Final answer:
If an aircraft has a tendency to increase a pitching moment that has been set in motion, it means that there is a positive feedback loop causing the pitching moment to continue increasing. This can occur due to imbalanced or damaged control surfaces or structural issues with the aircraft.
Step-by-step explanation:
If an aircraft has a tendency to increase a pitching moment that has been set in motion, it means that the aircraft has a positive feedback loop causing the pitching moment to continue increasing. This can occur if the aircraft's control surfaces, such as elevators or stabilizers, are not properly balanced or if there is a structural issue with the aircraft. For example, if an aircraft's elevator is misaligned or damaged, it may cause an increase in the pitching moment.
To prevent such issues, aircraft are designed and maintained with careful attention to their stability and control characteristics. This includes ensuring that control surfaces are properly aligned and balanced, and that the aircraft's structural components are in good condition.