Emergency Procedures, Emergency Equipment, and Survival Gear 5
PA.IX.C.K1 Partial or complete power loss related to the specific powerplant, including: PA.IX.C.K1a Engine roughness or overheat PA.IX.C.K1b Carburetor or induction icing PA.IX.C.K1c Loss of oil pressure PA.IX.C.K1d d. Fuel starvation
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1. During preflight in cold weather, crankcase breather lines should receive special attention because they are susceptible to being clogged by
Answer (C) is correct. (FAA-P-8740-24) Frozen crankcase breather lines prevent oil from circulating adequately in the engine and may even result in broken oil lines or oil being pumped out of the crankcase. Accordingly, you must always visually inspect to make sure that the crankcase breather lines are free of ice. The ice may have formed as a result of the crankcase vapors freezing in the lines after the engine has been turned off.
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2. What change occurs in the fuel/air mixture when carburetor heat is applied?
Answer (C) is correct. (FAA-H-8083-25B Chap 7) When carburetor heat is applied, hot air is introduced into the carburetor. Hot air is less dense than cold air; therefore, the decrease in air density with a constant amount of fuel makes a richer mixture.
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3. Applying carburetor heat will
Answer (C) is correct. (FAA-H-8083-25B Chap 7) Applying carburetor heat will enrich the fuel/air mixture. Warm air is less dense than cold air, hence the application of heat increases the fuel-to-air ratio.
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4. Generally speaking, the use of carburetor heat tends to
Answer (B) is correct. (FAA-H-8083-25B Chap 7) Use of carburetor heat tends to decrease the engine performance and also to increase the operating temperature. Warmer air is less dense, and engine performance decreases with density. Thus, carburetor heat should not be used when full power is required (as during takeoff) or during normal engine operation except as a check for the presence or removal of carburetor ice.
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5. The presence of carburetor ice in an aircraft equipped with a fixed-pitch propeller can be verified by applying carburetor heat and noting
Answer (A) is correct. (FAA-H-8083-25B Chap 7) The presence of carburetor ice in an airplane equipped with a fixed-pitch propeller can be verified by applying carburetor heat and noting a decrease in RPM and then a gradual increase. The decrease in RPM as heat is applied is caused by less dense hot air entering the engine and reducing power output. Also, if ice is present, melting water entering the engine may also cause a loss in performance. As the carburetor ice melts, however, the RPM gradually increases until it stabilizes when the ice is completely removed.
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6. The operating principle of float-type carburetors is based on the
Answer (B) is correct. (FAA-H-8083-25B Chap 7) In a float-type carburetor, air flows into the carburetor and through a venturi tube (a narrow throat in the carburetor). As the air flows more rapidly through the venturi, a low pressure area is created that draws the fuel from a main fuel jet located at the throat of the carburetor and into the airstream, where it is mixed with flowing air. It is called a float-type carburetor in that a ready supply of gasoline is kept in the float bowl by a float, which activates a fuel inlet valve.
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7. If an aircraft is equipped with a fixed-pitch propeller and a float-type carburetor, the first indication of carburetor ice would most likely be
Answer (B) is correct. (FAA-H-8083-25B Chap 7) In an airplane equipped with a fixed-pitch propeller and float-type carburetor, the first indication of carburetor ice would be a loss in RPM.
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8. If an aircraft is equipped with a fixed-pitch propeller and a float-type carburetor, the first indication of carburetor ice would most likely be
Answer (C) is correct. (FAA-H-8083-25B Chap 7) In an airplane equipped with a fixed-pitch propeller and float-type carburetor, the first indication of carburetor ice would be a decrease in RPM.
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9. The possibility of carburetor icing exists even when the ambient air temperature is as
Answer (C) is correct. (FAA-H-8083-25B Chap 7) The most favorable condition for carburetor icing is when the temperature is between 20°F and 70°F. Due to the sudden cooling that takes place in the carburetor, icing can occur even with temperatures as high as 100°F and humidity as low as 50%. During low or closed throttle settings, an engine is particularly susceptible to carburetor icing.
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10. Which condition is most favorable to the development of carburetor icing?
Answer (A) is correct. (FAA-H-8083-25B Chap 7) The most favorable condition for carburetor icing is when the temperature is between 20°F and 70°F. Due to the sudden cooling that takes place in the carburetor, icing can occur even with temperatures as high as 100°F and humidity as low as 50%. During low or closed throttle settings, an engine is particularly susceptible to carburetor icing.
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11. With regard to carburetor ice, float-type carburetor systems in comparison to fuel injection systems are generally considered to be
Answer (C) is correct. (FAA-H-8083-25B Chap 7) Float-type carburetor systems are generally more susceptible to icing than fuel-injected engines due to the cooling effect resulting from fuel vaporization and a decrease in air pressure at the venturi in a carburetor. When there is high humidity and the temperature is between 20°F and 70°F, there is a high potential for carburetor icing, particularly at low power settings.
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12. Which would most likely cause the cylinder head temperature and engine oil temperature gauges to exceed their normal operating ranges?
Answer (A) is correct. (FAA-H-8083-25B Chap 7) Use of fuel with lower-than-specified fuel ratings, e.g., 80 octane instead of 100, can cause many problems, including higher operating temperatures, detonation, etc.
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13. The uncontrolled firing of the fuel/air charge in advance of normal spark ignition is known as
Answer (A) is correct. (FAA-H-8083-25B Chap 7) Pre-ignition is the ignition of the fuel prior to normal ignition or ignition before the electrical arcing occurs at the spark plug. Pre-ignition may be caused by excessively hot exhaust valves, carbon particles, or spark plugs and electrodes heated to an incandescent, or glowing, state. These hot spots are usually caused by high temperatures encountered during detonation. A significant difference between pre-ignition and detonation is that, if the conditions for detonation exist in one cylinder, they usually exist in all cylinders, but pre-ignition often takes place in only one or two cylinders.
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14. If the grade of fuel used in an aircraft engine is lower than specified for the engine, it will most likely cause
Answer (C) is correct. (FAA-H-8083-25B Chap 7) If the grade of fuel used in an airplane engine is lower than specified for the engine, it will probably cause detonation. Lower grades of fuel ignite at lower temperatures. A higher temperature engine (which should use a higher grade of fuel) may cause lower grade fuel to explode (detonate) rather than burn evenly.
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15. If a pilot suspects that the engine (with a fixed-pitch propeller) is detonating during climb-out after takeoff, the initial corrective action to take would be to
Answer (C) is correct. (FAA-H-8083-25B Chap 7) If you suspect engine detonation during climb-out after takeoff, you would normally decrease the pitch to increase airspeed (more cooling) and decrease the load on the engine. Detonation is usually caused by a poor grade of fuel or an excessive engine temperature.
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16. Detonation may occur at high-power settings when
Answer (B) is correct. (FAA-H-8083-25B Chap 7) Detonation occurs when the fuel/air mixture in the cylinders explodes instead of burning progressively and evenly. This more rapid force slams the piston down instead of pushing it.
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17. Detonation occurs in a reciprocating aircraft engine when
Answer (C) is correct. (FAA-H-8083-25B Chap 7) Detonation occurs when the fuel/air mixture in the cylinders explodes instead of burning normally. This more rapid force slams the piston down instead of pushing it.
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18. During the run-up at a high-elevation airport, a pilot notes a slight engine roughness that is not affected by the magneto check but grows worse during the carburetor heat check. Under these circumstances, what would be the most logical initial action?
Answer (A) is correct. (FAA-H-8083-25B Chap 7) If, during a run-up at a high-elevation airport, you notice a slight roughness that is not affected by a magneto check but grows worse during the carburetor heat check, you should check the results obtained with a leaner setting of the mixture control. At a high-elevation field, the air is less dense and the application of carburetor heat increases the already too rich fuel-to-air mixture. By leaning the mixture during the run-up, the condition should improve.
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