Final answer:
Worn attachment fittings are the probable cause of vibration in control surfaces when control cables are properly adjusted. Regular inspections are important to prevent vibration-associated risks in flight. Other issues like excessive cable tension or oil can effects may affect control surfaces but are less likely to cause vibrations.
Step-by-step explanation:
If control cables are adjusted properly and the control surfaces tend to vibrate, the probable cause is worn attachment fittings. These fittings are crucial components that connect control surfaces such as ailerons, rudders, and elevators to the aircraft's structure. Over time and with use, these fittings can wear out, leading to gaps or play that can cause vibration during flight. It is important to regularly inspect these fittings as part of aircraft maintenance to ensure the safety and proper functioning of the control surfaces.
Excessive cable tension and oil can effects are other potential issues that can affect control surfaces, but these generally do not cause vibration if the cables are adjusted correctly. Excessive cable tension could lead to difficulties in operating the control surfaces and premature wear, while oil can effects — which refer to the flexing of skin panels on the control surface — are more likely to cause a bulging or deformation rather than vibration.