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Military

AL0993 Practice Exercise Answer Key & Review
Lesson 6: Lycoming T55

True - False
  1.   The power turbine extracts velocity energy from the hot gases and transmits mechanical power to the output shaft.

  True
  2.   In figure 5.5, station No. 4 is located from the beginning of the centrifugal compressor to the air diffuser.

  False
  3.   A 3.75-gallon oil tank is contained in the inner housing of the inlet housing assembly.

  True
  4.   The L-11 model has a two-stage gas producing turbine.

  True
  5.   The right and left sides of the engine are determined by looking at the engine from the front.

  False

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

FIRST GROUP
The T55-L-11 engine fuel system includes:
  6.   Fourteen vaporizing tubes instead of 28 dual atomizing nozzles.

  False
  7.   A fuel control unit is made up of the flow control and computer sections.

  True
  8.   Actuation of the compressor bleed band by the fuel control section.

  False
  9.   A cooler that uses fuel to cool engine oil.

  True
10.   Main and start fuel manifolds at the rear of the combustion chamber assembly.

  True
SECOND GROUP
Which of the following statements about the sections of the T55-L-11 are True and which False?
11.   The compressor has a seven-stage axial compressor.

  True
12.   The divergent shape of the diffuser decreases air pressure and increases velocity.

  False
13.   The struts between the inner and outer air inlet housing are hollow, with passages for oil and accessory drive shafts.

  True
14.   The combustor has 14 fuel nozzles in each one of its two main fuel manifolds.

  True
15.   A variable inlet guide vane assembly is mounted in the front of the compressor housing.

  True
THIRD GROUP
The following statements are about various systems in the T55-L-11 engine. Evaluate them by marking them True or False.
16.   The anti-icing system for the variable inlet guide vanes uses hot scavenge oil.

  False
17.   Bearing seals are pressurized by some of the cooling air.

  True
18.   The purpose of an interstage air bleed system is to avoid compressor stalls and to increase compressor rotor acceleration.

  True
19.   The control system for the variable inlet guide vanes schedules their positions according to gas producer speed and compressor inlet temperature.

  True
20.   Several passages throughout the engine receive air from the main airflow to cool components.

  True
21.   The torquemeter system gives a reading in the cockpit of percent of torque.

  True
FOURTH GROUP
The lubrication system in the T55 engine has the following characteristics.
22.   All oil filters can be changed at intermediate level maintenance.

  False
23.   The low-level warning switch in the cockpit signals when a 2-hour supply of usable oil remains.

  True
24.   After oil leaves the main oil pump, it goes through a filter in the accessory gearbox.

  True
25.   Chip detectors activate caution lights in the cockpit.

  True
26.   The main oil pump is used entirely to maintain pressure in the oil system.

  False
27.   The entire lubrication system is contained in the engine.

  True
FIFTH GROUP
Which of the following statements describe the T55 gas turbine engine?
28.   The accessory drive section is part of the annular flow path.

  False
29.   The speed of the power output shaft is the same as that of the power turbine.

  True
30.   The airflow is reversed twice in the combustor section.

  True
31.   In the combustor, the curl assembly reverses the airflow direction for the first time.

  False
32.   The swirl cups in the combustor contain dual-orifice, fuel-atomizing nozzles.

  True
33.   The T55 engine has six sections.

  True
SIXTH GROUP
In comparing the different models of the T55, you find that:
34.   The normal shp for the L-11 is the same as the military shp for the L-7C.

  False
35.   The L-7's all have 28 dual-orifice fuel spray nozzles.

  False
36.   The L-7B has the most accurate electric torquemeter.

  False
37.   The L-11 model has a two-stage GP turbine.

  True
38.   All models of the T55 have the same shaft horsepower.

  False
39.   The CH-47C cannot use the T55-L-11 engine.

  False
Matching

Match the specifications in column I with the model to which they apply in column II by writing the proper letter by each question. Each item in column II may be used once, more than once, or not at all.
40.   Power outlet 1,500 rpm..
  A.  T55-L-7.
41.   3,750 shp.
  C.  T55-L-11 .
42.   590 lb.
  B.  T55L-7C.
43.   Two-stage PT turbine.
  D.  All models.
44.   14 vaporizing tubes in combustor.
  A.  T55-L-7.
45.   Weight of 670 pounds.
  C.  T55-L-11 .
46.   Automatic and manual fuel control.
  D.  All models.

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Lesson 7
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