Answers - Propellers (Part 2)

61. a
Dye-penetrant inspection is normally used to detect cracks or other defects that are open to the surface.

62. c
Mechanical stops in the propeller hub limit the constant-speed range of a constant-speed propeller.

63. c
To allow an engine to develop its rated takeoff power, a constant-speed propeller is normally set in the low pitch, high rpm position. This places the lightest load on the engine, allowing it to develop maximum power.

64. b
The high and low pitch stops of Hamilton Standard propellers are located in the counterweight assembly. However, in some of the more modern constant-speed propeller assemblies, the pitch stops are located in the dome assembly.

65. a
The two-position and the constant-speed counterweight propellers both use hydraulic force to decrease blade angle and centrifugal force acting on counterweights to increase blade angle. The major difference between the two is that the constant-speed propeller utilizes a governor to boost the oil pressure to a higher level and automatically control the oil flow to and from the propeller, while the two-position propeller operates at engine lubrication system pressure with the oil flow controlled by a manual selector valve.

66. a
Propellers are subject to aerodynamic vibrations when the blade tips travel at near sonic speeds. In addition, mechanical vibrations are transmitted from the engine to the propeller. At certain combinations of airspeed and engine rpm these vibrations can create harmonic stresses that could lead to metal fatigue and eventual propeller blade failure. Therefore, the Type Certificate Data Sheets for engine/propeller combinations identify any critical rpm ranges that are to be avoided to prevent severe vibration. Regulations require that these ranges be marked on the tachometer with a red arc.

67. b
Oversize or elongated bolt holes on a wooden propeller are typically cause for rejection. However, some oversize or worn bolt holes may be repaired by the use of metal inserts to restore the original diameter. This is a major repair and must be performed by a certificated repair station.

68. a
Beta range refers to a reversing-type propeller that can operate in a zero or negative thrust range. During operation in beta range, propeller governor operation is locked out and all propeller control is accomplished with the power lever.

69. c
A blade cuff is a metal, wood, or plastic structure that is attaches to the shank of a propeller blade. The cuff surface transforms the round shank into an airfoil section and is designed primarily to increase the flow of cooling air to the engine nacelle.

70. a
A three-way propeller valve is a selector valve used in a two-position propeller control system. The three-way valve directs oil from the engine lubrication system to the propeller to control a propeller blade's pitch angle.

Answers for questions 71 to 116
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