Final answer:
Aircraft Engine Compression A hissing sound at the exhaust stacks during manual turning of an aircraft engine is indicative of a loss of compression caused by improper sealing in the combustion chamber.
Step-by-step explanation:
A hissing sound heard at the exhaust stacks when an aircraft engine is being manually turned often indicates a loss of compression. A hissing sound at the exhaust stacks during manual turning of an aircraft engine is indicative of a loss of compression caused by improper sealing in the combustion chamber.
This hissing sound can be due to air escaping from the combustion chamber because the valves, piston rings, or cylinder walls are not sealing properly.
While other issues like fuel leakage, overheating, and exhaust system damage can also affect an aircraft engine, they typically present with different symptoms.
For example, heat from cooking or the metal of an engine during gasoline combustion is lost into the surroundings as unused energy and is mostly converted into heat, according to the principle of energy conservation.