Final answer:
Signs of a mechanical issue in a machine or engine include unexpected changes in rpm (either increase or decrease) as well as unusual noises like a loud bang or pop, which require a professional diagnosis to pinpoint the exact problem.
Step-by-step explanation:
This category includes engine/power loss issues, landing gear functionality, loss of critical flight controls, and non-engine system/component failure. Includes failures or malfunctions of any of the following: propellers, rotors, propeller/main rotor drive train, reversers, and powerplant controls.
Potential signs of a mechanical issue in a machine or engine can vary, but there are common indicators to look out for. An increase in rpm or a decrease in rpm can signal an issue, especially if these changes are unexpected or out of the norm for the machine's standard operation.
A Loud bang or a pop sound can also be a clear sign that something within the machine has failed or is not functioning correctly. These noises can be a result of a variety of problems, such as a backfire in an engine, the snapping of a belt, or the breaking of a mechanical component.