Which line select key clears the Black-balled function for OSH VOR?

The key that clears the Black-balled function for the OSH VOR is associated with line select key 2. This line select key directly interacts with the systems that manage various navigation functions, including the control for VOR indications. When selected, it removes any temporary disabling or "black-balling" of the OSH VOR, allowing the system to accurately utilize its signals again.

Understanding the method of operation for line select keys is crucial for managing navigation systems effectively, as these keys facilitate the activation and deactivation of various functions. Thus, using line select key 2 to clear the Black-balled function ensures that the pilot can rely on the VOR for navigation, maintaining situational awareness and the ability to follow air traffic control instructions accurately.