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AL0993 Practice Exercise Answer Key & Review
Lesson 2: Major Engine Sections

True - False
  1.   Helicopter turboshaft engines develop thrust in their exhaust ducts.

  False
  2.   In an engine destination, a three-digit dash number means that the engine was procured after the new Army procurement system went into effect.

  True
  3.   Engine idling is one of the two most severe operating periods for combustion chambers.

  True
  4.   An axial-centrifugal-flow compressor is made up of two sets of axial-flow compressors and one centrifugal-flow compressor.

  False
  5.   When a number is placed after N, as is N2, it refers to a specific system in the gas turbine engine.

  True

Cluster True - False
(Each of the following groups of questions is related to the statement that precedes them.

FIRST GROUP
About the three basic compressors used in gas turbine engines, your text tells you that:
  6.   An axial-flow compressor is less susceptible to foreign-object damage than a centrifugal-flow one.

  False
  7.   Dual compressors are mounted on the same shaft and turn at the same speed.

  True
  8.   The centrifugal impeller in the axial-centrifugal-flow compressor decreases the air velocity.

  False
  9.   A centrifugal-flow compressor is made up of two rotors and a compressor manifold.

  False
10.   A series of alternating rotor and stator vane stages makes up the axial-flow compressor.

  True
SECOND GROUP
The turbine section of a gas turbine engine transforms energy into shaft horsepower. Which of these five statements are True and which are False about the different types of turbines?
11.   Axial-flow turbines are less expensive and easier to manufacture than radial-flow turbines.

  False
12.   A single-rotor turbine has its power developed by one rotor.

  True
13.   All gas-turbine-power aircraft in the Army today use the axial-flow turbine.

  True
14.   Axial-flow turbines are invariably the single-rotor type.

  False
15.   A single-rotor turbine is used where low weight and compactness are necessary.

  True
THIRD GROUP
The next six questions about compressor construction tell you that:
16.   A centrifugal-flow compressor is made of either heat-treated forged aluminum or of cast aluminum.

  False
17.   All manufacturers use the split compressor case for easier inspection.

  False
18.   Shrouds are used on stator vanes to provide an air seal between rotating and stationary parts.

  True
19.   In an axial-flow compressor, blades fit tightly in the turbine disk to reduce vibrational stress.

  False
20.   In both the axial- and centrifugal-flow compressors, the fit between the compressor and its case is important.

  True
21.   In a centrifugal-flow compressor, the rotor may be balanced by using balancing weights in the hub of the compressor.

  True
FOURTH GROUP
Evaluate the following five statements about engine model designations by selecting True or False.
22.   Each engine model designation begins with a letter or two letters.

  True
23.   The letters TP at the beginning of the designation identify a turboprop engine.

  False
24.   Even when a production model is changed, the dash number remains the same.

  False
25.   The letter or set of letters following the assigned model number identifies the manufacturer.

  True
26.   The Air Force always uses even numbers, both for the assigned number and the dash number.

  False
FIFTH GROUP
Which of the following five questions are True and which False about the compressor section of a gas turbine engine?
27.   Compressor efficiency determines the power necessary to create the pressure for a given airflow and affects the temperature in the combustion chamber.

  True
28.   The highest total air velocity is at the inlet of the combustion section.

  False
29.   The highest static pressure is at the inlet of the diffuser.

  False
30.   The volume of air pumped by the compressor is proportional to the rpm of the rotor.

  True
31.   The compressor is made up of alternating rotating and stationary vane assemblies.

  True
SIXTH GROUP
About turbine construction, your text tells you that:
32.   A turbine rotor operates at high temperatures, at high speeds.

  True
33.   A fir tree design is used in attaching the blades to the disk.

  True
34.   A moment weight number is stamped on each rotor blade to preserve rotor balance when they are replaced.

  True
35.   The fir tree blade design eliminates any need for rivets or other locking devices.

  False
36.   Shrouding is used in turbines subject to the highest temperatures and highest speeds.

  False
Matching

In questions 37 through 41, match the statements in column I with the laws or principles of physics in column II by selecting the proper letter under each question. Each item in column II may be used once, more than once, or not at all.
37.   Engine rotational speed.
  E.  N.
38.   Location of the combustor drain valve.
  B.  Bottom.
39.   Second rotating mass speed.
  D.  N2.
40.   180° from the combustor drain valve.
  A.  Top.
41.   First rotating mass speed.
  C.  N1.

Multiple Choice

(Each question in this group contains one and only one correct answer. Make your choices by selecting the proper letter for each question in the lesson.)
42.   Which of these is the most commonly used in Army aircraft?

  A. Annular reverse-flow combustion chamber.
43.   Which of these is not part of a combustion chamber?

  B. Stator vanes.
44.   Which statement is True of the air and fuel in a combustor?

  C. A ratio of 15 parts of air to 1 part of fuel by weight is the correct mixture.
45.   Which of these is True of the annular combustion chamber?

  D. Combustion takes place in a space between the combustor liner and the turbine shaft.

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Lesson 3
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