How should unserviceable instruments be marked?

Unserviceable instruments must be clearly marked as unserviceable to prevent their use and to ensure safety in operations. Marking instruments with a placard explicitly stating "unserviceable" serves to inform all personnel that the equipment is not functioning and should not be utilized. This helps to avoid potential accidents or operational failures due to reliance on faulty instruments.

While other options may suggest various methods of addressing unserviceable equipment, merely leaving them as is, marking them as inoperative, or simply reporting them does not provide the immediate visual indication necessary for safety compliance. Proper marking with a placard is crucial as it communicates the condition clearly and directly to all users and maintenance personnel.