During the inspection of a light, reciprocating twin-engine airplane, an inoperative instrument is discovered. How should this be documented?

Documenting an inoperative instrument as an unairworthy item in the maintenance record is crucial for maintaining safety and regulatory compliance in aviation operations. When an instrument is discovered to be inoperative, it is classified as unairworthy since all instruments must function correctly for safe operation of the aircraft. By recording this in the maintenance record, it ensures that this condition is officially noted and informs future maintenance actions or inspections.

Additionally, this documentation helps maintain transparency and accountability in aviation safety. It informs anyone who inspects or services the aircraft in the future that there is a known issue with the instrument, and it provides a legal record of the aircraft's condition at the time of inspection. This adherence to protocol supports compliance with Federal Aviation Administration (FAA) regulations, which emphasize the importance of documenting maintenance discrepancies accurately to ensure safety in aircraft operations.

In terms of the other choices, they may not align with the necessary protocol for handling an inoperative instrument and maintaining accurate maintenance records.