Test Your Knowledge On Engines

Check your knowledge of aircraft engines with the questions below.

A. Multiple Choice. Circle the one best answer.

1. In comparison to fuel injection systems, float-type carburetor systems are generally considered to be

(a) equally susceptible to icing as a fuel injection unit.

(b) less susceptible to icing than a fuel injection unit.

(c) susceptible to icing only when visible moisture is present.

(d) more susceptible to icing that a fuel injection unit.

2. The basic purpose of adjusting the fuel/air mixture control at altitude is to
(a) increase the fuel/air ratio for flying at altitude.

(b) decrease the fuel flow in order to compensate for decreased air density.

(c) increase the amount of fuel in the mixture to compensate for the decrease in pressure and density of the air.

(d) decrease the amount of fuel in the mixture in order to compensate for increased air density.

3. If the engine of an airplane is permitted to idle for a long period of time while on the ground,
(a) a hydraulic lock may develop in one or more cylinders.

(b) the lean mixture may cause the engine to miss or quit.

(c) the result may be an excessively high oil pressure.

(d) the spark plugs may become fouled.

4. Assume that on your run-up at an airport where the elevation is 6,000 feet MSL, you note a slight engine roughness that is not significantly affected by the magneto check but grows worse during the carburetor heat check. Under these circumstances, which of the following would be your most logical initial action?
(a) check to see that the mixture control is in the full rich position.

(b) reduce manifold pressure to control detonation.

(c) check the results obtained with a leaner setting of the mixture control.

(d) taxi back to the flight line for a maintenance check.

5. With regard to the use of aviation gasoline, which statement is true?
(a) use of a lower-than-specified grade of fuel may result in a reduced power output but is usually less harmful than higher rated fuel.

(b) use of the next higher-than-specified grade of fuel is permissible if the specified grade of fuel is not available.

(c) use of the next lower-than-specified grade of fuel is permissible if the specified grade of fuel is not available.

(d) use of a higher-than-specified grade of fuel usually results in lower-than-normal cylinder head temperatures.

6. If the grade of fuel used in an aircraft engine is lower than specified for the engine, it will most likely cause
(a) an increase in power which could overstress internal engine components.

(b) detonation.

(c) lower cylinder head temperatures.

(d) a non-uniform mixture of fuel and air in the cylinders.

7. Which statement is true regarding aircraft engines that are equipped with a fuel injection system instead of a carburetor?
(a) vapor locks during ground operations on hot days are less apt to occur with fuel injection.

(b) a disadvantage of fuel injection is the difficulty experienced in cold weather starting.

(c) slow throttle response is one of the disadvantages of fuel injection.

(d) fuel injection provides better fuel management and fuel distribution to the engine.

8. The presence of carburetor ice, in an airplane equipped with a fixed pitch propeller, can be verified by applying carburetor heat and noting
(a) a decrease in RPM and then a gradual increase in RPM.

(b) a decrease in RPM and then a constant RPM indication.

(c) an immediate increase in RPM with no further change in RPM.

(d) an increase in RPM and then a gradual decrease in RPM.

9. If the engine oil temperature and cylinder head temperature gauges have exceeded their normal operating range, you may have been
(a) operating with higher-than-normal oil pressure.

(b) using fuel that has a higher-than-specified fuel rating.

(c) operating with too much power and with the mixture set too lean.

(d) operating with the mixture set too rich.

10. What change occurs in the fuel/air mixture when carburetor heat is applied?
(a) the fuel/air mixture becomes leaner.

(b) the fuel/air mixture becomes richer.

(c) no change occurs in the fuel/air mixture.

(d) a decrease in RPM results from the lean mixture.

11. For maximum engine life and trouble-free operation, engine break-in during the first 25 to 50 hours of engine operation should be accomplished by
(a) limiting takeoff power to five minutes per flight and using 65% power maximum for cruise.

(b) running the engine continuously at 65% to 75% power with full power or maximum power available for climb.

(c) using less than 100% power for takeoff and cruising at 75% power or below.

(d) running the engine at 1200 RPM for at least twenty minutes before the first take off of the day.

12. The full flow oil filter is very useful in keeping an engine clean, but it will not filter out
(a) water

(b) acids

(c) lead sludge

(d) all of the above

13. For aircraft with an EGT gage, a good "rule of thumb" for most general aviation engines at cruise is to lean to
(a) 50o on lean side of peak EGT.

(b) Peak EGT.

(c) 50o on rich side of peak EGT.

(d) 100o on rich side of peak EGT.

14. With high relative humidity carburetor icing may be expected within which of the following ranges?
(a) 32o to 59o F

(b) 0o to 15o F

(c) 20o to 90o F

(d) 0o to 59o F

15. An aircraft engine which develops less and less power from the point of takeoff to the service ceiling is said to be
(a) supercharged

(b) normally aspirated

(c) turbocharged

(d) super critical

16. If full carburetor heat is used during cruise for the prevention of carburetor ice, some of the 15% of power loss incurred may be regained by
(a) enriching the mixture.

(b) squaring the power setting.

(c) applying one pump of the primer every 15 minutes.

(d) leaning the mixture.

17. The final authority regarding operation of the general aviation aircraft engine is
(a) engine operator’s manual provided by the engine manufacturer.

(b) Pilot’s Operating Handbook provided by the airframe manufacturer.

(c) aviation circulars distributed by the FAA.

(d) your local fixed base operator.

18. Use of partial heat to prevent carburetor icing is recommended only if the aircraft has
(a) a carburetor air temperature gage - CAT.

(b) a cylinder head temperature gage - CHT.

(c) an exhaust gas temperature gage - EGT.

(d) an outside air temperature gage - OAT.

B. Supply the best answer to the following essay questions:

1. Explain why aerobatics or inverted flight should not be attempted unless the engine has been modified for this type flying.

2. List two purposes of engine oil.

3. What are the two FAA approved oils for general aviation?

4. When operating at the manufacturers’ recommended cruise power, at what altitudes may leaning be accomplished?

5. Of what significance is the 5,000 foot density altitude reference point for normally aspirated engines?

6. What causes engine roughness when leaning an engine using a float-type carburetor at recommended cruise power?

7. The Exhaust Gas Temperature (EGT) system is more precise as a fuel management instrument with which of the following?

(a) Float-type carburetor.

(b) Fuel injection.

8. How can damage to an engine take place as a result of leaning?

9. What important consideration by the pilot for his engine must take place with a normally aspirated engine at airports where the density altitude is 5,000 feet or higher?

10. List two types of induction ice.



1. d 7. d 13. c

2. b 8. a 14. c

3. d 9. c 15. b

4. c 10. b 16. d

5. b 11. b 17. b

6. b 12. d 18. a


1. Loss of engine oil out the breather can cause engine damage or failure.

2. (a) Lubricate moving parts.

(b) Aid internal cooling of the engine.

3. (a) Straight mineral.

(b) Ashless Dispersant.

4. At any altitude.

5. It is a climb reference point for normally aspirated powerplants. Climb from sea level through 5,000 feet (some Cessna’s may use 3,000 feet) should be full rich. Continued climb beyond (3,000 feet) 5,000 feet should use some leaning to improve engine efficiency.

6. The roughness is not detonation at recommended cruise power. The leanest cylinder in the less than perfect distribution pattern is cutting out. Operation in the roughness area is not acceptable.

7. (b) Fuel injection.

8. Damage to an engine from leaning takes place at higher than recommended cruise power as detonation where an aircraft does not have the necessary engine instruments to indicate the powerplant is being abused.

9. Requires proper leaning for safest, efficient performance at takeoff.

10. Two types of induction ice:

(a) Impact ice - typically on the air filter.

(b) Refrigeration ice - forms in the float-type carburetor.