How must inoperative equipment be marked if it is not listed in the Minimum Equipment List?

Inoperative equipment that is not listed in the Minimum Equipment List (MEL) must be marked to clearly indicate that it is inoperative. This is essential for ensuring that both the pilot and anyone else who may be involved with the aircraft understand the condition of the equipment. Marking the equipment with tape and writing "INOP" (inoperative) provides a visual cue that the equipment is not functioning and should not be relied upon. This practice enhances safety by reducing the risk of confusion about the status of the aircraft's systems.

Some other options may not be suitable for various reasons. For instance, removing and replacing the equipment would involve additional maintenance actions that may not be necessary or appropriate if the equipment is not critical for flight operations. Leaving the equipment as is without any indication could lead to misunderstandings about its operability. Simply notifying maintenance, while important, does not provide immediate clarity to pilots or other personnel who may not be aware that the equipment is inoperative. Thus, marking the equipment appropriately is a straightforward and effective way to maintain safety and communication regarding inoperative systems.