Answers - Engine Exhaust and Reverser Systems

1. b
Exhaust system parts are subjected to corrosive exhaust gases and large changes in temperature. Therefore, the metals used in these areas must be able to resist corroding and have a low expansion coefficient. One metal that possesses these properties is nickel chromium steel (stainless steel).

2. c
Spring loaded ball/flexible joints and slip joints are commonly used to correct slight misalignments, allow movement and expansion, and simplify installation. Bellows, on the other hand, allow the exhaust components to expand and contract without causing buckling.

3. c
Most light aircraft have a carburetor heat system that draws air from within the cowling and routes it through a shroud that surrounds the exhaust pipe. With this type of system, the hot exhaust gases provide a source of heat that adequately heats the intake air to prevent or remove carburetor ice.

4. c
Because of the high heat encountered in the hot section of a turbine engine, cracks frequently develop on turbine blades, stator vanes, and exhaust system components.

5. a
As an exhaust system heats up, the various system components expand. One way to allow for this expansion so adjacent components do not start buckling against each other is to use slip joints to join different components.

6. c
Metallic sodium is used in some valves because it is an excellent heat conductor. In a metallic sodium valve, the sodium melts at approximately 208 degrees Fahrenheit. When this happens, the reciprocating motion of the valve circulates the liquid sodium enabling it to carry away excess heat and reduce valve operating temperatures.

7. a
Engine manufacturers typically use brass or heat-resistant nuts to fasten exhaust system components to cylinder heads.

8. c
Although repair of exhaust system components can be accomplished, it requires special equipment and techniques that are not typically available in the field. Therefore, it is recommended that exhaust stacks, mufflers, and tailpipes be replaced with new or reconditioned components rather than being repaired.

9. a
To satisfy the minimum braking requirements after landing, a thrust reverser should be able to produce reverse thrust that is between 35 and 50 percent of the full forward thrust for which the engine is capable.

10. c
Most exhaust systems that use a heat exchanger as a source of cabin heat can be inspected visually once the heater air shroud is removed. Although X-ray inspection can detect cracks in exhaust system components, these defects are more easily and economically found by frequent and thorough visual inspection.

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