A newly certificated private pilot's Reddit account of a checkride oral exam surfaces a subtlety in FAA regulations that trips up even seasoned flight instructors: whether a pilot may pull and secure a circuit breaker to deactivate inoperative equipment, such as a position light, without that action constituting maintenance beyond a pilot's authority under 14 CFR Part 43. The applicant's instinctive answer—pull the breaker, placard it inoperative, and log the discrepancy for maintenance—reflects widely taught guidance, but the Designated Pilot Examiner (DPE) pushed back, asking where in the FARs a pilot is authorized to do this. The applicant later learned the answer lies not in Part 43 at all, but in Advisory Circular 91-67A, paragraph 4.2.2, which states that deactivating an inoperative system by pulling and securing a circuit breaker is not preventive maintenance as defined in Part 43 Appendix A. That distinction matters: preventive maintenance items are enumerated and pilot-performable, but deactivation of a system via circuit breaker is treated as a separate action addressed in AC guidance rather than the regulatory maintenance list, meaning the authority to do it flows from the AC and the inoperative equipment provisions of 14 CFR 91.213, not from the preventive maintenance privileges of Part 43.
This exchange is a useful reminder for CFIs and pilots at every level that regulatory competence requires more than memorizing Part 43 Appendix A or the "acronym" flows commonly taught for equipment discrepancies. AC 91-67A is not required reading in most primary training syllabi, yet it directly governs how minimum equipment list (MEL) determinations and inoperative equipment placarding are supposed to work for non-MEL aircraft under 91.213(d). Examiners increasingly probe not just "what" a pilot would do but "where does that authority come from," and DPEs have latitude to construct oral scenarios that expose gaps between practical, hangar-taught procedures and the specific regulatory or advisory sourcing behind them. For working CFIs, this is a strong argument for periodically returning to primary source documents—ACs, FAA legal interpretations, and the actual regulatory text—rather than relying solely on secondhand ground school material or mnemonics passed down through generations of instructors.
The broader lesson extends well beyond Part 91 primary training. Part 135 and Part 121 operators live and breathe MEL/CDL procedures, dispatch deviation guides, and deferred maintenance logs, and the same underlying principle applies: deactivating equipment (breaker-pull, tagging, placarding) is a distinct action from performing maintenance, and the authority and procedure for doing so is spelled out in specific FAA guidance rather than general airworthiness regulations. Corporate and charter pilots operating under an approved MEL already have this codified, but those flying non-MEL aircraft under Part 91 or 91K—including many owner-flown singles, light twins, and even some fractional or Part 91 business jet operations without an MEL—are squarely in AC 91-67A territory and need to understand that inoperative equipment determinations there are made using the "kinds of operations equipment list," 91.205, and equipment-specific regulations, not preventive maintenance privileges.
The applicant's secondary takeaway—confusion over calendar-month-based inspection currency (e.g., annual inspections due "at the end of the month" one year later versus the exact anniversary date)—is another perennial trap in maintenance-logbook review, and one that DPEs routinely test because it has real operational consequences: flying past an inspection's regulatory due date renders an aircraft unairworthy regardless of pilot intent. The exchange underscores a pattern relevant to instructors preparing applicants at any certificate level: checkride preparation benefits from deep logbook review (annuals, 100-hour inspections, AD compliance, ELT battery/inspection dates) and from cross-referencing ACs alongside the FARs, since DPEs are known to test the boundaries of applicants' and instructors' regulatory knowledge precisely where common oral-exam scripts fall short.