Many pilots and flight instructors know about the temporary relief offered by FAR 91.213 in the event of inoperative equipment or instruments. However this regulation is often misinterpreted. For example, FAR 91.213 (d)(3) tells us that if a piece of equipment or instrument is inoperative – providing that it is not on the list above of (d)(2), it must either be removed or deactivated. Removal is straight-forward but “deactivation” is frequently misunderstood. According to AC 91-67 deactivation is not simply turning a switch off but rather “to make a piece of equipment or instrument unusable to the pilot or crew by preventing its operation”.
So, for example, a placard by a landing light switch of an inoperative landing light does not meet this requirement. The switch must be disabled in such a way as to prevent its use. A recent discussion and quiz on this subject appeared in the May 2018 “Rotating Beacon” and the commentary focused on the legalities of whether a single inoperative strobe light was considered to be part of the anti-collision light system. The correct answer and the inop requirements were properly discussed – that being it depends on whether the aircraft was certified under Part 23 before or after March 11,1996 as listed in FAR 91.205 (11). However, in terms of achieving airworthiness, this is a moot point if our action ends there.
We must remember that there is another important step after we determine that something can be rendered inoperative. That is, it must be deactivated if not repaired or removed. The precise definition of deactivation could be applied to many different situations and in my experience, we often see placards by themselves without any action to prevent their use or operation.
The separate question of how long inoperative instruments or equipment can remain so, was resolved in June 2018 through an FAA chief counsel opinion. It turns out they can remain inoperative indefinitely provided an inspection determines that the inoperative equipment “will not have an adverse effect on the safe operation of the aircraft” and proper documentation in the maintenance logbook is accomplished. Read the entire opinion here.