

4. wing leading edges; horizontal and vertical stabilizer leading edges; engine cowl leading edges; propellers, propeller spinner; air data probes; flight deck windows; water and waste system lines and drains.

5. heat surfaces with hot air; heat with electrical elements; breaking up ice with inflatable boots; chemical spray.

6. wing , leading edge slats, horizontal and vertical stabilizer, engine, and wind shield anti‐ice.

7. to heat both wings equally, keeping the airplane aerodynamically stable in icing conditions.

8. without a forward speed the leading edge can easily overheat if left on, therefore the ground sensing system (weight on wheels) will disable the system.

9. antifreeze solution is pumped from a reservoir through a mesh screen embedded in the leading edges of the wings and stabilizers. Activated by a switch in the cockpit, the liquid flows over the wing and tail surfaces, deicing as it flows.

10. When deice system is energized, the control valves in each nacelle and deflate valve receive power. The deice control valves route pressurized air from the discharge side of the pump to the deicer boots. At 17 psi, pressure switches on the deflate valve will de‐energize the deice control valves, and the boots will be deflated and vacuum pressure will hold the boots down against the leading edge surfaces.

11. a new layer of ice may begin to form on the expanded boots and become un‐removable.

12. large amounts of hot air can be bled off the compressor, providing a satisfactory source of anti‐icing and deicing heat.

13. pumps have carbon vanes and parts that self lubricate.

14. windshield wipers, chemical rain repellent, pneumatic rain removal (jet blast), or the windshields are treated with a hydrophobic surface seal coating.

Multiple Choices

1. c
Before installing pneumatic surface-bonded deicer boots, the installation area must be thoroughly cleaned and all paint removed before the glue is applied.

2. b
Laminated windshields which have integral heaters incorporate autotransformers, heat control relays, heat control toggle switches, and indicating lights. The heating elements are powered by the 115 volt AC bus.

3. a
To check if a pitot/static tube heater is operating properly, turn the heater on and observe the ammeter reading. The needle on the gage should move to indicate current flow.

4. c
In a pneumatic deicer boot system, the distributor valve accepts the air from the compressor and directs it to the boots in the proper sequence.

5. a
On a typical reciprocating engine airplane, the deicer boots are powered by a rotary, four-vane positive-displacement pump. The pressure side of the pump inflates the boots, and the suction side of the pump holds the boots down when they are not inflated.

5. c
The suction side of the pressure pump, regulated by a suction relief valve, holds the deicing boots deflated when they are not in use.

6. c
Deicer boots should be cleaned using mild soap and water solution.

7. a
Anti-icing systems which heat the leading edges of wings and intake ducts are generally operated when icing conditions are encountered or when they are expected to occur.

8. c
With the deicer system controls in the proper positions, the suction and pressure gages for the pneumatic deicer system can be checked. The pressure gage will fluctuate as the deicer tubes inflate and deflate. A relatively steady reading should be maintained on the vacuum gage.

9. c
An anti-icing system using surface combustion heaters is automatically controlled by overheat switches, thermal cycling switches, a balance control, and a duct pressure safety switch. The overheat and cycling switches allow the heaters to operate at periodic:: intervals, and they also stop the heater operation completely if overheating occurs.

10. a
In a pneumatic deicer boot system, the distributor valve sequences the inflating and deflating of the different boots in the system.

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