Questions and Answers - Aircraft Ice & Rain Control

Study Aid Questions

Fill in the Blanks

1. Under certain atmospheric conditions, ice can build rapidly on __________________ and __________________.

2. On days when there is visible ____________________in the air, ice can form on aircraft leading edge surfaces at altitudes where _____________________ start.

3. Rime ice is ________________ in weight than clear ice, and its weight is _______________ significance.

4. _________________ ice is brittle and more easily removed than ______________ ice.

5. Whenever _______________ conditions are encountered, the ________________ characteristics of the airplane will ____________________.

6. The most common systems used to prevent icing on wing leading edges are ___________________, ___________________, and ____________________________.

7. There are several methods used to provide heated air. These include bleeding hot air from the _____________________, _________________________, and ram air heated by a ___________________________.

8. Modern aircraft use several onboard ___________________ to control anti‐ice and de‐ice aircraft systems.

9. ____________________ anti‐icing systems are also often utilized for vertical and horizontal stabilizer anti‐ice systems.

10. Chemical anti‐icing systems are often called liquid freeze point depressant systems or ______________ systems.

11. General aviation (GA) aircraft and turboprop commuter type aircraft often use a ________________________ __________________ to break of the ice after it has formed on the ______________ surfaces.

12. Wing de‐ice boots are held against the airfoil surfaces by _______________ from the _________________ side of the pumps.

13. Deicer tubes are inflated by an ____________________________,

or by air bled from ________________________.

14. Propellers are de‐iced with _________________________ or _____________________ systems.

15. The electrical window heat system prevents ______________ and ______________ on the flight deck windows.

16. The windshields are heated by ____________________ embedded in the glass or by a
______________________ that is applied on the inside of the outer windshield ply.

17. Ice can be visibly detected but most modern aircraft have one or more _____________________ that warn the flight crew of icing conditions.


1. Clear ice forms a smooth sheet of solid ice. TRUE/FALSE

2. Rime ice has a white appearance. TRUE/FALSE

3. Ice buildup causes destructive vibration, and hampers true instrument readings. TRUE/FALSE

4. Control surfaces become unbalanced or frozen due to the buildup of ice. TRUE/FALSE

5. Radio reception is hampered and engine performance is affected due to the buildup of ice. TRUE/FALSE

6. For the most part, general aviation aircraft equipped to fly in icing conditions use thermal or electric anti‐icing systems that are controlled automatically to prevent the formation of ice. TRUE/FALSE

7. Large transport category aircraft are equipped with advanced deicing boots. TRUE/FALSE

8. Some modern large aircraft are using electrical thermal anti‐icing systems. TRUE/FALSE

9. A chemical anti‐icing is strictly a anti‐icing system to prevent the formation of ice and cannot be utilized as a de‐icing system. TRUE/FALSE

10. Air pressure for a pneumatic wings deice system is supplied by the vacuum pump. TRUE/FALSE

11. Engine driven air pumps are available in a wet and a dry type and used with Turbine engines. TRUE/FALSE

12. Most general aviation aircraft are equipped with a dry‐type of pump. TRUE/FALSE

13. The deice control valve is normally energized and releases air from the vacuum pump overboard. TRUE/FALSE

14. Frost deposits can be removed by placing the aircraft in a warm hangar or by using a deicing fluid. TRUE/FALSE

15. The rain repellant system should not be operated on dry windows because heavy undiluted repellant will restrict window visibility. TRUE/FALSE

Multiple Choices Questions

1. Ice buildup increases _________ and reduces ___________.

a. drag and lift
b. lift and drag
c. drag and temperature

2. Thermal wing anti‐ice systems for business jet and large transport category aircraft will typically use?

a. ram air from a combustion heater
b. air from engine exhaust heat exchangers
c. bleed air from turbine engine compressor
d. bleed air from turbine engine combustion section

3. What type of valve controls the flow of bleed air from the pneumatic system to the wing anti‐ice ducts?

a. bleed air valve
b. wing anti‐ice valve
c. cross feed valve

4. What type of circuits in the onboard computer continuously monitors the wing anti‐ice system?

a. build in test circuits (BITE)
b. wing anti‐ice circuits
c. bleed air circuits
d. warning circuits

5. Chemical anti‐icing systems are used to protect:

a. wings and stabilizers
b. windshields
c. propeller
d. all of the above

6. A pneumatic de‐icing system removes the ice after it has formed on the leading edge surface.

a. true
b. false
c. only in flight
d. only on the ground

7. Pneumatic de‐icing systems (boots) are used on?

a. general aviation aircraft
b. transport category aircraft
c. general aviation and transport category aircraft
d. helicopters

8. Engine driven pumps are used for?

a. gyros
b. pressurization
c. deicing system
d. 1 and 2

9. Why is an oil separator necessary in a de‐icing outfitted with a wet pump?

a. to improve lubrication of the pump
b. to improve vacuum pressure
c. to remove the oil from the air

10. On modern aircraft the deicer boots are __________________ to the leading edge of a wing.

a. riveted with flush rivets
b. bolted with rivnuts
c. bonded with an adhesive

Knowledge Application Questions

1. What are the two types of ice that are encountered during flight?

2. What are the two basic hazards associated with ice or frost forming on aircraft?

3. What could be the result of ice breaking of the wing and entering the engine intake?

4. Name the areas on an aircraft that could be equipped with deicing or anti‐icing systems?

5. Name four types of systems that are used to prevent or control ice formation in aircraft?

6. Describe for what type of applications thermal anti‐icing systems are used?

7. Why are the left and right wing anti‐ice valves operated at the same time?

8. Explain why and how an electric thermal deicing system is made inoperative when the aircraft is on the ground?

9. Explain how a chemical anti‐icing system works.

10. Explain how the pneumatic deice system in the figure below works.


11. Explain why the boot of a pneumatic de‐icing system should not stay inflated longer than 7 to 10 seconds?

12. Why do aircraft equipped with turbine engines use bleed air from the engine compressor?

13. What is the reason that dry vacuum pumps do not need any lubricants?

14. What type of rain control systems are used on aircraft?

Multiple Choices Questions

1. Arcing in an electrically heated windshield panel usually indicates a breakdown in the:

a. temperature sensing elements
b. autotransformers
c. conductive coating

2. How do deicer boots help remove ice accumulations?

a. By preventing the formation of ice
b. By breaking up ice formations
c. By allowing only a thin layer of ice to build up

3. Why are the tubes in deicer boots alternately inflated?

a. Alternate inflation of deicer boot tubes keeps disturbance of the airflow to a minimum
b. Alternate inflation of deicer boot tubes does not disturb airflow
c. Alternate inflation of deicer boot tubes relieves the load on the air pump

4. Carburetor icing may be eliminated by which of the following methods?

a. Alcohol spray and heated induction air
b. Ethylene glycol spray and heated induction air
c. Electrically heating air intake, ethylene glycol spray, or alcohol spray

5. Why should a chemical rain repellant not be used on a dry windshield?

a. It will etch the glass
b. It will restrict visibility
c. It will cause glass crazing

6. What mixture may be used as a deicing fluid to remove frost from an aircraft surface?

a. Ethylene glycol and isopropyl alcohol
b. Methyl ethyl ketone and ethylene glycol
c. Naphtha and isopropyl alcohol

7. What should be used to melt the ice in a turbine engine if the compressor is immobile because of ice?

a. Deicing fluid
b. Anti icing fluid
c. Hot air

8. What is used as a temperature sensing element in an electrically heated windshield?

a. Thermocouple
b. Thermistor
c. Thermometer

9. What maintains normal windshield temperature control in an electrically heated windshield system?

a. Thermal overheat switches
b. Thermistors
c. Electronic amplifiers

10. What is the principle of a windshield pneumatic rain removal system?

a. An air blast spreads a liquid rain repellant evenly over the windshield that prevents raindrops from clinging to the glass surface
b. An air blast forms a barrier that prevents raindrops from striking the windshield surface
c. A pneumatic rain removal system is simply a mechanical windshield wiper system that is powered by pneumatic system pressure

11. What are three methods of anti icing aircraft windshields?

1. Blanket type heating system
2. An electric heating element in the windshield
3. Heated air circulating system 4. Hot water system

5. Windshield wipers and anti icing fluid 6. Ribbon type heating system

a. 2, 3, 5
b. 1, 2, 6
c. 2, 3, 4

12. What controls the inflation sequence in a pneumatic deicer boot system?

a. Shuttle valve
b. Vacuum pump
c. Distributor valve

13. Which of the following is the best means to use when removing wet snow from an aircraft?

a. A brush or a squeegee
b. Hot air
c. Warm water

14. What is one check for proper operation of a pitot/static tube heater after replacement?

a. Ammeter reading
b. Voltmeter reading
c. Continuity check of system

15. What is the source of pressure for inflating deicer boots on reciprocating engine aircraft?

a. Vane type pump
b. Gear type pump
c. Piston type pump

16. Which of the following regulates the vacuum of the air pump to hold the deicing boots deflated when the pneumatic deicing system is off?

a. Distributor valve
b. Pressure regulator
c. Suction relief valve

17. What may be used to clean deicer boots?

a. Unleaded gasoline or Jet A fuel
b. Naphtha
c. Soap and water

18. Some aircraft are protected against airframe icing by heating the leading edges of the airfoils and intake ducts. When is this type of anti ice system usually operated during flight?

a. Continuously while the aircraft is in flight
b. In symmetric cycles during icing conditions to remove ice as it accumulates
c. Whenever icing conditions are first encountered or expected to occur

19. Which of the following indications occur during a normal operational check of a pneumatic deicer system?

a. Relatively steady readings on the pressure gauge and fluctuating readings on the vacuum gauge
b. Fluctuating readings on the pressure gauge and relatively steady readings on the vacuum gauge
c. Pressure and vacuum gauges will fluctuate as the deicer boots inflate and deflate

20. What method is usually employed to control the temperature of an anti icing system using surface combustion heaters?

a. Thermo cycling switches
b. Thermostats in the cockpit
c. Heater fuel shutoff valves

21. What is the purpose of the distributor valve in a deicing system utilizing deicer boots?

a. To equalize the air pressure to the left and right wings
b. To sequence the deicer boots inflations symmetrically
c. To distribute anti‐icing fluid to the deicer boots

22. What is the purpose of the oil separator in the pneumatic deicing system?

a. To protect the deicer boots from oil deterioration
b. To remove oil from air exhausted from the deicer boots
c. To prevent an accumulation of oil in the vacuum system

23. Where are the heat sensors located on most aircraft with electrically heated windshields?

a. Imbedded in the glass
b. Attached to the glass
c. Around the glass

24. Which of the following are found in a laminated integral electrically heated windshield system?

1. Autotransformer                2. Heat control relay           3. Heat control toggle switch
4. 24V dc power supply        5. Indicating light

a. 1, 2, 4, 5
b. 2, 3, 4, 5
c. 1, 2, 3, 5

Aircraft Pneumatic Systems
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