23.Which procedure has the objective to ensure that when the engine is in service and under load, its crankshaft axis is straight, uniformly supported by bearings, and properly positioned longitudinally? (A)Dynamic balancing (B)Engine trail (C)Engine alignment (D)Measurement of crank deflection

10.Longitudinal vibration of propulsion shafting systems is often excited by the variable thrust developed by the propeller due to the non-uniform wake pattern in which it operates. The predominant periodic component of the thrust developed by a propeller occurs at blade-rate frequency, i.e., the number of propeller blades times the rotational frequency of the shaft. For a four-blade propeller running at 60 rev/min, what is the predominant periodic frequency that excites the longitudinal vibration of the propulsion shafting systems? (A)1 Hz (B)2 Hz (C)3 Hz (D)4 Hz

23.Which procedure has the objective to ensure that when the engine is in service and under load, its crankshaft axis is straight, uniformly supported by bearings, and properly positioned longitudinally?
(A)Dynamic balancing
(B)Engine trail
(C)Engine alignment
(D)Measurement of crank deflection

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