Fill in the Blanks
1. Jet propulsion is a practical application of Newton's ____________ law of motion.
2. Both turboprop and turboshaft engines must use a ____________ between the engine and the propellers/rotors.
3. Engines that use a separate turbine that is not mechanically connected to a compressor to drive a propeller are called ____________ engines.
4. With modern high bypass engines, most of the engine’s thrust is produced by the ____________ rather than from the ____________ exhaust ____________ .
5. When subsonic air passes through a section of a duct that has a divergent shape, its velocity will
____________ .
6. Supersonic aircraft typically utilize a ____________ - ____________ inlet duct.
7. More than ________________ stages of compression is not practical using a centrifugal compressor.
8. Compressor blades which have a reduced thickness at the tips are called ____________ tips.
9. __________________ vane segments may be used to minimize vibration.
10. Compressor stalls may cause the air flowing in the compressor to ____________ or stagnate. In some cases the air may reverse direction.
11. To take advantage of the good points of both the centrifugal flow and axial flow compressors, some engines may use a ____________ compressor.
12.The section of a turbine engine directly behind the compressor is known as the ____________ .
13. As primary air flow enters a combustor, it passes through a set of ____________ , which give the air a radial motion.
14. Approximately _____________ (what percentage) of the total pressure energy from the exhaust gasses is absorbed by the turbine section is used to turn the compressor and drive the accessories.
15. The most common method of attaching turbine blades to the disk is the ____________ method.
TRUE or FALSE
1. The first flight by a jet propelled aircraft took place in 1939. True/False
2. A gas turbine engine that delivers power through a shaft to operate something other than a propeller is referred to as a turboprop engine. True/False
3. A high bypass ratio turbofan engine has a bypass ratio of 4 to 1 or greater. True/False
4. Bypass ratios of 30:1 are obtainable by what is called an Ultra High Bypass (UHB) engine. True/False
5. The inlet duct of a turbine engine is normally considered to be a part of the powerplant. True/False
6. Subsonic inlet ducts are usually of a fixed geometry and converging in shape. True/False
7. Modern centrifugal compressors can obtain a compression ratio as high as 15:1. True/False
8. Axial flow compressors have a pressure rise per stage of approximately 12.5 :1. True/False
9. The rotating elements of an axial flow compressor are referred to as vanes. True/False
10. On a multi-spool engine, the low-pressure compressor (N1) will slow down with an increase in altitude. True/False
11. High temperature, high pressure air taken from the compressor for various purposes is known as bleed air. True/False
12. The pressure in the diffuser section of a gas turbine engine is the highest of any section in the engine. True/False
13. Annular compressors which reverse the direction of the airflow are reverse-flow combustors. True/False
14. When turbine blades are installed on a turbine disk, the unit is known as a turbine wheel. True/False
15. The jet nozzle imparts a final increase in the velocity to the gases. True/False
Knowledge Application Questions
1. What are the four types of gas turbine engines are used?
__________________________________________________________________
2. Turbofans are generally divided into what three classifications?
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3. What is the primary function of the compressor section of a gas-turbine engine?
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4. What are the two basic types of compressors used on turbine engines?
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5. What are the three main components of a centrifugal compressor?
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6. What are the main elements of an axial flow compressor?
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7. Multi-spool axial flow compressors have the advantages of:
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8. What two factors determine the angle of attack of a compressor blade?
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9. Design factors which contribute to the prevention of compressor stalls include:
__________________________________________________________________
10. Some current applications of bleed air are:
__________________________________________________________________
Multiple Choices Questions
1. At what point in an axial-flow turbojet engine will the highest gas pressures occur?
a. At the turbine entrance.
b. Within the burner section.
c. At the compressor outlet.
2. One function of the nozzle diaphragm in a turbine engine is to?
a. Decrease the velocity of exhaust gases.
b. Center the fuel spray in the combustion chamber.
c. Direct the flow of gases to strike the turbine blades at a desired angle.
3. What is the profile of a turbine engine compressor blade?
a. The leading edge of the blade.
b. A cutout that reduces blade tip thickness.
c. The curvature of the blade root.
4. The fan rotational speed of a dual axial compressor forward fan engine is the same as the
a. low-pressure compressor.
b. forward turbine wheel.
c. high-pressure compressor.
5. The abbreviation "P" with subscript t7 used in turbine engine terminology means
a. the total inlet pressure.
b. pressure and temperature at station No.7
c. the total pressure at station No.7.
6. The blending of blades and vanes in a turbine engine
a. is usually accomplished only at engine overhaul.
b. should be performed parallel to the length of the blade using smooth contours to minimize stress points.
c. may sometimes be accomplished with the engine installed, ordinarily using power tools.
7. What turbine engine section provides for proper mixing of the fuel and air?
a. Combustion section.
b. Compressor section.
c. Diffuser section.
8. In a gas turbine engine, combustion occurs at a constant
a. volume.
b. pressure.
c. density.
9. Which statement is true regarding jet engines?
a. At the lower engine speeds, thrust increases rapidly with small increases in RPM.
b. At the higher engine speeds, thrust increases rapidly with small increases in RPM.
c. The thrust delivered per pound of air consumed is less at high altitude than at low altitude.
10. Some high-volume turboprop and turbojet engines are equipped with two-spool or split compressors. When these engines are operated at high altitudes, the
a. low-pressure rotor will increase in speed as the compressor load decreases in the lower density air.
b. throttle must be retarded to prevent overspeeding of the high-pressure rotor due to the lower density air.
c. low-pressure rotor will decrease in speed as the compressor load decreases in the lower density air.
11. Turbine nozzle diaphragms located on the upstream side of each turbine wheel are used in the gas turbine engine to
a. decrease the velocity of the heated gases flowing past this point.
b. direct the flow of gases parallel to the vertical line of the turbine blades.
c. increase the velocity of the heated gases flowing past this point.
12. Where is the highest gas pressure in a turbojet engine?
a. At the outlet of the tailpipe section.
b. At the entrance of the turbine section.
c. In the entrance of the burner section.
13. An exhaust cone placed aft of the turbine in a jet engine will cause the pressure in the first part of the exhaust duct to
a. increase and the velocity to decrease.
b. increase and the velocity to increase.
c. decrease and the velocity to increase.
14. What is the function of the stator vane assembly at the discharge end of a typical axial-flow compressor?
a. To straighten airflow to eliminate turbulence.
b. To direct the flow of gases into the combustion chambers.
c. To increase air swirling motion into the combustion chambers.
15. The turbine section of a jet engine
a. increases air velocity to generate thrust forces.
b. utilizes heat energy to expand and accelerate the incoming gas flow.
c. drives the compressor section.
16. When starting a turbine engine,
a. a hot start is indicated if the exhaust gas temperature exceeds specified limits.
b. an excessively lean mixture is likely to cause a hot start.
c. release the starter switch as soon as indication of light-off occurs.
17. In the dual axial-flow or twin spool compressor system, the first stage turbine drives the
a. N1 and N2 compressors.
b. N2 compressor.
c. N1 compressor.
18. During inspection, turbine engine components exposed to high temperatures may only be marked with such materials as allowed by the manufacturer. These materials generally include
- layout dye.
- commercial felt tip marker.
- wax or grease pencil.
- chalk.
- graphite lead pencil.
b. 1, 3 and 4.
c. 2, 4 and 5.
19. When starting a turbine engine, a hung start is indicated if the engine
a. exhaust gas temperature exceeds specified limits.
b. fails to reach idle RPM.
c. RPM exceeds specified operating speed.
20. What are the two basic elements of the turbine section in a turbine engine?
a. Impeller and diffuser.
b. Hot and cold.
c. Stator and rotor.
21. The function of the exhaust cone assembly of a turbine engine is to
a. collect the exhaust gases and act as a noise suppressor.
b. swirl and collect the exhaust gases into a single exhaust jet.
c. straighten and collect the exhaust gases into a solid exhaust jet.
22. What are the two functional elements in a centrifugal compressor?
a. Turbine and compressor.
b. Bucket and expander.
c. Impeller and diffuser.
23. What must be done after the fuel control unit has been replaced on an aircraft gas turbine engine?
a. Perform a full power engine run to check fuel flow.
b. Recalibrate the fuel nozzles.
c. Retrim the engine.
24. If, during inspection at engine overhaul, ball or roller bearings are found to have magnetism but otherwise have no defects, they
a. cannot be used again.
b. are in an acceptable service condition.
c. must be degaussed before use.
25. A turbine engine compressor which contains vanes on both sides of the impeller is a
a. double entry centrifugal compressor.
b. double entry axial-flow compressor.
c. single entry axial-flow compressor.
26. What is the first engine instrument indication of a successful start of a turbine engine?
a. A rise in the engine fuel flow.
b. A rise in oil pressure.
c. A rise in the exhaust gas temperature.
27. Some engine manufacturers of twin spool gas turbine engines identify turbine discharge pressure in their maintenance manuals as
a. Pt7
b. Pt2
c. Tt7
28. Who establishes the recommended operating time between overhauls (TBO) of a turbine engine used in general aviation?
a. The engine manufacturer.
b. The operator (utilizing manufacturer data and trend analysis) working in conjunction with the FAA.
c. The FAA.
29. The basic gas turbine engine is divided into two main sections: the cold section and the hot section.
(1) The cold section includes the engine inlet, compressor, and turbine sections.
(2) The hot section includes the combustor, diffuser, and exhaust sections.
Regarding the above statements,
a. only No. 1 is true.
b. only No. 2 is true.
c. neither No. 1 nor No. 2 is true.
30. (1) Welding and straightening of turbine engine rotating airfoils does not require special equipment.
(2) Welding and straightening of turbine engine rotating airfoils is commonly recommended by the manufacturer.
Regarding the above statements,
a. only No. 1 is true.
b. only No. 2 is true.
c. neither No. 1 nor No. 2 is true.
31. Turbine engine components exposed to high temperatures generally may NOT be marked with
- layout dye.
- commercial felt tip marker.
- wax or grease pencil.
- chalk.
- graphite lead pencil.
b. 3 and 5.
c. 4 and 5.
32. Who establishes mandatory replacement times for critical components of turbine engines?
a. The FAA.
b. The operator working in conjunction with the FAA.
c. The engine manufacturer.
33. Main bearing oil seals used with turbine engines are usually what type(s)?
a. Labyrinth and/or carbon rubbing.
b. Teflon and synthetic rubber.
c. Labyrinth and/or silicone rubber.
34. How does a dual axial-flow compressor improve the efficiency of a turbojet engine?
a. More turbine wheels can be used.
b. Higher compression ratios can be obtained.
c. The velocity of the air entering the combustion chamber is increased.
35. Three types of turbine blades are
a. reaction, converging, and diverging.
b. impulse, reaction, and impulse-reaction.
c. impulse, vector, and impulse-vector.
36. Which statements are true regarding aircraft engine propulsion?
1. An engine driven propeller imparts a relatively small amount of acceleration to a large mass of air.
2. Turbojet and turbofan engines impart a relatively large amount of acceleration to a smaller mass of air.
3. In modern turboprop engines, nearly 50 percent of the exhaust gas energy is extracted by turbines to drive the propeller and compressor with the rest providing exhaust thrust.
a. 1, 2, 3.
b. 1, 2.
c. 1, 3.
37. An advantage of the axial-flow compressor is its
a. low starting power requirements.
b. low weight.
c. high peak efficiency.
38. What is one purpose of the stator blades in the compressor section of a turbine engine?
a. Stabilize the pressure of the airflow.
b. Control the direction of the airflow.
c. Increase the velocity of the airflow.
39. What is the purpose of the diffuser section in a turbine engine?
a. To increase pressure and reduce velocity.
b. To convert pressure to velocity.
c. To reduce pressure and increase velocity.
40. Where do stress rupture cracks usually appear on turbine blades?
a. Across the blade root, parallel to the fir tree.
b. Along the leading edge, parallel to the edge.
c. Across the leading or trailing edge at a right angle to the edge length.
41. In which type of turbine engine combustion chamber is the case and liner removed and installed as one unit during routine maintenance?
a. Can.
b. Can annular.
c. Annular.
42. The diffuser section of a jet engine is located between
a. the burner section and the turbine section.
b. station No.7 and station No.8.
c. the compressor section and the burner section.
43. When the leading edge of a first-stage turbine blade is found to have stress rupture cracks, which of the following should be suspected?
a. Faulty cooling shield.
b. Overtemperature condition.
c. Overspeed condition.
44. Turbine blades are generally more susceptible to operating damage than compressor blades because of
a. higher centrifugal loading.
b. exposure to high temperatures.
c. high pressure and high velocity gas flow.
45. Which of the following is the ultimate limiting factor of turbine engine operation?
a. Compressor inlet air temperature.
b. Turbine inlet temperature.
c. Burner-can pressure.
46. The recurrent ingestion of dust or other fine airborne particulates into a turbine engine can result in
a. foreign object damage to the compressor section.
b. the need for less frequent abrasive grit cleaning of the engine.
c. erosion damage to the compressor and turbine sections.
47. Which of the following engine variables is the most critical during turbine engine operation?
a. Compressor inlet air temperature.
b. Compressor RPM.
c. Turbine inlet temperature.
48. Reduced blade vibration and improved airflow characteristics in gas turbines are brought about by
a. fir-tree blade attachment.
b. impulse type blades.
c. shrouded turbine rotor blades.
49. Which turbine engine compressor offers the greatest advantages for both starting flexibility and improved high-altitude performance?
a. Dual-stage, centrifugal-flow.
b. Split-spool, axial-flow.
c. Single-spool, axial-flow.
50. Jet engine turbine blades removed for detailed inspection must be reinstalled in
a. a specified slot 180' away.
b. a specified slot 90' away in the direction of rotation.
c. the same slot
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