Final answer:
If any engine is left running on an aircraft, there will be an imbalance in thrust and potential control issues.
Step-by-step explanation:
In regards to an aircraft's engine(s), if any engine is left running, the aircraft will experience an imbalance in thrust and may experience control issues.
When an aircraft is in flight, it relies on a combination of all its engines to generate thrust and maintain stability. Each engine produces a specific amount of thrust, and if one engine is left running while the others are shut down, the thrust generated by the active engine will cause an imbalance. This imbalance can result in a yawing motion, where the aircraft deviates from its intended flight path.
To maintain control and stability, it is crucial for all engines to be shut down if an aircraft is parked or not in use. This ensures that the thrust is evenly distributed and minimizes the risk of control issues.